Merge experimental/a64 to bleeding_edge.

src/a64/code-stubs-a64.cc

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#if V8_TARGET_ARCH_A64
+
+#include "bootstrapper.h"
+#include "code-stubs.h"
+#include "regexp-macro-assembler.h"
+#include "stub-cache.h"
+
+namespace v8 {
+namespace internal {
+
+
+void FastNewClosureStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x2: function info
+  static Register registers[] = { x2 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kNewClosureFromStubFailure)->entry;
+}
+
+
+void FastNewContextStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: function
+  static Register registers[] = { x1 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
+void ToNumberStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: value
+  static Register registers[] = { x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
+void NumberToStringStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: value
+  static Register registers[] = { x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kNumberToString)->entry;
+}
+
+
+void FastCloneShallowArrayStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x3: array literals array
+  // x2: array literal index
+  // x1: constant elements
+  static Register registers[] = { x3, x2, x1 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kCreateArrayLiteralStubBailout)->entry;
+}
+
+
+void FastCloneShallowObjectStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x3: object literals array
+  // x2: object literal index
+  // x1: constant properties
+  // x0: object literal flags
+  static Register registers[] = { x3, x2, x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kCreateObjectLiteral)->entry;
+}
+
+
+void CreateAllocationSiteStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x2: feedback vector
+  // x3: call feedback slot
+  static Register registers[] = { x2, x3 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
+void KeyedLoadFastElementStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: receiver
+  // x0: key
+  static Register registers[] = { x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(KeyedLoadIC_MissFromStubFailure);
+}
+
+
+void KeyedLoadDictionaryElementStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: receiver
+  // x0: key
+  static Register registers[] = { x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(KeyedLoadIC_MissFromStubFailure);
+}
+
+
+void RegExpConstructResultStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x2: length
+  // x1: index (of last match)
+  // x0: string
+  static Register registers[] = { x2, x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kRegExpConstructResult)->entry;
+}
+
+
+void LoadFieldStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: receiver
+  static Register registers[] = { x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
+void KeyedLoadFieldStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: receiver
+  static Register registers[] = { x1 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
+void KeyedStoreFastElementStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x2: receiver
+  // x1: key
+  // x0: value
+  static Register registers[] = { x2, x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(KeyedStoreIC_MissFromStubFailure);
+}
+
+
+void TransitionElementsKindStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: value (js_array)
+  // x1: to_map
+  static Register registers[] = { x0, x1 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  Address entry =
+      Runtime::FunctionForId(Runtime::kTransitionElementsKind)->entry;
+  descriptor->deoptimization_handler_ = FUNCTION_ADDR(entry);
+}
+
+
+void CompareNilICStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: value to compare
+  static Register registers[] = { x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(CompareNilIC_Miss);
+  descriptor->SetMissHandler(
+      ExternalReference(IC_Utility(IC::kCompareNilIC_Miss), isolate));
+}
+
+
+static void InitializeArrayConstructorDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor,
+    int constant_stack_parameter_count) {
+  // x1: function
+  // x2: allocation site with elements kind
+  // x0: number of arguments to the constructor function
+  static Register registers_variable_args[] = { x1, x2, x0 };
+  static Register registers_no_args[] = { x1, x2 };
+
+  if (constant_stack_parameter_count == 0) {
+    descriptor->register_param_count_ =
+        sizeof(registers_no_args) / sizeof(registers_no_args[0]);
+    descriptor->register_params_ = registers_no_args;
+  } else {
+    // stack param count needs (constructor pointer, and single argument)
+    descriptor->handler_arguments_mode_ = PASS_ARGUMENTS;
+    descriptor->stack_parameter_count_ = x0;
+    descriptor->register_param_count_ =
+        sizeof(registers_variable_args) / sizeof(registers_variable_args[0]);
+    descriptor->register_params_ = registers_variable_args;
+  }
+
+  descriptor->hint_stack_parameter_count_ = constant_stack_parameter_count;
+  descriptor->function_mode_ = JS_FUNCTION_STUB_MODE;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kArrayConstructor)->entry;
+}
+
+
+void ArrayNoArgumentConstructorStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  InitializeArrayConstructorDescriptor(isolate, descriptor, 0);
+}
+
+
+void ArraySingleArgumentConstructorStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  InitializeArrayConstructorDescriptor(isolate, descriptor, 1);
+}
+
+
+void ArrayNArgumentsConstructorStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  InitializeArrayConstructorDescriptor(isolate, descriptor, -1);
+}
+
+
+static void InitializeInternalArrayConstructorDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor,
+    int constant_stack_parameter_count) {
+  // x1: constructor function
+  // x0: number of arguments to the constructor function
+  static Register registers_variable_args[] = { x1, x0 };
+  static Register registers_no_args[] = { x1 };
+
+  if (constant_stack_parameter_count == 0) {
+    descriptor->register_param_count_ =
+        sizeof(registers_no_args) / sizeof(registers_no_args[0]);
+    descriptor->register_params_ = registers_no_args;
+  } else {
+    // stack param count needs (constructor pointer, and single argument)
+    descriptor->handler_arguments_mode_ = PASS_ARGUMENTS;
+    descriptor->stack_parameter_count_ = x0;
+    descriptor->register_param_count_ =
+        sizeof(registers_variable_args) / sizeof(registers_variable_args[0]);
+    descriptor->register_params_ = registers_variable_args;
+  }
+
+  descriptor->hint_stack_parameter_count_ = constant_stack_parameter_count;
+  descriptor->function_mode_ = JS_FUNCTION_STUB_MODE;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kInternalArrayConstructor)->entry;
+}
+
+
+void InternalArrayNoArgumentConstructorStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  InitializeInternalArrayConstructorDescriptor(isolate, descriptor, 0);
+}
+
+
+void InternalArraySingleArgumentConstructorStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  InitializeInternalArrayConstructorDescriptor(isolate, descriptor, 1);
+}
+
+
+void InternalArrayNArgumentsConstructorStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  InitializeInternalArrayConstructorDescriptor(isolate, descriptor, -1);
+}
+
+
+void ToBooleanStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: value
+  static Register registers[] = { x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = FUNCTION_ADDR(ToBooleanIC_Miss);
+  descriptor->SetMissHandler(
+      ExternalReference(IC_Utility(IC::kToBooleanIC_Miss), isolate));
+}
+
+
+void StoreGlobalStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: receiver
+  // x2: key (unused)
+  // x0: value
+  static Register registers[] = { x1, x2, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(StoreIC_MissFromStubFailure);
+}
+
+
+void ElementsTransitionAndStoreStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x0: value
+  // x3: target map
+  // x1: key
+  // x2: receiver
+  static Register registers[] = { x0, x3, x1, x2 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(ElementsTransitionAndStoreIC_Miss);
+}
+
+
+void BinaryOpICStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: left operand
+  // x0: right operand
+  static Register registers[] = { x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = FUNCTION_ADDR(BinaryOpIC_Miss);
+  descriptor->SetMissHandler(
+      ExternalReference(IC_Utility(IC::kBinaryOpIC_Miss), isolate));
+}
+
+
+void BinaryOpWithAllocationSiteStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x2: allocation site
+  // x1: left operand
+  // x0: right operand
+  static Register registers[] = { x2, x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(BinaryOpIC_MissWithAllocationSite);
+}
+
+
+void StringAddStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  // x1: left operand
+  // x0: right operand
+  static Register registers[] = { x1, x0 };
+  descriptor->register_param_count_ = sizeof(registers) / sizeof(registers[0]);
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Runtime::FunctionForId(Runtime::kStringAdd)->entry;
+}
+
+
+void CallDescriptors::InitializeForIsolate(Isolate* isolate) {
+  static PlatformCallInterfaceDescriptor default_descriptor =
+      PlatformCallInterfaceDescriptor(CAN_INLINE_TARGET_ADDRESS);
+
+  static PlatformCallInterfaceDescriptor noInlineDescriptor =
+      PlatformCallInterfaceDescriptor(NEVER_INLINE_TARGET_ADDRESS);
+
+  {
+    CallInterfaceDescriptor* descriptor =
+        isolate->call_descriptor(Isolate::ArgumentAdaptorCall);
+    static Register registers[] = { x1,  // JSFunction
+                                    cp,  // context
+                                    x0,  // actual number of arguments
+                                    x2,  // expected number of arguments
+    };
+    static Representation representations[] = {
+        Representation::Tagged(),     // JSFunction
+        Representation::Tagged(),     // context
+        Representation::Integer32(),  // actual number of arguments
+        Representation::Integer32(),  // expected number of arguments
+    };
+    descriptor->register_param_count_ = 4;
+    descriptor->register_params_ = registers;
+    descriptor->param_representations_ = representations;
+    descriptor->platform_specific_descriptor_ = &default_descriptor;
+  }
+  {
+    CallInterfaceDescriptor* descriptor =
+        isolate->call_descriptor(Isolate::KeyedCall);
+    static Register registers[] = { cp,  // context
+                                    x2,  // key
+    };
+    static Representation representations[] = {
+        Representation::Tagged(),     // context
+        Representation::Tagged(),     // key
+    };
+    descriptor->register_param_count_ = 2;
+    descriptor->register_params_ = registers;
+    descriptor->param_representations_ = representations;
+    descriptor->platform_specific_descriptor_ = &noInlineDescriptor;
+  }
+  {
+    CallInterfaceDescriptor* descriptor =
+        isolate->call_descriptor(Isolate::NamedCall);
+    static Register registers[] = { cp,  // context
+                                    x2,  // name
+    };
+    static Representation representations[] = {
+        Representation::Tagged(),     // context
+        Representation::Tagged(),     // name
+    };
+    descriptor->register_param_count_ = 2;
+    descriptor->register_params_ = registers;
+    descriptor->param_representations_ = representations;
+    descriptor->platform_specific_descriptor_ = &noInlineDescriptor;
+  }
+  {
+    CallInterfaceDescriptor* descriptor =
+        isolate->call_descriptor(Isolate::CallHandler);
+    static Register registers[] = { cp,  // context
+                                    x0,  // receiver
+    };
+    static Representation representations[] = {
+        Representation::Tagged(),  // context
+        Representation::Tagged(),  // receiver
+    };
+    descriptor->register_param_count_ = 2;
+    descriptor->register_params_ = registers;
+    descriptor->param_representations_ = representations;
+    descriptor->platform_specific_descriptor_ = &default_descriptor;
+  }
+  {
+    CallInterfaceDescriptor* descriptor =
+        isolate->call_descriptor(Isolate::ApiFunctionCall);
+    static Register registers[] = { x0,  // callee
+                                    x4,  // call_data
+                                    x2,  // holder
+                                    x1,  // api_function_address
+                                    cp,  // context
+    };
+    static Representation representations[] = {
+        Representation::Tagged(),    // callee
+        Representation::Tagged(),    // call_data
+        Representation::Tagged(),    // holder
+        Representation::External(),  // api_function_address
+        Representation::Tagged(),    // context
+    };
+    descriptor->register_param_count_ = 5;
+    descriptor->register_params_ = registers;
+    descriptor->param_representations_ = representations;
+    descriptor->platform_specific_descriptor_ = &default_descriptor;
+  }
+}
+
+
+#define __ ACCESS_MASM(masm)
+
+
+void HydrogenCodeStub::GenerateLightweightMiss(MacroAssembler* masm) {
+  // Update the static counter each time a new code stub is generated.
+  Isolate* isolate = masm->isolate();
+  isolate->counters()->code_stubs()->Increment();
+
+  CodeStubInterfaceDescriptor* descriptor = GetInterfaceDescriptor(isolate);
+  int param_count = descriptor->register_param_count_;
+  {
+    // Call the runtime system in a fresh internal frame.
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    ASSERT((descriptor->register_param_count_ == 0) ||
+           x0.Is(descriptor->register_params_[param_count - 1]));
+    // Push arguments
+    // TODO(jbramley): Try to push these in blocks.
+    for (int i = 0; i < param_count; ++i) {
+      __ Push(descriptor->register_params_[i]);
+    }
+    ExternalReference miss = descriptor->miss_handler();
+    __ CallExternalReference(miss, descriptor->register_param_count_);
+  }
+
+  __ Ret();
+}
+
+
+// See call site for description.
+static void EmitIdenticalObjectComparison(MacroAssembler* masm,
+                                          Register left,
+                                          Register right,
+                                          Register scratch,
+                                          FPRegister double_scratch,
+                                          Label* slow,
+                                          Condition cond) {
+  ASSERT(!AreAliased(left, right, scratch));
+  Label not_identical, return_equal, heap_number;
+  Register result = x0;
+
+  __ Cmp(right, left);
+  __ B(ne, &not_identical);
+
+  // Test for NaN. Sadly, we can't just compare to factory::nan_value(),
+  // so we do the second best thing - test it ourselves.
+  // They are both equal and they are not both Smis so both of them are not
+  // Smis.  If it's not a heap number, then return equal.
+  if ((cond == lt) || (cond == gt)) {
+    __ JumpIfObjectType(right, scratch, scratch, FIRST_SPEC_OBJECT_TYPE, slow,
+                        ge);
+  } else {
+    Register right_type = scratch;
+    __ JumpIfObjectType(right, right_type, right_type, HEAP_NUMBER_TYPE,
+                        &heap_number);
+    // Comparing JS objects with <=, >= is complicated.
+    if (cond != eq) {
+      __ Cmp(right_type, FIRST_SPEC_OBJECT_TYPE);
+      __ B(ge, slow);
+      // Normally here we fall through to return_equal, but undefined is
+      // special: (undefined == undefined) == true, but
+      // (undefined <= undefined) == false!  See ECMAScript 11.8.5.
+      if ((cond == le) || (cond == ge)) {
+        __ Cmp(right_type, ODDBALL_TYPE);
+        __ B(ne, &return_equal);
+        __ JumpIfNotRoot(right, Heap::kUndefinedValueRootIndex, &return_equal);
+        if (cond == le) {
+          // undefined <= undefined should fail.
+          __ Mov(result, GREATER);
+        } else  {
+          // undefined >= undefined should fail.
+          __ Mov(result, LESS);
+        }
+        __ Ret();
+      }
+    }
+  }
+
+  __ Bind(&return_equal);
+  if (cond == lt) {
+    __ Mov(result, GREATER);  // Things aren't less than themselves.
+  } else if (cond == gt) {
+    __ Mov(result, LESS);     // Things aren't greater than themselves.
+  } else {
+    __ Mov(result, EQUAL);    // Things are <=, >=, ==, === themselves.
+  }
+  __ Ret();
+
+  // Cases lt and gt have been handled earlier, and case ne is never seen, as
+  // it is handled in the parser (see Parser::ParseBinaryExpression). We are
+  // only concerned with cases ge, le and eq here.
+  if ((cond != lt) && (cond != gt)) {
+    ASSERT((cond == ge) || (cond == le) || (cond == eq));
+    __ Bind(&heap_number);
+    // Left and right are identical pointers to a heap number object. Return
+    // non-equal if the heap number is a NaN, and equal otherwise. Comparing
+    // the number to itself will set the overflow flag iff the number is NaN.
+    __ Ldr(double_scratch, FieldMemOperand(right, HeapNumber::kValueOffset));
+    __ Fcmp(double_scratch, double_scratch);
+    __ B(vc, &return_equal);  // Not NaN, so treat as normal heap number.
+
+    if (cond == le) {
+      __ Mov(result, GREATER);
+    } else {
+      __ Mov(result, LESS);
+    }
+    __ Ret();
+  }
+
+  // No fall through here.
+  if (FLAG_debug_code) {
+    __ Unreachable();
+  }
+
+  __ Bind(&not_identical);
+}
+
+
+// See call site for description.
+static void EmitStrictTwoHeapObjectCompare(MacroAssembler* masm,
+                                           Register left,
+                                           Register right,
+                                           Register left_type,
+                                           Register right_type,
+                                           Register scratch) {
+  ASSERT(!AreAliased(left, right, left_type, right_type, scratch));
+
+  if (masm->emit_debug_code()) {
+    // We assume that the arguments are not identical.
+    __ Cmp(left, right);
+    __ Assert(ne, kExpectedNonIdenticalObjects);
+  }
+
+  // If either operand is a JS object or an oddball value, then they are not
+  // equal since their pointers are different.
+  // There is no test for undetectability in strict equality.
+  STATIC_ASSERT(LAST_TYPE == LAST_SPEC_OBJECT_TYPE);
+  Label right_non_object;
+
+  __ Cmp(right_type, FIRST_SPEC_OBJECT_TYPE);
+  __ B(lt, &right_non_object);
+
+  // Return non-zero - x0 already contains a non-zero pointer.
+  ASSERT(left.is(x0) || right.is(x0));
+  Label return_not_equal;
+  __ Bind(&return_not_equal);
+  __ Ret();
+
+  __ Bind(&right_non_object);
+
+  // Check for oddballs: true, false, null, undefined.
+  __ Cmp(right_type, ODDBALL_TYPE);
+
+  // If right is not ODDBALL, test left. Otherwise, set eq condition.
+  __ Ccmp(left_type, ODDBALL_TYPE, ZFlag, ne);
+
+  // If right or left is not ODDBALL, test left >= FIRST_SPEC_OBJECT_TYPE.
+  // Otherwise, right or left is ODDBALL, so set a ge condition.
+  __ Ccmp(left_type, FIRST_SPEC_OBJECT_TYPE, NVFlag, ne);
+
+  __ B(ge, &return_not_equal);
+
+  // Internalized strings are unique, so they can only be equal if they are the
+  // same object. We have already tested that case, so if left and right are
+  // both internalized strings, they cannot be equal.
+  STATIC_ASSERT((kInternalizedTag == 0) && (kStringTag == 0));
+  __ Orr(scratch, left_type, right_type);
+  __ TestAndBranchIfAllClear(
+      scratch, kIsNotStringMask | kIsNotInternalizedMask, &return_not_equal);
+}
+
+
+// See call site for description.
+static void EmitSmiNonsmiComparison(MacroAssembler* masm,
+                                    Register left,
+                                    Register right,
+                                    FPRegister left_d,
+                                    FPRegister right_d,
+                                    Register scratch,
+                                    Label* slow,
+                                    bool strict) {
+  ASSERT(!AreAliased(left, right, scratch));
+  ASSERT(!AreAliased(left_d, right_d));
+  ASSERT((left.is(x0) && right.is(x1)) ||
+         (right.is(x0) && left.is(x1)));
+  Register result = x0;
+
+  Label right_is_smi, done;
+  __ JumpIfSmi(right, &right_is_smi);
+
+  // Left is the smi. Check whether right is a heap number.
+  if (strict) {
+    // If right is not a number and left is a smi, then strict equality cannot
+    // succeed. Return non-equal.
+    Label is_heap_number;
+    __ JumpIfObjectType(right, scratch, scratch, HEAP_NUMBER_TYPE,
+                        &is_heap_number);
+    // Register right is a non-zero pointer, which is a valid NOT_EQUAL result.
+    if (!right.is(result)) {
+      __ Mov(result, NOT_EQUAL);
+    }
+    __ Ret();
+    __ Bind(&is_heap_number);
+  } else {
+    // Smi compared non-strictly with a non-smi, non-heap-number. Call the
+    // runtime.
+    __ JumpIfNotObjectType(right, scratch, scratch, HEAP_NUMBER_TYPE, slow);
+  }
+
+  // Left is the smi. Right is a heap number. Load right value into right_d, and
+  // convert left smi into double in left_d.
+  __ Ldr(right_d, FieldMemOperand(right, HeapNumber::kValueOffset));
+  __ SmiUntagToDouble(left_d, left);
+  __ B(&done);
+
+  __ Bind(&right_is_smi);
+  // Right is a smi. Check whether the non-smi left is a heap number.
+  if (strict) {
+    // If left is not a number and right is a smi then strict equality cannot
+    // succeed. Return non-equal.
+    Label is_heap_number;
+    __ JumpIfObjectType(left, scratch, scratch, HEAP_NUMBER_TYPE,
+                        &is_heap_number);
+    // Register left is a non-zero pointer, which is a valid NOT_EQUAL result.
+    if (!left.is(result)) {
+      __ Mov(result, NOT_EQUAL);
+    }
+    __ Ret();
+    __ Bind(&is_heap_number);
+  } else {
+    // Smi compared non-strictly with a non-smi, non-heap-number. Call the
+    // runtime.
+    __ JumpIfNotObjectType(left, scratch, scratch, HEAP_NUMBER_TYPE, slow);
+  }
+
+  // Right is the smi. Left is a heap number. Load left value into left_d, and
+  // convert right smi into double in right_d.
+  __ Ldr(left_d, FieldMemOperand(left, HeapNumber::kValueOffset));
+  __ SmiUntagToDouble(right_d, right);
+
+  // Fall through to both_loaded_as_doubles.
+  __ Bind(&done);
+}
+
+
+// Fast negative check for internalized-to-internalized equality.
+// See call site for description.
+static void EmitCheckForInternalizedStringsOrObjects(MacroAssembler* masm,
+                                                     Register left,
+                                                     Register right,
+                                                     Register left_map,
+                                                     Register right_map,
+                                                     Register left_type,
+                                                     Register right_type,
+                                                     Label* possible_strings,
+                                                     Label* not_both_strings) {
+  ASSERT(!AreAliased(left, right, left_map, right_map, left_type, right_type));
+  Register result = x0;
+
+  Label object_test;
+  STATIC_ASSERT((kInternalizedTag == 0) && (kStringTag == 0));
+  // TODO(all): reexamine this branch sequence for optimisation wrt branch
+  // prediction.
+  __ Tbnz(right_type, MaskToBit(kIsNotStringMask), &object_test);
+  __ Tbnz(right_type, MaskToBit(kIsNotInternalizedMask), possible_strings);
+  __ Tbnz(left_type, MaskToBit(kIsNotStringMask), not_both_strings);
+  __ Tbnz(left_type, MaskToBit(kIsNotInternalizedMask), possible_strings);
+
+  // Both are internalized. We already checked that they weren't the same
+  // pointer, so they are not equal.
+  __ Mov(result, NOT_EQUAL);
+  __ Ret();
+
+  __ Bind(&object_test);
+
+  __ Cmp(right_type, FIRST_SPEC_OBJECT_TYPE);
+
+  // If right >= FIRST_SPEC_OBJECT_TYPE, test left.
+  // Otherwise, right < FIRST_SPEC_OBJECT_TYPE, so set lt condition.
+  __ Ccmp(left_type, FIRST_SPEC_OBJECT_TYPE, NFlag, ge);
+
+  __ B(lt, not_both_strings);
+
+  // If both objects are undetectable, they are equal. Otherwise, they are not
+  // equal, since they are different objects and an object is not equal to
+  // undefined.
+
+  // Returning here, so we can corrupt right_type and left_type.
+  Register right_bitfield = right_type;
+  Register left_bitfield = left_type;
+  __ Ldrb(right_bitfield, FieldMemOperand(right_map, Map::kBitFieldOffset));
+  __ Ldrb(left_bitfield, FieldMemOperand(left_map, Map::kBitFieldOffset));
+  __ And(result, right_bitfield, left_bitfield);
+  __ And(result, result, 1 << Map::kIsUndetectable);
+  __ Eor(result, result, 1 << Map::kIsUndetectable);
+  __ Ret();
+}
+
+
+static void ICCompareStub_CheckInputType(MacroAssembler* masm,
+                                         Register input,
+                                         Register scratch,
+                                         CompareIC::State expected,
+                                         Label* fail) {
+  Label ok;
+  if (expected == CompareIC::SMI) {
+    __ JumpIfNotSmi(input, fail);
+  } else if (expected == CompareIC::NUMBER) {
+    __ JumpIfSmi(input, &ok);
+    __ CheckMap(input, scratch, Heap::kHeapNumberMapRootIndex, fail,
+                DONT_DO_SMI_CHECK);
+  }
+  // We could be strict about internalized/non-internalized here, but as long as
+  // hydrogen doesn't care, the stub doesn't have to care either.
+  __ Bind(&ok);
+}
+
+
+void ICCompareStub::GenerateGeneric(MacroAssembler* masm) {
+  Register lhs = x1;
+  Register rhs = x0;
+  Register result = x0;
+  Condition cond = GetCondition();
+
+  Label miss;
+  ICCompareStub_CheckInputType(masm, lhs, x2, left_, &miss);
+  ICCompareStub_CheckInputType(masm, rhs, x3, right_, &miss);
+
+  Label slow;  // Call builtin.
+  Label not_smis, both_loaded_as_doubles;
+  Label not_two_smis, smi_done;
+  __ JumpIfEitherNotSmi(lhs, rhs, &not_two_smis);
+  __ SmiUntag(lhs);
+  __ Sub(result, lhs, Operand::UntagSmi(rhs));
+  __ Ret();
+
+  __ Bind(&not_two_smis);
+
+  // NOTICE! This code is only reached after a smi-fast-case check, so it is
+  // certain that at least one operand isn't a smi.
+
+  // Handle the case where the objects are identical. Either returns the answer
+  // or goes to slow. Only falls through if the objects were not identical.
+  EmitIdenticalObjectComparison(masm, lhs, rhs, x10, d0, &slow, cond);
+
+  // If either is a smi (we know that at least one is not a smi), then they can
+  // only be strictly equal if the other is a HeapNumber.
+  __ JumpIfBothNotSmi(lhs, rhs, &not_smis);
+
+  // Exactly one operand is a smi. EmitSmiNonsmiComparison generates code that
+  // can:
+  //  1) Return the answer.
+  //  2) Branch to the slow case.
+  //  3) Fall through to both_loaded_as_doubles.
+  // In case 3, we have found out that we were dealing with a number-number
+  // comparison. The double values of the numbers have been loaded, right into
+  // rhs_d, left into lhs_d.
+  FPRegister rhs_d = d0;
+  FPRegister lhs_d = d1;
+  EmitSmiNonsmiComparison(masm, lhs, rhs, lhs_d, rhs_d, x10, &slow, strict());
+
+  __ Bind(&both_loaded_as_doubles);
+  // The arguments have been converted to doubles and stored in rhs_d and
+  // lhs_d.
+  Label nan;
+  __ Fcmp(lhs_d, rhs_d);
+  __ B(vs, &nan);  // Overflow flag set if either is NaN.
+  STATIC_ASSERT((LESS == -1) && (EQUAL == 0) && (GREATER == 1));
+  __ Cset(result, gt);  // gt => 1, otherwise (lt, eq) => 0 (EQUAL).
+  __ Csinv(result, result, xzr, ge);  // lt => -1, gt => 1, eq => 0.
+  __ Ret();
+
+  __ Bind(&nan);
+  // Left and/or right is a NaN. Load the result register with whatever makes
+  // the comparison fail, since comparisons with NaN always fail (except ne,
+  // which is filtered out at a higher level.)
+  ASSERT(cond != ne);
+  if ((cond == lt) || (cond == le)) {
+    __ Mov(result, GREATER);
+  } else {
+    __ Mov(result, LESS);
+  }
+  __ Ret();
+
+  __ Bind(&not_smis);
+  // At this point we know we are dealing with two different objects, and
+  // neither of them is a smi. The objects are in rhs_ and lhs_.
+
+  // Load the maps and types of the objects.
+  Register rhs_map = x10;
+  Register rhs_type = x11;
+  Register lhs_map = x12;
+  Register lhs_type = x13;
+  __ Ldr(rhs_map, FieldMemOperand(rhs, HeapObject::kMapOffset));
+  __ Ldr(lhs_map, FieldMemOperand(lhs, HeapObject::kMapOffset));
+  __ Ldrb(rhs_type, FieldMemOperand(rhs_map, Map::kInstanceTypeOffset));
+  __ Ldrb(lhs_type, FieldMemOperand(lhs_map, Map::kInstanceTypeOffset));
+
+  if (strict()) {
+    // This emits a non-equal return sequence for some object types, or falls
+    // through if it was not lucky.
+    EmitStrictTwoHeapObjectCompare(masm, lhs, rhs, lhs_type, rhs_type, x14);
+  }
+
+  Label check_for_internalized_strings;
+  Label flat_string_check;
+  // Check for heap number comparison. Branch to earlier double comparison code
+  // if they are heap numbers, otherwise, branch to internalized string check.
+  __ Cmp(rhs_type, HEAP_NUMBER_TYPE);
+  __ B(ne, &check_for_internalized_strings);
+  __ Cmp(lhs_map, rhs_map);
+
+  // If maps aren't equal, lhs_ and rhs_ are not heap numbers. Branch to flat
+  // string check.
+  __ B(ne, &flat_string_check);
+
+  // Both lhs_ and rhs_ are heap numbers. Load them and branch to the double
+  // comparison code.
