Out-of-line constant pool on Arm: Stage 1 - Free up r7 for use as constant pool pointer register

src/arm/code-stubs-arm.cc

 // Copyright 2012 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
@@ skipping 315 matching lines @@
   Counters* counters = masm->isolate()->counters();
 
   Label gc;
 
   // Pop the function info from the stack.
   __ pop(r3);
 
   // Attempt to allocate new JSFunction in new space.
   __ Allocate(JSFunction::kSize, r0, r1, r2, &gc, TAG_OBJECT);
 
-  __ IncrementCounter(counters->fast_new_closure_total(), 1, r6, r7);
+  __ IncrementCounter(counters->fast_new_closure_total(), 1, r6, r4);
 
   int map_index = Context::FunctionMapIndex(language_mode_, is_generator_);
 
   // Compute the function map in the current native context and set that
   // as the map of the allocated object.
   __ ldr(r2, MemOperand(cp, Context::SlotOffset(Context::GLOBAL_OBJECT_INDEX)));
   __ ldr(r2, FieldMemOperand(r2, GlobalObject::kNativeContextOffset));
   __ ldr(r5, MemOperand(r2, Context::SlotOffset(map_index)));
   __ str(r5, FieldMemOperand(r0, HeapObject::kMapOffset));
 
@@ skipping 24 matching lines @@
   __ str(r4, FieldMemOperand(r0, JSFunction::kNextFunctionLinkOffset));
   __ ldr(r3, FieldMemOperand(r3, SharedFunctionInfo::kCodeOffset));
   __ add(r3, r3, Operand(Code::kHeaderSize - kHeapObjectTag));
   __ str(r3, FieldMemOperand(r0, JSFunction::kCodeEntryOffset));
 
   // Return result. The argument function info has been popped already.
   __ Ret();
 
   __ bind(&check_optimized);
 
-  __ IncrementCounter(counters->fast_new_closure_try_optimized(), 1, r6, r7);
+  __ IncrementCounter(counters->fast_new_closure_try_optimized(), 1, r6, r4);
 
   // r2 holds native context, r1 points to fixed array of 3-element entries
   // (native context, optimized code, literals).
   // The optimized code map must never be empty, so check the first elements.
   Label install_optimized;
   // Speculatively move code object into r4.
   __ ldr(r4, FieldMemOperand(r1, SharedFunctionInfo::kFirstCodeSlot));
   __ ldr(r5, FieldMemOperand(r1, SharedFunctionInfo::kFirstContextSlot));
   __ cmp(r2, r5);
   __ b(eq, &install_optimized);
@@ skipping 12 matching lines @@
   __ cmp(r2, r5);
   __ b(ne, &loop);
   // Hit: fetch the optimized code.
   __ add(r5, r1, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
   __ add(r5, r5, Operand::PointerOffsetFromSmiKey(r4));
   __ add(r5, r5, Operand(kPointerSize));
   __ ldr(r4, MemOperand(r5));
 
   __ bind(&install_optimized);
   __ IncrementCounter(counters->fast_new_closure_install_optimized(),
-                      1, r6, r7);
+                      1, r6, r5);
 
   // TODO(fschneider): Idea: store proper code pointers in the map and either
   // unmangle them on marking or do nothing as the whole map is discarded on
   // major GC anyway.
   __ add(r4, r4, Operand(Code::kHeaderSize - kHeapObjectTag));
   __ str(r4, FieldMemOperand(r0, JSFunction::kCodeEntryOffset));
 
   // Now link a function into a list of optimized functions.
   __ ldr(r4, ContextOperand(r2, Context::OPTIMIZED_FUNCTIONS_LIST));
 
@@ skipping 417 matching lines @@
   } else {
     // Smi compared non-strictly with a non-Smi non-heap-number.  Call
     // the runtime.
     __ b(ne, slow);
   }
 
   // Lhs is a smi, rhs is a number.
   // Convert lhs to a double in d7.
   __ SmiToDouble(d7, lhs);
   // Load the double from rhs, tagged HeapNumber r0, to d6.
-  __ sub(r7, rhs, Operand(kHeapObjectTag));
-  __ vldr(d6, r7, HeapNumber::kValueOffset);
+  __ vldr(d6, rhs, HeapNumber::kValueOffset - kHeapObjectTag);
 
   // We now have both loaded as doubles but we can skip the lhs nan check
   // since it's a smi.
   __ jmp(lhs_not_nan);
 
   __ bind(&rhs_is_smi);
   // Rhs is a smi.  Check whether the non-smi lhs is a heap number.
   __ CompareObjectType(lhs, r4, r4, HEAP_NUMBER_TYPE);
   if (strict) {
     // If lhs is not a number and rhs is a smi then strict equality cannot
     // succeed.  Return non-equal.
     // If lhs is r0 then there is already a non zero value in it.
     if (!lhs.is(r0)) {
       __ mov(r0, Operand(NOT_EQUAL), LeaveCC, ne);
     }
     __ Ret(ne);
   } else {
     // Smi compared non-strictly with a non-smi non-heap-number.  Call
     // the runtime.
     __ b(ne, slow);
   }
 
   // Rhs is a smi, lhs is a heap number.
   // Load the double from lhs, tagged HeapNumber r1, to d7.
-  __ sub(r7, lhs, Operand(kHeapObjectTag));
-  __ vldr(d7, r7, HeapNumber::kValueOffset);
+  __ vldr(d7, lhs, HeapNumber::kValueOffset - kHeapObjectTag);
   // Convert rhs to a double in d6              .
   __ SmiToDouble(d6, rhs);
   // Fall through to both_loaded_as_doubles.
 }
 
 
 // See comment at call site.
 static void EmitStrictTwoHeapObjectCompare(MacroAssembler* masm,
                                            Register lhs,
                                            Register rhs) {
@@ skipping 47 matching lines @@
          (lhs.is(r1) && rhs.is(r0)));
 
   __ CompareObjectType(rhs, r3, r2, HEAP_NUMBER_TYPE);
   __ b(ne, not_heap_numbers);
   __ ldr(r2, FieldMemOperand(lhs, HeapObject::kMapOffset));
   __ cmp(r2, r3);
   __ b(ne, slow);  // First was a heap number, second wasn't.  Go slow case.
 