+  __ Ldr(lhs_d, FieldMemOperand(lhs, HeapNumber::kValueOffset));
+  __ Ldr(rhs_d, FieldMemOperand(rhs, HeapNumber::kValueOffset));
+  __ B(&both_loaded_as_doubles);
+
+  __ Bind(&check_for_internalized_strings);
+  // In the strict case, the EmitStrictTwoHeapObjectCompare already took care
+  // of internalized strings.
+  if ((cond == eq) && !strict()) {
+    // Returns an answer for two internalized strings or two detectable objects.
+    // Otherwise branches to the string case or not both strings case.
+    EmitCheckForInternalizedStringsOrObjects(masm, lhs, rhs, lhs_map, rhs_map,
+                                             lhs_type, rhs_type,
+                                             &flat_string_check, &slow);
+  }
+
+  // Check for both being sequential ASCII strings, and inline if that is the
+  // case.
+  __ Bind(&flat_string_check);
+  __ JumpIfBothInstanceTypesAreNotSequentialAscii(lhs_type, rhs_type, x14,
+                                                  x15, &slow);
+
+  Isolate* isolate = masm->isolate();
+  __ IncrementCounter(isolate->counters()->string_compare_native(), 1, x10,
+                      x11);
+  if (cond == eq) {
+    StringCompareStub::GenerateFlatAsciiStringEquals(masm, lhs, rhs,
+                                                     x10, x11, x12);
+  } else {
+    StringCompareStub::GenerateCompareFlatAsciiStrings(masm, lhs, rhs,
+                                                       x10, x11, x12, x13);
+  }
+
+  // Never fall through to here.
+  if (FLAG_debug_code) {
+    __ Unreachable();
+  }
+
+  __ Bind(&slow);
+
+  __ Push(lhs, rhs);
+  // Figure out which native to call and setup the arguments.
+  Builtins::JavaScript native;
+  if (cond == eq) {
+    native = strict() ? Builtins::STRICT_EQUALS : Builtins::EQUALS;
+  } else {
+    native = Builtins::COMPARE;
+    int ncr;  // NaN compare result
+    if ((cond == lt) || (cond == le)) {
+      ncr = GREATER;
+    } else {
+      ASSERT((cond == gt) || (cond == ge));  // remaining cases
+      ncr = LESS;
+    }
+    __ Mov(x10, Operand(Smi::FromInt(ncr)));
+    __ Push(x10);
+  }
+
+  // Call the native; it returns -1 (less), 0 (equal), or 1 (greater)
+  // tagged as a small integer.
+  __ InvokeBuiltin(native, JUMP_FUNCTION);
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void StoreBufferOverflowStub::Generate(MacroAssembler* masm) {
+  // Preserve caller-saved registers x0-x7 and x10-x15. We don't care if x8, x9,
+  // ip0 and ip1 are corrupted by the call into C.
+  CPURegList saved_regs = kCallerSaved;
+  saved_regs.Remove(ip0);
+  saved_regs.Remove(ip1);
+  saved_regs.Remove(x8);
+  saved_regs.Remove(x9);
+
+  // We don't allow a GC during a store buffer overflow so there is no need to
+  // store the registers in any particular way, but we do have to store and
+  // restore them.
+  __ PushCPURegList(saved_regs);
+  if (save_doubles_ == kSaveFPRegs) {
+    __ PushCPURegList(kCallerSavedFP);
+  }
+
+  AllowExternalCallThatCantCauseGC scope(masm);
+  __ Mov(x0, Operand(ExternalReference::isolate_address(masm->isolate())));
+  __ CallCFunction(
+      ExternalReference::store_buffer_overflow_function(masm->isolate()),
+                                                        1, 0);
+
+  if (save_doubles_ == kSaveFPRegs) {
+    __ PopCPURegList(kCallerSavedFP);
+  }
+  __ PopCPURegList(saved_regs);
+  __ Ret();
+}
+
+
+void StoreBufferOverflowStub::GenerateFixedRegStubsAheadOfTime(
+    Isolate* isolate) {
+  StoreBufferOverflowStub stub1(kDontSaveFPRegs);
+  stub1.GetCode(isolate);
+  StoreBufferOverflowStub stub2(kSaveFPRegs);
+  stub2.GetCode(isolate);
+}
+
+
+void MathPowStub::Generate(MacroAssembler* masm) {
+  // Stack on entry:
+  // jssp[0]: Exponent (as a tagged value).
+  // jssp[1]: Base (as a tagged value).
+  //
+  // The (tagged) result will be returned in x0, as a heap number.
+
+  Register result_tagged = x0;
+  Register base_tagged = x10;
+  Register exponent_tagged = x11;
+  Register exponent_integer = x12;
+  Register scratch1 = x14;
+  Register scratch0 = x15;
+  Register saved_lr = x19;
+  FPRegister result_double = d0;
+  FPRegister base_double = d0;
+  FPRegister exponent_double = d1;
+  FPRegister base_double_copy = d2;
+  FPRegister scratch1_double = d6;
+  FPRegister scratch0_double = d7;
+
+  // A fast-path for integer exponents.
+  Label exponent_is_smi, exponent_is_integer;
+  // Bail out to runtime.
+  Label call_runtime;
+  // Allocate a heap number for the result, and return it.
+  Label done;
+
+  // Unpack the inputs.
+  if (exponent_type_ == ON_STACK) {
+    Label base_is_smi;
+    Label unpack_exponent;
+
+    __ Pop(exponent_tagged, base_tagged);
+
+    __ JumpIfSmi(base_tagged, &base_is_smi);
+    __ JumpIfNotHeapNumber(base_tagged, &call_runtime);
+    // base_tagged is a heap number, so load its double value.
+    __ Ldr(base_double, FieldMemOperand(base_tagged, HeapNumber::kValueOffset));
+    __ B(&unpack_exponent);
+    __ Bind(&base_is_smi);
+    // base_tagged is a SMI, so untag it and convert it to a double.
+    __ SmiUntagToDouble(base_double, base_tagged);
+
+    __ Bind(&unpack_exponent);
+    //  x10   base_tagged       The tagged base (input).
+    //  x11   exponent_tagged   The tagged exponent (input).
+    //  d1    base_double       The base as a double.
+    __ JumpIfSmi(exponent_tagged, &exponent_is_smi);
+    __ JumpIfNotHeapNumber(exponent_tagged, &call_runtime);
+    // exponent_tagged is a heap number, so load its double value.
+    __ Ldr(exponent_double,
+           FieldMemOperand(exponent_tagged, HeapNumber::kValueOffset));
+  } else if (exponent_type_ == TAGGED) {
+    __ JumpIfSmi(exponent_tagged, &exponent_is_smi);
+    __ Ldr(exponent_double,
+           FieldMemOperand(exponent_tagged, HeapNumber::kValueOffset));
+  }
+
+  // Handle double (heap number) exponents.
+  if (exponent_type_ != INTEGER) {
+    // Detect integer exponents stored as doubles and handle those in the
+    // integer fast-path.
+    __ TryConvertDoubleToInt64(exponent_integer, exponent_double,
+                               scratch0_double, &exponent_is_integer);
+
+    if (exponent_type_ == ON_STACK) {
+      FPRegister  half_double = d3;
+      FPRegister  minus_half_double = d4;
+      FPRegister  zero_double = d5;
+      // Detect square root case. Crankshaft detects constant +/-0.5 at compile
+      // time and uses DoMathPowHalf instead. We then skip this check for
+      // non-constant cases of +/-0.5 as these hardly occur.
+
+      __ Fmov(minus_half_double, -0.5);
+      __ Fmov(half_double, 0.5);
+      __ Fcmp(minus_half_double, exponent_double);
+      __ Fccmp(half_double, exponent_double, NZFlag, ne);
+      // Condition flags at this point:
+      //    0.5;  nZCv    // Identified by eq && pl
+      //   -0.5:  NZcv    // Identified by eq && mi
+      //  other:  ?z??    // Identified by ne
+      __ B(ne, &call_runtime);
+
+      // The exponent is 0.5 or -0.5.
+
+      // Given that exponent is known to be either 0.5 or -0.5, the following
+      // special cases could apply (according to ECMA-262 15.8.2.13):
+      //
+      //  base.isNaN():                   The result is NaN.
+      //  (base == +INFINITY) || (base == -INFINITY)
+      //    exponent == 0.5:              The result is +INFINITY.
+      //    exponent == -0.5:             The result is +0.
+      //  (base == +0) || (base == -0)
+      //    exponent == 0.5:              The result is +0.
+      //    exponent == -0.5:             The result is +INFINITY.
+      //  (base < 0) && base.isFinite():  The result is NaN.
+      //
+      // Fsqrt (and Fdiv for the -0.5 case) can handle all of those except
+      // where base is -INFINITY or -0.
+
+      // Add +0 to base. This has no effect other than turning -0 into +0.
+      __ Fmov(zero_double, 0.0);
+      __ Fadd(base_double, base_double, zero_double);
+      // The operation -0+0 results in +0 in all cases except where the
+      // FPCR rounding mode is 'round towards minus infinity' (RM). The
+      // A64 simulator does not currently simulate FPCR (where the rounding
+      // mode is set), so test the operation with some debug code.
+      if (masm->emit_debug_code()) {
+        Register temp = masm->Tmp1();
+        //  d5  zero_double   The value +0.0 as a double.
+        __ Fneg(scratch0_double, zero_double);
+        // Verify that we correctly generated +0.0 and -0.0.
+        //  bits(+0.0) = 0x0000000000000000
+        //  bits(-0.0) = 0x8000000000000000
+        __ Fmov(temp, zero_double);
+        __ CheckRegisterIsClear(temp, kCouldNotGenerateZero);
+        __ Fmov(temp, scratch0_double);
+        __ Eor(temp, temp, kDSignMask);
+        __ CheckRegisterIsClear(temp, kCouldNotGenerateNegativeZero);
+        // Check that -0.0 + 0.0 == +0.0.
+        __ Fadd(scratch0_double, scratch0_double, zero_double);
+        __ Fmov(temp, scratch0_double);
+        __ CheckRegisterIsClear(temp, kExpectedPositiveZero);
+      }
+
+      // If base is -INFINITY, make it +INFINITY.
+      //  * Calculate base - base: All infinities will become NaNs since both
+      //    -INFINITY+INFINITY and +INFINITY-INFINITY are NaN in A64.
+      //  * If the result is NaN, calculate abs(base).
+      __ Fsub(scratch0_double, base_double, base_double);
+      __ Fcmp(scratch0_double, 0.0);
+      __ Fabs(scratch1_double, base_double);
+      __ Fcsel(base_double, scratch1_double, base_double, vs);
+
+      // Calculate the square root of base.
+      __ Fsqrt(result_double, base_double);
+      __ Fcmp(exponent_double, 0.0);
+      __ B(ge, &done);  // Finish now for exponents of 0.5.
+      // Find the inverse for exponents of -0.5.
+      __ Fmov(scratch0_double, 1.0);
+      __ Fdiv(result_double, scratch0_double, result_double);
+      __ B(&done);
+    }
+
+    {
+      AllowExternalCallThatCantCauseGC scope(masm);
+      __ Mov(saved_lr, lr);
+      __ CallCFunction(
+          ExternalReference::power_double_double_function(masm->isolate()),
+          0, 2);
+      __ Mov(lr, saved_lr);
+      __ B(&done);
+    }
+
+    // Handle SMI exponents.
+    __ Bind(&exponent_is_smi);
+    //  x10   base_tagged       The tagged base (input).
+    //  x11   exponent_tagged   The tagged exponent (input).
+    //  d1    base_double       The base as a double.
+    __ SmiUntag(exponent_integer, exponent_tagged);
+  }
+
+  __ Bind(&exponent_is_integer);
+  //  x10   base_tagged       The tagged base (input).
+  //  x11   exponent_tagged   The tagged exponent (input).
+  //  x12   exponent_integer  The exponent as an integer.
+  //  d1    base_double       The base as a double.
+
+  // Find abs(exponent). For negative exponents, we can find the inverse later.
+  Register exponent_abs = x13;
+  __ Cmp(exponent_integer, 0);
+  __ Cneg(exponent_abs, exponent_integer, mi);
+  //  x13   exponent_abs      The value of abs(exponent_integer).
+
+  // Repeatedly multiply to calculate the power.
+  //  result = 1.0;
+  //  For each bit n (exponent_integer{n}) {
+  //    if (exponent_integer{n}) {
+  //      result *= base;
+  //    }
+  //    base *= base;
+  //    if (remaining bits in exponent_integer are all zero) {
+  //      break;
+  //    }
+  //  }
+  Label power_loop, power_loop_entry, power_loop_exit;
+  __ Fmov(scratch1_double, base_double);
+  __ Fmov(base_double_copy, base_double);
+  __ Fmov(result_double, 1.0);
+  __ B(&power_loop_entry);
+
+  __ Bind(&power_loop);
+  __ Fmul(scratch1_double, scratch1_double, scratch1_double);
+  __ Lsr(exponent_abs, exponent_abs, 1);
+  __ Cbz(exponent_abs, &power_loop_exit);
+
+  __ Bind(&power_loop_entry);
+  __ Tbz(exponent_abs, 0, &power_loop);
+  __ Fmul(result_double, result_double, scratch1_double);
+  __ B(&power_loop);
+
+  __ Bind(&power_loop_exit);
+
+  // If the exponent was positive, result_double holds the result.
+  __ Tbz(exponent_integer, kXSignBit, &done);
+
+  // The exponent was negative, so find the inverse.
+  __ Fmov(scratch0_double, 1.0);
+  __ Fdiv(result_double, scratch0_double, result_double);
+  // ECMA-262 only requires Math.pow to return an 'implementation-dependent
+  // approximation' of base^exponent. However, mjsunit/math-pow uses Math.pow
+  // to calculate the subnormal value 2^-1074. This method of calculating
+  // negative powers doesn't work because 2^1074 overflows to infinity. To
+  // catch this corner-case, we bail out if the result was 0. (This can only
+  // occur if the divisor is infinity or the base is zero.)
+  __ Fcmp(result_double, 0.0);
+  __ B(&done, ne);
+
+  if (exponent_type_ == ON_STACK) {
+    // Bail out to runtime code.
+    __ Bind(&call_runtime);
+    // Put the arguments back on the stack.
+    __ Push(base_tagged, exponent_tagged);
+    __ TailCallRuntime(Runtime::kMath_pow_cfunction, 2, 1);
+
+    // Return.
+    __ Bind(&done);
+    __ AllocateHeapNumber(result_tagged, &call_runtime, scratch0, scratch1);
+    __ Str(result_double,
+        FieldMemOperand(result_tagged, HeapNumber::kValueOffset));
+    ASSERT(result_tagged.is(x0));
+    __ IncrementCounter(
+        masm->isolate()->counters()->math_pow(), 1, scratch0, scratch1);
+    __ Ret();
+  } else {
+    AllowExternalCallThatCantCauseGC scope(masm);
+    __ Mov(saved_lr, lr);
+    __ Fmov(base_double, base_double_copy);
+    __ Scvtf(exponent_double, exponent_integer);
+    __ CallCFunction(
+        ExternalReference::power_double_double_function(masm->isolate()),
+        0, 2);
+    __ Mov(lr, saved_lr);
+    __ Bind(&done);
+    __ IncrementCounter(
+        masm->isolate()->counters()->math_pow(), 1, scratch0, scratch1);
+    __ Ret();
+  }
+}
+
+
+void CodeStub::GenerateStubsAheadOfTime(Isolate* isolate) {
+  // It is important that the following stubs are generated in this order
+  // because pregenerated stubs can only call other pregenerated stubs.
+  // RecordWriteStub uses StoreBufferOverflowStub, which in turn uses
+  // CEntryStub.
+  CEntryStub::GenerateAheadOfTime(isolate);
+  StoreBufferOverflowStub::GenerateFixedRegStubsAheadOfTime(isolate);
+  StubFailureTrampolineStub::GenerateAheadOfTime(isolate);
+  ArrayConstructorStubBase::GenerateStubsAheadOfTime(isolate);
+  CreateAllocationSiteStub::GenerateAheadOfTime(isolate);
+  BinaryOpICStub::GenerateAheadOfTime(isolate);
+  BinaryOpICWithAllocationSiteStub::GenerateAheadOfTime(isolate);
+}
+
+
+void CodeStub::GenerateFPStubs(Isolate* isolate) {
+  // Floating-point code doesn't get special handling in A64, so there's
+  // nothing to do here.
+  USE(isolate);
+}
+
+
+static void JumpIfOOM(MacroAssembler* masm,
+                      Register value,
+                      Register scratch,
+                      Label* oom_label) {
+  STATIC_ASSERT(Failure::OUT_OF_MEMORY_EXCEPTION == 3);
+  STATIC_ASSERT(kFailureTag == 3);
+  __ And(scratch, value, 0xf);
+  __ Cmp(scratch, 0xf);
+  __ B(eq, oom_label);
+}
+
+
+bool CEntryStub::NeedsImmovableCode() {
+  // CEntryStub stores the return address on the stack before calling into
+  // C++ code. In some cases, the VM accesses this address, but it is not used
+  // when the C++ code returns to the stub because LR holds the return address
+  // in AAPCS64. If the stub is moved (perhaps during a GC), we could end up
+  // returning to dead code.
+  // TODO(jbramley): Whilst this is the only analysis that makes sense, I can't
+  // find any comment to confirm this, and I don't hit any crashes whatever
+  // this function returns. The anaylsis should be properly confirmed.
+  return true;
+}
+
+
+void CEntryStub::GenerateAheadOfTime(Isolate* isolate) {
+  CEntryStub stub(1, kDontSaveFPRegs);
+  stub.GetCode(isolate);
+  CEntryStub stub_fp(1, kSaveFPRegs);
+  stub_fp.GetCode(isolate);
+}
+
+
+void CEntryStub::GenerateCore(MacroAssembler* masm,
+                              Label* throw_normal,
+                              Label* throw_termination,
+                              Label* throw_out_of_memory,
+                              bool do_gc,
+                              bool always_allocate) {
+  // x0  : Result parameter for PerformGC, if do_gc is true.
+  // x21 : argv
+  // x22 : argc
+  // x23 : target
+  //
+  // The stack (on entry) holds the arguments and the receiver, with the
+  // receiver at the highest address:
+  //
+  //         argv[8]:     receiver
+  // argv -> argv[0]:     arg[argc-2]
+  //         ...          ...
+  //         argv[...]:   arg[1]
+  //         argv[...]:   arg[0]
+  //
+  // Immediately below (after) this is the exit frame, as constructed by
+  // EnterExitFrame:
+  //         fp[8]:    CallerPC (lr)
+  //   fp -> fp[0]:    CallerFP (old fp)
+  //         fp[-8]:   Space reserved for SPOffset.
+  //         fp[-16]:  CodeObject()
+  //         csp[...]: Saved doubles, if saved_doubles is true.
+  //         csp[32]:  Alignment padding, if necessary.
+  //         csp[24]:  Preserved x23 (used for target).
+  //         csp[16]:  Preserved x22 (used for argc).
+  //         csp[8]:   Preserved x21 (used for argv).
+  //  csp -> csp[0]:   Space reserved for the return address.
+  //
+  // After a successful call, the exit frame, preserved registers (x21-x23) and
+  // the arguments (including the receiver) are dropped or popped as
+  // appropriate. The stub then returns.
+  //
+  // After an unsuccessful call, the exit frame and suchlike are left
+  // untouched, and the stub either throws an exception by jumping to one of
+  // the provided throw_ labels, or it falls through. The failure details are
+  // passed through in x0.
+  ASSERT(csp.Is(__ StackPointer()));
+
+  Isolate* isolate = masm->isolate();
+
+  const Register& argv = x21;
+  const Register& argc = x22;
+  const Register& target = x23;
+
+  if (do_gc) {
+    // Call Runtime::PerformGC, passing x0 (the result parameter for
+    // PerformGC) and x1 (the isolate).
+    __ Mov(x1, Operand(ExternalReference::isolate_address(masm->isolate())));
+    __ CallCFunction(
+        ExternalReference::perform_gc_function(isolate), 2, 0);
+  }
+
+  ExternalReference scope_depth =
+      ExternalReference::heap_always_allocate_scope_depth(isolate);
+  if (always_allocate) {
+    __ Mov(x10, Operand(scope_depth));
+    __ Ldr(x11, MemOperand(x10));
+    __ Add(x11, x11, 1);
+    __ Str(x11, MemOperand(x10));
+  }
+
+  // Prepare AAPCS64 arguments to pass to the builtin.
+  __ Mov(x0, argc);
+  __ Mov(x1, argv);
+  __ Mov(x2, Operand(ExternalReference::isolate_address(isolate)));
+
+  // Store the return address on the stack, in the space previously allocated
+  // by EnterExitFrame. The return address is queried by
+  // ExitFrame::GetStateForFramePointer.
+  Label return_location;
+  __ Adr(x12, &return_location);
+  __ Poke(x12, 0);
+  if (__ emit_debug_code()) {
+    // Verify that the slot below fp[kSPOffset]-8 points to the return location
+    // (currently in x12).
+    Register temp = masm->Tmp1();
+    __ Ldr(temp, MemOperand(fp, ExitFrameConstants::kSPOffset));
+    __ Ldr(temp, MemOperand(temp, -static_cast<int64_t>(kXRegSizeInBytes)));
+    __ Cmp(temp, x12);
+    __ Check(eq, kReturnAddressNotFoundInFrame);
+  }
+
+  // Call the builtin.
+  __ Blr(target);
+  __ Bind(&return_location);
+  const Register& result = x0;
+
+  if (always_allocate) {
+    __ Mov(x10, Operand(scope_depth));
+    __ Ldr(x11, MemOperand(x10));
+    __ Sub(x11, x11, 1);
+    __ Str(x11, MemOperand(x10));
+  }
+
+  //  x0    result      The return code from the call.
+  //  x21   argv
+  //  x22   argc
+  //  x23   target
+  //
+  // If all of the result bits matching kFailureTagMask are '1', the result is
+  // a failure. Otherwise, it's an ordinary tagged object and the call was a
+  // success.
+  Label failure;
+  __ And(x10, result, kFailureTagMask);
+  __ Cmp(x10, kFailureTagMask);
+  __ B(&failure, eq);
+
+  // The call succeeded, so unwind the stack and return.
+
+  // Restore callee-saved registers x21-x23.
+  __ Mov(x11, argc);
+
+  __ Peek(argv, 1 * kPointerSize);
+  __ Peek(argc, 2 * kPointerSize);
+  __ Peek(target, 3 * kPointerSize);
+
+  __ LeaveExitFrame(save_doubles_, x10, true);
+  ASSERT(jssp.Is(__ StackPointer()));
+  // Pop or drop the remaining stack slots and return from the stub.
+  //         jssp[24]:    Arguments array (of size argc), including receiver.
+  //         jssp[16]:    Preserved x23 (used for target).
+  //         jssp[8]:     Preserved x22 (used for argc).
+  //         jssp[0]:     Preserved x21 (used for argv).
+  __ Drop(x11);
+  __ Ret();
+
+  // The stack pointer is still csp if we aren't returning, and the frame
+  // hasn't changed (except for the return address).
+  __ SetStackPointer(csp);
+
+  __ Bind(&failure);
+  // The call failed, so check if we need to throw an exception, and fall
+  // through (to retry) otherwise.
+
+  Label retry;
+  //  x0    result      The return code from the call, including the failure
+  //                    code and details.
+  //  x21   argv
+  //  x22   argc
+  //  x23   target
+  // Refer to the Failure class for details of the bit layout.
+  STATIC_ASSERT(Failure::RETRY_AFTER_GC == 0);
+  __ Tst(result, kFailureTypeTagMask << kFailureTagSize);
+  __ B(eq, &retry);   // RETRY_AFTER_GC
+
+  // Special handling of out-of-memory exceptions: Pass the failure result,
+  // rather than the exception descriptor.
+  JumpIfOOM(masm, result, x10, throw_out_of_memory);
+
+  // Retrieve the pending exception.
+  const Register& exception = result;
+  const Register& exception_address = x11;
+  __ Mov(exception_address,
+         Operand(ExternalReference(Isolate::kPendingExceptionAddress,
+                                   isolate)));
+  __ Ldr(exception, MemOperand(exception_address));
+
+  // See if we just retrieved an OOM exception.
+  JumpIfOOM(masm, exception, x10, throw_out_of_memory);
+
+  // Clear the pending exception.
+  __ Mov(x10, Operand(isolate->factory()->the_hole_value()));
+  __ Str(x10, MemOperand(exception_address));
+
+  //  x0    exception   The exception descriptor.
+  //  x21   argv
+  //  x22   argc
+  //  x23   target
+
+  // Special handling of termination exceptions, which are uncatchable by
+  // JavaScript code.
+  __ Cmp(exception, Operand(isolate->factory()->termination_exception()));
+  __ B(eq, throw_termination);
+
+  // Handle normal exception.
+  __ B(throw_normal);
+
+  __ Bind(&retry);
+  // The result (x0) is passed through as the next PerformGC parameter.
+}
+
+
+void CEntryStub::Generate(MacroAssembler* masm) {
+  // The Abort mechanism relies on CallRuntime, which in turn relies on
+  // CEntryStub, so until this stub has been generated, we have to use a
+  // fall-back Abort mechanism.
+  //
+  // Note that this stub must be generated before any use of Abort.
+  MacroAssembler::NoUseRealAbortsScope no_use_real_aborts(masm);
+
+  ASM_LOCATION("CEntryStub::Generate entry");
+  ProfileEntryHookStub::MaybeCallEntryHook(masm);
+
+  // Register parameters:
+  //    x0: argc (including receiver, untagged)
+  //    x1: target
+  //
+  // The stack on entry holds the arguments and the receiver, with the receiver
+  // at the highest address:
+  //
+  //    jssp]argc-1]: receiver
+  //    jssp[argc-2]: arg[argc-2]
+  //    ...           ...
+  //    jssp[1]:      arg[1]
+  //    jssp[0]:      arg[0]
+  //
+  // The arguments are in reverse order, so that arg[argc-2] is actually the
+  // first argument to the target function and arg[0] is the last.
+  ASSERT(jssp.Is(__ StackPointer()));
+  const Register& argc_input = x0;
+  const Register& target_input = x1;
+
+  // Calculate argv, argc and the target address, and store them in
+  // callee-saved registers so we can retry the call without having to reload
+  // these arguments.
+  // TODO(jbramley): If the first call attempt succeeds in the common case (as
+  // it should), then we might be better off putting these parameters directly
+  // into their argument registers, rather than using callee-saved registers and
+  // preserving them on the stack.
+  const Register& argv = x21;
+  const Register& argc = x22;
+  const Register& target = x23;
+
+  // Derive argv from the stack pointer so that it points to the first argument
+  // (arg[argc-2]), or just below the receiver in case there are no arguments.
+  //  - Adjust for the arg[] array.
+  Register temp_argv = x11;
+  __ Add(temp_argv, jssp, Operand(x0, LSL, kPointerSizeLog2));
+  //  - Adjust for the receiver.
+  __ Sub(temp_argv, temp_argv, 1 * kPointerSize);
+
+  // Enter the exit frame. Reserve three slots to preserve x21-x23 callee-saved
+  // registers.
+  FrameScope scope(masm, StackFrame::MANUAL);
+  __ EnterExitFrame(save_doubles_, x10, 3);
+  ASSERT(csp.Is(__ StackPointer()));
+
+  // Poke callee-saved registers into reserved space.
+  __ Poke(argv, 1 * kPointerSize);
+  __ Poke(argc, 2 * kPointerSize);
+  __ Poke(target, 3 * kPointerSize);
+
+  // We normally only keep tagged values in callee-saved registers, as they
+  // could be pushed onto the stack by called stubs and functions, and on the
+  // stack they can confuse the GC. However, we're only calling C functions
+  // which can push arbitrary data onto the stack anyway, and so the GC won't
+  // examine that part of the stack.
+  __ Mov(argc, argc_input);
+  __ Mov(target, target_input);
+  __ Mov(argv, temp_argv);
+
+  Label throw_normal;
+  Label throw_termination;
+  Label throw_out_of_memory;
+
+  // Call the runtime function.
+  GenerateCore(masm,
+               &throw_normal,
+               &throw_termination,
+               &throw_out_of_memory,
+               false,
+               false);
+
+  // If successful, the previous GenerateCore will have returned to the
+  // calling code. Otherwise, we fall through into the following.
+
+  // Do space-specific GC and retry runtime call.
+  GenerateCore(masm,
+               &throw_normal,
+               &throw_termination,
+               &throw_out_of_memory,
+               true,
+               false);
+
+  // Do full GC and retry runtime call one final time.
+  __ Mov(x0, reinterpret_cast<uint64_t>(Failure::InternalError()));
+  GenerateCore(masm,
+               &throw_normal,
+               &throw_termination,
+               &throw_out_of_memory,
+               true,
+               true);
+
+  // We didn't execute a return case, so the stack frame hasn't been updated
+  // (except for the return address slot). However, we don't need to initialize
+  // jssp because the throw method will immediately overwrite it when it
+  // unwinds the stack.