   // Both are heap numbers.  Load them up then jump to the code we have
   // for that.
-  __ sub(r7, rhs, Operand(kHeapObjectTag));
-  __ vldr(d6, r7, HeapNumber::kValueOffset);
-  __ sub(r7, lhs, Operand(kHeapObjectTag));
-  __ vldr(d7, r7, HeapNumber::kValueOffset);
+  __ vldr(d6, rhs, HeapNumber::kValueOffset - kHeapObjectTag);
+  __ vldr(d7, lhs, HeapNumber::kValueOffset - kHeapObjectTag);
   __ jmp(both_loaded_as_doubles);
 }
 
 
 // Fast negative check for internalized-to-internalized equality.
 static void EmitCheckForInternalizedStringsOrObjects(MacroAssembler* masm,
                                                      Register lhs,
                                                      Register rhs,
                                                      Label* possible_strings,
                                                      Label* not_both_strings) {
@@ skipping 409 matching lines @@
 }
 
 
 void BinaryOpStub::GenerateTypeTransitionWithSavedArgs(
     MacroAssembler* masm) {
   UNIMPLEMENTED();
 }
 
 
 void BinaryOpStub_GenerateSmiSmiOperation(MacroAssembler* masm,
-                                          Token::Value op) {
+                                          Token::Value op,
+                                          Register scratch1,
+                                          Register scratch2) {
   Register left = r1;
   Register right = r0;
-  Register scratch1 = r7;
-  Register scratch2 = r9;
 

[Rodolph Perfetta, 2013/07/30 15:19:08]

assert that left, right, ip, scratch1 and scratch2 are not aliased

[rmcilroy, 2013/07/30 17:12:37]

Done.

   ASSERT(right.is(r0));
   STATIC_ASSERT(kSmiTag == 0);
 
   Label not_smi_result;
   switch (op) {
     case Token::ADD:
       __ add(right, left, Operand(right), SetCC);  // Add optimistically.
       __ Ret(vc);
       __ sub(right, right, Operand(left));  // Revert optimistic add.
       break;
@@ skipping 195 matching lines @@
 
 
 void BinaryOpStub_GenerateFPOperation(MacroAssembler* masm,
                                       BinaryOpIC::TypeInfo left_type,
                                       BinaryOpIC::TypeInfo right_type,
                                       bool smi_operands,
                                       Label* not_numbers,
                                       Label* gc_required,
                                       Label* miss,
                                       Token::Value op,
-                                      OverwriteMode mode) {
+                                      OverwriteMode mode,
+                                      Register scratch1,
+                                      Register scratch2,
+                                      Register scratch3,
+                                      Register scratch4) {
   Register left = r1;
   Register right = r0;
-  Register scratch1 = r6;
-  Register scratch2 = r7;
-  Register scratch3 = r4;
+  Register result = scratch3;
 

[Rodolph Perfetta, 2013/07/30 15:19:08]

assert the various scratches are not aliased.

[rmcilroy, 2013/07/30 17:12:37]

Done.

   ASSERT(smi_operands || (not_numbers != NULL));
   if (smi_operands) {
     __ AssertSmi(left);
     __ AssertSmi(right);
   }
   if (left_type == BinaryOpIC::SMI) {
     __ JumpIfNotSmi(left, miss);
   }
   if (right_type == BinaryOpIC::SMI) {
     __ JumpIfNotSmi(right, miss);
   }
 
-  Register heap_number_map = r9;
+  Register heap_number_map = scratch4;
   __ LoadRoot(heap_number_map, Heap::kHeapNumberMapRootIndex);
 
   switch (op) {
     case Token::ADD:
     case Token::SUB:
     case Token::MUL:
     case Token::DIV:
     case Token::MOD: {
       // Allocate new heap number for result.
-      Register result = r5;
       BinaryOpStub_GenerateHeapResultAllocation(
           masm, result, heap_number_map, scratch1, scratch2, gc_required, mode);
 
       // Load left and right operands into d0 and d1.
       if (smi_operands) {
         __ SmiToDouble(d1, right);
         __ SmiToDouble(d0, left);
       } else {
         // Load right operand into d1.
         if (right_type == BinaryOpIC::INT32) {
@@ skipping 102 matching lines @@
         default:
           UNREACHABLE();
       }
 
       // Check that the *signed* result fits in a smi.
       __ TrySmiTag(r0, r2, &result_not_a_smi);
       __ Ret();
 
       // Allocate new heap number for result.
       __ bind(&result_not_a_smi);
-      Register result = r5;
       if (smi_operands) {
         __ AllocateHeapNumber(
             result, scratch1, scratch2, heap_number_map, gc_required);
       } else {
         BinaryOpStub_GenerateHeapResultAllocation(
             masm, result, heap_number_map, scratch1, scratch2, gc_required,
             mode);
       }
 
       // r2: Answer as signed int32.
-      // r5: Heap number to write answer into.
+      // result: Heap number to write answer into.
 
       // Nothing can go wrong now, so move the heap number to r0, which is the
       // result.
-      __ mov(r0, Operand(r5));
+      __ mov(r0, Operand(result));
 
       // Convert the int32 in r2 to the heap number in r0. r3 is corrupted. As
       // mentioned above SHR needs to always produce a positive result.
       __ vmov(s0, r2);
       if (op == Token::SHR) {
         __ vcvt_f64_u32(d0, s0);
       } else {
         __ vcvt_f64_s32(d0, s0);
       }
       __ sub(r3, r0, Operand(kHeapObjectTag));
@@ skipping 10 matching lines @@
 // Generate the smi code. If the operation on smis are successful this return is
 // generated. If the result is not a smi and heap number allocation is not
 // requested the code falls through. If number allocation is requested but a
 // heap number cannot be allocated the code jumps to the label gc_required.
 void BinaryOpStub_GenerateSmiCode(
     MacroAssembler* masm,
     Label* use_runtime,
     Label* gc_required,
     Token::Value op,
     BinaryOpStub::SmiCodeGenerateHeapNumberResults allow_heapnumber_results,
-    OverwriteMode mode) {
+    OverwriteMode mode,
+    Register scratch1,
+    Register scratch2,
+    Register scratch3,
+    Register scratch4) {
   Label not_smis;
 
   Register left = r1;
   Register right = r0;
-  Register scratch1 = r7;
 

[Rodolph Perfetta, 2013/07/30 15:19:08]

assert scratchx do not alias with left and right.

[rmcilroy, 2013/07/30 17:12:37]

Done.

   // Perform combined smi check on both operands.
   __ orr(scratch1, left, Operand(right));
   __ JumpIfNotSmi(scratch1, &not_smis);
 
   // If the smi-smi operation results in a smi return is generated.
-  BinaryOpStub_GenerateSmiSmiOperation(masm, op);
+  BinaryOpStub_GenerateSmiSmiOperation(masm, op, scratch1, scratch2);
 
   // If heap number results are possible generate the result in an allocated
   // heap number.
   if (allow_heapnumber_results == BinaryOpStub::ALLOW_HEAPNUMBER_RESULTS) {
     BinaryOpStub_GenerateFPOperation(
         masm, BinaryOpIC::UNINITIALIZED, BinaryOpIC::UNINITIALIZED, true,
-        use_runtime, gc_required, &not_smis, op, mode);
+        use_runtime, gc_required, &not_smis, op, mode, scratch2, scratch3,
+        scratch1, scratch4);
   }
   __ bind(&not_smis);
 }
 
 
 void BinaryOpStub::GenerateSmiStub(MacroAssembler* masm) {
   Label right_arg_changed, call_runtime;
 
   if (op_ == Token::MOD && encoded_right_arg_.has_value) {
     // It is guaranteed that the value will fit into a Smi, because if it
     // didn't, we wouldn't be here, see BinaryOp_Patch.
     __ cmp(r0, Operand(Smi::FromInt(fixed_right_arg_value())));
     __ b(ne, &right_arg_changed);
   }
 
   if (result_type_ == BinaryOpIC::UNINITIALIZED ||
       result_type_ == BinaryOpIC::SMI) {
     // Only allow smi results.
-    BinaryOpStub_GenerateSmiCode(
-        masm, &call_runtime, NULL, op_, NO_HEAPNUMBER_RESULTS, mode_);
+    BinaryOpStub_GenerateSmiCode(masm, &call_runtime, NULL, op_,
+        NO_HEAPNUMBER_RESULTS, mode_, r5, r6, r4, r9);
   } else {
     // Allow heap number result and don't make a transition if a heap number
     // cannot be allocated.
-    BinaryOpStub_GenerateSmiCode(
-        masm, &call_runtime, &call_runtime, op_, ALLOW_HEAPNUMBER_RESULTS,
-        mode_);
+    BinaryOpStub_GenerateSmiCode(masm, &call_runtime, &call_runtime, op_,
+      ALLOW_HEAPNUMBER_RESULTS, mode_, r5, r6, r4, r9);
   }
 
   // Code falls through if the result is not returned as either a smi or heap
   // number.
   __ bind(&right_arg_changed);
   GenerateTypeTransition(masm);
 
   __ bind(&call_runtime);
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
@@ skipping 33 matching lines @@
   __ bind(&call_runtime);
   GenerateTypeTransition(masm);
 }
 
 
 void BinaryOpStub::GenerateInt32Stub(MacroAssembler* masm) {
   ASSERT(Max(left_type_, right_type_) == BinaryOpIC::INT32);
 
   Register left = r1;
   Register right = r0;
-  Register scratch1 = r7;
+  Register scratch1 = r4;
   Register scratch2 = r9;
+  Register scratch3 = r5;
   LowDwVfpRegister double_scratch = d0;
 
   Register heap_number_result = no_reg;
   Register heap_number_map = r6;
   __ LoadRoot(heap_number_map, Heap::kHeapNumberMapRootIndex);
 
   Label call_runtime;
   // Labels for type transition, used for wrong input or output types.
   // Both label are currently actually bound to the same position. We use two
   // different label to differentiate the cause leading to type transition.
   Label transition;
 
   // Smi-smi fast case.
   Label skip;
   __ orr(scratch1, left, right);
   __ JumpIfNotSmi(scratch1, &skip);
-  BinaryOpStub_GenerateSmiSmiOperation(masm, op_);
+  BinaryOpStub_GenerateSmiSmiOperation(masm, op_, scratch2, scratch3);
   // Fall through if the result is not a smi.
   __ bind(&skip);
 
   switch (op_) {
     case Token::ADD:
     case Token::SUB:
     case Token::MUL:
     case Token::DIV:
     case Token::MOD: {
       // It could be that only SMIs have been seen at either the left
@@ skipping 73 matching lines @@
         // A DIV operation expecting an integer result falls through
         // to type transition.
 
       } else {
         if (encoded_right_arg_.has_value) {
           __ Vmov(d8, fixed_right_arg_value(), scratch1);
           __ VFPCompareAndSetFlags(d1, d8);
           __ b(ne, &transition);
         }
 
-        // We preserved r0 and r1 to be able to call runtime.
-        // Save the left value on the stack.
-        __ Push(r5, r4);
-
-        Label pop_and_call_runtime;
-
         // Allocate a heap number to store the result.
         heap_number_result = r5;
         BinaryOpStub_GenerateHeapResultAllocation(masm,
                                                   heap_number_result,
                                                   heap_number_map,
                                                   scratch1,
                                                   scratch2,
-                                                  &pop_and_call_runtime,
+                                                  &call_runtime,
                                                   mode_);
 
-        // Load the left value from the value saved on the stack.
-        __ Pop(r1, r0);
-
         // Call the C function to handle the double operation.
         CallCCodeForDoubleOperation(masm, op_, heap_number_result, scratch1);
         if (FLAG_debug_code) {
           __ stop("Unreachable code.");
         }
 
-        __ bind(&pop_and_call_runtime);
-        __ Drop(2);
         __ b(&call_runtime);
       }
 
       break;
     }
 
     case Token::BIT_OR:
     case Token::BIT_XOR:
     case Token::BIT_AND:
     case Token::SAR:
@@ skipping 130 matching lines @@
   __ bind(&done);
 