+  if (__ emit_debug_code()) {
+    __ Mov(jssp, kDebugZapValue);
+  }
+  __ SetStackPointer(jssp);
+
+  // Throw exceptions.
+  // If we throw an exception, we can end up re-entering CEntryStub before we
+  // pop the exit frame, so need to ensure that x21-x23 contain GC-safe values
+  // here.
+  __ Bind(&throw_out_of_memory);
+  ASM_LOCATION("Throw out of memory");
+  __ Mov(argv, 0);
+  __ Mov(argc, 0);
+  __ Mov(target, 0);
+  // Set external caught exception to false.
+  Isolate* isolate = masm->isolate();
+  __ Mov(x2, Operand(ExternalReference(Isolate::kExternalCaughtExceptionAddress,
+                                       isolate)));
+  __ Str(xzr, MemOperand(x2));
+
+  // Set pending exception and x0 to out of memory exception.
+  Label already_have_failure;
+  JumpIfOOM(masm, x0, x10, &already_have_failure);
+  Failure* out_of_memory = Failure::OutOfMemoryException(0x1);
+  __ Mov(x0, Operand(reinterpret_cast<uint64_t>(out_of_memory)));
+  __ Bind(&already_have_failure);
+  __ Mov(x2, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
+                                       isolate)));
+  __ Str(x0, MemOperand(x2));
+  // Fall through to the next label.
+
+  __ Bind(&throw_termination);
+  ASM_LOCATION("Throw termination");
+  __ Mov(argv, 0);
+  __ Mov(argc, 0);
+  __ Mov(target, 0);
+  __ ThrowUncatchable(x0, x10, x11, x12, x13);
+
+  __ Bind(&throw_normal);
+  ASM_LOCATION("Throw normal");
+  __ Mov(argv, 0);
+  __ Mov(argc, 0);
+  __ Mov(target, 0);
+  __ Throw(x0, x10, x11, x12, x13);
+}
+
+
+// This is the entry point from C++. 5 arguments are provided in x0-x4.
+// See use of the CALL_GENERATED_CODE macro for example in src/execution.cc.
+// Input:
+//   x0: code entry.
+//   x1: function.
+//   x2: receiver.
+//   x3: argc.
+//   x4: argv.
+// Output:
+//   x0: result.
+void JSEntryStub::GenerateBody(MacroAssembler* masm, bool is_construct) {
+  ASSERT(jssp.Is(__ StackPointer()));
+  Register code_entry = x0;
+
+  // Enable instruction instrumentation. This only works on the simulator, and
+  // will have no effect on the model or real hardware.
+  __ EnableInstrumentation();
+
+  Label invoke, handler_entry, exit;
+
+  // Push callee-saved registers and synchronize the system stack pointer (csp)
+  // and the JavaScript stack pointer (jssp).
+  //
+  // We must not write to jssp until after the PushCalleeSavedRegisters()
+  // call, since jssp is itself a callee-saved register.
+  __ SetStackPointer(csp);
+  __ PushCalleeSavedRegisters();
+  __ Mov(jssp, csp);
+  __ SetStackPointer(jssp);
+
+  ProfileEntryHookStub::MaybeCallEntryHook(masm);
+
+  // Build an entry frame (see layout below).
+  Isolate* isolate = masm->isolate();
+
+  // Build an entry frame.
+  int marker = is_construct ? StackFrame::ENTRY_CONSTRUCT : StackFrame::ENTRY;
+  int64_t bad_frame_pointer = -1L;  // Bad frame pointer to fail if it is used.
+  __ Mov(x13, bad_frame_pointer);
+  __ Mov(x12, Operand(Smi::FromInt(marker)));
+  __ Mov(x11, Operand(ExternalReference(Isolate::kCEntryFPAddress, isolate)));
+  __ Ldr(x10, MemOperand(x11));
+
+  // TODO(all): Pushing the marker twice seems unnecessary.
+  // In this case perhaps we could push xzr in the slot for the context
+  // (see MAsm::EnterFrame).
+  __ Push(x13, x12, x12, x10);
+  // Set up fp.
+  __ Sub(fp, jssp, EntryFrameConstants::kCallerFPOffset);
+
+  // Push the JS entry frame marker. Also set js_entry_sp if this is the
+  // outermost JS call.
+  Label non_outermost_js, done;
+  ExternalReference js_entry_sp(Isolate::kJSEntrySPAddress, isolate);
+  __ Mov(x10, Operand(ExternalReference(js_entry_sp)));
+  __ Ldr(x11, MemOperand(x10));
+  __ Cbnz(x11, &non_outermost_js);
+  __ Str(fp, MemOperand(x10));
+  __ Mov(x12, Operand(Smi::FromInt(StackFrame::OUTERMOST_JSENTRY_FRAME)));
+  __ Push(x12);
+  __ B(&done);
+  __ Bind(&non_outermost_js);
+  // We spare one instruction by pushing xzr since the marker is 0.
+  ASSERT(Smi::FromInt(StackFrame::INNER_JSENTRY_FRAME) == NULL);
+  __ Push(xzr);
+  __ Bind(&done);
+
+  // The frame set up looks like this:
+  // jssp[0] : JS entry frame marker.
+  // jssp[1] : C entry FP.
+  // jssp[2] : stack frame marker.
+  // jssp[3] : stack frmae marker.
+  // jssp[4] : bad frame pointer 0xfff...ff   <- fp points here.
+
+
+  // Jump to a faked try block that does the invoke, with a faked catch
+  // block that sets the pending exception.
+  __ B(&invoke);
+
+  // Prevent the constant pool from being emitted between the record of the
+  // handler_entry position and the first instruction of the sequence here.
+  // There is no risk because Assembler::Emit() emits the instruction before
+  // checking for constant pool emission, but we do not want to depend on
+  // that.
+  {
+    Assembler::BlockConstPoolScope block_const_pool(masm);
+    __ bind(&handler_entry);
+    handler_offset_ = handler_entry.pos();
+    // Caught exception: Store result (exception) in the pending exception
+    // field in the JSEnv and return a failure sentinel. Coming in here the
+    // fp will be invalid because the PushTryHandler below sets it to 0 to
+    // signal the existence of the JSEntry frame.
+    // TODO(jbramley): Do this in the Assembler.
+    __ Mov(x10, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
+           isolate)));
+  }
+  __ Str(code_entry, MemOperand(x10));
+  __ Mov(x0, Operand(reinterpret_cast<int64_t>(Failure::Exception())));
+  __ B(&exit);
+
+  // Invoke: Link this frame into the handler chain.  There's only one
+  // handler block in this code object, so its index is 0.
+  __ Bind(&invoke);
+  __ PushTryHandler(StackHandler::JS_ENTRY, 0);
+  // If an exception not caught by another handler occurs, this handler
+  // returns control to the code after the B(&invoke) above, which
+  // restores all callee-saved registers (including cp and fp) to their
+  // saved values before returning a failure to C.
+
+  // Clear any pending exceptions.
+  __ Mov(x10, Operand(isolate->factory()->the_hole_value()));
+  __ Mov(x11, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
+                                        isolate)));
+  __ Str(x10, MemOperand(x11));
+
+  // Invoke the function by calling through the JS entry trampoline builtin.
+  // Notice that we cannot store a reference to the trampoline code directly in
+  // this stub, because runtime stubs are not traversed when doing GC.
+
+  // Expected registers by Builtins::JSEntryTrampoline
+  // x0: code entry.
+  // x1: function.
+  // x2: receiver.
+  // x3: argc.
+  // x4: argv.
+  // TODO(jbramley): The latest ARM code checks is_construct and conditionally
+  // uses construct_entry. We probably need to do the same here.
+  ExternalReference entry(is_construct ? Builtins::kJSConstructEntryTrampoline
+                                       : Builtins::kJSEntryTrampoline,
+                          isolate);
+  __ Mov(x10, Operand(entry));
+
+  // Call the JSEntryTrampoline.
+  __ Ldr(x11, MemOperand(x10));  // Dereference the address.
+  __ Add(x12, x11, Code::kHeaderSize - kHeapObjectTag);
+  __ Blr(x12);
+
+  // Unlink this frame from the handler chain.
+  __ PopTryHandler();
+
+
+  __ Bind(&exit);
+  // x0 holds the result.
+  // The stack pointer points to the top of the entry frame pushed on entry from
+  // C++ (at the beginning of this stub):
+  // jssp[0] : JS entry frame marker.
+  // jssp[1] : C entry FP.
+  // jssp[2] : stack frame marker.
+  // jssp[3] : stack frmae marker.
+  // jssp[4] : bad frame pointer 0xfff...ff   <- fp points here.
+
+  // Check if the current stack frame is marked as the outermost JS frame.
+  Label non_outermost_js_2;
+  __ Pop(x10);
+  __ Cmp(x10, Operand(Smi::FromInt(StackFrame::OUTERMOST_JSENTRY_FRAME)));
+  __ B(ne, &non_outermost_js_2);
+  __ Mov(x11, Operand(ExternalReference(js_entry_sp)));
+  __ Str(xzr, MemOperand(x11));
+  __ Bind(&non_outermost_js_2);
+
+  // Restore the top frame descriptors from the stack.
+  __ Pop(x10);
+  __ Mov(x11, Operand(ExternalReference(Isolate::kCEntryFPAddress, isolate)));
+  __ Str(x10, MemOperand(x11));
+
+  // Reset the stack to the callee saved registers.
+  __ Drop(-EntryFrameConstants::kCallerFPOffset, kByteSizeInBytes);
+  // Restore the callee-saved registers and return.
+  ASSERT(jssp.Is(__ StackPointer()));
+  __ Mov(csp, jssp);
+  __ SetStackPointer(csp);
+  __ PopCalleeSavedRegisters();
+  // After this point, we must not modify jssp because it is a callee-saved
+  // register which we have just restored.
+  __ Ret();
+}
+
+
+void FunctionPrototypeStub::Generate(MacroAssembler* masm) {
+  Label miss;
+  Register receiver;
+  if (kind() == Code::KEYED_LOAD_IC) {
+    // ----------- S t a t e -------------
+    //  -- lr    : return address
+    //  -- x1    : receiver
+    //  -- x0    : key
+    // -----------------------------------
+    Register key = x0;
+    receiver = x1;
+    __ Cmp(key, Operand(masm->isolate()->factory()->prototype_string()));
+    __ B(ne, &miss);
+  } else {
+    ASSERT(kind() == Code::LOAD_IC);
+    // ----------- S t a t e -------------
+    //  -- lr    : return address
+    //  -- x2    : name
+    //  -- x0    : receiver
+    //  -- sp[0] : receiver
+    // -----------------------------------
+    receiver = x0;
+  }
+
+  StubCompiler::GenerateLoadFunctionPrototype(masm, receiver, x10, x11, &miss);
+
+  __ Bind(&miss);
+  StubCompiler::TailCallBuiltin(masm,
+                                BaseLoadStoreStubCompiler::MissBuiltin(kind()));
+}
+
+
+void StringLengthStub::Generate(MacroAssembler* masm) {
+  Label miss;
+  Register receiver;
+  if (kind() == Code::KEYED_LOAD_IC) {
+    // ----------- S t a t e -------------
+    //  -- lr    : return address
+    //  -- x1    : receiver
+    //  -- x0    : key
+    // -----------------------------------
+    Register key = x0;
+    receiver = x1;
+    __ Cmp(key, Operand(masm->isolate()->factory()->length_string()));
+    __ B(ne, &miss);
+  } else {
+    ASSERT(kind() == Code::LOAD_IC);
+    // ----------- S t a t e -------------
+    //  -- lr    : return address
+    //  -- x2    : name
+    //  -- x0    : receiver
+    //  -- sp[0] : receiver
+    // -----------------------------------
+    receiver = x0;
+  }
+
+  StubCompiler::GenerateLoadStringLength(masm, receiver, x10, x11, &miss);
+
+  __ Bind(&miss);
+  StubCompiler::TailCallBuiltin(masm,
+                                BaseLoadStoreStubCompiler::MissBuiltin(kind()));
+}
+
+
+void StoreArrayLengthStub::Generate(MacroAssembler* masm) {
+  ASM_LOCATION("StoreArrayLengthStub::Generate");
+  // This accepts as a receiver anything JSArray::SetElementsLength accepts
+  // (currently anything except for external arrays which means anything with
+  // elements of FixedArray type).  Value must be a number, but only smis are
+  // accepted as the most common case.
+  Label miss;
+
+  Register receiver;
+  Register value;
+  if (kind() == Code::KEYED_STORE_IC) {
+    // ----------- S t a t e -------------
+    //  -- lr    : return address
+    //  -- x2    : receiver
+    //  -- x1    : key
+    //  -- x0    : value
+    // -----------------------------------
+    Register key = x1;
+    receiver = x2;
+    value = x0;
+    __ Cmp(key, Operand(masm->isolate()->factory()->length_string()));
+    __ B(ne, &miss);
+  } else {
+    ASSERT(kind() == Code::STORE_IC);
+    // ----------- S t a t e -------------
+    //  -- lr    : return address
+    //  -- x2    : key
+    //  -- x1    : receiver
+    //  -- x0    : value
+    // -----------------------------------
+    receiver = x1;
+    value = x0;
+  }
+
+  // Check that the receiver isn't a smi.
+  __ JumpIfSmi(receiver, &miss);
+
+  // Check that the object is a JS array.
+  __ CompareObjectType(receiver, x10, x11, JS_ARRAY_TYPE);
+  __ B(ne, &miss);
+
+  // Check that elements are FixedArray.
+  // We rely on StoreIC_ArrayLength below to deal with all types of
+  // fast elements (including COW).
+  __ Ldr(x10, FieldMemOperand(receiver, JSArray::kElementsOffset));
+  __ CompareObjectType(x10, x11, x12, FIXED_ARRAY_TYPE);
+  __ B(ne, &miss);
+
+  // Check that the array has fast properties, otherwise the length
+  // property might have been redefined.
+  __ Ldr(x10, FieldMemOperand(receiver, JSArray::kPropertiesOffset));
+  __ Ldr(x10, FieldMemOperand(x10, FixedArray::kMapOffset));
+  __ CompareRoot(x10, Heap::kHashTableMapRootIndex);
+  __ B(eq, &miss);
+
+  // Check that value is a smi.
+  __ JumpIfNotSmi(value, &miss);
+
+  // Prepare tail call to StoreIC_ArrayLength.
+  __ Push(receiver, value);
+
+  ExternalReference ref =
+      ExternalReference(IC_Utility(IC::kStoreIC_ArrayLength), masm->isolate());
+  __ TailCallExternalReference(ref, 2, 1);
+
+  __ Bind(&miss);
+  StubCompiler::TailCallBuiltin(masm,
+                                BaseLoadStoreStubCompiler::MissBuiltin(kind()));
+}
+
+
+void InstanceofStub::Generate(MacroAssembler* masm) {
+  // Stack on entry:
+  // jssp[0]: function.
+  // jssp[8]: object.
+  //
+  // Returns result in x0. Zero indicates instanceof, smi 1 indicates not
+  // instanceof.
+
+  Register result = x0;
+  Register function = right();
+  Register object = left();
+  Register scratch1 = x6;
+  Register scratch2 = x7;
+  Register res_true = x8;
+  Register res_false = x9;
+  // Only used if there was an inline map check site. (See
+  // LCodeGen::DoInstanceOfKnownGlobal().)
+  Register map_check_site = x4;
+  // Delta for the instructions generated between the inline map check and the
+  // instruction setting the result.
+  const int32_t kDeltaToLoadBoolResult = 4 * kInstructionSize;
+
+  Label not_js_object, slow;
+
+  if (!HasArgsInRegisters()) {
+    __ Pop(function, object);
+  }
+
+  if (ReturnTrueFalseObject()) {
+    __ LoadTrueFalseRoots(res_true, res_false);
+  } else {
+    // This is counter-intuitive, but correct.
+    __ Mov(res_true, Operand(Smi::FromInt(0)));
+    __ Mov(res_false, Operand(Smi::FromInt(1)));
+  }
+
+  // Check that the left hand side is a JS object and load its map as a side
+  // effect.
+  Register map = x12;
+  __ JumpIfSmi(object, &not_js_object);
+  __ IsObjectJSObjectType(object, map, scratch2, &not_js_object);
+
+  // If there is a call site cache, don't look in the global cache, but do the
+  // real lookup and update the call site cache.
+  if (!HasCallSiteInlineCheck()) {
+    Label miss;
+    __ JumpIfNotRoot(function, Heap::kInstanceofCacheFunctionRootIndex, &miss);
+    __ JumpIfNotRoot(map, Heap::kInstanceofCacheMapRootIndex, &miss);
+    __ LoadRoot(result, Heap::kInstanceofCacheAnswerRootIndex);
+    __ Ret();
+    __ Bind(&miss);
+  }
+
+  // Get the prototype of the function.
+  Register prototype = x13;
+  __ TryGetFunctionPrototype(function, prototype, scratch2, &slow,
+                             MacroAssembler::kMissOnBoundFunction);
+
+  // Check that the function prototype is a JS object.
+  __ JumpIfSmi(prototype, &slow);
+  __ IsObjectJSObjectType(prototype, scratch1, scratch2, &slow);
+
+  // Update the global instanceof or call site inlined cache with the current
+  // map and function. The cached answer will be set when it is known below.
+  if (HasCallSiteInlineCheck()) {
+    // Patch the (relocated) inlined map check.
+    __ GetRelocatedValueLocation(map_check_site, scratch1);
+    // We have a cell, so need another level of dereferencing.
+    __ Ldr(scratch1, MemOperand(scratch1));
+    __ Str(map, FieldMemOperand(scratch1, Cell::kValueOffset));
+  } else {
+    __ StoreRoot(function, Heap::kInstanceofCacheFunctionRootIndex);
+    __ StoreRoot(map, Heap::kInstanceofCacheMapRootIndex);
+  }
+
+  Label return_true, return_result;
+  {
+    // Loop through the prototype chain looking for the function prototype.
+    Register chain_map = x1;
+    Register chain_prototype = x14;
+    Register null_value = x15;
+    Label loop;
+    __ Ldr(chain_prototype, FieldMemOperand(map, Map::kPrototypeOffset));
+    __ LoadRoot(null_value, Heap::kNullValueRootIndex);
+    // Speculatively set a result.
+    __ Mov(result, res_false);
+
+    __ Bind(&loop);
+
+    // If the chain prototype is the object prototype, return true.
+    __ Cmp(chain_prototype, prototype);
+    __ B(eq, &return_true);
+
+    // If the chain prototype is null, we've reached the end of the chain, so
+    // return false.
+    __ Cmp(chain_prototype, null_value);
+    __ B(eq, &return_result);
+
+    // Otherwise, load the next prototype in the chain, and loop.
+    __ Ldr(chain_map, FieldMemOperand(chain_prototype, HeapObject::kMapOffset));
+    __ Ldr(chain_prototype, FieldMemOperand(chain_map, Map::kPrototypeOffset));
+    __ B(&loop);
+  }
+
+  // Return sequence when no arguments are on the stack.
+  // We cannot fall through to here.
+  __ Bind(&return_true);
+  __ Mov(result, res_true);
+  __ Bind(&return_result);
+  if (HasCallSiteInlineCheck()) {
+    ASSERT(ReturnTrueFalseObject());
+    __ Add(map_check_site, map_check_site, kDeltaToLoadBoolResult);
+    __ GetRelocatedValueLocation(map_check_site, scratch2);
+    __ Str(result, MemOperand(scratch2));
+  } else {
+    __ StoreRoot(result, Heap::kInstanceofCacheAnswerRootIndex);
+  }
+  __ Ret();
+
+  Label object_not_null, object_not_null_or_smi;
+
+  __ Bind(&not_js_object);
+  Register object_type = x14;
+  //   x0   result        result return register (uninit)
+  //   x10  function      pointer to function
+  //   x11  object        pointer to object
+  //   x14  object_type   type of object (uninit)
+
+  // Before null, smi and string checks, check that the rhs is a function.
+  // For a non-function rhs, an exception must be thrown.
+  __ JumpIfSmi(function, &slow);
+  __ JumpIfNotObjectType(
+      function, scratch1, object_type, JS_FUNCTION_TYPE, &slow);
+
+  __ Mov(result, res_false);
+
+  // Null is not instance of anything.
+  __ Cmp(object_type, Operand(masm->isolate()->factory()->null_value()));
+  __ B(ne, &object_not_null);
+  __ Ret();
+
+  __ Bind(&object_not_null);
+  // Smi values are not instances of anything.
+  __ JumpIfNotSmi(object, &object_not_null_or_smi);
+  __ Ret();
+
+  __ Bind(&object_not_null_or_smi);
+  // String values are not instances of anything.
+  __ IsObjectJSStringType(object, scratch2, &slow);
+  __ Ret();
+
+  // Slow-case. Tail call builtin.
+  __ Bind(&slow);
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    // Arguments have either been passed into registers or have been previously
+    // popped. We need to push them before calling builtin.
+    __ Push(object, function);
+    __ InvokeBuiltin(Builtins::INSTANCE_OF, CALL_FUNCTION);
+  }
+  if (ReturnTrueFalseObject()) {
+    // Reload true/false because they were clobbered in the builtin call.
+    __ LoadTrueFalseRoots(res_true, res_false);
+    __ Cmp(result, 0);
+    __ Csel(result, res_true, res_false, eq);
+  }
+  __ Ret();
+}
+
+
+Register InstanceofStub::left() {
+  // Object to check (instanceof lhs).
+  return x11;
+}
+
+
+Register InstanceofStub::right() {
+  // Constructor function (instanceof rhs).
+  return x10;
+}
+
+
+void ArgumentsAccessStub::GenerateReadElement(MacroAssembler* masm) {
+  Register arg_count = x0;
+  Register key = x1;
+
+  // The displacement is the offset of the last parameter (if any) relative
+  // to the frame pointer.
+  static const int kDisplacement =
+      StandardFrameConstants::kCallerSPOffset - kPointerSize;
+
+  // Check that the key is a smi.
+  Label slow;
+  __ JumpIfNotSmi(key, &slow);
+
+  // Check if the calling frame is an arguments adaptor frame.
+  Register local_fp = x11;
+  Register caller_fp = x11;
+  Register caller_ctx = x12;
+  Label skip_adaptor;
+  __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ Ldr(caller_ctx, MemOperand(caller_fp,
+                                StandardFrameConstants::kContextOffset));
+  __ Cmp(caller_ctx, Operand(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
+  __ Csel(local_fp, fp, caller_fp, ne);
+  __ B(ne, &skip_adaptor);
+
+  // Load the actual arguments limit found in the arguments adaptor frame.
+  __ Ldr(arg_count, MemOperand(caller_fp,
+                               ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ Bind(&skip_adaptor);
+
+  // Check index against formal parameters count limit. Use unsigned comparison
+  // to get negative check for free: branch if key < 0 or key >= arg_count.
+  __ Cmp(key, arg_count);
+  __ B(hs, &slow);
+
+  // Read the argument from the stack and return it.
+  __ Sub(x10, arg_count, key);
+  __ Add(x10, local_fp, Operand::UntagSmiAndScale(x10, kPointerSizeLog2));
+  __ Ldr(x0, MemOperand(x10, kDisplacement));
+  __ Ret();
+
+  // Slow case: handle non-smi or out-of-bounds access to arguments by calling
+  // the runtime system.
+  __ Bind(&slow);
+  __ Push(key);
+  __ TailCallRuntime(Runtime::kGetArgumentsProperty, 1, 1);
+}
+
+
+void ArgumentsAccessStub::GenerateNewNonStrictSlow(MacroAssembler* masm) {
+  // Stack layout on entry.
+  //  jssp[0]:  number of parameters (tagged)
+  //  jssp[8]:  address of receiver argument
+  //  jssp[16]: function
+
+  // Check if the calling frame is an arguments adaptor frame.
+  Label runtime;
+  Register caller_fp = x10;
+  __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  // Load and untag the context.
+  STATIC_ASSERT((kSmiShift / kBitsPerByte) == 4);
+  __ Ldr(w11, MemOperand(caller_fp, StandardFrameConstants::kContextOffset +
+                         (kSmiShift / kBitsPerByte)));
+  __ Cmp(w11, StackFrame::ARGUMENTS_ADAPTOR);
+  __ B(ne, &runtime);
+
+  // Patch the arguments.length and parameters pointer in the current frame.
+  __ Ldr(x11, MemOperand(caller_fp,
+                         ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ Poke(x11, 0 * kXRegSizeInBytes);
+  __ Add(x10, caller_fp, Operand::UntagSmiAndScale(x11, kPointerSizeLog2));
+  __ Add(x10, x10, Operand(StandardFrameConstants::kCallerSPOffset));
+  __ Poke(x10, 1 * kXRegSizeInBytes);
+
+  __ Bind(&runtime);
+  __ TailCallRuntime(Runtime::kNewArgumentsFast, 3, 1);
+}
+
+
+void ArgumentsAccessStub::GenerateNewNonStrictFast(MacroAssembler* masm) {
+  // Stack layout on entry.
+  //  jssp[0]:  number of parameters (tagged)
+  //  jssp[8]:  address of receiver argument
+  //  jssp[16]: function
+  //
+  // Returns pointer to result object in x0.
+
+  // Note: arg_count_smi is an alias of param_count_smi.
+  Register arg_count_smi = x3;
+  Register param_count_smi = x3;
+  Register param_count = x7;
+  Register recv_arg = x14;
+  Register function = x4;
+  __ Pop(param_count_smi, recv_arg, function);
+  __ SmiUntag(param_count, param_count_smi);
+
+  // Check if the calling frame is an arguments adaptor frame.
+  Register caller_fp = x11;
+  Register caller_ctx = x12;
+  Label runtime;
+  Label adaptor_frame, try_allocate;
+  __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ Ldr(caller_ctx, MemOperand(caller_fp,
+                                StandardFrameConstants::kContextOffset));
+  __ Cmp(caller_ctx, Operand(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
+  __ B(eq, &adaptor_frame);
+
+  // No adaptor, parameter count = argument count.
+
+  //   x1   mapped_params number of mapped params, min(params, args) (uninit)
+  //   x2   arg_count     number of function arguments (uninit)
+  //   x3   arg_count_smi number of function arguments (smi)
+  //   x4   function      function pointer
+  //   x7   param_count   number of function parameters
+  //   x11  caller_fp     caller's frame pointer
+  //   x14  recv_arg      pointer to receiver arguments
+
+  Register arg_count = x2;
+  __ Mov(arg_count, param_count);
+  __ B(&try_allocate);
+
+  // We have an adaptor frame. Patch the parameters pointer.
+  __ Bind(&adaptor_frame);
+  __ Ldr(arg_count_smi,
+         MemOperand(caller_fp,
+                    ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ SmiUntag(arg_count, arg_count_smi);
+  __ Add(x10, caller_fp, Operand(arg_count, LSL, kPointerSizeLog2));
+  __ Add(recv_arg, x10, StandardFrameConstants::kCallerSPOffset);
+
+  // Compute the mapped parameter count = min(param_count, arg_count)
+  Register mapped_params = x1;
+  __ Cmp(param_count, arg_count);
+  __ Csel(mapped_params, param_count, arg_count, lt);
+
+  __ Bind(&try_allocate);
+
+  //   x0   alloc_obj     pointer to allocated objects: param map, backing
+  //                      store, arguments (uninit)
+  //   x1   mapped_params number of mapped parameters, min(params, args)
+  //   x2   arg_count     number of function arguments
+  //   x3   arg_count_smi number of function arguments (smi)
+  //   x4   function      function pointer
+  //   x7   param_count   number of function parameters
+  //   x10  size          size of objects to allocate (uninit)
+  //   x14  recv_arg      pointer to receiver arguments
+
+  // Compute the size of backing store, parameter map, and arguments object.
+  // 1. Parameter map, has two extra words containing context and backing
+  // store.
+  const int kParameterMapHeaderSize =
+      FixedArray::kHeaderSize + 2 * kPointerSize;
+
+  // Calculate the parameter map size, assuming it exists.
+  Register size = x10;
+  __ Mov(size, Operand(mapped_params, LSL, kPointerSizeLog2));
+  __ Add(size, size, kParameterMapHeaderSize);
+
+  // If there are no mapped parameters, set the running size total to zero.
+  // Otherwise, use the parameter map size calculated earlier.
+  __ Cmp(mapped_params, 0);
+  __ CzeroX(size, eq);
+
+  // 2. Add the size of the backing store and arguments object.
+  __ Add(size, size, Operand(arg_count, LSL, kPointerSizeLog2));
+  __ Add(size, size, FixedArray::kHeaderSize + Heap::kArgumentsObjectSize);
+
+  // Do the allocation of all three objects in one go. Assign this to x0, as it
+  // will be returned to the caller.