   GenerateNumberStub(masm);
 }
 
 
 void BinaryOpStub::GenerateNumberStub(MacroAssembler* masm) {
   Label call_runtime, transition;
   BinaryOpStub_GenerateFPOperation(
       masm, left_type_, right_type_, false,
-      &transition, &call_runtime, &transition, op_, mode_);
+      &transition, &call_runtime, &transition, op_, mode_, r6, r4, r5, r9);
 
   __ bind(&transition);
   GenerateTypeTransition(masm);
 
   __ bind(&call_runtime);
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
     GenerateRegisterArgsPush(masm);
     GenerateCallRuntime(masm);
   }
   __ Ret();
 }
 
 
 void BinaryOpStub::GenerateGeneric(MacroAssembler* masm) {
   Label call_runtime, call_string_add_or_runtime, transition;
 
   BinaryOpStub_GenerateSmiCode(
-      masm, &call_runtime, &call_runtime, op_, ALLOW_HEAPNUMBER_RESULTS, mode_);
+      masm, &call_runtime, &call_runtime, op_, ALLOW_HEAPNUMBER_RESULTS, mode_,
+      r5, r6, r4, r9);
 
   BinaryOpStub_GenerateFPOperation(
       masm, left_type_, right_type_, false,
-      &call_string_add_or_runtime, &call_runtime, &transition, op_, mode_);
+      &call_string_add_or_runtime, &call_runtime, &transition, op_, mode_, r6,
+      r4, r5, r9);
 
   __ bind(&transition);
   GenerateTypeTransition(masm);
 
   __ bind(&call_string_add_or_runtime);
   if (op_ == Token::ADD) {
     GenerateAddStrings(masm);
   }
 
   __ bind(&call_runtime);
@@ skipping 81 matching lines @@
   // Untagged case: double input in d2, double result goes
   //   into d2.
   // Tagged case: tagged input on top of stack and in r0,
   //   tagged result (heap number) goes into r0.
 
   Label input_not_smi;
   Label loaded;
   Label calculate;
   Label invalid_cache;
   const Register scratch0 = r9;
-  const Register scratch1 = r7;
+  const Register scratch1 = r4;
   const Register cache_entry = r0;
   const bool tagged = (argument_type_ == TAGGED);
 
   if (tagged) {
     // Argument is a number and is on stack and in r0.
     // Load argument and check if it is a smi.
     __ JumpIfNotSmi(r0, &input_not_smi);
 
     // Input is a smi. Convert to double and load the low and high words
     // of the double into r2, r3.
@@ skipping 211 matching lines @@
   const Register base = r1;
   const Register exponent = r2;
   const Register heapnumbermap = r5;
   const Register heapnumber = r0;
   const DwVfpRegister double_base = d1;
   const DwVfpRegister double_exponent = d2;
   const DwVfpRegister double_result = d3;
   const DwVfpRegister double_scratch = d0;
   const SwVfpRegister single_scratch = s0;
   const Register scratch = r9;
-  const Register scratch2 = r7;
+  const Register scratch2 = r4;
 
   Label call_runtime, done, int_exponent;
   if (exponent_type_ == ON_STACK) {
     Label base_is_smi, unpack_exponent;
     // The exponent and base are supplied as arguments on the stack.
     // This can only happen if the stub is called from non-optimized code.
     // Load input parameters from stack to double registers.
     __ ldr(base, MemOperand(sp, 1 * kPointerSize));
     __ ldr(exponent, MemOperand(sp, 0 * kPointerSize));
 
@@ skipping 488 matching lines @@
   offset_to_argv += kNumDoubleCalleeSaved * kDoubleSize;
   __ ldr(r4, MemOperand(sp, offset_to_argv));
 
   // Push a frame with special values setup to mark it as an entry frame.
   // r0: code entry
   // r1: function
   // r2: receiver
   // r3: argc
   // r4: argv
   Isolate* isolate = masm->isolate();
-  __ mov(r8, Operand(-1));  // Push a bad frame pointer to fail if it is used.
   int marker = is_construct ? StackFrame::ENTRY_CONSTRUCT : StackFrame::ENTRY;
-  __ mov(r7, Operand(Smi::FromInt(marker)));
+  __ mov(r8, Operand(Smi::FromInt(marker)));
   __ mov(r6, Operand(Smi::FromInt(marker)));
   __ mov(r5,
          Operand(ExternalReference(Isolate::kCEntryFPAddress, isolate)));
   __ ldr(r5, MemOperand(r5));
-  __ Push(r8, r7, r6, r5);
+  __ mov(ip, Operand(-1));  // Push a bad frame pointer to fail if it is used.
+  __ Push(ip, r8, r6, r5);
 
   // Set up frame pointer for the frame to be pushed.
   __ add(fp, sp, Operand(-EntryFrameConstants::kCallerFPOffset));
 
   // If this is the outermost JS call, set js_entry_sp value.
   Label non_outermost_js;
   ExternalReference js_entry_sp(Isolate::kJSEntrySPAddress, isolate);
   __ mov(r5, Operand(ExternalReference(js_entry_sp)));
   __ ldr(r6, MemOperand(r5));
   __ cmp(r6, Operand::Zero());
@@ skipping 25 matching lines @@
     __ mov(ip, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
                                          isolate)));
   }
   __ str(r0, MemOperand(ip));
   __ mov(r0, Operand(reinterpret_cast<int32_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);
-  // Must preserve r0-r4, r5-r7 are available.
+  // Must preserve r0-r4, r5-r6 are available.
   __ PushTryHandler(StackHandler::JS_ENTRY, 0);
   // If an exception not caught by another handler occurs, this handler
   // returns control to the code after the bl(&invoke) above, which
   // restores all kCalleeSaved registers (including cp and fp) to their
   // saved values before returning a failure to C.
 
   // Clear any pending exceptions.
   __ mov(r5, Operand(isolate->factory()->the_hole_value()));
   __ mov(ip, Operand(ExternalReference(Isolate::kPendingExceptionAddress,
                                        isolate)));
@@ skipping 587 matching lines @@
   //   MIN_CONTEXT_SLOTS .. MIN_CONTEXT_SLOTS+parameter_count-1
   // The mapped parameter thus need to get indices
   //   MIN_CONTEXT_SLOTS+parameter_count-1 ..
   //       MIN_CONTEXT_SLOTS+parameter_count-mapped_parameter_count
   // We loop from right to left.
   Label parameters_loop, parameters_test;
   __ mov(r6, r1);
   __ ldr(r9, MemOperand(sp, 0 * kPointerSize));
   __ add(r9, r9, Operand(Smi::FromInt(Context::MIN_CONTEXT_SLOTS)));
   __ sub(r9, r9, Operand(r1));
-  __ LoadRoot(r7, Heap::kTheHoleValueRootIndex);
+  __ LoadRoot(r5, Heap::kTheHoleValueRootIndex);
   __ add(r3, r4, Operand(r6, LSL, 1));
   __ add(r3, r3, Operand(kParameterMapHeaderSize));
 
   // r6 = loop variable (tagged)
   // r1 = mapping index (tagged)
   // r3 = address of backing store (tagged)
   // r4 = address of parameter map (tagged)
-  // r5 = temporary scratch (a.o., for address calculation)
-  // r7 = the hole value
+  // r0 = temporary scratch (a.o., for address calculation)
+  // r5 = the hole value
   __ jmp(&parameters_test);
 
   __ bind(&parameters_loop);
   __ sub(r6, r6, Operand(Smi::FromInt(1)));
-  __ mov(r5, Operand(r6, LSL, 1));
-  __ add(r5, r5, Operand(kParameterMapHeaderSize - kHeapObjectTag));
-  __ str(r9, MemOperand(r4, r5));
-  __ sub(r5, r5, Operand(kParameterMapHeaderSize - FixedArray::kHeaderSize));
-  __ str(r7, MemOperand(r3, r5));
+  __ mov(r0, Operand(r6, LSL, 1));
+  __ add(r0, r0, Operand(kParameterMapHeaderSize - kHeapObjectTag));
+  __ str(r9, MemOperand(r4, r0));
+  __ sub(r0, r0, Operand(kParameterMapHeaderSize - FixedArray::kHeaderSize));
+  __ str(r5, MemOperand(r3, r0));
   __ add(r9, r9, Operand(Smi::FromInt(1)));
   __ bind(&parameters_test);
   __ cmp(r6, Operand(Smi::FromInt(0)));
   __ b(ne, &parameters_loop);
 
+  __ sub(r0, r4, Operand(Heap::kArgumentsObjectSize));
+
   __ bind(&skip_parameter_map);
+  // r0 = address of new object (tagged)
   // r2 = argument count (tagged)
   // r3 = address of backing store (tagged)
   // r5 = scratch
   // Copy arguments header and remaining slots (if there are any).
   __ LoadRoot(r5, Heap::kFixedArrayMapRootIndex);
   __ str(r5, FieldMemOperand(r3, FixedArray::kMapOffset));
   __ str(r2, FieldMemOperand(r3, FixedArray::kLengthOffset));
 
   Label arguments_loop, arguments_test;
   __ mov(r9, r1);
@@ skipping 10 matching lines @@
 
   __ bind(&arguments_test);
   __ cmp(r9, Operand(r2));
   __ b(lt, &arguments_loop);
 
   // Return and remove the on-stack parameters.
   __ add(sp, sp, Operand(3 * kPointerSize));
   __ Ret();
 
   // Do the runtime call to allocate the arguments object.
+  // r0 = address of new object (tagged)
   // r2 = argument count (tagged)
   __ bind(&runtime);
   __ str(r2, MemOperand(sp, 0 * kPointerSize));  // Patch argument count.
   __ TailCallRuntime(Runtime::kNewArgumentsFast, 3, 1);
 }
 
 
 void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
   // sp[0] : number of parameters
   // sp[4] : receiver displacement
@@ skipping 108 matching lines @@
   const int kJSRegExpOffset = 3 * kPointerSize;
 
   Label runtime;
   // Allocation of registers for this function. 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.
   Register subject = r4;
   Register regexp_data = r5;
-  Register last_match_info_elements = r6;
+  Register last_match_info_elements = no_reg;  // will be r6;
 
   // 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(r0, Operand(address_of_regexp_stack_memory_size));
   __ ldr(r0, MemOperand(r0, 0));
   __ cmp(r0, Operand::Zero());
@@ skipping 112 matching lines @@
   __ JumpIfNotSmi(r1, &runtime);
   __ ldr(r3, FieldMemOperand(r3, String::kLengthOffset));
   __ cmp(r3, Operand(r1));
   __ b(ls, &runtime);
   __ SmiUntag(r1);
 
   STATIC_ASSERT(4 == kOneByteStringTag);
   STATIC_ASSERT(kTwoByteStringTag == 0);
   __ and_(r0, r0, Operand(kStringEncodingMask));
   __ mov(r3, Operand(r0, ASR, 2), SetCC);
-  __ ldr(r7, FieldMemOperand(regexp_data, JSRegExp::kDataAsciiCodeOffset), ne);
-  __ ldr(r7, FieldMemOperand(regexp_data, JSRegExp::kDataUC16CodeOffset), eq);
+  __ ldr(r6, FieldMemOperand(regexp_data, JSRegExp::kDataAsciiCodeOffset), ne);
+  __ ldr(r6, FieldMemOperand(regexp_data, JSRegExp::kDataUC16CodeOffset), eq);
 
   // (E) Carry on.  String handling is done.
-  // r7: irregexp code
+  // r6: irregexp code
   // 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(r7, &runtime);
+  __ JumpIfSmi(r6, &runtime);
 
   // r1: previous index
   // r3: encoding of subject string (1 if ASCII, 0 if two_byte);
-  // r7: code
+  // r6: code
   // subject: Subject string
   // regexp_data: RegExp data (FixedArray)
   // All checks done. Now push arguments for native regexp code.
   __ IncrementCounter(isolate->counters()->regexp_entry_native(), 1, r0, r2);
 
   // Isolates: note we add an additional parameter here (isolate pointer).
   const int kRegExpExecuteArguments = 9;
   const int kParameterRegisters = 4;
   __ EnterExitFrame(false, kRegExpExecuteArguments - kParameterRegisters);
 
@@ skipping 46 matching lines @@
   __ SmiUntag(r8);
   __ add(r3, r9, Operand(r8, LSL, r3));
 