+  Register alloc_obj = x0;
+  __ Allocate(size, alloc_obj, x11, x12, &runtime, TAG_OBJECT);
+
+  // Get the arguments boilerplate from the current (global) context.
+
+  //   x0   alloc_obj     pointer to allocated objects (param map, backing
+  //                      store, arguments)
+  //   x1   mapped_params number of mapped parameters, min(params, args)
+  //   x2   arg_count     number of function arguments
+  //   x3   arg_count_smi number of function arguments (smi)
+  //   x4   function      function pointer
+  //   x7   param_count   number of function parameters
+  //   x11  args_offset   offset to args (or aliased args) boilerplate (uninit)
+  //   x14  recv_arg      pointer to receiver arguments
+
+  Register global_object = x10;
+  Register global_ctx = x10;
+  Register args_offset = x11;
+  Register aliased_args_offset = x10;
+  __ Ldr(global_object, GlobalObjectMemOperand());
+  __ Ldr(global_ctx, FieldMemOperand(global_object,
+                                     GlobalObject::kNativeContextOffset));
+
+  __ Ldr(args_offset, ContextMemOperand(global_ctx,
+                                        Context::ARGUMENTS_BOILERPLATE_INDEX));
+  __ Ldr(aliased_args_offset,
+         ContextMemOperand(global_ctx,
+                           Context::ALIASED_ARGUMENTS_BOILERPLATE_INDEX));
+  __ Cmp(mapped_params, 0);
+  __ CmovX(args_offset, aliased_args_offset, ne);
+
+  // Copy the JS object part.
+  __ CopyFields(alloc_obj, args_offset, CPURegList(x10, x12, x13),
+                JSObject::kHeaderSize / kPointerSize);
+
+  // Set up the callee in-object property.
+  STATIC_ASSERT(Heap::kArgumentsCalleeIndex == 1);
+  const int kCalleeOffset = JSObject::kHeaderSize +
+                            Heap::kArgumentsCalleeIndex * kPointerSize;
+  __ Str(function, FieldMemOperand(alloc_obj, kCalleeOffset));
+
+  // Use the length and set that as an in-object property.
+  STATIC_ASSERT(Heap::kArgumentsLengthIndex == 0);
+  const int kLengthOffset = JSObject::kHeaderSize +
+                            Heap::kArgumentsLengthIndex * kPointerSize;
+  __ Str(arg_count_smi, FieldMemOperand(alloc_obj, kLengthOffset));
+
+  // Set up the elements pointer in the allocated arguments object.
+  // If we allocated a parameter map, "elements" will point there, otherwise
+  // it will point to the backing store.
+
+  //   x0   alloc_obj     pointer to allocated objects (param map, backing
+  //                      store, arguments)
+  //   x1   mapped_params number of mapped parameters, min(params, args)
+  //   x2   arg_count     number of function arguments
+  //   x3   arg_count_smi number of function arguments (smi)
+  //   x4   function      function pointer
+  //   x5   elements      pointer to parameter map or backing store (uninit)
+  //   x6   backing_store pointer to backing store (uninit)
+  //   x7   param_count   number of function parameters
+  //   x14  recv_arg      pointer to receiver arguments
+
+  Register elements = x5;
+  __ Add(elements, alloc_obj, Heap::kArgumentsObjectSize);
+  __ Str(elements, FieldMemOperand(alloc_obj, JSObject::kElementsOffset));
+
+  // Initialize parameter map. If there are no mapped arguments, we're done.
+  Label skip_parameter_map;
+  __ Cmp(mapped_params, 0);
+  // Set up backing store address, because it is needed later for filling in
+  // the unmapped arguments.
+  Register backing_store = x6;
+  __ CmovX(backing_store, elements, eq);
+  __ B(eq, &skip_parameter_map);
+
+  __ LoadRoot(x10, Heap::kNonStrictArgumentsElementsMapRootIndex);
+  __ Str(x10, FieldMemOperand(elements, FixedArray::kMapOffset));
+  __ Add(x10, mapped_params, 2);
+  __ SmiTag(x10);
+  __ Str(x10, FieldMemOperand(elements, FixedArray::kLengthOffset));
+  __ Str(cp, FieldMemOperand(elements,
+                             FixedArray::kHeaderSize + 0 * kPointerSize));
+  __ Add(x10, elements, Operand(mapped_params, LSL, kPointerSizeLog2));
+  __ Add(x10, x10, kParameterMapHeaderSize);
+  __ Str(x10, FieldMemOperand(elements,
+                              FixedArray::kHeaderSize + 1 * kPointerSize));
+
+  // Copy the parameter slots and the holes in the arguments.
+  // We need to fill in mapped_parameter_count slots. Then index the context,
+  // where parameters are stored in reverse order, at:
+  //
+  //   MIN_CONTEXT_SLOTS .. MIN_CONTEXT_SLOTS + parameter_count - 1
+  //
+  // The mapped parameter thus needs to get indices:
+  //
+  //   MIN_CONTEXT_SLOTS + parameter_count - 1 ..
+  //     MIN_CONTEXT_SLOTS + parameter_count - mapped_parameter_count
+  //
+  // We loop from right to left.
+
+  //   x0   alloc_obj     pointer to allocated objects (param map, backing
+  //                      store, arguments)
+  //   x1   mapped_params number of mapped parameters, min(params, args)
+  //   x2   arg_count     number of function arguments
+  //   x3   arg_count_smi number of function arguments (smi)
+  //   x4   function      function pointer
+  //   x5   elements      pointer to parameter map or backing store (uninit)
+  //   x6   backing_store pointer to backing store (uninit)
+  //   x7   param_count   number of function parameters
+  //   x11  loop_count    parameter loop counter (uninit)
+  //   x12  index         parameter index (smi, uninit)
+  //   x13  the_hole      hole value (uninit)
+  //   x14  recv_arg      pointer to receiver arguments
+
+  Register loop_count = x11;
+  Register index = x12;
+  Register the_hole = x13;
+  Label parameters_loop, parameters_test;
+  __ Mov(loop_count, mapped_params);
+  __ Add(index, param_count, Context::MIN_CONTEXT_SLOTS);
+  __ Sub(index, index, mapped_params);
+  __ SmiTag(index);
+  __ LoadRoot(the_hole, Heap::kTheHoleValueRootIndex);
+  __ Add(backing_store, elements, Operand(loop_count, LSL, kPointerSizeLog2));
+  __ Add(backing_store, backing_store, kParameterMapHeaderSize);
+
+  __ B(&parameters_test);
+
+  __ Bind(&parameters_loop);
+  __ Sub(loop_count, loop_count, 1);
+  __ Mov(x10, Operand(loop_count, LSL, kPointerSizeLog2));
+  __ Add(x10, x10, kParameterMapHeaderSize - kHeapObjectTag);
+  __ Str(index, MemOperand(elements, x10));
+  __ Sub(x10, x10, kParameterMapHeaderSize - FixedArray::kHeaderSize);
+  __ Str(the_hole, MemOperand(backing_store, x10));
+  __ Add(index, index, Operand(Smi::FromInt(1)));
+  __ Bind(&parameters_test);
+  __ Cbnz(loop_count, &parameters_loop);
+
+  __ Bind(&skip_parameter_map);
+  // Copy arguments header and remaining slots (if there are any.)
+  __ LoadRoot(x10, Heap::kFixedArrayMapRootIndex);
+  __ Str(x10, FieldMemOperand(backing_store, FixedArray::kMapOffset));
+  __ Str(arg_count_smi, FieldMemOperand(backing_store,
+                                        FixedArray::kLengthOffset));
+
+  //   x0   alloc_obj     pointer to allocated objects (param map, backing
+  //                      store, arguments)
+  //   x1   mapped_params number of mapped parameters, min(params, args)
+  //   x2   arg_count     number of function arguments
+  //   x4   function      function pointer
+  //   x3   arg_count_smi number of function arguments (smi)
+  //   x6   backing_store pointer to backing store (uninit)
+  //   x14  recv_arg      pointer to receiver arguments
+
+  Label arguments_loop, arguments_test;
+  __ Mov(x10, mapped_params);
+  __ Sub(recv_arg, recv_arg, Operand(x10, LSL, kPointerSizeLog2));
+  __ B(&arguments_test);
+
+  __ Bind(&arguments_loop);
+  __ Sub(recv_arg, recv_arg, kPointerSize);
+  __ Ldr(x11, MemOperand(recv_arg));
+  __ Add(x12, backing_store, Operand(x10, LSL, kPointerSizeLog2));
+  __ Str(x11, FieldMemOperand(x12, FixedArray::kHeaderSize));
+  __ Add(x10, x10, 1);
+
+  __ Bind(&arguments_test);
+  __ Cmp(x10, arg_count);
+  __ B(lt, &arguments_loop);
+
+  __ Ret();
+
+  // Do the runtime call to allocate the arguments object.
+  __ Bind(&runtime);
+  __ Push(function, recv_arg, arg_count_smi);
+  __ TailCallRuntime(Runtime::kNewArgumentsFast, 3, 1);
+}
+
+
+void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
+  // Stack layout on entry.
+  //  jssp[0]:  number of parameters (tagged)
+  //  jssp[8]:  address of receiver argument
+  //  jssp[16]: function
+  //
+  // Returns pointer to result object in x0.
+
+  // Get the stub arguments from the frame, and make an untagged copy of the
+  // parameter count.
+  Register param_count_smi = x1;
+  Register params = x2;
+  Register function = x3;
+  Register param_count = x13;
+  __ Pop(param_count_smi, params, function);
+  __ SmiUntag(param_count, param_count_smi);
+
+  // Test if arguments adaptor needed.
+  Register caller_fp = x11;
+  Register caller_ctx = x12;
+  Label try_allocate, runtime;
+  __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ Ldr(caller_ctx, MemOperand(caller_fp,
+                                StandardFrameConstants::kContextOffset));
+  __ Cmp(caller_ctx, Operand(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
+  __ B(ne, &try_allocate);
+
+  //   x1   param_count_smi   number of parameters passed to function (smi)
+  //   x2   params            pointer to parameters
+  //   x3   function          function pointer
+  //   x11  caller_fp         caller's frame pointer
+  //   x13  param_count       number of parameters passed to function
+
+  // Patch the argument length and parameters pointer.
+  __ Ldr(param_count_smi,
+         MemOperand(caller_fp,
+                    ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ SmiUntag(param_count, param_count_smi);
+  __ Add(x10, caller_fp, Operand(param_count, LSL, kPointerSizeLog2));
+  __ Add(params, x10, StandardFrameConstants::kCallerSPOffset);
+
+  // Try the new space allocation. Start out with computing the size of the
+  // arguments object and the elements array in words.
+  Register size = x10;
+  __ Bind(&try_allocate);
+  __ Add(size, param_count, FixedArray::kHeaderSize / kPointerSize);
+  __ Cmp(param_count, 0);
+  __ CzeroX(size, eq);
+  __ Add(size, size, Heap::kArgumentsObjectSizeStrict / kPointerSize);
+
+  // Do the allocation of both objects in one go. Assign this to x0, as it will
+  // be returned to the caller.
+  Register alloc_obj = x0;
+  __ Allocate(size, alloc_obj, x11, x12, &runtime,
+              static_cast<AllocationFlags>(TAG_OBJECT | SIZE_IN_WORDS));
+
+  // Get the arguments boilerplate from the current (native) context.
+  Register global_object = x10;
+  Register global_ctx = x10;
+  Register args_offset = x4;
+  __ Ldr(global_object, GlobalObjectMemOperand());
+  __ Ldr(global_ctx, FieldMemOperand(global_object,
+                                     GlobalObject::kNativeContextOffset));
+  __ Ldr(args_offset,
+         ContextMemOperand(global_ctx,
+                           Context::STRICT_MODE_ARGUMENTS_BOILERPLATE_INDEX));
+
+  //   x0   alloc_obj         pointer to allocated objects: parameter array and
+  //                          arguments object
+  //   x1   param_count_smi   number of parameters passed to function (smi)
+  //   x2   params            pointer to parameters
+  //   x3   function          function pointer
+  //   x4   args_offset       offset to arguments boilerplate
+  //   x13  param_count       number of parameters passed to function
+
+  // Copy the JS object part.
+  __ CopyFields(alloc_obj, args_offset, CPURegList(x5, x6, x7),
+                JSObject::kHeaderSize / kPointerSize);
+
+  // Set the smi-tagged length as an in-object property.
+  STATIC_ASSERT(Heap::kArgumentsLengthIndex == 0);
+  const int kLengthOffset = JSObject::kHeaderSize +
+                            Heap::kArgumentsLengthIndex * kPointerSize;
+  __ Str(param_count_smi, FieldMemOperand(alloc_obj, kLengthOffset));
+
+  // If there are no actual arguments, we're done.
+  Label done;
+  __ Cbz(param_count, &done);
+
+  // Set up the elements pointer in the allocated arguments object and
+  // initialize the header in the elements fixed array.
+  Register elements = x5;
+  __ Add(elements, alloc_obj, Heap::kArgumentsObjectSizeStrict);
+  __ Str(elements, FieldMemOperand(alloc_obj, JSObject::kElementsOffset));
+  __ LoadRoot(x10, Heap::kFixedArrayMapRootIndex);
+  __ Str(x10, FieldMemOperand(elements, FixedArray::kMapOffset));
+  __ Str(param_count_smi, FieldMemOperand(elements, FixedArray::kLengthOffset));
+
+  //   x0   alloc_obj         pointer to allocated objects: parameter array and
+  //                          arguments object
+  //   x1   param_count_smi   number of parameters passed to function (smi)
+  //   x2   params            pointer to parameters
+  //   x3   function          function pointer
+  //   x4   array             pointer to array slot (uninit)
+  //   x5   elements          pointer to elements array of alloc_obj
+  //   x13  param_count       number of parameters passed to function
+
+  // Copy the fixed array slots.
+  Label loop;
+  Register array = x4;
+  // Set up pointer to first array slot.
+  __ Add(array, elements, FixedArray::kHeaderSize - kHeapObjectTag);
+
+  __ Bind(&loop);
+  // Pre-decrement the parameters pointer by kPointerSize on each iteration.
+  // Pre-decrement in order to skip receiver.
+  __ Ldr(x10, MemOperand(params, -kPointerSize, PreIndex));
+  // Post-increment elements by kPointerSize on each iteration.
+  __ Str(x10, MemOperand(array, kPointerSize, PostIndex));
+  __ Sub(param_count, param_count, 1);
+  __ Cbnz(param_count, &loop);
+
+  // Return from stub.
+  __ Bind(&done);
+  __ Ret();
+
+  // Do the runtime call to allocate the arguments object.
+  __ Bind(&runtime);
+  __ Push(function, params, param_count_smi);
+  __ TailCallRuntime(Runtime::kNewStrictArgumentsFast, 3, 1);
+}
+
+
+void RegExpExecStub::Generate(MacroAssembler* masm) {
+#ifdef V8_INTERPRETED_REGEXP
+  __ TailCallRuntime(Runtime::kRegExpExec, 4, 1);
+#else  // V8_INTERPRETED_REGEXP
+
+  // Stack frame on entry.
+  //  jssp[0]: last_match_info (expected JSArray)
+  //  jssp[8]: previous index
+  //  jssp[16]: subject string
+  //  jssp[24]: JSRegExp object
+  Label runtime;
+
+  // Use of registers for this function.
+
+  // Variable registers:
+  //   x10-x13                                  used as scratch registers
+  //   w0       string_type                     type of subject string
+  //   x2       jsstring_length                 subject string length
+  //   x3       jsregexp_object                 JSRegExp object
+  //   w4       string_encoding                 ASCII or UC16
+  //   w5       sliced_string_offset            if the string is a SlicedString
+  //                                            offset to the underlying string
+  //   w6       string_representation           groups attributes of the string:
+  //                                              - is a string
+  //                                              - type of the string
+  //                                              - is a short external string
+  Register string_type = w0;
+  Register jsstring_length = x2;
+  Register jsregexp_object = x3;
+  Register string_encoding = w4;
+  Register sliced_string_offset = w5;
+  Register string_representation = w6;
+
+  // These are in callee save registers and will be preserved by the call
+  // to the native RegExp code, as this code is called using the normal
+  // C calling convention. When calling directly from generated code the
+  // native RegExp code will not do a GC and therefore the content of
+  // these registers are safe to use after the call.
+
+  //   x19       subject                        subject string
+  //   x20       regexp_data                    RegExp data (FixedArray)
+  //   x21       last_match_info_elements       info relative to the last match
+  //                                            (FixedArray)
+  //   x22       code_object                    generated regexp code
+  Register subject = x19;
+  Register regexp_data = x20;
+  Register last_match_info_elements = x21;
+  Register code_object = x22;
+
+  // TODO(jbramley): Is it necessary to preserve these? I don't think ARM does.
+  CPURegList used_callee_saved_registers(subject,
+                                         regexp_data,
+                                         last_match_info_elements,
+                                         code_object);
+  __ PushCPURegList(used_callee_saved_registers);
+
+  // Stack frame.
+  //  jssp[0] : x19
+  //  jssp[8] : x20
+  //  jssp[16]: x21
+  //  jssp[24]: x22
+  //  jssp[32]: last_match_info (JSArray)
+  //  jssp[40]: previous index
+  //  jssp[48]: subject string
+  //  jssp[56]: JSRegExp object
+
+  const int kLastMatchInfoOffset = 4 * kPointerSize;
+  const int kPreviousIndexOffset = 5 * kPointerSize;
+  const int kSubjectOffset = 6 * kPointerSize;
+  const int kJSRegExpOffset = 7 * kPointerSize;
+
+  // Ensure that a RegExp stack is allocated.
+  Isolate* isolate = masm->isolate();
+  ExternalReference address_of_regexp_stack_memory_address =
+      ExternalReference::address_of_regexp_stack_memory_address(isolate);
+  ExternalReference address_of_regexp_stack_memory_size =
+      ExternalReference::address_of_regexp_stack_memory_size(isolate);
+  __ Mov(x10, Operand(address_of_regexp_stack_memory_size));
+  __ Ldr(x10, MemOperand(x10));
+  __ Cbz(x10, &runtime);
+
+  // Check that the first argument is a JSRegExp object.
+  ASSERT(jssp.Is(__ StackPointer()));
+  __ Peek(jsregexp_object, kJSRegExpOffset);
+  __ JumpIfSmi(jsregexp_object, &runtime);
+  __ JumpIfNotObjectType(jsregexp_object, x10, x10, JS_REGEXP_TYPE, &runtime);
+
+  // Check that the RegExp has been compiled (data contains a fixed array).
+  __ Ldr(regexp_data, FieldMemOperand(jsregexp_object, JSRegExp::kDataOffset));
+  if (FLAG_debug_code) {
+    STATIC_ASSERT(kSmiTag == 0);
+    __ Tst(regexp_data, kSmiTagMask);
+    __ Check(ne, kUnexpectedTypeForRegExpDataFixedArrayExpected);
+    __ CompareObjectType(regexp_data, x10, x10, FIXED_ARRAY_TYPE);
+    __ Check(eq, kUnexpectedTypeForRegExpDataFixedArrayExpected);
+  }
+
+  // Check the type of the RegExp. Only continue if type is JSRegExp::IRREGEXP.
+  __ Ldr(x10, FieldMemOperand(regexp_data, JSRegExp::kDataTagOffset));
+  __ Cmp(x10, Operand(Smi::FromInt(JSRegExp::IRREGEXP)));
+  __ B(ne, &runtime);
+
+  // Check that the number of captures fit in the static offsets vector buffer.
+  // We have always at least one capture for the whole match, plus additional
+  // ones due to capturing parentheses. A capture takes 2 registers.
+  // The number of capture registers then is (number_of_captures + 1) * 2.
+  __ Ldrsw(x10,
+           UntagSmiFieldMemOperand(regexp_data,
+                                   JSRegExp::kIrregexpCaptureCountOffset));
+  // Check (number_of_captures + 1) * 2 <= offsets vector size
+  //             number_of_captures * 2 <= offsets vector size - 2
+  STATIC_ASSERT(Isolate::kJSRegexpStaticOffsetsVectorSize >= 2);
+  __ Add(x10, x10, x10);
+  __ Cmp(x10, Isolate::kJSRegexpStaticOffsetsVectorSize - 2);
+  __ B(hi, &runtime);
+
+  // Initialize offset for possibly sliced string.
+  __ Mov(sliced_string_offset, 0);
+
+  ASSERT(jssp.Is(__ StackPointer()));
+  __ Peek(subject, kSubjectOffset);
+  __ JumpIfSmi(subject, &runtime);
+
+  __ Ldr(x10, FieldMemOperand(subject, HeapObject::kMapOffset));
+  __ Ldrb(string_type, FieldMemOperand(x10, Map::kInstanceTypeOffset));
+
+  __ Ldr(jsstring_length, FieldMemOperand(subject, String::kLengthOffset));
+
+  // Handle subject string according to its encoding and representation:
+  // (1) Sequential string?  If yes, go to (5).
+  // (2) Anything but sequential or cons?  If yes, go to (6).
+  // (3) Cons string.  If the string is flat, replace subject with first string.
+  //     Otherwise bailout.
+  // (4) Is subject external?  If yes, go to (7).
+  // (5) Sequential string.  Load regexp code according to encoding.
+  // (E) Carry on.
+  /// [...]
+
+  // Deferred code at the end of the stub:
+  // (6) Not a long external string?  If yes, go to (8).
+  // (7) External string.  Make it, offset-wise, look like a sequential string.
+  //     Go to (5).
+  // (8) Short external string or not a string?  If yes, bail out to runtime.
+  // (9) Sliced string.  Replace subject with parent.  Go to (4).
+
+  Label check_underlying;   // (4)
+  Label seq_string;         // (5)
+  Label not_seq_nor_cons;   // (6)
+  Label external_string;    // (7)
+  Label not_long_external;  // (8)
+
+  // (1) Sequential string?  If yes, go to (5).
+  __ And(string_representation,
+         string_type,
+         kIsNotStringMask |
+             kStringRepresentationMask |
+             kShortExternalStringMask);
+  // We depend on the fact that Strings of type
+  // SeqString and not ShortExternalString are defined
+  // by the following pattern:
+  //   string_type: 0XX0 XX00
+  //                ^  ^   ^^
+  //                |  |   ||
+  //                |  |   is a SeqString
+  //                |  is not a short external String
+  //                is a String
+  STATIC_ASSERT((kStringTag | kSeqStringTag) == 0);
+  STATIC_ASSERT(kShortExternalStringTag != 0);
+  __ Cbz(string_representation, &seq_string);  // Go to (5).
+
+  // (2) Anything but sequential or cons?  If yes, go to (6).
+  STATIC_ASSERT(kConsStringTag < kExternalStringTag);
+  STATIC_ASSERT(kSlicedStringTag > kExternalStringTag);
+  STATIC_ASSERT(kIsNotStringMask > kExternalStringTag);
+  STATIC_ASSERT(kShortExternalStringTag > kExternalStringTag);
+  __ Cmp(string_representation, kExternalStringTag);
+  __ B(ge, &not_seq_nor_cons);  // Go to (6).
+
+  // (3) Cons string.  Check that it's flat.
+  __ Ldr(x10, FieldMemOperand(subject, ConsString::kSecondOffset));
+  __ JumpIfNotRoot(x10, Heap::kempty_stringRootIndex, &runtime);
+  // Replace subject with first string.
+  __ Ldr(subject, FieldMemOperand(subject, ConsString::kFirstOffset));
+
+  // (4) Is subject external?  If yes, go to (7).
+  __ Bind(&check_underlying);
+  // Reload the string type.
+  __ Ldr(x10, FieldMemOperand(subject, HeapObject::kMapOffset));
+  __ Ldrb(string_type, FieldMemOperand(x10, Map::kInstanceTypeOffset));
+  STATIC_ASSERT(kSeqStringTag == 0);
+  // The underlying external string is never a short external string.
+  STATIC_CHECK(ExternalString::kMaxShortLength < ConsString::kMinLength);
+  STATIC_CHECK(ExternalString::kMaxShortLength < SlicedString::kMinLength);
+  __ TestAndBranchIfAnySet(string_type.X(),
+                           kStringRepresentationMask,
+                           &external_string);  // Go to (7).
+
+  // (5) Sequential string.  Load regexp code according to encoding.
+  __ Bind(&seq_string);
+
+  // Check that the third argument is a positive smi less than the subject
+  // string length. A negative value will be greater (unsigned comparison).
+  ASSERT(jssp.Is(__ StackPointer()));
+  __ Peek(x10, kPreviousIndexOffset);
+  __ JumpIfNotSmi(x10, &runtime);
+  __ Cmp(jsstring_length, x10);
+  __ B(ls, &runtime);
+
+  // Argument 2 (x1): We need to load argument 2 (the previous index) into x1
+  // before entering the exit frame.
+  __ SmiUntag(x1, x10);
+
+  // The third bit determines the string encoding in string_type.
+  STATIC_ASSERT(kOneByteStringTag == 0x04);
+  STATIC_ASSERT(kTwoByteStringTag == 0x00);
+  STATIC_ASSERT(kStringEncodingMask == 0x04);
+
+  // Find the code object based on the assumptions above.
+  // kDataAsciiCodeOffset and kDataUC16CodeOffset are adjacent, adds an offset
+  // of kPointerSize to reach the latter.
+  ASSERT_EQ(JSRegExp::kDataAsciiCodeOffset + kPointerSize,
+            JSRegExp::kDataUC16CodeOffset);
+  __ Mov(x10, kPointerSize);
+  // We will need the encoding later: ASCII = 0x04
+  //                                  UC16  = 0x00
+  __ Ands(string_encoding, string_type, kStringEncodingMask);
+  __ CzeroX(x10, ne);
+  __ Add(x10, regexp_data, x10);
+  __ Ldr(code_object, FieldMemOperand(x10, JSRegExp::kDataAsciiCodeOffset));
+
+  // (E) Carry on.  String handling is done.
+
+  // Check that the irregexp code has been generated for the actual string
+  // encoding. If it has, the field contains a code object otherwise it contains
+  // a smi (code flushing support).
+  __ JumpIfSmi(code_object, &runtime);
+
+  // All checks done. Now push arguments for native regexp code.
+  __ IncrementCounter(isolate->counters()->regexp_entry_native(), 1,
+                      x10,
+                      x11);
+
+  // Isolates: note we add an additional parameter here (isolate pointer).
+  __ EnterExitFrame(false, x10, 1);
+  ASSERT(csp.Is(__ StackPointer()));
+
+  // We have 9 arguments to pass to the regexp code, therefore we have to pass
+  // one on the stack and the rest as registers.
+
+  // Note that the placement of the argument on the stack isn't standard
+  // AAPCS64:
+  // csp[0]: Space for the return address placed by DirectCEntryStub.
+  // csp[8]: Argument 9, the current isolate address.
+
+  __ Mov(x10, Operand(ExternalReference::isolate_address(isolate)));
+  __ Poke(x10, kPointerSize);
+
+  Register length = w11;
+  Register previous_index_in_bytes = w12;
+  Register start = x13;
+
+  // Load start of the subject string.
+  __ Add(start, subject, SeqString::kHeaderSize - kHeapObjectTag);
+  // Load the length from the original subject string from the previous stack
+  // frame. Therefore we have to use fp, which points exactly to two pointer
+  // sizes below the previous sp. (Because creating a new stack frame pushes
+  // the previous fp onto the stack and decrements sp by 2 * kPointerSize.)
+  __ Ldr(subject, MemOperand(fp, kSubjectOffset + 2 * kPointerSize));
+  __ Ldr(length, UntagSmiFieldMemOperand(subject, String::kLengthOffset));
+
+  // Handle UC16 encoding, two bytes make one character.
+  //   string_encoding: if ASCII: 0x04
+  //                    if UC16:  0x00
+  STATIC_ASSERT(kStringEncodingMask == 0x04);
+  __ Ubfx(string_encoding, string_encoding, 2, 1);
+  __ Eor(string_encoding, string_encoding, 1);
+  //   string_encoding: if ASCII: 0
+  //                    if UC16:  1
+
+  // Convert string positions from characters to bytes.
+  // Previous index is in x1.
+  __ Lsl(previous_index_in_bytes, w1, string_encoding);
+  __ Lsl(length, length, string_encoding);
+  __ Lsl(sliced_string_offset, sliced_string_offset, string_encoding);
+
+  // Argument 1 (x0): Subject string.
+  __ Mov(x0, subject);
+
+  // Argument 2 (x1): Previous index, already there.
+
+  // Argument 3 (x2): Get the start of input.
+  // Start of input = start of string + previous index + substring offset
+  //                                                     (0 if the string
+  //                                                      is not sliced).
+  __ Add(w10, previous_index_in_bytes, sliced_string_offset);
+  __ Add(x2, start, Operand(w10, UXTW));
+
+  // Argument 4 (x3):
+  // End of input = start of input + (length of input - previous index)
+  __ Sub(w10, length, previous_index_in_bytes);
+  __ Add(x3, x2, Operand(w10, UXTW));
+
+  // Argument 5 (x4): static offsets vector buffer.
+  __ Mov(x4,
+         Operand(ExternalReference::address_of_static_offsets_vector(isolate)));
+
+  // Argument 6 (x5): Set the number of capture registers to zero to force
+  // global regexps to behave as non-global. This stub is not used for global
+  // regexps.
+  __ Mov(x5, 0);
+
+  // Argument 7 (x6): Start (high end) of backtracking stack memory area.
+  __ Mov(x10, Operand(address_of_regexp_stack_memory_address));
+  __ Ldr(x10, MemOperand(x10));
+  __ Mov(x11, Operand(address_of_regexp_stack_memory_size));
+  __ Ldr(x11, MemOperand(x11));
+  __ Add(x6, x10, x11);
+
+  // Argument 8 (x7): Indicate that this is a direct call from JavaScript.
+  __ Mov(x7, 1);
+
+  // Locate the code entry and call it.
+  __ Add(code_object, code_object, Code::kHeaderSize - kHeapObjectTag);
+  DirectCEntryStub stub;
+  stub.GenerateCall(masm, code_object);
+
+  __ LeaveExitFrame(false, x10, true);
+
+  // The generated regexp code returns an int32 in w0.
+  Label failure, exception;
+  __ CompareAndBranch(w0, NativeRegExpMacroAssembler::FAILURE, eq, &failure);
+  __ CompareAndBranch(w0,
+                      NativeRegExpMacroAssembler::EXCEPTION,
+                      eq,
+                      &exception);
+  __ CompareAndBranch(w0, NativeRegExpMacroAssembler::RETRY, eq, &runtime);
+
+  // Success: process the result from the native regexp code.
+  Register number_of_capture_registers = x12;
+
+  // Calculate number of capture registers (number_of_captures + 1) * 2
+  // and store it in the last match info.
+  __ Ldrsw(x10,
+           UntagSmiFieldMemOperand(regexp_data,
+                                   JSRegExp::kIrregexpCaptureCountOffset));
+  __ Add(x10, x10, x10);
+  __ Add(number_of_capture_registers, x10, 2);
+
+  // Check that the fourth object is a JSArray object.
+  ASSERT(jssp.Is(__ StackPointer()));
+  __ Peek(x10, kLastMatchInfoOffset);
+  __ JumpIfSmi(x10, &runtime);
+  __ JumpIfNotObjectType(x10, x11, x11, JS_ARRAY_TYPE, &runtime);
+
+  // Check that the JSArray is the fast case.
+  __ Ldr(last_match_info_elements,
+         FieldMemOperand(x10, JSArray::kElementsOffset));
+  __ Ldr(x10,
+         FieldMemOperand(last_match_info_elements, HeapObject::kMapOffset));
+  __ JumpIfNotRoot(x10, Heap::kFixedArrayMapRootIndex, &runtime);
+
+  // Check that the last match info has space for the capture registers and the
+  // additional information (overhead).
+  //     (number_of_captures + 1) * 2 + overhead <= last match info size
+  //     (number_of_captures * 2) + 2 + overhead <= last match info size
+  //      number_of_capture_registers + overhead <= last match info size
+  __ Ldrsw(x10,
+           UntagSmiFieldMemOperand(last_match_info_elements,
+                                   FixedArray::kLengthOffset));
+  __ Add(x11, number_of_capture_registers, RegExpImpl::kLastMatchOverhead);
+  __ Cmp(x11, x10);
+  __ B(gt, &runtime);
+
+  // Store the capture count.
+  __ SmiTag(x10, number_of_capture_registers);
+  __ Str(x10,
+         FieldMemOperand(last_match_info_elements,
+                         RegExpImpl::kLastCaptureCountOffset));
+  // Store last subject and last input.
+  __ Str(subject,
+         FieldMemOperand(last_match_info_elements,
+                         RegExpImpl::kLastSubjectOffset));
+  // Use x10 as the subject string in order to only need
+  // one RecordWriteStub.
+  __ Mov(x10, subject);
+  __ RecordWriteField(last_match_info_elements,
+                      RegExpImpl::kLastSubjectOffset,
+                      x10,
+                      x11,
+                      kLRHasNotBeenSaved,
+                      kDontSaveFPRegs);
+  __ Str(subject,
+         FieldMemOperand(last_match_info_elements,
+                         RegExpImpl::kLastInputOffset));
+  __ Mov(x10, subject);
+  __ RecordWriteField(last_match_info_elements,
+                      RegExpImpl::kLastInputOffset,
+                      x10,
+                      x11,
+                      kLRHasNotBeenSaved,
+                      kDontSaveFPRegs);
+
+  Register last_match_offsets = x13;
+  Register offsets_vector_index = x14;
+  Register current_offset = x15;
+
+  // Get the static offsets vector filled by the native regexp code
+  // and fill the last match info.
+  ExternalReference address_of_static_offsets_vector =
+      ExternalReference::address_of_static_offsets_vector(isolate);
+  __ Mov(offsets_vector_index, Operand(address_of_static_offsets_vector));
+
+  Label next_capture, done;
+  // Capture register counter starts from number of capture registers and
+  // iterates down to zero (inclusive).
+  __ Add(last_match_offsets,
+         last_match_info_elements,
+         RegExpImpl::kFirstCaptureOffset - kHeapObjectTag);
+  __ Bind(&next_capture);
+  __ Subs(number_of_capture_registers, number_of_capture_registers, 2);
+  __ B(mi, &done);
+  // Read two 32 bit values from the static offsets vector buffer into
+  // an X register
+  __ Ldr(current_offset,
+         MemOperand(offsets_vector_index, kWRegSizeInBytes * 2, PostIndex));
+  // Store the smi values in the last match info.
+  __ SmiTag(x10, current_offset);
+  // Clearing the 32 bottom bits gives us a Smi.
+  STATIC_ASSERT(kSmiShift == 32);
+  __ And(x11, current_offset, ~kWRegMask);
+  __ Stp(x10,
+         x11,
+         MemOperand(last_match_offsets, kXRegSizeInBytes * 2, PostIndex));
+  __ B(&next_capture);
+  __ Bind(&done);
+
+  // Return last match info.
+  __ Peek(x0, kLastMatchInfoOffset);
+  __ PopCPURegList(used_callee_saved_registers);
+  // Drop the 4 arguments of the stub from the stack.
+  __ Drop(4);
+  __ Ret();
+
+  __ Bind(&exception);
+  Register exception_value = x0;
+  // A stack overflow (on the backtrack stack) may have occured
+  // in the RegExp code but no exception has been created yet.
+  // If there is no pending exception, handle that in the runtime system.
+  __ Mov(x10, Operand(isolate->factory()->the_hole_value()));
+  __ Mov(x11,
+         Operand(ExternalReference(Isolate::kPendingExceptionAddress,
+                                   isolate)));
+  __ Ldr(exception_value, MemOperand(x11));
+  __ Cmp(x10, exception_value);
+  __ B(eq, &runtime);
+
+  __ Str(x10, MemOperand(x11));  // Clear pending exception.
+
+  // Check if the exception is a termination. If so, throw as uncatchable.
+  Label termination_exception;
+  __ JumpIfRoot(exception_value,
+                Heap::kTerminationExceptionRootIndex,
+                &termination_exception);
+
+  __ Throw(exception_value, x10, x11, x12, x13);
+
+  __ Bind(&termination_exception);
+  __ ThrowUncatchable(exception_value, x10, x11, x12, x13);
+
+  __ Bind(&failure);
+  __ Mov(x0, Operand(masm->isolate()->factory()->null_value()));
+  __ PopCPURegList(used_callee_saved_registers);
+  // Drop the 4 arguments of the stub from the stack.
+  __ Drop(4);
+  __ Ret();
+
+  __ Bind(&runtime);
+  __ PopCPURegList(used_callee_saved_registers);
+  __ TailCallRuntime(Runtime::kRegExpExec, 4, 1);
+
+  // Deferred code for string handling.
+  // (6) Not a long external string?  If yes, go to (8).
+  __ Bind(&not_seq_nor_cons);
+  // Compare flags are still set.
+  __ B(ne, &not_long_external);  // Go to (8).
+
+  // (7) External string. Make it, offset-wise, look like a sequential string.
+  __ Bind(&external_string);
+  if (masm->emit_debug_code()) {
+    // Assert that we do not have a cons or slice (indirect strings) here.
+    // Sequential strings have already been ruled out.
+    __ Ldr(x10, FieldMemOperand(subject, HeapObject::kMapOffset));
+    __ Ldrb(x10, FieldMemOperand(x10, Map::kInstanceTypeOffset));
+    __ Tst(x10, kIsIndirectStringMask);
+    __ Check(eq, kExternalStringExpectedButNotFound);
+    __ And(x10, x10, kStringRepresentationMask);
+    __ Cmp(x10, 0);
+    __ Check(ne, kExternalStringExpectedButNotFound);
+  }
+  __ Ldr(subject,
+         FieldMemOperand(subject, ExternalString::kResourceDataOffset));
+  // Move the pointer so that offset-wise, it looks like a sequential string.
+  STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
+  __ Sub(subject, subject, SeqTwoByteString::kHeaderSize - kHeapObjectTag);
+  __ B(&seq_string);    // Go to (5).
+
+  // (8) If this is a short external string or not a string, bail out to
+  // runtime.
+  __ Bind(&not_long_external);
+  STATIC_ASSERT(kShortExternalStringTag != 0);
+  __ TestAndBranchIfAnySet(string_representation,
+                           kShortExternalStringMask | kIsNotStringMask,
+                           &runtime);
+
+  // (9) Sliced string. Replace subject with parent.
+  __ Ldr(sliced_string_offset,
+         UntagSmiFieldMemOperand(subject, SlicedString::kOffsetOffset));
+  __ Ldr(subject, FieldMemOperand(subject, SlicedString::kParentOffset));
+  __ B(&check_underlying);    // Go to (4).
+#endif
+}
+
+
+// TODO(jbramley): Don't use static registers here, but take them as arguments.
+static void GenerateRecordCallTarget(MacroAssembler* masm) {
+  ASM_LOCATION("GenerateRecordCallTarget");
+  // Cache the called function in a feedback vector slot. Cache states are
+  // uninitialized, monomorphic (indicated by a JSFunction), and megamorphic.
+  //  x0 : number of arguments to the construct function
+  //  x1 : the function to call
+  //  x2 : feedback vector
+  //  x3 : slot in feedback vector (smi)
+  Label initialize, done, miss, megamorphic, not_array_function;
+
+  ASSERT_EQ(*TypeFeedbackInfo::MegamorphicSentinel(masm->isolate()),
+            masm->isolate()->heap()->undefined_value());
+  ASSERT_EQ(*TypeFeedbackInfo::UninitializedSentinel(masm->isolate()),
+            masm->isolate()->heap()->the_hole_value());
+
+  // Load the cache state.
+  __ Add(x4, x2, Operand::UntagSmiAndScale(x3, kPointerSizeLog2));
+  __ Ldr(x4, FieldMemOperand(x4, FixedArray::kHeaderSize));
+
+  // A monomorphic cache hit or an already megamorphic state: invoke the
+  // function without changing the state.
+  __ Cmp(x4, x1);
+  __ B(eq, &done);
+
+  // If we came here, we need to see if we are the array function.
+  // If we didn't have a matching function, and we didn't find the megamorph
+  // sentinel, then we have in the slot either some other function or an
+  // AllocationSite. Do a map check on the object in ecx.
+  __ Ldr(x5, FieldMemOperand(x4, AllocationSite::kMapOffset));
+  __ JumpIfNotRoot(x5, Heap::kAllocationSiteMapRootIndex, &miss);
+
+  // Make sure the function is the Array() function
+  __ LoadArrayFunction(x4);
+  __ Cmp(x1, x4);
+  __ B(ne, &megamorphic);
+  __ B(&done);
+
+  __ Bind(&miss);
+
+  // A monomorphic miss (i.e, here the cache is not uninitialized) goes
+  // megamorphic.
+  __ JumpIfRoot(x4, Heap::kTheHoleValueRootIndex, &initialize);
+  // MegamorphicSentinel is an immortal immovable object (undefined) so no
+  // write-barrier is needed.
+  __ Bind(&megamorphic);
+  __ Add(x4, x2, Operand::UntagSmiAndScale(x3, kPointerSizeLog2));
+  __ LoadRoot(x10, Heap::kUndefinedValueRootIndex);
+  __ Str(x10, FieldMemOperand(x4, FixedArray::kHeaderSize));
+  __ B(&done);
+
+  // An uninitialized cache is patched with the function or sentinel to
+  // indicate the ElementsKind if function is the Array constructor.
+  __ Bind(&initialize);
+  // Make sure the function is the Array() function
+  __ LoadArrayFunction(x4);
+  __ Cmp(x1, x4);
+  __ B(ne, &not_array_function);
+
+  // The target function is the Array constructor,
+  // Create an AllocationSite if we don't already have it, store it in the slot.
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    CreateAllocationSiteStub create_stub;
+
+    // Arguments register must be smi-tagged to call out.
+    __ SmiTag(x0);
+    __ Push(x0, x1, x2, x3);
+
+    __ CallStub(&create_stub);
+
+    __ Pop(x3, x2, x1, x0);
+    __ SmiUntag(x0);
+  }
+  __ B(&done);
+
+  __ Bind(&not_array_function);
+  // An uninitialized cache is patched with the function.
+
+  __ Add(x4, x2, Operand::UntagSmiAndScale(x3, kPointerSizeLog2));
+  // TODO(all): Does the value need to be left in x4? If not, FieldMemOperand
+  // could be used to avoid this add.
+  __ Add(x4, x4, FixedArray::kHeaderSize - kHeapObjectTag);
+  __ Str(x1, MemOperand(x4, 0));
+
+  __ Push(x4, x2, x1);
+  __ RecordWrite(x2, x4, x1, kLRHasNotBeenSaved, kDontSaveFPRegs,
+                 EMIT_REMEMBERED_SET, OMIT_SMI_CHECK);
+  __ Pop(x1, x2, x4);
+
+  // TODO(all): Are x4, x2 and x1 outputs? This isn't clear.
+
+  __ Bind(&done);
+}
+
+
+void CallFunctionStub::Generate(MacroAssembler* masm) {
+  ASM_LOCATION("CallFunctionStub::Generate");
+  // x1  function    the function to call
+  // x2 : feedback vector
+  // x3 : slot in feedback vector (smi) (if x2 is not undefined)
+  Register function = x1;
+  Register cache_cell = x2;
+  Register slot = x3;
+  Register type = x4;
+  Label slow, non_function, wrap, cont;
+
+  // TODO(jbramley): This function has a lot of unnamed registers. Name them,
+  // and tidy things up a bit.
+
+  if (NeedsChecks()) {
+    // Check that the function is really a JavaScript function.
+    __ JumpIfSmi(function, &non_function);
+
+    // Goto slow case if we do not have a function.
+    __ JumpIfNotObjectType(function, x10, type, JS_FUNCTION_TYPE, &slow);
+
+    if (RecordCallTarget()) {
+      GenerateRecordCallTarget(masm);
+    }
+  }
+
+  // Fast-case: Invoke the function now.
+  // x1  function  pushed function
+  ParameterCount actual(argc_);
+
+  if (CallAsMethod()) {
+    if (NeedsChecks()) {
+      // Do not transform the receiver for strict mode functions.
+      __ Ldr(x3, FieldMemOperand(x1, JSFunction::kSharedFunctionInfoOffset));
+      __ Ldr(w4, FieldMemOperand(x3, SharedFunctionInfo::kCompilerHintsOffset));
+      __ Tbnz(w4, SharedFunctionInfo::kStrictModeFunction, &cont);
+
+      // Do not transform the receiver for native (Compilerhints already in x3).
+      __ Tbnz(w4, SharedFunctionInfo::kNative, &cont);
+    }
+
+    // Compute the receiver in non-strict mode.
+    __ Peek(x3, argc_ * kPointerSize);
+
+    if (NeedsChecks()) {
+      __ JumpIfSmi(x3, &wrap);
+      __ JumpIfObjectType(x3, x10, type, FIRST_SPEC_OBJECT_TYPE, &wrap, lt);
+    } else {
+      __ B(&wrap);
+    }
+
+    __ Bind(&cont);
+  }
+  __ InvokeFunction(function,
+                    actual,
+                    JUMP_FUNCTION,
+                    NullCallWrapper());
+
+  if (NeedsChecks()) {
+    // Slow-case: Non-function called.
+    __ Bind(&slow);
+    if (RecordCallTarget()) {
+      // If there is a call target cache, mark it megamorphic in the
+      // non-function case. MegamorphicSentinel is an immortal immovable object
+      // (undefined) so no write barrier is needed.
+      ASSERT_EQ(*TypeFeedbackInfo::MegamorphicSentinel(masm->isolate()),
+                masm->isolate()->heap()->undefined_value());
+      __ Add(x12, cache_cell, Operand::UntagSmiAndScale(slot,
+                                                        kPointerSizeLog2));
+      __ LoadRoot(x11, Heap::kUndefinedValueRootIndex);
+      __ Str(x11, FieldMemOperand(x12, FixedArray::kHeaderSize));
+    }
+    // Check for function proxy.
+    // x10 : function type.
+    __ CompareAndBranch(type, JS_FUNCTION_PROXY_TYPE, ne, &non_function);
+    __ Push(function);  // put proxy as additional argument
+    __ Mov(x0, argc_ + 1);
+    __ Mov(x2, 0);
+    __ GetBuiltinFunction(x1, Builtins::CALL_FUNCTION_PROXY);
+    {
+      Handle<Code> adaptor =
+          masm->isolate()->builtins()->ArgumentsAdaptorTrampoline();
+      __ Jump(adaptor, RelocInfo::CODE_TARGET);
+    }
+
+    // CALL_NON_FUNCTION expects the non-function callee as receiver (instead
+    // of the original receiver from the call site).
+    __ Bind(&non_function);
+    __ Poke(function, argc_ * kXRegSizeInBytes);
+    __ Mov(x0, argc_);  // Set up the number of arguments.
+    __ Mov(x2, 0);
+    __ GetBuiltinFunction(function, Builtins::CALL_NON_FUNCTION);
+    __ Jump(masm->isolate()->builtins()->ArgumentsAdaptorTrampoline(),
+            RelocInfo::CODE_TARGET);
+  }
+
+  if (CallAsMethod()) {
+    __ Bind(&wrap);
+    // Wrap the receiver and patch it back onto the stack.
+    { FrameScope frame_scope(masm, StackFrame::INTERNAL);
+      __ Push(x1, x3);
+      __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
+      __ Pop(x1);
+    }
+    __ Poke(x0, argc_ * kPointerSize);
+    __ B(&cont);
+  }
+}
+
+
+void CallConstructStub::Generate(MacroAssembler* masm) {
+  ASM_LOCATION("CallConstructStub::Generate");
+  // x0 : number of arguments
+  // x1 : the function to call
+  // x2 : feedback vector
+  // x3 : slot in feedback vector (smi) (if r2 is not undefined)
+  Register function = x1;
+  Label slow, non_function_call;
+
+  // Check that the function is not a smi.
+  __ JumpIfSmi(function, &non_function_call);
+  // Check that the function is a JSFunction.
+  Register object_type = x10;
+  __ JumpIfNotObjectType(function, object_type, object_type, JS_FUNCTION_TYPE,
+                         &slow);
+
+  if (RecordCallTarget()) {
+    GenerateRecordCallTarget(masm);
+  }
+
+  // Jump to the function-specific construct stub.
+  Register jump_reg = x4;
+  Register shared_func_info = jump_reg;
+  Register cons_stub = jump_reg;
+  Register cons_stub_code = jump_reg;
+  __ Ldr(shared_func_info,
+         FieldMemOperand(function, JSFunction::kSharedFunctionInfoOffset));
+  __ Ldr(cons_stub,
+         FieldMemOperand(shared_func_info,
+                         SharedFunctionInfo::kConstructStubOffset));
+  __ Add(cons_stub_code, cons_stub, Code::kHeaderSize - kHeapObjectTag);
+  __ Br(cons_stub_code);
+
+  Label do_call;
+  __ Bind(&slow);
+  __ Cmp(object_type, JS_FUNCTION_PROXY_TYPE);
+  __ B(ne, &non_function_call);
+  __ GetBuiltinFunction(x1, Builtins::CALL_FUNCTION_PROXY_AS_CONSTRUCTOR);
+  __ B(&do_call);
+
+  __ Bind(&non_function_call);
+  __ GetBuiltinFunction(x1, Builtins::CALL_NON_FUNCTION_AS_CONSTRUCTOR);
+
+  __ Bind(&do_call);
+  // Set expected number of arguments to zero (not changing x0).
+  __ Mov(x2, 0);
+  __ Jump(masm->isolate()->builtins()->ArgumentsAdaptorTrampoline(),
+          RelocInfo::CODE_TARGET);
+}
+
+
+void StringCharCodeAtGenerator::GenerateFast(MacroAssembler* masm) {
+  // If the receiver is a smi trigger the non-string case.
+  __ JumpIfSmi(object_, receiver_not_string_);
+
+  // Fetch the instance type of the receiver into result register.
+  __ Ldr(result_, FieldMemOperand(object_, HeapObject::kMapOffset));
+  __ Ldrb(result_, FieldMemOperand(result_, Map::kInstanceTypeOffset));
+
+  // If the receiver is not a string trigger the non-string case.
+  __ TestAndBranchIfAnySet(result_, kIsNotStringMask, receiver_not_string_);
+
+  // If the index is non-smi trigger the non-smi case.
+  __ JumpIfNotSmi(index_, &index_not_smi_);
+
+  __ Bind(&got_smi_index_);
+  // Check for index out of range.
+  __ Ldrsw(result_, UntagSmiFieldMemOperand(object_, String::kLengthOffset));
+  __ Cmp(result_, Operand::UntagSmi(index_));
+  __ B(ls, index_out_of_range_);
+
+  __ SmiUntag(index_);
+
+  StringCharLoadGenerator::Generate(masm,
+                                    object_,
+                                    index_,
+                                    result_,
+                                    &call_runtime_);
+  __ SmiTag(result_);
+  __ Bind(&exit_);
+}
+
+
+void StringCharCodeAtGenerator::GenerateSlow(
+    MacroAssembler* masm,
+    const RuntimeCallHelper& call_helper) {
+  __ Abort(kUnexpectedFallthroughToCharCodeAtSlowCase);
+
+  __ Bind(&index_not_smi_);
+  // If index is a heap number, try converting it to an integer.
+  __ CheckMap(index_,
+              result_,
+              Heap::kHeapNumberMapRootIndex,
+              index_not_number_,
+              DONT_DO_SMI_CHECK);
+  call_helper.BeforeCall(masm);
+  // Save object_ on the stack and pass index_ as argument for runtime call.
+  __ Push(object_, index_);
+  if (index_flags_ == STRING_INDEX_IS_NUMBER) {
+    __ CallRuntime(Runtime::kNumberToIntegerMapMinusZero, 1);
+  } else {
+    ASSERT(index_flags_ == STRING_INDEX_IS_ARRAY_INDEX);
+    // NumberToSmi discards numbers that are not exact integers.
+    __ CallRuntime(Runtime::kNumberToSmi, 1);
+  }
+  // Save the conversion result before the pop instructions below
+  // have a chance to overwrite it.
+  __ Mov(index_, x0);
+  __ Pop(object_);
+  // Reload the instance type.
+  __ Ldr(result_, FieldMemOperand(object_, HeapObject::kMapOffset));
+  __ Ldrb(result_, FieldMemOperand(result_, Map::kInstanceTypeOffset));
+  call_helper.AfterCall(masm);
+
+  // If index is still not a smi, it must be out of range.
+  __ JumpIfNotSmi(index_, index_out_of_range_);
+  // Otherwise, return to the fast path.
+  __ B(&got_smi_index_);
+
+  // Call runtime. We get here when the receiver is a string and the
+  // index is a number, but the code of getting the actual character
+  // is too complex (e.g., when the string needs to be flattened).
+  __ Bind(&call_runtime_);
+  call_helper.BeforeCall(masm);
+  __ SmiTag(index_);
+  __ Push(object_, index_);
+  __ CallRuntime(Runtime::kStringCharCodeAt, 2);
+  __ Mov(result_, x0);
+  call_helper.AfterCall(masm);
+  __ B(&exit_);
+
+  __ Abort(kUnexpectedFallthroughFromCharCodeAtSlowCase);
+}
+
+
+void StringCharFromCodeGenerator::GenerateFast(MacroAssembler* masm) {
+  __ JumpIfNotSmi(code_, &slow_case_);
+  __ Cmp(code_, Operand(Smi::FromInt(String::kMaxOneByteCharCode)));
+  __ B(hi, &slow_case_);
+
+  __ LoadRoot(result_, Heap::kSingleCharacterStringCacheRootIndex);
+  // At this point code register contains smi tagged ASCII char code.
+  STATIC_ASSERT(kSmiShift > kPointerSizeLog2);
+  __ Add(result_, result_, Operand(code_, LSR, kSmiShift - kPointerSizeLog2));
+  __ Ldr(result_, FieldMemOperand(result_, FixedArray::kHeaderSize));
+  __ JumpIfRoot(result_, Heap::kUndefinedValueRootIndex, &slow_case_);
+  __ Bind(&exit_);
+}
+
+
+void StringCharFromCodeGenerator::GenerateSlow(
+    MacroAssembler* masm,
+    const RuntimeCallHelper& call_helper) {
+  __ Abort(kUnexpectedFallthroughToCharFromCodeSlowCase);
+
+  __ Bind(&slow_case_);
+  call_helper.BeforeCall(masm);
+  __ Push(code_);
+  __ CallRuntime(Runtime::kCharFromCode, 1);
+  __ Mov(result_, x0);
+  call_helper.AfterCall(masm);
+  __ B(&exit_);
+
+  __ Abort(kUnexpectedFallthroughFromCharFromCodeSlowCase);
+}
+
+
+void ICCompareStub::GenerateSmis(MacroAssembler* masm) {
+  // Inputs are in x0 (lhs) and x1 (rhs).
+  ASSERT(state_ == CompareIC::SMI);
+  ASM_LOCATION("ICCompareStub[Smis]");
+  Label miss;
+  // Bail out (to 'miss') unless both x0 and x1 are smis.
+  __ JumpIfEitherNotSmi(x0, x1, &miss);
+
+  // TODO(jbramley): Why do we only set the flags for EQ?
+  if (GetCondition() == eq) {
+    // For equality we do not care about the sign of the result.
+    __ Subs(x0, x0, x1);
+  } else {
+    // Untag before subtracting to avoid handling overflow.
+    __ SmiUntag(x1);
+    __ Sub(x0, x1, Operand::UntagSmi(x0));
+  }
+  __ Ret();
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void ICCompareStub::GenerateNumbers(MacroAssembler* masm) {
+  ASSERT(state_ == CompareIC::NUMBER);
+  ASM_LOCATION("ICCompareStub[HeapNumbers]");
+
+  Label unordered, maybe_undefined1, maybe_undefined2;
+  Label miss, handle_lhs, values_in_d_regs;
+  Label untag_rhs, untag_lhs;
+
+  Register result = x0;
+  Register rhs = x0;
+  Register lhs = x1;
+  FPRegister rhs_d = d0;
+  FPRegister lhs_d = d1;
+
+  if (left_ == CompareIC::SMI) {
+    __ JumpIfNotSmi(lhs, &miss);
+  }
+  if (right_ == CompareIC::SMI) {
+    __ JumpIfNotSmi(rhs, &miss);
+  }
+
+  __ SmiUntagToDouble(rhs_d, rhs, kSpeculativeUntag);
+  __ SmiUntagToDouble(lhs_d, lhs, kSpeculativeUntag);
+
+  // Load rhs if it's a heap number.
+  __ JumpIfSmi(rhs, &handle_lhs);
+  __ CheckMap(rhs, x10, Heap::kHeapNumberMapRootIndex, &maybe_undefined1,
+              DONT_DO_SMI_CHECK);
+  __ Ldr(rhs_d, FieldMemOperand(rhs, HeapNumber::kValueOffset));
+
+  // Load lhs if it's a heap number.
+  __ Bind(&handle_lhs);
+  __ JumpIfSmi(lhs, &values_in_d_regs);
+  __ CheckMap(lhs, x10, Heap::kHeapNumberMapRootIndex, &maybe_undefined2,
+              DONT_DO_SMI_CHECK);
+  __ Ldr(lhs_d, FieldMemOperand(lhs, HeapNumber::kValueOffset));
+
+  __ Bind(&values_in_d_regs);
+  __ Fcmp(lhs_d, rhs_d);
+  __ B(vs, &unordered);  // Overflow flag set if either is NaN.