   // Argument 2 (r1): Previous index.
   // Already there
 
   // Argument 1 (r0): Subject string.
   __ mov(r0, subject);
 
   // Locate the code entry and call it.
-  __ add(r7, r7, Operand(Code::kHeaderSize - kHeapObjectTag));
+  __ add(r6, r6, Operand(Code::kHeaderSize - kHeapObjectTag));
   DirectCEntryStub stub;
-  stub.GenerateCall(masm, r7);
+  stub.GenerateCall(masm, r6);
 
   __ LeaveExitFrame(false, no_reg);
 
+  last_match_info_elements = r6;
+
   // r0: result
   // subject: subject string (callee saved)
   // regexp_data: RegExp data (callee saved)
   // last_match_info_elements: Last match info elements (callee saved)
   // Check the result.
   Label success;
   __ cmp(r0, Operand(1));
   // We expect exactly one result since we force the called regexp to behave
   // as non-global.
   __ b(eq, &success);
@@ skipping 68 matching lines @@
   __ str(r2, FieldMemOperand(last_match_info_elements,
                              RegExpImpl::kLastCaptureCountOffset));
   // Store last subject and last input.
   __ str(subject,
          FieldMemOperand(last_match_info_elements,
                          RegExpImpl::kLastSubjectOffset));
   __ mov(r2, subject);
   __ RecordWriteField(last_match_info_elements,
                       RegExpImpl::kLastSubjectOffset,
                       subject,
-                      r7,
+                      r3,
                       kLRHasNotBeenSaved,
                       kDontSaveFPRegs);
   __ mov(subject, r2);
   __ str(subject,
          FieldMemOperand(last_match_info_elements,
                          RegExpImpl::kLastInputOffset));
   __ RecordWriteField(last_match_info_elements,
                       RegExpImpl::kLastInputOffset,
                       subject,
-                      r7,
+                      r3,
                       kLRHasNotBeenSaved,
                       kDontSaveFPRegs);
 
   // Get the static offsets vector filled by the native regexp code.
   ExternalReference address_of_static_offsets_vector =
       ExternalReference::address_of_static_offsets_vector(isolate);
   __ mov(r2, Operand(address_of_static_offsets_vector));
 
   // r1: number of capture registers
   // r2: offsets vector
@@ skipping 545 matching lines @@
 
 
 void StringHelper::GenerateCopyCharactersLong(MacroAssembler* masm,
                                               Register dest,
                                               Register src,
                                               Register count,
                                               Register scratch1,
                                               Register scratch2,
                                               Register scratch3,
                                               Register scratch4,
-                                              Register scratch5,
                                               int flags) {
   bool ascii = (flags & COPY_ASCII) != 0;
   bool dest_always_aligned = (flags & DEST_ALWAYS_ALIGNED) != 0;
 
   if (dest_always_aligned && FLAG_debug_code) {
     // Check that destination is actually word aligned if the flag says
     // that it is.
     __ tst(dest, Operand(kPointerAlignmentMask));
     __ Check(eq, "Destination of copy not aligned.");
   }
@@ skipping 54 matching lines @@
     __ and_(src, src, Operand(~3));  // Round down to load previous word.
     __ ldr(scratch1, MemOperand(src, 4, PostIndex));
     // Store the "shift" most significant bits of scratch in the least
     // signficant bits (i.e., shift down by (32-shift)).
     __ rsb(scratch2, left_shift, Operand(32));
     Register right_shift = scratch2;
     __ mov(scratch1, Operand(scratch1, LSR, right_shift));
 
     __ bind(&loop);
     __ ldr(scratch3, MemOperand(src, 4, PostIndex));
-    __ sub(scratch5, limit, Operand(dest));
     __ orr(scratch1, scratch1, Operand(scratch3, LSL, left_shift));
     __ str(scratch1, MemOperand(dest, 4, PostIndex));
     __ mov(scratch1, Operand(scratch3, LSR, right_shift));
     // Loop if four or more bytes left to copy.
-    // Compare to eight, because we did the subtract before increasing dst.
-    __ sub(scratch5, scratch5, Operand(8), SetCC);
+    __ sub(scratch3, limit, Operand(dest));
+    __ sub(scratch3, scratch3, Operand(4), SetCC);
     __ b(ge, &loop);
   }
   // There is now between zero and three bytes left to copy (negative that
-  // number is in scratch5), and between one and three bytes already read into
+  // number is in scratch3), and between one and three bytes already read into
   // scratch1 (eight times that number in scratch4). We may have read past
   // the end of the string, but because objects are aligned, we have not read
   // past the end of the object.
   // Find the minimum of remaining characters to move and preloaded characters
   // and write those as bytes.
-  __ add(scratch5, scratch5, Operand(4), SetCC);
+  __ add(scratch3, scratch3, Operand(4), SetCC);
   __ b(eq, &done);
-  __ cmp(scratch4, Operand(scratch5, LSL, 3), ne);
+  __ cmp(scratch4, Operand(scratch3, LSL, 3), ne);
   // Move minimum of bytes read and bytes left to copy to scratch4.
-  __ mov(scratch5, Operand(scratch4, LSR, 3), LeaveCC, lt);
-  // Between one and three (value in scratch5) characters already read into
+  __ mov(scratch3, Operand(scratch4, LSR, 3), LeaveCC, lt);
+  // Between one and three (value in scratch3) characters already read into
   // scratch ready to write.
-  __ cmp(scratch5, Operand(2));
+  __ cmp(scratch3, Operand(2));
   __ strb(scratch1, MemOperand(dest, 1, PostIndex));
   __ mov(scratch1, Operand(scratch1, LSR, 8), LeaveCC, ge);
   __ strb(scratch1, MemOperand(dest, 1, PostIndex), ge);
   __ mov(scratch1, Operand(scratch1, LSR, 8), LeaveCC, gt);
   __ strb(scratch1, MemOperand(dest, 1, PostIndex), gt);
   // Copy any remaining bytes.
   __ b(&byte_loop);
 