+  STATIC_ASSERT((LESS == -1) && (EQUAL == 0) && (GREATER == 1));
+  __ Cset(result, gt);  // gt => 1, otherwise (lt, eq) => 0 (EQUAL).
+  __ Csinv(result, result, xzr, ge);  // lt => -1, gt => 1, eq => 0.
+  __ Ret();
+
+  __ Bind(&unordered);
+  ICCompareStub stub(op_, CompareIC::GENERIC, CompareIC::GENERIC,
+                     CompareIC::GENERIC);
+  __ Jump(stub.GetCode(masm->isolate()), RelocInfo::CODE_TARGET);
+
+  __ Bind(&maybe_undefined1);
+  if (Token::IsOrderedRelationalCompareOp(op_)) {
+    __ JumpIfNotRoot(rhs, Heap::kUndefinedValueRootIndex, &miss);
+    __ JumpIfSmi(lhs, &unordered);
+    __ JumpIfNotObjectType(lhs, x10, x10, HEAP_NUMBER_TYPE, &maybe_undefined2);
+    __ B(&unordered);
+  }
+
+  __ Bind(&maybe_undefined2);
+  if (Token::IsOrderedRelationalCompareOp(op_)) {
+    __ JumpIfRoot(lhs, Heap::kUndefinedValueRootIndex, &unordered);
+  }
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void ICCompareStub::GenerateInternalizedStrings(MacroAssembler* masm) {
+  ASSERT(state_ == CompareIC::INTERNALIZED_STRING);
+  ASM_LOCATION("ICCompareStub[InternalizedStrings]");
+  Label miss;
+
+  Register result = x0;
+  Register rhs = x0;
+  Register lhs = x1;
+
+  // Check that both operands are heap objects.
+  __ JumpIfEitherSmi(lhs, rhs, &miss);
+
+  // Check that both operands are internalized strings.
+  Register rhs_map = x10;
+  Register lhs_map = x11;
+  Register rhs_type = x10;
+  Register lhs_type = x11;
+  __ Ldr(lhs_map, FieldMemOperand(lhs, HeapObject::kMapOffset));
+  __ Ldr(rhs_map, FieldMemOperand(rhs, HeapObject::kMapOffset));
+  __ Ldrb(lhs_type, FieldMemOperand(lhs_map, Map::kInstanceTypeOffset));
+  __ Ldrb(rhs_type, FieldMemOperand(rhs_map, Map::kInstanceTypeOffset));
+
+  STATIC_ASSERT((kInternalizedTag == 0) && (kStringTag == 0));
+  __ Orr(x12, lhs_type, rhs_type);
+  __ TestAndBranchIfAnySet(
+      x12, kIsNotStringMask | kIsNotInternalizedMask, &miss);
+
+  // Internalized strings are compared by identity.
+  STATIC_ASSERT(EQUAL == 0);
+  __ Cmp(lhs, rhs);
+  __ Cset(result, ne);
+  __ Ret();
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void ICCompareStub::GenerateUniqueNames(MacroAssembler* masm) {
+  ASSERT(state_ == CompareIC::UNIQUE_NAME);
+  ASM_LOCATION("ICCompareStub[UniqueNames]");
+  ASSERT(GetCondition() == eq);
+  Label miss;
+
+  Register result = x0;
+  Register rhs = x0;
+  Register lhs = x1;
+
+  Register lhs_instance_type = w2;
+  Register rhs_instance_type = w3;
+
+  // Check that both operands are heap objects.
+  __ JumpIfEitherSmi(lhs, rhs, &miss);
+
+  // Check that both operands are unique names. This leaves the instance
+  // types loaded in tmp1 and tmp2.
+  __ Ldr(x10, FieldMemOperand(lhs, HeapObject::kMapOffset));
+  __ Ldr(x11, FieldMemOperand(rhs, HeapObject::kMapOffset));
+  __ Ldrb(lhs_instance_type, FieldMemOperand(x10, Map::kInstanceTypeOffset));
+  __ Ldrb(rhs_instance_type, FieldMemOperand(x11, Map::kInstanceTypeOffset));
+
+  // To avoid a miss, each instance type should be either SYMBOL_TYPE or it
+  // should have kInternalizedTag set.
+  __ JumpIfNotUniqueName(lhs_instance_type, &miss);
+  __ JumpIfNotUniqueName(rhs_instance_type, &miss);
+
+  // Unique names are compared by identity.
+  STATIC_ASSERT(EQUAL == 0);
+  __ Cmp(lhs, rhs);
+  __ Cset(result, ne);
+  __ Ret();
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void ICCompareStub::GenerateStrings(MacroAssembler* masm) {
+  ASSERT(state_ == CompareIC::STRING);
+  ASM_LOCATION("ICCompareStub[Strings]");
+
+  Label miss;
+
+  bool equality = Token::IsEqualityOp(op_);
+
+  Register result = x0;
+  Register rhs = x0;
+  Register lhs = x1;
+
+  // Check that both operands are heap objects.
+  __ JumpIfEitherSmi(rhs, lhs, &miss);
+
+  // Check that both operands are strings.
+  Register rhs_map = x10;
+  Register lhs_map = x11;
+  Register rhs_type = x10;
+  Register lhs_type = x11;
+  __ Ldr(lhs_map, FieldMemOperand(lhs, HeapObject::kMapOffset));
+  __ Ldr(rhs_map, FieldMemOperand(rhs, HeapObject::kMapOffset));
+  __ Ldrb(lhs_type, FieldMemOperand(lhs_map, Map::kInstanceTypeOffset));
+  __ Ldrb(rhs_type, FieldMemOperand(rhs_map, Map::kInstanceTypeOffset));
+  STATIC_ASSERT(kNotStringTag != 0);
+  __ Orr(x12, lhs_type, rhs_type);
+  __ Tbnz(x12, MaskToBit(kIsNotStringMask), &miss);
+
+  // Fast check for identical strings.
+  Label not_equal;
+  __ Cmp(lhs, rhs);
+  __ B(ne, &not_equal);
+  __ Mov(result, EQUAL);
+  __ Ret();
+
+  __ Bind(&not_equal);
+  // Handle not identical strings
+
+  // Check that both strings are internalized strings. If they are, we're done
+  // because we already know they are not identical. We know they are both
+  // strings.
+  if (equality) {
+    ASSERT(GetCondition() == eq);
+    STATIC_ASSERT(kInternalizedTag == 0);
+    Label not_internalized_strings;
+    __ Orr(x12, lhs_type, rhs_type);
+    __ TestAndBranchIfAnySet(
+        x12, kIsNotInternalizedMask, &not_internalized_strings);
+    // Result is in rhs (x0), and not EQUAL, as rhs is not a smi.
+    __ Ret();
+    __ Bind(&not_internalized_strings);
+  }
+
+  // Check that both strings are sequential ASCII.
+  Label runtime;
+  __ JumpIfBothInstanceTypesAreNotSequentialAscii(
+      lhs_type, rhs_type, x12, x13, &runtime);
+
+  // Compare flat ASCII strings. Returns when done.
+  if (equality) {
+    StringCompareStub::GenerateFlatAsciiStringEquals(
+        masm, lhs, rhs, x10, x11, x12);
+  } else {
+    StringCompareStub::GenerateCompareFlatAsciiStrings(
+        masm, lhs, rhs, x10, x11, x12, x13);
+  }
+
+  // Handle more complex cases in runtime.
+  __ Bind(&runtime);
+  __ Push(lhs, rhs);
+  if (equality) {
+    __ TailCallRuntime(Runtime::kStringEquals, 2, 1);
+  } else {
+    __ TailCallRuntime(Runtime::kStringCompare, 2, 1);
+  }
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void ICCompareStub::GenerateObjects(MacroAssembler* masm) {
+  ASSERT(state_ == CompareIC::OBJECT);
+  ASM_LOCATION("ICCompareStub[Objects]");
+
+  Label miss;
+
+  Register result = x0;
+  Register rhs = x0;
+  Register lhs = x1;
+
+  __ JumpIfEitherSmi(rhs, lhs, &miss);
+
+  __ JumpIfNotObjectType(rhs, x10, x10, JS_OBJECT_TYPE, &miss);
+  __ JumpIfNotObjectType(lhs, x10, x10, JS_OBJECT_TYPE, &miss);
+
+  ASSERT(GetCondition() == eq);
+  __ Sub(result, rhs, lhs);
+  __ Ret();
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+void ICCompareStub::GenerateKnownObjects(MacroAssembler* masm) {
+  ASM_LOCATION("ICCompareStub[KnownObjects]");
+
+  Label miss;
+
+  Register result = x0;
+  Register rhs = x0;
+  Register lhs = x1;
+
+  __ JumpIfEitherSmi(rhs, lhs, &miss);
+
+  Register rhs_map = x10;
+  Register lhs_map = x11;
+  __ Ldr(rhs_map, FieldMemOperand(rhs, HeapObject::kMapOffset));
+  __ Ldr(lhs_map, FieldMemOperand(lhs, HeapObject::kMapOffset));
+  __ Cmp(rhs_map, Operand(known_map_));
+  __ B(ne, &miss);
+  __ Cmp(lhs_map, Operand(known_map_));
+  __ B(ne, &miss);
+
+  __ Sub(result, rhs, lhs);
+  __ Ret();
+
+  __ Bind(&miss);
+  GenerateMiss(masm);
+}
+
+
+// This method handles the case where a compare stub had the wrong
+// implementation. It calls a miss handler, which re-writes the stub. All other
+// ICCompareStub::Generate* methods should fall back into this one if their
+// operands were not the expected types.
+void ICCompareStub::GenerateMiss(MacroAssembler* masm) {
+  ASM_LOCATION("ICCompareStub[Miss]");
+
+  Register stub_entry = x11;
+  {
+    ExternalReference miss =
+      ExternalReference(IC_Utility(IC::kCompareIC_Miss), masm->isolate());
+
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    Register op = x10;
+    Register left = x1;
+    Register right = x0;
+    // Preserve some caller-saved registers.
+    __ Push(x1, x0, lr);
+    // Push the arguments.
+    __ Mov(op, Operand(Smi::FromInt(op_)));
+    __ Push(left, right, op);
+
+    // Call the miss handler. This also pops the arguments.
+    __ CallExternalReference(miss, 3);
+
+    // Compute the entry point of the rewritten stub.
+    __ Add(stub_entry, x0, Code::kHeaderSize - kHeapObjectTag);
+    // Restore caller-saved registers.
+    __ Pop(lr, x0, x1);
+  }
+
+  // Tail-call to the new stub.
+  __ Jump(stub_entry);
+}
+
+
+void StringHelper::GenerateHashInit(MacroAssembler* masm,
+                                    Register hash,
+                                    Register character) {
+  ASSERT(!AreAliased(hash, character));
+
+  // hash = character + (character << 10);
+  __ LoadRoot(hash, Heap::kHashSeedRootIndex);
+  // Untag smi seed and add the character.
+  __ Add(hash, character, Operand(hash, LSR, kSmiShift));
+
+  // Compute hashes modulo 2^32 using a 32-bit W register.
+  Register hash_w = hash.W();
+
+  // hash += hash << 10;
+  __ Add(hash_w, hash_w, Operand(hash_w, LSL, 10));
+  // hash ^= hash >> 6;
+  __ Eor(hash_w, hash_w, Operand(hash_w, LSR, 6));
+}
+
+
+void StringHelper::GenerateHashAddCharacter(MacroAssembler* masm,
+                                            Register hash,
+                                            Register character) {
+  ASSERT(!AreAliased(hash, character));
+
+  // hash += character;
+  __ Add(hash, hash, character);
+
+  // Compute hashes modulo 2^32 using a 32-bit W register.
+  Register hash_w = hash.W();
+
+  // hash += hash << 10;
+  __ Add(hash_w, hash_w, Operand(hash_w, LSL, 10));
+  // hash ^= hash >> 6;
+  __ Eor(hash_w, hash_w, Operand(hash_w, LSR, 6));
+}
+
+
+void StringHelper::GenerateHashGetHash(MacroAssembler* masm,
+                                       Register hash,
+                                       Register scratch) {
+  // Compute hashes modulo 2^32 using a 32-bit W register.
+  Register hash_w = hash.W();
+  Register scratch_w = scratch.W();
+  ASSERT(!AreAliased(hash_w, scratch_w));
+
+  // hash += hash << 3;
+  __ Add(hash_w, hash_w, Operand(hash_w, LSL, 3));
+  // hash ^= hash >> 11;
+  __ Eor(hash_w, hash_w, Operand(hash_w, LSR, 11));
+  // hash += hash << 15;
+  __ Add(hash_w, hash_w, Operand(hash_w, LSL, 15));
+
+  __ Ands(hash_w, hash_w, String::kHashBitMask);
+
+  // if (hash == 0) hash = 27;
+  __ Mov(scratch_w, StringHasher::kZeroHash);
+  __ Csel(hash_w, scratch_w, hash_w, eq);
+}
+
+
+void SubStringStub::Generate(MacroAssembler* masm) {
+  ASM_LOCATION("SubStringStub::Generate");
+  Label runtime;
+
+  // Stack frame on entry.
+  //  lr: return address
+  //  jssp[0]:  substring "to" offset
+  //  jssp[8]:  substring "from" offset
+  //  jssp[16]: pointer to string object
+
+  // This stub is called from the native-call %_SubString(...), so
+  // nothing can be assumed about the arguments. It is tested that:
+  //  "string" is a sequential string,
+  //  both "from" and "to" are smis, and
+  //  0 <= from <= to <= string.length (in debug mode.)
+  // If any of these assumptions fail, we call the runtime system.
+
+  static const int kToOffset = 0 * kPointerSize;
+  static const int kFromOffset = 1 * kPointerSize;
+  static const int kStringOffset = 2 * kPointerSize;
+
+  Register to = x0;
+  Register from = x15;
+  Register input_string = x10;
+  Register input_length = x11;
+  Register input_type = x12;
+  Register result_string = x0;
+  Register result_length = x1;
+  Register temp = x3;
+
+  __ Peek(to, kToOffset);
+  __ Peek(from, kFromOffset);
+
+  // Check that both from and to are smis. If not, jump to runtime.
+  __ JumpIfEitherNotSmi(from, to, &runtime);
+  __ SmiUntag(from);
+  __ SmiUntag(to);
+
+  // Calculate difference between from and to. If to < from, branch to runtime.
+  __ Subs(result_length, to, from);
+  __ B(mi, &runtime);
+
+  // Check from is positive.
+  __ Tbnz(from, kWSignBit, &runtime);
+
+  // Make sure first argument is a string.
+  __ Peek(input_string, kStringOffset);
+  __ JumpIfSmi(input_string, &runtime);
+  __ IsObjectJSStringType(input_string, input_type, &runtime);
+
+  Label single_char;
+  __ Cmp(result_length, 1);
+  __ B(eq, &single_char);
+
+  // Short-cut for the case of trivial substring.
+  Label return_x0;
+  __ Ldrsw(input_length,
+           UntagSmiFieldMemOperand(input_string, String::kLengthOffset));
+
+  __ Cmp(result_length, input_length);
+  __ CmovX(x0, input_string, eq);
+  // Return original string.
+  __ B(eq, &return_x0);
+
+  // Longer than original string's length or negative: unsafe arguments.
+  __ B(hi, &runtime);
+
+  // Shorter than original string's length: an actual substring.
+
+  //   x0   to               substring end character offset
+  //   x1   result_length    length of substring result
+  //   x10  input_string     pointer to input string object
+  //   x10  unpacked_string  pointer to unpacked string object
+  //   x11  input_length     length of input string
+  //   x12  input_type       instance type of input string
+  //   x15  from             substring start character offset
+
+  // Deal with different string types: update the index if necessary and put
+  // the underlying string into register unpacked_string.
+  Label underlying_unpacked, sliced_string, seq_or_external_string;
+  Label update_instance_type;
+  // If the string is not indirect, it can only be sequential or external.
+  STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
+  STATIC_ASSERT(kIsIndirectStringMask != 0);
+
+  // Test for string types, and branch/fall through to appropriate unpacking
+  // code.
+  __ Tst(input_type, kIsIndirectStringMask);
+  __ B(eq, &seq_or_external_string);
+  __ Tst(input_type, kSlicedNotConsMask);
+  __ B(ne, &sliced_string);
+
+  Register unpacked_string = input_string;
+
+  // Cons string. Check whether it is flat, then fetch first part.
+  __ Ldr(temp, FieldMemOperand(input_string, ConsString::kSecondOffset));
+  __ JumpIfNotRoot(temp, Heap::kempty_stringRootIndex, &runtime);
+  __ Ldr(unpacked_string,
+         FieldMemOperand(input_string, ConsString::kFirstOffset));
+  __ B(&update_instance_type);
+
+  __ Bind(&sliced_string);
+  // Sliced string. Fetch parent and correct start index by offset.
+  __ Ldrsw(temp,
+           UntagSmiFieldMemOperand(input_string, SlicedString::kOffsetOffset));
+  __ Add(from, from, temp);
+  __ Ldr(unpacked_string,
+         FieldMemOperand(input_string, SlicedString::kParentOffset));
+
+  __ Bind(&update_instance_type);
+  __ Ldr(temp, FieldMemOperand(unpacked_string, HeapObject::kMapOffset));
+  __ Ldrb(input_type, FieldMemOperand(temp, Map::kInstanceTypeOffset));
+  // TODO(all): This generates "b #+0x4". Can these be optimised out?
+  __ B(&underlying_unpacked);
+
+  __ Bind(&seq_or_external_string);
+  // Sequential or external string. Registers unpacked_string and input_string
+  // alias, so there's nothing to do here.
+
+  //   x0   result_string    pointer to result string object (uninit)
+  //   x1   result_length    length of substring result
+  //   x10  unpacked_string  pointer to unpacked string object
+  //   x11  input_length     length of input string
+  //   x12  input_type       instance type of input string
+  //   x15  from             substring start character offset
+  __ Bind(&underlying_unpacked);
+
+  if (FLAG_string_slices) {
+    Label copy_routine;
+    __ Cmp(result_length, SlicedString::kMinLength);
+    // Short slice. Copy instead of slicing.
+    __ B(lt, &copy_routine);
+    // Allocate new sliced string. At this point we do not reload the instance
+    // type including the string encoding because we simply rely on the info
+    // provided by the original string. It does not matter if the original
+    // string's encoding is wrong because we always have to recheck encoding of
+    // the newly created string's parent anyway due to externalized strings.
+    Label two_byte_slice, set_slice_header;
+    STATIC_ASSERT((kStringEncodingMask & kOneByteStringTag) != 0);
+    STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
+    __ Tbz(input_type, MaskToBit(kStringEncodingMask), &two_byte_slice);
+    __ AllocateAsciiSlicedString(result_string, result_length, x3, x4,
+                                 &runtime);
+    __ B(&set_slice_header);
+
+    __ Bind(&two_byte_slice);
+    __ AllocateTwoByteSlicedString(result_string, result_length, x3, x4,
+                                   &runtime);
+
+    __ Bind(&set_slice_header);
+    __ SmiTag(from);
+    __ Str(from, FieldMemOperand(result_string, SlicedString::kOffsetOffset));
+    __ Str(unpacked_string,
+           FieldMemOperand(result_string, SlicedString::kParentOffset));
+    __ B(&return_x0);
+
+    __ Bind(&copy_routine);
+  }
+
+  //   x0   result_string    pointer to result string object (uninit)
+  //   x1   result_length    length of substring result
+  //   x10  unpacked_string  pointer to unpacked string object
+  //   x11  input_length     length of input string
+  //   x12  input_type       instance type of input string
+  //   x13  unpacked_char0   pointer to first char of unpacked string (uninit)
+  //   x13  substring_char0  pointer to first char of substring (uninit)
+  //   x14  result_char0     pointer to first char of result (uninit)
+  //   x15  from             substring start character offset
+  Register unpacked_char0 = x13;
+  Register substring_char0 = x13;
+  Register result_char0 = x14;
+  Label two_byte_sequential, sequential_string, allocate_result;
+  STATIC_ASSERT(kExternalStringTag != 0);
+  STATIC_ASSERT(kSeqStringTag == 0);
+
+  __ Tst(input_type, kExternalStringTag);
+  __ B(eq, &sequential_string);
+
+  __ Tst(input_type, kShortExternalStringTag);
+  __ B(ne, &runtime);
+  __ Ldr(unpacked_char0,
+         FieldMemOperand(unpacked_string, ExternalString::kResourceDataOffset));
+  // unpacked_char0 points to the first character of the underlying string.
+  __ B(&allocate_result);
+
+  __ Bind(&sequential_string);
+  // Locate first character of underlying subject string.
+  STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
+  __ Add(unpacked_char0, unpacked_string,
+         SeqOneByteString::kHeaderSize - kHeapObjectTag);
+
+  __ Bind(&allocate_result);
+  // Sequential ASCII string. Allocate the result.
+  STATIC_ASSERT((kOneByteStringTag & kStringEncodingMask) != 0);
+  __ Tbz(input_type, MaskToBit(kStringEncodingMask), &two_byte_sequential);
+
+  // Allocate and copy the resulting ASCII string.
+  __ AllocateAsciiString(result_string, result_length, x3, x4, x5, &runtime);
+
+  // Locate first character of substring to copy.
+  __ Add(substring_char0, unpacked_char0, from);
+
+  // Locate first character of result.
+  __ Add(result_char0, result_string,
+         SeqOneByteString::kHeaderSize - kHeapObjectTag);
+
+  STATIC_ASSERT((SeqOneByteString::kHeaderSize & kObjectAlignmentMask) == 0);
+  __ CopyBytes(result_char0, substring_char0, result_length, x3, kCopyLong);
+  __ B(&return_x0);
+
+  // Allocate and copy the resulting two-byte string.
+  __ Bind(&two_byte_sequential);
+  __ AllocateTwoByteString(result_string, result_length, x3, x4, x5, &runtime);
+
+  // Locate first character of substring to copy.
+  __ Add(substring_char0, unpacked_char0, Operand(from, LSL, 1));
+
+  // Locate first character of result.
+  __ Add(result_char0, result_string,
+         SeqTwoByteString::kHeaderSize - kHeapObjectTag);
+
+  STATIC_ASSERT((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) == 0);
+  __ Add(result_length, result_length, result_length);
+  __ CopyBytes(result_char0, substring_char0, result_length, x3, kCopyLong);
+
+  __ Bind(&return_x0);
+  Counters* counters = masm->isolate()->counters();
+  __ IncrementCounter(counters->sub_string_native(), 1, x3, x4);
+  __ Drop(3);
+  __ Ret();
+
+  __ Bind(&runtime);
+  __ TailCallRuntime(Runtime::kSubString, 3, 1);
+
+  __ bind(&single_char);
+  // x1: result_length
+  // x10: input_string
+  // x12: input_type
+  // x15: from (untagged)
+  __ SmiTag(from);
+  StringCharAtGenerator generator(
+      input_string, from, result_length, x0,
+      &runtime, &runtime, &runtime, STRING_INDEX_IS_NUMBER);
+  generator.GenerateFast(masm);
+  // TODO(jbramley): Why doesn't this jump to return_x0?
+  __ Drop(3);
+  __ Ret();
+  generator.SkipSlow(masm, &runtime);
+}
+
+
+void StringCompareStub::GenerateFlatAsciiStringEquals(MacroAssembler* masm,
+                                                      Register left,
+                                                      Register right,
+                                                      Register scratch1,
+                                                      Register scratch2,
+                                                      Register scratch3) {
+  ASSERT(!AreAliased(left, right, scratch1, scratch2, scratch3));
+  Register result = x0;
+  Register left_length = scratch1;
+  Register right_length = scratch2;
+
+  // Compare lengths. If lengths differ, strings can't be equal. Lengths are
+  // smis, and don't need to be untagged.
+  Label strings_not_equal, check_zero_length;
+  __ Ldr(left_length, FieldMemOperand(left, String::kLengthOffset));
+  __ Ldr(right_length, FieldMemOperand(right, String::kLengthOffset));
+  __ Cmp(left_length, right_length);
+  __ B(eq, &check_zero_length);
+
+  __ Bind(&strings_not_equal);
+  __ Mov(result, Operand(Smi::FromInt(NOT_EQUAL)));
+  __ Ret();
+
+  // Check if the length is zero. If so, the strings must be equal (and empty.)
+  Label compare_chars;
+  __ Bind(&check_zero_length);
+  STATIC_ASSERT(kSmiTag == 0);
+  __ Cbnz(left_length, &compare_chars);
+  __ Mov(result, Operand(Smi::FromInt(EQUAL)));
+  __ Ret();
+
+  // Compare characters. Falls through if all characters are equal.
+  __ Bind(&compare_chars);
+  GenerateAsciiCharsCompareLoop(masm, left, right, left_length, scratch2,
+                                scratch3, &strings_not_equal);
+
+  // Characters in strings are equal.
+  __ Mov(result, Operand(Smi::FromInt(EQUAL)));
+  __ Ret();
+}
+
+
+void StringCompareStub::GenerateCompareFlatAsciiStrings(MacroAssembler* masm,
+                                                        Register left,
+                                                        Register right,
+                                                        Register scratch1,
+                                                        Register scratch2,
+                                                        Register scratch3,
+                                                        Register scratch4) {
+  ASSERT(!AreAliased(left, right, scratch1, scratch2, scratch3, scratch4));
+  Label result_not_equal, compare_lengths;
+
+  // Find minimum length and length difference.
+  Register length_delta = scratch3;
+  __ Ldr(scratch1, FieldMemOperand(left, String::kLengthOffset));
+  __ Ldr(scratch2, FieldMemOperand(right, String::kLengthOffset));
+  __ Subs(length_delta, scratch1, scratch2);
+
+  Register min_length = scratch1;
+  __ Csel(min_length, scratch2, scratch1, gt);
+  __ Cbz(min_length, &compare_lengths);
+
+  // Compare loop.
+  GenerateAsciiCharsCompareLoop(masm,
+                                left, right, min_length, scratch2, scratch4,
+                                &result_not_equal);
+
+  // Compare lengths - strings up to min-length are equal.
+  __ Bind(&compare_lengths);
+
+  ASSERT(Smi::FromInt(EQUAL) == static_cast<Smi*>(0));
+
+  // Use length_delta as result if it's zero.
+  Register result = x0;
+  __ Subs(result, length_delta, 0);
+
+  __ Bind(&result_not_equal);
+  Register greater = x10;
+  Register less = x11;
+  __ Mov(greater, Operand(Smi::FromInt(GREATER)));
+  __ Mov(less, Operand(Smi::FromInt(LESS)));
+  __ CmovX(result, greater, gt);
+  __ CmovX(result, less, lt);
+  __ Ret();
+}
+
+
+void StringCompareStub::GenerateAsciiCharsCompareLoop(
+    MacroAssembler* masm,
+    Register left,
+    Register right,
+    Register length,
+    Register scratch1,
+    Register scratch2,
+    Label* chars_not_equal) {
+  ASSERT(!AreAliased(left, right, length, scratch1, scratch2));
+
+  // Change index to run from -length to -1 by adding length to string
+  // start. This means that loop ends when index reaches zero, which
+  // doesn't need an additional compare.
+  __ SmiUntag(length);
+  __ Add(scratch1, length, SeqOneByteString::kHeaderSize - kHeapObjectTag);
+  __ Add(left, left, scratch1);
+  __ Add(right, right, scratch1);
+
+  Register index = length;
+  __ Neg(index, length);  // index = -length;
+
+  // Compare loop
+  Label loop;
+  __ Bind(&loop);
+  __ Ldrb(scratch1, MemOperand(left, index));
+  __ Ldrb(scratch2, MemOperand(right, index));
+  __ Cmp(scratch1, scratch2);
+  __ B(ne, chars_not_equal);
+  __ Add(index, index, 1);
+  __ Cbnz(index, &loop);
+}
+
+
+void StringCompareStub::Generate(MacroAssembler* masm) {
+  Label runtime;
+
+  Counters* counters = masm->isolate()->counters();
+
+  // Stack frame on entry.
+  //  sp[0]: right string
+  //  sp[8]: left string
+  Register right = x10;
+  Register left = x11;
+  Register result = x0;
+  __ Pop(right, left);
+
+  Label not_same;
+  __ Subs(result, right, left);
+  __ B(ne, &not_same);
+  STATIC_ASSERT(EQUAL == 0);
+  __ IncrementCounter(counters->string_compare_native(), 1, x3, x4);
+  __ Ret();
+
+  __ Bind(&not_same);
+
+  // Check that both objects are sequential ASCII strings.
+  __ JumpIfEitherIsNotSequentialAsciiStrings(left, right, x12, x13, &runtime);
+
+  // Compare flat ASCII strings natively. Remove arguments from stack first,
+  // as this function will generate a return.
+  __ IncrementCounter(counters->string_compare_native(), 1, x3, x4);
+  GenerateCompareFlatAsciiStrings(masm, left, right, x12, x13, x14, x15);
+
+  __ Bind(&runtime);
+
+  // Push arguments back on to the stack.
+  //  sp[0] = right string
+  //  sp[8] = left string.
+  __ Push(left, right);
+
+  // Call the runtime.
+  // Returns -1 (less), 0 (equal), or 1 (greater) tagged as a small integer.
+  __ TailCallRuntime(Runtime::kStringCompare, 2, 1);
+}
+
+
+void ArrayPushStub::Generate(MacroAssembler* masm) {
+  Register receiver = x0;
+
+  int argc = arguments_count();
+
+  if (argc == 0) {
+    // Nothing to do, just return the length.
+    __ Ldr(x0, FieldMemOperand(receiver, JSArray::kLengthOffset));
+    __ Drop(argc + 1);
+    __ Ret();
+    return;
+  }
+
+  Isolate* isolate = masm->isolate();
+
+  if (argc != 1) {
+    __ TailCallExternalReference(
+        ExternalReference(Builtins::c_ArrayPush, isolate), argc + 1, 1);
+    return;
+  }
+
+  Label call_builtin, attempt_to_grow_elements, with_write_barrier;
+
+  Register elements_length = x8;
+  Register length = x7;
+  Register elements = x6;
+  Register end_elements = x5;
+  Register value = x4;
+  // Get the elements array of the object.
+  __ Ldr(elements, FieldMemOperand(receiver, JSArray::kElementsOffset));
+
+  if (IsFastSmiOrObjectElementsKind(elements_kind())) {
+    // Check that the elements are in fast mode and writable.
+    __ CheckMap(elements,
+                x10,
+                Heap::kFixedArrayMapRootIndex,
+                &call_builtin,
+                DONT_DO_SMI_CHECK);
+  }
+
+  // Get the array's length and calculate new length.
+  __ Ldr(length, FieldMemOperand(receiver, JSArray::kLengthOffset));
+  STATIC_ASSERT(kSmiTag == 0);
+  __ Add(length, length, Operand(Smi::FromInt(argc)));
+
+  // Check if we could survive without allocation.
+  __ Ldr(elements_length,
+         FieldMemOperand(elements, FixedArray::kLengthOffset));
+  __ Cmp(length, elements_length);
+
+  const int kEndElementsOffset =
+      FixedArray::kHeaderSize - kHeapObjectTag - argc * kPointerSize;
+
+  if (IsFastSmiOrObjectElementsKind(elements_kind())) {
+    __ B(gt, &attempt_to_grow_elements);
+
+    // Check if value is a smi.
+    __ Peek(value, (argc - 1) * kPointerSize);
+    __ JumpIfNotSmi(value, &with_write_barrier);
+
+    // Store the value.
+    // We may need a register containing the address end_elements below,
+    // so write back the value in end_elements.
+    __ Add(end_elements, elements,
+           Operand::UntagSmiAndScale(length, kPointerSizeLog2));
+    __ Str(value, MemOperand(end_elements, kEndElementsOffset, PreIndex));
+  } else {
+    // TODO(all): ARM has a redundant cmp here.
+    __ B(gt, &call_builtin);
+
+    __ Peek(value, (argc - 1) * kPointerSize);
+    __ StoreNumberToDoubleElements(value, length, elements, x10, d0, d1,
+                                   &call_builtin, argc * kDoubleSize);
+  }
+
+  // Save new length.
+  __ Str(length, FieldMemOperand(receiver, JSArray::kLengthOffset));
+
+  // Return length.
+  __ Drop(argc + 1);
+  __ Mov(x0, length);
+  __ Ret();
+
+  if (IsFastDoubleElementsKind(elements_kind())) {
+    __ Bind(&call_builtin);
+    __ TailCallExternalReference(
+        ExternalReference(Builtins::c_ArrayPush, isolate), argc + 1, 1);
+    return;
+  }
+
+  __ Bind(&with_write_barrier);
+
+  if (IsFastSmiElementsKind(elements_kind())) {
+    if (FLAG_trace_elements_transitions) {
+      __ B(&call_builtin);
+    }
+
+    __ Ldr(x10, FieldMemOperand(value, HeapObject::kMapOffset));
+    __ JumpIfHeapNumber(x10, &call_builtin);
+
+    ElementsKind target_kind = IsHoleyElementsKind(elements_kind())
+        ? FAST_HOLEY_ELEMENTS : FAST_ELEMENTS;
+    __ Ldr(x10, GlobalObjectMemOperand());
+    __ Ldr(x10, FieldMemOperand(x10, GlobalObject::kNativeContextOffset));
+    __ Ldr(x10, ContextMemOperand(x10, Context::JS_ARRAY_MAPS_INDEX));
+    const int header_size = FixedArrayBase::kHeaderSize;
+    // Verify that the object can be transitioned in place.
+    const int origin_offset = header_size + elements_kind() * kPointerSize;
+    __ ldr(x11, FieldMemOperand(receiver, origin_offset));
+    __ ldr(x12, FieldMemOperand(x10, HeapObject::kMapOffset));
+    __ cmp(x11, x12);
+    __ B(ne, &call_builtin);
+
+    const int target_offset = header_size + target_kind * kPointerSize;
+    __ Ldr(x10, FieldMemOperand(x10, target_offset));
+    __ Mov(x11, receiver);
+    ElementsTransitionGenerator::GenerateMapChangeElementsTransition(
+        masm, DONT_TRACK_ALLOCATION_SITE, NULL);
+  }
+
+  // Save new length.
+  __ Str(length, FieldMemOperand(receiver, JSArray::kLengthOffset));
+
+  // Store the value.
+  // We may need a register containing the address end_elements below,
+  // so write back the value in end_elements.
+  __ Add(end_elements, elements,
+         Operand::UntagSmiAndScale(length, kPointerSizeLog2));
+  __ Str(value, MemOperand(end_elements, kEndElementsOffset, PreIndex));
+
+  __ RecordWrite(elements,
+                 end_elements,
+                 value,
+                 kLRHasNotBeenSaved,
+                 kDontSaveFPRegs,
+                 EMIT_REMEMBERED_SET,
+                 OMIT_SMI_CHECK);
+  __ Drop(argc + 1);
+  __ Mov(x0, length);
+  __ Ret();
+
+  __ Bind(&attempt_to_grow_elements);
+
+  if (!FLAG_inline_new) {
+    __ B(&call_builtin);
+  }
+
+  Register argument = x2;
+  __ Peek(argument, (argc - 1) * kPointerSize);
+  // Growing elements that are SMI-only requires special handling in case
+  // the new element is non-Smi. For now, delegate to the builtin.
+  if (IsFastSmiElementsKind(elements_kind())) {
+    __ JumpIfNotSmi(argument, &call_builtin);
+  }
+
+  // We could be lucky and the elements array could be at the top of new-space.
+  // In this case we can just grow it in place by moving the allocation pointer
+  // up.
+  ExternalReference new_space_allocation_top =
+      ExternalReference::new_space_allocation_top_address(isolate);
+  ExternalReference new_space_allocation_limit =
+      ExternalReference::new_space_allocation_limit_address(isolate);
+
+  const int kAllocationDelta = 4;
+  ASSERT(kAllocationDelta >= argc);
+  Register allocation_top_addr = x5;
+  Register allocation_top = x9;
+  // Load top and check if it is the end of elements.
+  __ Add(end_elements, elements,
+         Operand::UntagSmiAndScale(length, kPointerSizeLog2));
+  __ Add(end_elements, end_elements, kEndElementsOffset);
+  __ Mov(allocation_top_addr, Operand(new_space_allocation_top));
+  __ Ldr(allocation_top, MemOperand(allocation_top_addr));
+  __ Cmp(end_elements, allocation_top);
+  __ B(ne, &call_builtin);
+
+  __ Mov(x10, Operand(new_space_allocation_limit));
+  __ Ldr(x10, MemOperand(x10));
+  __ Add(allocation_top, allocation_top, kAllocationDelta * kPointerSize);
+  __ Cmp(allocation_top, x10);
+  __ B(hi, &call_builtin);
+
+  // We fit and could grow elements.
+  // Update new_space_allocation_top.
+  __ Str(allocation_top, MemOperand(allocation_top_addr));
+  // Push the argument.
+  __ Str(argument, MemOperand(end_elements));
+  // Fill the rest with holes.
+  __ LoadRoot(x10, Heap::kTheHoleValueRootIndex);
+  for (int i = 1; i < kAllocationDelta; i++) {
+    // TODO(all): Try to use stp here.
+    __ Str(x10, MemOperand(end_elements, i * kPointerSize));
+  }
+
+  // Update elements' and array's sizes.
+  __ Str(length, FieldMemOperand(receiver, JSArray::kLengthOffset));
+  __ Add(elements_length,
+         elements_length,
+         Operand(Smi::FromInt(kAllocationDelta)));
+  __ Str(elements_length,
+         FieldMemOperand(elements, FixedArray::kLengthOffset));
+
+  // Elements are in new space, so write barrier is not required.
+  __ Drop(argc + 1);
+  __ Mov(x0, length);
+  __ Ret();
+
+  __ Bind(&call_builtin);
+  __ TailCallExternalReference(
+      ExternalReference(Builtins::c_ArrayPush, isolate), argc + 1, 1);
+}
+
+
+void BinaryOpICWithAllocationSiteStub::Generate(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- x1    : left
+  //  -- x0    : right
+  //  -- lr    : return address
+  // -----------------------------------
+  Isolate* isolate = masm->isolate();
+
+  // Load x2 with the allocation site.  We stick an undefined dummy value here
+  // and replace it with the real allocation site later when we instantiate this
+  // stub in BinaryOpICWithAllocationSiteStub::GetCodeCopyFromTemplate().
+  __ LoadObject(x2, handle(isolate->heap()->undefined_value()));
+
+  // Make sure that we actually patched the allocation site.
+  if (FLAG_debug_code) {
+    __ AssertNotSmi(x2, kExpectedAllocationSite);
+    __ Ldr(x10, FieldMemOperand(x2, HeapObject::kMapOffset));
+    __ AssertRegisterIsRoot(x10, Heap::kAllocationSiteMapRootIndex,
+                            kExpectedAllocationSite);
+  }
+
+  // Tail call into the stub that handles binary operations with allocation
+  // sites.
+  BinaryOpWithAllocationSiteStub stub(state_);
+  __ TailCallStub(&stub);
+}
+
+
+bool CodeStub::CanUseFPRegisters() {
+  // FP registers always available on A64.
+  return true;
+}
+
+
+void RecordWriteStub::GenerateIncremental(MacroAssembler* masm, Mode mode) {
+  // We need some extra registers for this stub, they have been allocated
+  // but we need to save them before using them.
+  regs_.Save(masm);
+
+  if (remembered_set_action_ == EMIT_REMEMBERED_SET) {
+    Label dont_need_remembered_set;
+
+    Register value = regs_.scratch0();
+    __ Ldr(value, MemOperand(regs_.address()));
+    __ JumpIfNotInNewSpace(value, &dont_need_remembered_set);
+
+    __ CheckPageFlagSet(regs_.object(),
+                        value,
+                        1 << MemoryChunk::SCAN_ON_SCAVENGE,
+                        &dont_need_remembered_set);
+
+    // First notify the incremental marker if necessary, then update the
+    // remembered set.
+    CheckNeedsToInformIncrementalMarker(
+        masm, kUpdateRememberedSetOnNoNeedToInformIncrementalMarker, mode);
+    InformIncrementalMarker(masm, mode);
+    regs_.Restore(masm);  // Restore the extra scratch registers we used.
+    __ RememberedSetHelper(object_,
+                           address_,
+                           value_,
+                           save_fp_regs_mode_,
+                           MacroAssembler::kReturnAtEnd);
+
+    __ Bind(&dont_need_remembered_set);
+  }
+
+  CheckNeedsToInformIncrementalMarker(
+      masm, kReturnOnNoNeedToInformIncrementalMarker, mode);
+  InformIncrementalMarker(masm, mode);
+  regs_.Restore(masm);  // Restore the extra scratch registers we used.
+  __ Ret();
+}
+
+
+void RecordWriteStub::InformIncrementalMarker(MacroAssembler* masm, Mode mode) {
+  regs_.SaveCallerSaveRegisters(masm, save_fp_regs_mode_);
+  Register address =
+    x0.Is(regs_.address()) ? regs_.scratch0() : regs_.address();
+  ASSERT(!address.Is(regs_.object()));
+  ASSERT(!address.Is(x0));
+  __ Mov(address, regs_.address());
+  __ Mov(x0, regs_.object());
+  __ Mov(x1, address);
+  __ Mov(x2, Operand(ExternalReference::isolate_address(masm->isolate())));
+
+  AllowExternalCallThatCantCauseGC scope(masm);
+  ExternalReference function = (mode == INCREMENTAL_COMPACTION)
+      ? ExternalReference::incremental_evacuation_record_write_function(
+          masm->isolate())
+      : ExternalReference::incremental_marking_record_write_function(
+          masm->isolate());
+  __ CallCFunction(function, 3, 0);
+
+  regs_.RestoreCallerSaveRegisters(masm, save_fp_regs_mode_);
+}
+
+
+void RecordWriteStub::CheckNeedsToInformIncrementalMarker(
+    MacroAssembler* masm,
+    OnNoNeedToInformIncrementalMarker on_no_need,
+    Mode mode) {
+  Label on_black;
+  Label need_incremental;
+  Label need_incremental_pop_scratch;
+
+  Register mem_chunk = regs_.scratch0();
+  Register counter = regs_.scratch1();
+  __ Bic(mem_chunk, regs_.object(), Page::kPageAlignmentMask);
+  __ Ldr(counter,
+         MemOperand(mem_chunk, MemoryChunk::kWriteBarrierCounterOffset));
+  __ Subs(counter, counter, 1);
+  __ Str(counter,
+         MemOperand(mem_chunk, MemoryChunk::kWriteBarrierCounterOffset));
+  __ B(mi, &need_incremental);
+
+  // If the object is not black we don't have to inform the incremental marker.
+  __ JumpIfBlack(regs_.object(), regs_.scratch0(), regs_.scratch1(), &on_black);
+
+  regs_.Restore(masm);  // Restore the extra scratch registers we used.
+  if (on_no_need == kUpdateRememberedSetOnNoNeedToInformIncrementalMarker) {
+    __ RememberedSetHelper(object_,
+                           address_,
+                           value_,
+                           save_fp_regs_mode_,
+                           MacroAssembler::kReturnAtEnd);
+  } else {
+    __ Ret();
+  }
+
+  __ Bind(&on_black);
+  // Get the value from the slot.
+  Register value = regs_.scratch0();
+  __ Ldr(value, MemOperand(regs_.address()));
+
+  if (mode == INCREMENTAL_COMPACTION) {
+    Label ensure_not_white;
+
+    __ CheckPageFlagClear(value,
+                          regs_.scratch1(),
+                          MemoryChunk::kEvacuationCandidateMask,
+                          &ensure_not_white);
+
+    __ CheckPageFlagClear(regs_.object(),
+                          regs_.scratch1(),
+                          MemoryChunk::kSkipEvacuationSlotsRecordingMask,
+                          &need_incremental);
+
+    __ Bind(&ensure_not_white);
+  }
+
+  // We need extra registers for this, so we push the object and the address
+  // register temporarily.
+  __ Push(regs_.address(), regs_.object());
+  __ EnsureNotWhite(value,
+                    regs_.scratch1(),  // Scratch.
+                    regs_.object(),    // Scratch.
+                    regs_.address(),   // Scratch.
+                    regs_.scratch2(),  // Scratch.
+                    &need_incremental_pop_scratch);
+  __ Pop(regs_.object(), regs_.address());
+
+  regs_.Restore(masm);  // Restore the extra scratch registers we used.
+  if (on_no_need == kUpdateRememberedSetOnNoNeedToInformIncrementalMarker) {
+    __ RememberedSetHelper(object_,
+                           address_,
+                           value_,
+                           save_fp_regs_mode_,
+                           MacroAssembler::kReturnAtEnd);
+  } else {
+    __ Ret();
+  }
+
+  __ Bind(&need_incremental_pop_scratch);
+  __ Pop(regs_.object(), regs_.address());
+
+  __ Bind(&need_incremental);
+  // Fall through when we need to inform the incremental marker.
+}
+
+
+void RecordWriteStub::Generate(MacroAssembler* masm) {
+  Label skip_to_incremental_noncompacting;
+  Label skip_to_incremental_compacting;
+
+  // We patch these two first instructions back and forth between a nop and
+  // real branch when we start and stop incremental heap marking.
+  // Initially the stub is expected to be in STORE_BUFFER_ONLY mode, so 2 nops
+  // are generated.
+  // See RecordWriteStub::Patch for details.
+  {
+    InstructionAccurateScope scope(masm, 2);
+    __ adr(xzr, &skip_to_incremental_noncompacting);
+    __ adr(xzr, &skip_to_incremental_compacting);
+  }
+
+  if (remembered_set_action_ == EMIT_REMEMBERED_SET) {
+    __ RememberedSetHelper(object_,
+                           address_,
+                           value_,
+                           save_fp_regs_mode_,
+                           MacroAssembler::kReturnAtEnd);
+  }
+  __ Ret();
+
+  __ Bind(&skip_to_incremental_noncompacting);
+  GenerateIncremental(masm, INCREMENTAL);
+
+  __ Bind(&skip_to_incremental_compacting);
+  GenerateIncremental(masm, INCREMENTAL_COMPACTION);
+}
+
+
+void StoreArrayLiteralElementStub::Generate(MacroAssembler* masm) {
+  // TODO(all): Possible optimisations in this function:
+  // 1. Merge CheckFastElements and CheckFastSmiElements, so that the map
+  //    bitfield is loaded only once.
+  // 2. Refactor the Ldr/Add sequence at the start of fast_elements and
+  //    smi_element.
+
+  // x0     value            element value to store
+  // x3     index_smi        element index as smi
+  // sp[0]  array_index_smi  array literal index in function as smi
+  // sp[1]  array            array literal
+
+  Register value = x0;
+  Register index_smi = x3;
+
+  Register array = x1;
+  Register array_map = x2;
+  Register array_index_smi = x4;
+  __ PeekPair(array_index_smi, array, 0);
+  __ Ldr(array_map, FieldMemOperand(array, JSObject::kMapOffset));
+
+  Label double_elements, smi_element, fast_elements, slow_elements;
+  __ CheckFastElements(array_map, x10, &double_elements);
+  __ JumpIfSmi(value, &smi_element);
+  __ CheckFastSmiElements(array_map, x10, &fast_elements);
+
+  // Store into the array literal requires an elements transition. Call into
+  // the runtime.
+  __ Bind(&slow_elements);
+  __ Push(array, index_smi, value);
+  __ Ldr(x10, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+  __ Ldr(x11, FieldMemOperand(x10, JSFunction::kLiteralsOffset));
+  __ Push(x11, array_index_smi);
+  __ TailCallRuntime(Runtime::kStoreArrayLiteralElement, 5, 1);
+
+  // Array literal has ElementsKind of FAST_*_ELEMENTS and value is an object.
+  __ Bind(&fast_elements);
+  __ Ldr(x10, FieldMemOperand(array, JSObject::kElementsOffset));
+  __ Add(x11, x10, Operand::UntagSmiAndScale(index_smi, kPointerSizeLog2));
+  __ Add(x11, x11, FixedArray::kHeaderSize - kHeapObjectTag);
+  __ Str(value, MemOperand(x11));
+  // Update the write barrier for the array store.
+  __ RecordWrite(x10, x11, value, kLRHasNotBeenSaved, kDontSaveFPRegs,
+                 EMIT_REMEMBERED_SET, OMIT_SMI_CHECK);
+  __ Ret();
+
+  // Array literal has ElementsKind of FAST_*_SMI_ELEMENTS or FAST_*_ELEMENTS,
+  // and value is Smi.
+  __ Bind(&smi_element);
+  __ Ldr(x10, FieldMemOperand(array, JSObject::kElementsOffset));
+  __ Add(x11, x10, Operand::UntagSmiAndScale(index_smi, kPointerSizeLog2));
+  __ Str(value, FieldMemOperand(x11, FixedArray::kHeaderSize));
+  __ Ret();
+
+  __ Bind(&double_elements);
+  __ Ldr(x10, FieldMemOperand(array, JSObject::kElementsOffset));
+  __ StoreNumberToDoubleElements(value, index_smi, x10, x11, d0, d1,
+                                 &slow_elements);
+  __ Ret();
+}
+
+
+void StubFailureTrampolineStub::Generate(MacroAssembler* masm) {
+  // TODO(jbramley): The ARM code leaves the (shifted) offset in r1. Why?
+  CEntryStub ces(1, kSaveFPRegs);
+  __ Call(ces.GetCode(masm->isolate()), RelocInfo::CODE_TARGET);
+  int parameter_count_offset =
+      StubFailureTrampolineFrame::kCallerStackParameterCountFrameOffset;
+  __ Ldr(x1, MemOperand(fp, parameter_count_offset));
+  if (function_mode_ == JS_FUNCTION_STUB_MODE) {
+    __ Add(x1, x1, 1);
+  }
+  masm->LeaveFrame(StackFrame::STUB_FAILURE_TRAMPOLINE);
+  __ Drop(x1);
+  // Return to IC Miss stub, continuation still on stack.
+  __ Ret();
+}
+
+
+void ProfileEntryHookStub::MaybeCallEntryHook(MacroAssembler* masm) {
+  if (masm->isolate()->function_entry_hook() != NULL) {
+    // TODO(all): This needs to be reliably consistent with
+    // kReturnAddressDistanceFromFunctionStart in ::Generate.
+    Assembler::BlockConstPoolScope no_const_pools(masm);
+    ProfileEntryHookStub stub;
+    __ Push(lr);
+    __ CallStub(&stub);
+    __ Pop(lr);
+  }
+}
+
+
+void ProfileEntryHookStub::Generate(MacroAssembler* masm) {
+  MacroAssembler::NoUseRealAbortsScope no_use_real_aborts(masm);
+  // The entry hook is a "BumpSystemStackPointer" instruction (sub), followed by
+  // a "Push lr" instruction, followed by a call.
+  // TODO(jbramley): Verify that this call is always made with relocation.
+  static const int kReturnAddressDistanceFromFunctionStart =
+      Assembler::kCallSizeWithRelocation + (2 * kInstructionSize);
+
+  // Save all kCallerSaved registers (including lr), since this can be called
+  // from anywhere.
+  // TODO(jbramley): What about FP registers?
+  __ PushCPURegList(kCallerSaved);
+  ASSERT(kCallerSaved.IncludesAliasOf(lr));
+  const int kNumSavedRegs = kCallerSaved.Count();
+
+  // Compute the function's address as the first argument.
+  __ Sub(x0, lr, kReturnAddressDistanceFromFunctionStart);
+
+#if V8_HOST_ARCH_A64
+  uintptr_t entry_hook =
+      reinterpret_cast<uintptr_t>(masm->isolate()->function_entry_hook());
+  __ Mov(x10, entry_hook);
+#else
+  // Under the simulator we need to indirect the entry hook through a trampoline
+  // function at a known address.
+  ApiFunction dispatcher(FUNCTION_ADDR(EntryHookTrampoline));
+  __ Mov(x10, Operand(ExternalReference(&dispatcher,
+                                        ExternalReference::BUILTIN_CALL,
+                                        masm->isolate())));
+  // It additionally takes an isolate as a third parameter
+  __ Mov(x2, Operand(ExternalReference::isolate_address(masm->isolate())));
+#endif
+
+  // The caller's return address is above the saved temporaries.
+  // Grab its location for the second argument to the hook.
+  __ Add(x1, __ StackPointer(), kNumSavedRegs * kPointerSize);
+
+  {
+    // Create a dummy frame, as CallCFunction requires this.
+    FrameScope frame(masm, StackFrame::MANUAL);
+    __ CallCFunction(x10, 2, 0);
+  }
+
+  __ PopCPURegList(kCallerSaved);
+  __ Ret();
+}
+
+
+void DirectCEntryStub::Generate(MacroAssembler* masm) {
+  // When calling into C++ code the stack pointer must be csp.
+  // Therefore this code must use csp for peek/poke operations when the
+  // stub is generated. When the stub is called
+  // (via DirectCEntryStub::GenerateCall), the caller must setup an ExitFrame
+  // and configure the stack pointer *before* doing the call.
+  const Register old_stack_pointer = __ StackPointer();
+  __ SetStackPointer(csp);
+
+  // Put return address on the stack (accessible to GC through exit frame pc).
+  __ Poke(lr, 0);
+  // Call the C++ function.
+  __ Blr(x10);
+  // Return to calling code.
+  __ Peek(lr, 0);
+  __ Ret();
+
+  __ SetStackPointer(old_stack_pointer);
+}
+
+void DirectCEntryStub::GenerateCall(MacroAssembler* masm,
+                                    Register target) {
+  // Make sure the caller configured the stack pointer (see comment in
+  // DirectCEntryStub::Generate).
+  ASSERT(csp.Is(__ StackPointer()));
+
+  intptr_t code =
+      reinterpret_cast<intptr_t>(GetCode(masm->isolate()).location());
+  __ Mov(lr, Operand(code, RelocInfo::CODE_TARGET));
+  __ Mov(x10, target);
+  // Branch to the stub.
+  __ Blr(lr);
+}
+
+
+// Probe the name dictionary in the 'elements' register.
+// Jump to the 'done' label if a property with the given name is found.
+// Jump to the 'miss' label otherwise.
+//
+// If lookup was successful 'scratch2' will be equal to elements + 4 * index.
+// 'elements' and 'name' registers are preserved on miss.
+void NameDictionaryLookupStub::GeneratePositiveLookup(
+    MacroAssembler* masm,
+    Label* miss,
+    Label* done,
+    Register elements,
+    Register name,
+    Register scratch1,
+    Register scratch2) {
+  ASSERT(!AreAliased(elements, name, scratch1, scratch2));
+
+  // Assert that name contains a string.
+  __ AssertName(name);
+
+  // Compute the capacity mask.
+  __ Ldrsw(scratch1, UntagSmiFieldMemOperand(elements, kCapacityOffset));
+  __ Sub(scratch1, scratch1, 1);
+
+  // Generate an unrolled loop that performs a few probes before giving up.
+  for (int i = 0; i < kInlinedProbes; i++) {
+    // Compute the masked index: (hash + i + i * i) & mask.
+    __ Ldr(scratch2, FieldMemOperand(name, Name::kHashFieldOffset));
+    if (i > 0) {
+      // Add the probe offset (i + i * i) left shifted to avoid right shifting
+      // the hash in a separate instruction. The value hash + i + i * i is right
+      // shifted in the following and instruction.
+      ASSERT(NameDictionary::GetProbeOffset(i) <
+          1 << (32 - Name::kHashFieldOffset));
+      __ Add(scratch2, scratch2, Operand(
+          NameDictionary::GetProbeOffset(i) << Name::kHashShift));
+    }
+    __ And(scratch2, scratch1, Operand(scratch2, LSR, Name::kHashShift));
+
+    // Scale the index by multiplying by the element size.
+    ASSERT(NameDictionary::kEntrySize == 3);
+    __ Add(scratch2, scratch2, Operand(scratch2, LSL, 1));
+
+    // Check if the key is identical to the name.
+    __ Add(scratch2, elements, Operand(scratch2, LSL, kPointerSizeLog2));
+    // TODO(jbramley): We need another scratch here, but some callers can't
+    // provide a scratch3 so we have to use Tmp1(). We should find a clean way
+    // to make it unavailable to the MacroAssembler for a short time.
+    __ Ldr(__ Tmp1(), FieldMemOperand(scratch2, kElementsStartOffset));
+    __ Cmp(name, __ Tmp1());
+    __ B(eq, done);
+  }
+
+  // The inlined probes didn't find the entry.
+  // Call the complete stub to scan the whole dictionary.
+
+  CPURegList spill_list(CPURegister::kRegister, kXRegSize, 0, 6);
+  spill_list.Combine(lr);
+  spill_list.Remove(scratch1);
+  spill_list.Remove(scratch2);
+
+  __ PushCPURegList(spill_list);
+
+  if (name.is(x0)) {
+    ASSERT(!elements.is(x1));
+    __ Mov(x1, name);
+    __ Mov(x0, elements);
+  } else {
+    __ Mov(x0, elements);
+    __ Mov(x1, name);
+  }
+
+  Label not_found;
+  NameDictionaryLookupStub stub(POSITIVE_LOOKUP);
+  __ CallStub(&stub);
+  __ Cbz(x0, &not_found);
+  __ Mov(scratch2, x2);  // Move entry index into scratch2.