   // Simple loop.
   // Copy words from src to dst, until less than four bytes left.
@@ skipping 319 matching lines @@
     // 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 anyways due to externalized strings.
     Label two_byte_slice, set_slice_header;
     STATIC_ASSERT((kStringEncodingMask & kOneByteStringTag) != 0);
     STATIC_ASSERT((kStringEncodingMask & kTwoByteStringTag) == 0);
     __ tst(r1, Operand(kStringEncodingMask));
     __ b(eq, &two_byte_slice);
-    __ AllocateAsciiSlicedString(r0, r2, r6, r7, &runtime);
+    __ AllocateAsciiSlicedString(r0, r2, r6, r4, &runtime);
     __ jmp(&set_slice_header);
     __ bind(&two_byte_slice);
-    __ AllocateTwoByteSlicedString(r0, r2, r6, r7, &runtime);
+    __ AllocateTwoByteSlicedString(r0, r2, r6, r4, &runtime);
     __ bind(&set_slice_header);
     __ mov(r3, Operand(r3, LSL, 1));
     __ str(r5, FieldMemOperand(r0, SlicedString::kParentOffset));
     __ str(r3, FieldMemOperand(r0, SlicedString::kOffsetOffset));
     __ jmp(&return_r0);
 
     __ bind(&copy_routine);
   }
 
   // r5: underlying subject string
@@ skipping 20 matching lines @@
   STATIC_ASSERT(SeqTwoByteString::kHeaderSize == SeqOneByteString::kHeaderSize);
   __ add(r5, r5, Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
 
   __ bind(&allocate_result);
   // Sequential acii string.  Allocate the result.
   STATIC_ASSERT((kOneByteStringTag & kStringEncodingMask) != 0);
   __ tst(r1, Operand(kStringEncodingMask));
   __ b(eq, &two_byte_sequential);
 
   // Allocate and copy the resulting ASCII string.
-  __ AllocateAsciiString(r0, r2, r4, r6, r7, &runtime);
+  __ AllocateAsciiString(r0, r2, r4, r6, r1, &runtime);
 
   // Locate first character of substring to copy.
   __ add(r5, r5, r3);
   // Locate first character of result.
   __ add(r1, r0, Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
 
   // r0: result string
   // r1: first character of result string
   // r2: result string length
   // r5: first character of substring to copy
   STATIC_ASSERT((SeqOneByteString::kHeaderSize & kObjectAlignmentMask) == 0);
-  StringHelper::GenerateCopyCharactersLong(masm, r1, r5, r2, r3, r4, r6, r7, r9,
+  StringHelper::GenerateCopyCharactersLong(masm, r1, r5, r2, r3, r4, r6, r9,
                                            COPY_ASCII | DEST_ALWAYS_ALIGNED);
   __ jmp(&return_r0);
 
   // Allocate and copy the resulting two-byte string.
   __ bind(&two_byte_sequential);
-  __ AllocateTwoByteString(r0, r2, r4, r6, r7, &runtime);
+  __ AllocateTwoByteString(r0, r2, r4, r6, r1, &runtime);
 
   // Locate first character of substring to copy.
   STATIC_ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
   __ add(r5, r5, Operand(r3, LSL, 1));
   // Locate first character of result.
   __ add(r1, r0, Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
 
   // r0: result string.
   // r1: first character of result.
   // r2: result length.
   // r5: first character of substring to copy.
   STATIC_ASSERT((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) == 0);
   StringHelper::GenerateCopyCharactersLong(
-      masm, r1, r5, r2, r3, r4, r6, r7, r9, DEST_ALWAYS_ALIGNED);
+      masm, r1, r5, r2, r3, r4, r6, r9, DEST_ALWAYS_ALIGNED);
 
   __ bind(&return_r0);
   Counters* counters = masm->isolate()->counters();
   __ IncrementCounter(counters->sub_string_native(), 1, r3, r4);
   __ Drop(3);
   __ Ret();
 
   // Just jump to runtime to create the sub string.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kSubString, 3, 1);
@@ skipping 245 matching lines @@
   __ cmp(r6, Operand(2));
   __ b(ne, &longer_than_two);
 
   // Check that both strings are non-external ASCII strings.
   if ((flags_ & STRING_ADD_CHECK_BOTH) != STRING_ADD_CHECK_BOTH) {
     __ ldr(r4, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ ldr(r5, FieldMemOperand(r1, HeapObject::kMapOffset));
     __ ldrb(r4, FieldMemOperand(r4, Map::kInstanceTypeOffset));
     __ ldrb(r5, FieldMemOperand(r5, Map::kInstanceTypeOffset));
   }
-  __ JumpIfBothInstanceTypesAreNotSequentialAscii(r4, r5, r6, r7,
+  __ JumpIfBothInstanceTypesAreNotSequentialAscii(r4, r5, r6, r3,
                                                   &call_runtime);
 
   // Get the two characters forming the sub string.
   __ ldrb(r2, FieldMemOperand(r0, SeqOneByteString::kHeaderSize));
   __ ldrb(r3, FieldMemOperand(r1, SeqOneByteString::kHeaderSize));
 
   // Try to lookup two character string in string table. If it is not found
   // just allocate a new one.
   Label make_two_character_string;
   StringHelper::GenerateTwoCharacterStringTableProbe(
-      masm, r2, r3, r6, r7, r4, r5, r9, &make_two_character_string);
+      masm, r2, r3, r6, r0, r4, r5, r9, &make_two_character_string);
   __ IncrementCounter(counters->string_add_native(), 1, r2, r3);
   __ add(sp, sp, Operand(2 * kPointerSize));
   __ Ret();
 
   __ bind(&make_two_character_string);
   // Resulting string has length 2 and first chars of two strings
   // are combined into single halfword in r2 register.
   // So we can fill resulting string without two loops by a single
   // halfword store instruction (which assumes that processor is
   // in a little endian mode)
@@ skipping 24 matching lines @@
     __ ldrb(r5, FieldMemOperand(r5, Map::kInstanceTypeOffset));
   }
   Label non_ascii, allocated, ascii_data;
   STATIC_ASSERT(kTwoByteStringTag == 0);
   __ tst(r4, Operand(kStringEncodingMask));
   __ tst(r5, Operand(kStringEncodingMask), ne);
   __ b(eq, &non_ascii);
 