+  __ PopCPURegList(spill_list);
+  __ B(done);
+
+  __ Bind(&not_found);
+  __ PopCPURegList(spill_list);
+  __ B(miss);
+}
+
+
+void NameDictionaryLookupStub::GenerateNegativeLookup(MacroAssembler* masm,
+                                                      Label* miss,
+                                                      Label* done,
+                                                      Register receiver,
+                                                      Register properties,
+                                                      Handle<Name> name,
+                                                      Register scratch0) {
+  ASSERT(!AreAliased(receiver, properties, scratch0));
+  ASSERT(name->IsUniqueName());
+  // If names of slots in range from 1 to kProbes - 1 for the hash value are
+  // not equal to the name and kProbes-th slot is not used (its name is the
+  // undefined value), it guarantees the hash table doesn't contain the
+  // property. It's true even if some slots represent deleted properties
+  // (their names are the hole value).
+  for (int i = 0; i < kInlinedProbes; i++) {
+    // scratch0 points to properties hash.
+    // Compute the masked index: (hash + i + i * i) & mask.
+    Register index = scratch0;
+    // Capacity is smi 2^n.
+    __ Ldrsw(index, UntagSmiFieldMemOperand(properties, kCapacityOffset));
+    __ Sub(index, index, 1);
+    __ And(index, index, name->Hash() + NameDictionary::GetProbeOffset(i));
+
+    // Scale the index by multiplying by the entry size.
+    ASSERT(NameDictionary::kEntrySize == 3);
+    __ Add(index, index, Operand(index, LSL, 1));  // index *= 3.
+
+    Register entity_name = scratch0;
+    // Having undefined at this place means the name is not contained.
+    Register tmp = index;
+    __ Add(tmp, properties, Operand(index, LSL, kPointerSizeLog2));
+    __ Ldr(entity_name, FieldMemOperand(tmp, kElementsStartOffset));
+
+    __ JumpIfRoot(entity_name, Heap::kUndefinedValueRootIndex, done);
+
+    // Stop if found the property.
+    __ Cmp(entity_name, Operand(name));
+    __ B(eq, miss);
+
+    Label good;
+    __ JumpIfRoot(entity_name, Heap::kTheHoleValueRootIndex, &good);
+
+    // Check if the entry name is not a unique name.
+    __ Ldr(entity_name, FieldMemOperand(entity_name, HeapObject::kMapOffset));
+    __ Ldrb(entity_name,
+            FieldMemOperand(entity_name, Map::kInstanceTypeOffset));
+    __ JumpIfNotUniqueName(entity_name, miss);
+    __ Bind(&good);
+  }
+
+  CPURegList spill_list(CPURegister::kRegister, kXRegSize, 0, 6);
+  spill_list.Combine(lr);
+  spill_list.Remove(scratch0);  // Scratch registers don't need to be preserved.
+
+  __ PushCPURegList(spill_list);
+
+  __ Ldr(x0, FieldMemOperand(receiver, JSObject::kPropertiesOffset));
+  __ Mov(x1, Operand(name));
+  NameDictionaryLookupStub stub(NEGATIVE_LOOKUP);
+  __ CallStub(&stub);
+  // Move stub return value to scratch0. Note that scratch0 is not included in
+  // spill_list and won't be clobbered by PopCPURegList.
+  __ Mov(scratch0, x0);
+  __ PopCPURegList(spill_list);
+
+  __ Cbz(scratch0, done);
+  __ B(miss);
+}
+
+
+void NameDictionaryLookupStub::Generate(MacroAssembler* masm) {
+  // This stub overrides SometimesSetsUpAFrame() to return false. That means
+  // we cannot call anything that could cause a GC from this stub.
+  //
+  // Arguments are in x0 and x1:
+  //   x0: property dictionary.
+  //   x1: the name of the property we are looking for.
+  //
+  // Return value is in x0 and is zero if lookup failed, non zero otherwise.
+  // If the lookup is successful, x2 will contains the index of the entry.
+
+  Register result = x0;
+  Register dictionary = x0;
+  Register key = x1;
+  Register index = x2;
+  Register mask = x3;
+  Register hash = x4;
+  Register undefined = x5;
+  Register entry_key = x6;
+
+  Label in_dictionary, maybe_in_dictionary, not_in_dictionary;
+
+  __ Ldrsw(mask, UntagSmiFieldMemOperand(dictionary, kCapacityOffset));
+  __ Sub(mask, mask, 1);
+
+  __ Ldr(hash, FieldMemOperand(key, Name::kHashFieldOffset));
+  __ LoadRoot(undefined, Heap::kUndefinedValueRootIndex);
+
+  for (int i = kInlinedProbes; i < kTotalProbes; i++) {
+    // Compute the masked index: (hash + i + i * i) & mask.
+    // Capacity is smi 2^n.
+    if (i > 0) {
+      // Add the probe offset (i + i * i) left shifted to avoid right shifting
+      // the hash in a separate instruction. The value hash + i + i * i is right
+      // shifted in the following and instruction.
+      ASSERT(NameDictionary::GetProbeOffset(i) <
+             1 << (32 - Name::kHashFieldOffset));
+      __ Add(index, hash,
+             NameDictionary::GetProbeOffset(i) << Name::kHashShift);
+    } else {
+      __ Mov(index, hash);
+    }
+    __ And(index, mask, Operand(index, LSR, Name::kHashShift));
+
+    // Scale the index by multiplying by the entry size.
+    ASSERT(NameDictionary::kEntrySize == 3);
+    __ Add(index, index, Operand(index, LSL, 1));  // index *= 3.
+
+    __ Add(index, dictionary, Operand(index, LSL, kPointerSizeLog2));
+    __ Ldr(entry_key, FieldMemOperand(index, kElementsStartOffset));
+
+    // Having undefined at this place means the name is not contained.
+    __ Cmp(entry_key, undefined);
+    __ B(eq, &not_in_dictionary);
+
+    // Stop if found the property.
+    __ Cmp(entry_key, key);
+    __ B(eq, &in_dictionary);
+
+    if (i != kTotalProbes - 1 && mode_ == NEGATIVE_LOOKUP) {
+      // Check if the entry name is not a unique name.
+      __ Ldr(entry_key, FieldMemOperand(entry_key, HeapObject::kMapOffset));
+      __ Ldrb(entry_key, FieldMemOperand(entry_key, Map::kInstanceTypeOffset));
+      __ JumpIfNotUniqueName(entry_key, &maybe_in_dictionary);
+    }
+  }
+
+  __ Bind(&maybe_in_dictionary);
+  // If we are doing negative lookup then probing failure should be
+  // treated as a lookup success. For positive lookup, probing failure
+  // should be treated as lookup failure.
+  if (mode_ == POSITIVE_LOOKUP) {
+    __ Mov(result, 0);
+    __ Ret();
+  }
+
+  __ Bind(&in_dictionary);
+  __ Mov(result, 1);
+  __ Ret();
+
+  __ Bind(&not_in_dictionary);
+  __ Mov(result, 0);
+  __ Ret();
+}
+
+
+template<class T>
+static void CreateArrayDispatch(MacroAssembler* masm,
+                                AllocationSiteOverrideMode mode) {
+  ASM_LOCATION("CreateArrayDispatch");
+  if (mode == DISABLE_ALLOCATION_SITES) {
+    T stub(GetInitialFastElementsKind(), mode);
+     __ TailCallStub(&stub);
+
+  } else if (mode == DONT_OVERRIDE) {
+    Register kind = x3;
+    int last_index =
+        GetSequenceIndexFromFastElementsKind(TERMINAL_FAST_ELEMENTS_KIND);
+    for (int i = 0; i <= last_index; ++i) {
+      Label next;
+      ElementsKind candidate_kind = GetFastElementsKindFromSequenceIndex(i);
+      // TODO(jbramley): Is this the best way to handle this? Can we make the
+      // tail calls conditional, rather than hopping over each one?
+      __ CompareAndBranch(kind, candidate_kind, ne, &next);
+      T stub(candidate_kind);
+      __ TailCallStub(&stub);
+      __ Bind(&next);
+    }
+
+    // If we reached this point there is a problem.
+    __ Abort(kUnexpectedElementsKindInArrayConstructor);
+
+  } else {
+    UNREACHABLE();
+  }
+}
+
+
+// TODO(jbramley): If this needs to be a special case, make it a proper template
+// specialization, and not a separate function.
+static void CreateArrayDispatchOneArgument(MacroAssembler* masm,
+                                           AllocationSiteOverrideMode mode) {
+  ASM_LOCATION("CreateArrayDispatchOneArgument");
+  // x0 - argc
+  // x1 - constructor?
+  // x2 - allocation site (if mode != DISABLE_ALLOCATION_SITES)
+  // x3 - kind (if mode != DISABLE_ALLOCATION_SITES)
+  // sp[0] - last argument
+
+  Register allocation_site = x2;
+  Register kind = x3;
+
+  Label normal_sequence;
+  if (mode == DONT_OVERRIDE) {
+    STATIC_ASSERT(FAST_SMI_ELEMENTS == 0);
+    STATIC_ASSERT(FAST_HOLEY_SMI_ELEMENTS == 1);
+    STATIC_ASSERT(FAST_ELEMENTS == 2);
+    STATIC_ASSERT(FAST_HOLEY_ELEMENTS == 3);
+    STATIC_ASSERT(FAST_DOUBLE_ELEMENTS == 4);
+    STATIC_ASSERT(FAST_HOLEY_DOUBLE_ELEMENTS == 5);
+
+    // Is the low bit set? If so, the array is holey.
+    __ Tbnz(kind, 0, &normal_sequence);
+  }
+
+  // Look at the last argument.
+  // TODO(jbramley): What does a 0 argument represent?
+  __ Peek(x10, 0);
+  __ Cbz(x10, &normal_sequence);
+
+  if (mode == DISABLE_ALLOCATION_SITES) {
+    ElementsKind initial = GetInitialFastElementsKind();
+    ElementsKind holey_initial = GetHoleyElementsKind(initial);
+
+    ArraySingleArgumentConstructorStub stub_holey(holey_initial,
+                                                  DISABLE_ALLOCATION_SITES);
+    __ TailCallStub(&stub_holey);
+
+    __ Bind(&normal_sequence);
+    ArraySingleArgumentConstructorStub stub(initial,
+                                            DISABLE_ALLOCATION_SITES);
+    __ TailCallStub(&stub);
+  } else if (mode == DONT_OVERRIDE) {
+    // We are going to create a holey array, but our kind is non-holey.
+    // Fix kind and retry (only if we have an allocation site in the slot).
+    __ Orr(kind, kind, 1);
+
+    if (FLAG_debug_code) {
+      __ Ldr(x10, FieldMemOperand(allocation_site, 0));
+      __ JumpIfNotRoot(x10, Heap::kAllocationSiteMapRootIndex,
+                       &normal_sequence);
+      __ Assert(eq, kExpectedAllocationSite);
+    }
+
+    // Save the resulting elements kind in type info. We can't just store 'kind'
+    // in the AllocationSite::transition_info field because elements kind is
+    // restricted to a portion of the field; upper bits need to be left alone.
+    STATIC_ASSERT(AllocationSite::ElementsKindBits::kShift == 0);
+    __ Ldr(x11, FieldMemOperand(allocation_site,
+                                AllocationSite::kTransitionInfoOffset));
+    __ Add(x11, x11, Operand(Smi::FromInt(kFastElementsKindPackedToHoley)));
+    __ Str(x11, FieldMemOperand(allocation_site,
+                                AllocationSite::kTransitionInfoOffset));
+
+    __ Bind(&normal_sequence);
+    int last_index =
+        GetSequenceIndexFromFastElementsKind(TERMINAL_FAST_ELEMENTS_KIND);
+    for (int i = 0; i <= last_index; ++i) {
+      Label next;
+      ElementsKind candidate_kind = GetFastElementsKindFromSequenceIndex(i);
+      // TODO(jbramley): Is this the best way to handle this? Can we make the
+      // tail calls conditional, rather than hopping over each one?
+      __ CompareAndBranch(kind, candidate_kind, ne, &next);
+      ArraySingleArgumentConstructorStub stub(candidate_kind);
+      __ TailCallStub(&stub);
+      __ Bind(&next);
+    }
+
+    // If we reached this point there is a problem.
+    __ Abort(kUnexpectedElementsKindInArrayConstructor);
+  } else {
+    UNREACHABLE();
+  }
+}
+
+
+template<class T>
+static void ArrayConstructorStubAheadOfTimeHelper(Isolate* isolate) {
+  int to_index = GetSequenceIndexFromFastElementsKind(
+      TERMINAL_FAST_ELEMENTS_KIND);
+  for (int i = 0; i <= to_index; ++i) {
+    ElementsKind kind = GetFastElementsKindFromSequenceIndex(i);
+    T stub(kind);
+    stub.GetCode(isolate);
+    if (AllocationSite::GetMode(kind) != DONT_TRACK_ALLOCATION_SITE) {
+      T stub1(kind, DISABLE_ALLOCATION_SITES);
+      stub1.GetCode(isolate);
+    }
+  }
+}
+
+
+void ArrayConstructorStubBase::GenerateStubsAheadOfTime(Isolate* isolate) {
+  ArrayConstructorStubAheadOfTimeHelper<ArrayNoArgumentConstructorStub>(
+      isolate);
+  ArrayConstructorStubAheadOfTimeHelper<ArraySingleArgumentConstructorStub>(
+      isolate);
+  ArrayConstructorStubAheadOfTimeHelper<ArrayNArgumentsConstructorStub>(
+      isolate);
+}
+
+
+void InternalArrayConstructorStubBase::GenerateStubsAheadOfTime(
+    Isolate* isolate) {
+  ElementsKind kinds[2] = { FAST_ELEMENTS, FAST_HOLEY_ELEMENTS };
+  for (int i = 0; i < 2; i++) {
+    // For internal arrays we only need a few things
+    InternalArrayNoArgumentConstructorStub stubh1(kinds[i]);
+    stubh1.GetCode(isolate);
+    InternalArraySingleArgumentConstructorStub stubh2(kinds[i]);
+    stubh2.GetCode(isolate);
+    InternalArrayNArgumentsConstructorStub stubh3(kinds[i]);
+    stubh3.GetCode(isolate);
+  }
+}
+
+
+void ArrayConstructorStub::GenerateDispatchToArrayStub(
+    MacroAssembler* masm,
+    AllocationSiteOverrideMode mode) {
+  Register argc = x0;
+  if (argument_count_ == ANY) {
+    Label zero_case, n_case;
+    __ Cbz(argc, &zero_case);
+    __ Cmp(argc, 1);
+    __ B(ne, &n_case);
+
+    // One argument.
+    CreateArrayDispatchOneArgument(masm, mode);
+
+    __ Bind(&zero_case);
+    // No arguments.
+    CreateArrayDispatch<ArrayNoArgumentConstructorStub>(masm, mode);
+
+    __ Bind(&n_case);
+    // N arguments.
+    CreateArrayDispatch<ArrayNArgumentsConstructorStub>(masm, mode);
+
+  } else if (argument_count_ == NONE) {
+    CreateArrayDispatch<ArrayNoArgumentConstructorStub>(masm, mode);
+  } else if (argument_count_ == ONE) {
+    CreateArrayDispatchOneArgument(masm, mode);
+  } else if (argument_count_ == MORE_THAN_ONE) {
+    CreateArrayDispatch<ArrayNArgumentsConstructorStub>(masm, mode);
+  } else {
+    UNREACHABLE();
+  }
+}
+
+
+void ArrayConstructorStub::Generate(MacroAssembler* masm) {
+  ASM_LOCATION("ArrayConstructorStub::Generate");
+  // ----------- S t a t e -------------
+  //  -- x0 : argc (only if argument_count_ == ANY)
+  //  -- x1 : constructor
+  //  -- x2 : feedback vector (fixed array or undefined)
+  //  -- x3 : slot index (if x2 is fixed array)
+  //  -- sp[0] : return address
+  //  -- sp[4] : last argument
+  // -----------------------------------
+  Register constructor = x1;
+  Register feedback_vector = x2;
+  Register slot_index = x3;
+
+  if (FLAG_debug_code) {
+    // The array construct code is only set for the global and natives
+    // builtin Array functions which always have maps.
+
+    Label unexpected_map, map_ok;
+    // Initial map for the builtin Array function should be a map.
+    __ Ldr(x10, FieldMemOperand(constructor,
+                                JSFunction::kPrototypeOrInitialMapOffset));
+    // Will both indicate a NULL and a Smi.
+    __ JumpIfSmi(x10, &unexpected_map);
+    __ JumpIfObjectType(x10, x10, x11, MAP_TYPE, &map_ok);
+    __ Bind(&unexpected_map);
+    __ Abort(kUnexpectedInitialMapForArrayFunction);
+    __ Bind(&map_ok);
+
+    // In feedback_vector, we expect either undefined or a valid fixed array.
+    Label okay_here;
+    Handle<Map> fixed_array_map = masm->isolate()->factory()->fixed_array_map();
+    __ JumpIfRoot(feedback_vector, Heap::kUndefinedValueRootIndex, &okay_here);
+    __ Ldr(x10, FieldMemOperand(feedback_vector, FixedArray::kMapOffset));
+    __ Cmp(x10, Operand(fixed_array_map));
+    __ Assert(eq, kExpectedFixedArrayInFeedbackVector);
+
+    // slot_index should be a smi if we don't have undefined in feedback_vector.
+    __ AssertSmi(slot_index);
+
+    __ Bind(&okay_here);
+  }
+
+  Register allocation_site = x2;  // Overwrites feedback_vector.
+  Register kind = x3;
+  Label no_info;
+  // Get the elements kind and case on that.
+  __ JumpIfRoot(feedback_vector, Heap::kUndefinedValueRootIndex, &no_info);
+  __ Add(feedback_vector, feedback_vector,
+         Operand::UntagSmiAndScale(slot_index, kPointerSizeLog2));
+  __ Ldr(allocation_site, FieldMemOperand(feedback_vector,
+                                          FixedArray::kHeaderSize));
+
+  // If the feedback vector is undefined, or contains anything other than an
+  // AllocationSite, call an array constructor that doesn't use AllocationSites.
+  __ Ldr(x10, FieldMemOperand(allocation_site, AllocationSite::kMapOffset));
+  __ JumpIfNotRoot(x10, Heap::kAllocationSiteMapRootIndex, &no_info);
+
+  __ Ldrsw(kind,
+           UntagSmiFieldMemOperand(allocation_site,
+                                   AllocationSite::kTransitionInfoOffset));
+  __ And(kind, kind, AllocationSite::ElementsKindBits::kMask);
+  GenerateDispatchToArrayStub(masm, DONT_OVERRIDE);
+
+  __ Bind(&no_info);
+  GenerateDispatchToArrayStub(masm, DISABLE_ALLOCATION_SITES);
+}
+
+
+void InternalArrayConstructorStub::GenerateCase(
+    MacroAssembler* masm, ElementsKind kind) {
+  Label zero_case, n_case;
+  Register argc = x0;
+
+  __ Cbz(argc, &zero_case);
+  __ CompareAndBranch(argc, 1, ne, &n_case);
+
+  // One argument.
+  if (IsFastPackedElementsKind(kind)) {
+    Label packed_case;
+
+    // We might need to create a holey array; look at the first argument.
+    __ Peek(x10, 0);
+    __ Cbz(x10, &packed_case);
+
+    InternalArraySingleArgumentConstructorStub
+        stub1_holey(GetHoleyElementsKind(kind));
+    __ TailCallStub(&stub1_holey);
+
+    __ Bind(&packed_case);
+  }
+  InternalArraySingleArgumentConstructorStub stub1(kind);
+  __ TailCallStub(&stub1);
+
+  __ Bind(&zero_case);
+  // No arguments.
+  InternalArrayNoArgumentConstructorStub stub0(kind);
+  __ TailCallStub(&stub0);
+
+  __ Bind(&n_case);
+  // N arguments.
+  InternalArrayNArgumentsConstructorStub stubN(kind);
+  __ TailCallStub(&stubN);
+}
+
+
+void InternalArrayConstructorStub::Generate(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- x0 : argc
+  //  -- x1 : constructor
+  //  -- sp[0] : return address
+  //  -- sp[4] : last argument
+  // -----------------------------------
+  Handle<Object> undefined_sentinel(
+      masm->isolate()->heap()->undefined_value(), masm->isolate());
+
+  Register constructor = x1;
+
+  if (FLAG_debug_code) {
+    // The array construct code is only set for the global and natives
+    // builtin Array functions which always have maps.
+
+    Label unexpected_map, map_ok;
+    // Initial map for the builtin Array function should be a map.
+    __ Ldr(x10, FieldMemOperand(constructor,
+                                JSFunction::kPrototypeOrInitialMapOffset));
+    // Will both indicate a NULL and a Smi.
+    __ JumpIfSmi(x10, &unexpected_map);
+    __ JumpIfObjectType(x10, x10, x11, MAP_TYPE, &map_ok);
+    __ Bind(&unexpected_map);
+    __ Abort(kUnexpectedInitialMapForArrayFunction);
+    __ Bind(&map_ok);
+  }
+
+  Register kind = w3;
+  // Figure out the right elements kind
+  __ Ldr(x10, FieldMemOperand(constructor,
+                              JSFunction::kPrototypeOrInitialMapOffset));
+
+  // TODO(jbramley): Add a helper function to read elements kind from an
+  // existing map.
+  // Load the map's "bit field 2" into result.
+  __ Ldr(kind, FieldMemOperand(x10, Map::kBitField2Offset));
+  // Retrieve elements_kind from bit field 2.
+  __ Ubfx(kind, kind, Map::kElementsKindShift, Map::kElementsKindBitCount);
+
+  if (FLAG_debug_code) {
+    Label done;
+    __ Cmp(x3, FAST_ELEMENTS);
+    __ Ccmp(x3, FAST_HOLEY_ELEMENTS, ZFlag, ne);
+    __ Assert(eq, kInvalidElementsKindForInternalArrayOrInternalPackedArray);
+  }
+
+  Label fast_elements_case;
+  __ CompareAndBranch(kind, FAST_ELEMENTS, eq, &fast_elements_case);
+  GenerateCase(masm, FAST_HOLEY_ELEMENTS);
+
+  __ Bind(&fast_elements_case);
+  GenerateCase(masm, FAST_ELEMENTS);
+}
+
+
+void CallApiFunctionStub::Generate(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- x0                  : callee
+  //  -- x4                  : call_data
+  //  -- x2                  : holder
+  //  -- x1                  : api_function_address
+  //  -- cp                  : context
+  //  --
+  //  -- sp[0]               : last argument
+  //  -- ...
+  //  -- sp[(argc - 1) * 8]  : first argument
+  //  -- sp[argc * 8]        : receiver
+  // -----------------------------------
+
+  Register callee = x0;
+  Register call_data = x4;
+  Register holder = x2;
+  Register api_function_address = x1;
+  Register context = cp;
+
+  int argc = ArgumentBits::decode(bit_field_);
+  bool restore_context = RestoreContextBits::decode(bit_field_);
+  bool call_data_undefined = CallDataUndefinedBits::decode(bit_field_);
+
+  typedef FunctionCallbackArguments FCA;
+
+  STATIC_ASSERT(FCA::kContextSaveIndex == 6);
+  STATIC_ASSERT(FCA::kCalleeIndex == 5);
+  STATIC_ASSERT(FCA::kDataIndex == 4);
+  STATIC_ASSERT(FCA::kReturnValueOffset == 3);
+  STATIC_ASSERT(FCA::kReturnValueDefaultValueIndex == 2);
+  STATIC_ASSERT(FCA::kIsolateIndex == 1);
+  STATIC_ASSERT(FCA::kHolderIndex == 0);
+  STATIC_ASSERT(FCA::kArgsLength == 7);
+
+  Isolate* isolate = masm->isolate();
+
+  // FunctionCallbackArguments: context, callee and call data.
+  __ Push(context, callee, call_data);
+
+  // Load context from callee
+  __ Ldr(context, FieldMemOperand(callee, JSFunction::kContextOffset));
+
+  if (!call_data_undefined) {
+    __ LoadRoot(call_data, Heap::kUndefinedValueRootIndex);
+  }
+  Register isolate_reg = x5;
+  __ Mov(isolate_reg, Operand(ExternalReference::isolate_address(isolate)));
+
+  // FunctionCallbackArguments:
+  //    return value, return value default, isolate, holder.
+  __ Push(call_data, call_data, isolate_reg, holder);
+
+  // Prepare arguments.
+  Register args = x6;
+  __ Mov(args, masm->StackPointer());
+
+  // Allocate the v8::Arguments structure in the arguments' space, since it's
+  // not controlled by GC.
+  const int kApiStackSpace = 4;
+
+  // Allocate space for CallApiFunctionAndReturn can store some scratch
+  // registeres on the stack.
+  const int kCallApiFunctionSpillSpace = 4;
+
+  FrameScope frame_scope(masm, StackFrame::MANUAL);
+  __ EnterExitFrame(false, x10, kApiStackSpace + kCallApiFunctionSpillSpace);
+
+  // TODO(all): Optimize this with stp and suchlike.
+  ASSERT(!AreAliased(x0, api_function_address));
+  // x0 = FunctionCallbackInfo&
+  // Arguments is after the return address.
+  __ Add(x0, masm->StackPointer(), 1 * kPointerSize);
+  // FunctionCallbackInfo::implicit_args_
+  __ Str(args, MemOperand(x0, 0 * kPointerSize));
+  // FunctionCallbackInfo::values_
+  __ Add(x10, args, Operand((FCA::kArgsLength - 1 + argc) * kPointerSize));
+  __ Str(x10, MemOperand(x0, 1 * kPointerSize));
+  // FunctionCallbackInfo::length_ = argc
+  __ Mov(x10, argc);
+  __ Str(x10, MemOperand(x0, 2 * kPointerSize));
+  // FunctionCallbackInfo::is_construct_call = 0
+  __ Str(xzr, MemOperand(x0, 3 * kPointerSize));
+
+  const int kStackUnwindSpace = argc + FCA::kArgsLength + 1;
+  Address thunk_address = FUNCTION_ADDR(&InvokeFunctionCallback);
+  ExternalReference::Type thunk_type = ExternalReference::PROFILING_API_CALL;
+  ApiFunction thunk_fun(thunk_address);
+  ExternalReference thunk_ref = ExternalReference(&thunk_fun, thunk_type,
+      masm->isolate());
+
+  AllowExternalCallThatCantCauseGC scope(masm);
+  MemOperand context_restore_operand(
+      fp, (2 + FCA::kContextSaveIndex) * kPointerSize);
+  MemOperand return_value_operand(fp,
+                                  (2 + FCA::kReturnValueOffset) * kPointerSize);
+
+  const int spill_offset = 1 + kApiStackSpace;
+  __ CallApiFunctionAndReturn(api_function_address,
+                              thunk_ref,
+                              kStackUnwindSpace,
+                              spill_offset,
+                              return_value_operand,
+                              restore_context ?
+                                  &context_restore_operand : NULL);
+}
+
+
+void CallApiGetterStub::Generate(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- sp[0]                  : name
+  //  -- sp[8 - kArgsLength*8]  : PropertyCallbackArguments object
+  //  -- ...
+  //  -- x2                     : api_function_address
+  // -----------------------------------
+
+  Register api_function_address = x2;
+
+  __ Mov(x0, masm->StackPointer());  // x0 = Handle<Name>
+  __ Add(x1, x0, 1 * kPointerSize);  // x1 = PCA
+
+  const int kApiStackSpace = 1;
+
+  // Allocate space for CallApiFunctionAndReturn can store some scratch
+  // registeres on the stack.
+  const int kCallApiFunctionSpillSpace = 4;
+
+  FrameScope frame_scope(masm, StackFrame::MANUAL);
+  __ EnterExitFrame(false, x10, kApiStackSpace + kCallApiFunctionSpillSpace);
+
+  // Create PropertyAccessorInfo instance on the stack above the exit frame with
+  // x1 (internal::Object** args_) as the data.
+  __ Poke(x1, 1 * kPointerSize);
+  __ Add(x1, masm->StackPointer(), 1 * kPointerSize);  // x1 = AccessorInfo&
+
+  const int kStackUnwindSpace = PropertyCallbackArguments::kArgsLength + 1;
+
+  Address thunk_address = FUNCTION_ADDR(&InvokeAccessorGetterCallback);
+  ExternalReference::Type thunk_type =
+      ExternalReference::PROFILING_GETTER_CALL;
+  ApiFunction thunk_fun(thunk_address);
+  ExternalReference thunk_ref = ExternalReference(&thunk_fun, thunk_type,
+      masm->isolate());
+
+  const int spill_offset = 1 + kApiStackSpace;
+  __ CallApiFunctionAndReturn(api_function_address,
+                              thunk_ref,
+                              kStackUnwindSpace,
+                              spill_offset,
+                              MemOperand(fp, 6 * kPointerSize),
+                              NULL);
+}
+
+
+#undef __
+
+} }  // namespace v8::internal
+
+#endif  // V8_TARGET_ARCH_A64