   // Allocate an ASCII cons string.
   __ bind(&ascii_data);
-  __ AllocateAsciiConsString(r7, r6, r4, r5, &call_runtime);
+  __ AllocateAsciiConsString(r3, r6, r4, r5, &call_runtime);
   __ bind(&allocated);
   // Fill the fields of the cons string.
   Label skip_write_barrier, after_writing;
   ExternalReference high_promotion_mode = ExternalReference::
       new_space_high_promotion_mode_active_address(masm->isolate());
   __ mov(r4, Operand(high_promotion_mode));
   __ ldr(r4, MemOperand(r4, 0));
   __ cmp(r4, Operand::Zero());
   __ b(eq, &skip_write_barrier);
 
-  __ str(r0, FieldMemOperand(r7, ConsString::kFirstOffset));
-  __ RecordWriteField(r7,
+  __ str(r0, FieldMemOperand(r3, ConsString::kFirstOffset));
+  __ RecordWriteField(r3,
                       ConsString::kFirstOffset,
                       r0,
                       r4,
                       kLRHasNotBeenSaved,
                       kDontSaveFPRegs);
-  __ str(r1, FieldMemOperand(r7, ConsString::kSecondOffset));
-  __ RecordWriteField(r7,
+  __ str(r1, FieldMemOperand(r3, ConsString::kSecondOffset));
+  __ RecordWriteField(r3,
                       ConsString::kSecondOffset,
                       r1,
                       r4,
                       kLRHasNotBeenSaved,
                       kDontSaveFPRegs);
   __ jmp(&after_writing);
 
   __ bind(&skip_write_barrier);
-  __ str(r0, FieldMemOperand(r7, ConsString::kFirstOffset));
-  __ str(r1, FieldMemOperand(r7, ConsString::kSecondOffset));
+  __ str(r0, FieldMemOperand(r3, ConsString::kFirstOffset));
+  __ str(r1, FieldMemOperand(r3, ConsString::kSecondOffset));
 
   __ bind(&after_writing);
 
-  __ mov(r0, Operand(r7));
+  __ mov(r0, Operand(r3));
   __ IncrementCounter(counters->string_add_native(), 1, r2, r3);
   __ add(sp, sp, Operand(2 * kPointerSize));
   __ Ret();
 
   __ bind(&non_ascii);
   // At least one of the strings is two-byte. Check whether it happens
   // to contain only one byte characters.
   // r4: first instance type.
   // r5: second instance type.
   __ tst(r4, Operand(kOneByteDataHintMask));
   __ tst(r5, Operand(kOneByteDataHintMask), ne);
   __ b(ne, &ascii_data);
   __ eor(r4, r4, Operand(r5));
   STATIC_ASSERT(kOneByteStringTag != 0 && kOneByteDataHintTag != 0);
   __ and_(r4, r4, Operand(kOneByteStringTag | kOneByteDataHintTag));
   __ cmp(r4, Operand(kOneByteStringTag | kOneByteDataHintTag));
   __ b(eq, &ascii_data);
 
   // Allocate a two byte cons string.
-  __ AllocateTwoByteConsString(r7, r6, r4, r5, &call_runtime);
+  __ AllocateTwoByteConsString(r3, r6, r4, r5, &call_runtime);
   __ jmp(&allocated);
 
   // We cannot encounter sliced strings or cons strings here since:
   STATIC_ASSERT(SlicedString::kMinLength >= ConsString::kMinLength);
   // Handle creating a flat result from either external or sequential strings.
   // Locate the first characters' locations.
   // r0: first string
   // r1: second string
   // r2: length of first string
   // r3: length of second string
   // r4: first string instance type (if flags_ == NO_STRING_ADD_FLAGS)
   // r5: second string instance type (if flags_ == NO_STRING_ADD_FLAGS)
   // r6: sum of lengths.
   Label first_prepared, second_prepared;
   __ bind(&string_add_flat_result);
   if ((flags_ & STRING_ADD_CHECK_BOTH) != STRING_ADD_CHECK_BOTH) {
     __ ldr(r4, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ ldr(r5, FieldMemOperand(r1, HeapObject::kMapOffset));
     __ ldrb(r4, FieldMemOperand(r4, Map::kInstanceTypeOffset));
     __ ldrb(r5, FieldMemOperand(r5, Map::kInstanceTypeOffset));
   }
 
   // Check whether both strings have same encoding
-  __ eor(r7, r4, Operand(r5));
-  __ tst(r7, Operand(kStringEncodingMask));
+  __ eor(ip, r4, Operand(r5));
+  __ tst(ip, Operand(kStringEncodingMask));

[Rodolph Perfetta, 2013/07/30 15:19:08]

if you want to use ip you need  to make sure kStringEncodingMask fits in an
inline arm constant: 8 bits shifted by a even number.

[rmcilroy, 2013/07/30 17:12:37]

Done.

   __ b(ne, &call_runtime);
 
   STATIC_ASSERT(kSeqStringTag == 0);
   __ tst(r4, Operand(kStringRepresentationMask));
   STATIC_ASSERT(SeqOneByteString::kHeaderSize == SeqTwoByteString::kHeaderSize);
-  __ add(r7,
+  __ add(r6,
          r0,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag),
          LeaveCC,
          eq);
   __ b(eq, &first_prepared);
   // External string: rule out short external string and load string resource.
   STATIC_ASSERT(kShortExternalStringTag != 0);
   __ tst(r4, Operand(kShortExternalStringMask));
   __ b(ne, &call_runtime);
-  __ ldr(r7, FieldMemOperand(r0, ExternalString::kResourceDataOffset));
+  __ ldr(r6, FieldMemOperand(r0, ExternalString::kResourceDataOffset));
   __ bind(&first_prepared);
 
   STATIC_ASSERT(kSeqStringTag == 0);
   __ tst(r5, Operand(kStringRepresentationMask));
   STATIC_ASSERT(SeqOneByteString::kHeaderSize == SeqTwoByteString::kHeaderSize);
   __ add(r1,
          r1,
          Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag),
          LeaveCC,
          eq);
   __ b(eq, &second_prepared);
   // External string: rule out short external string and load string resource.
   STATIC_ASSERT(kShortExternalStringTag != 0);
   __ tst(r5, Operand(kShortExternalStringMask));
   __ b(ne, &call_runtime);
   __ ldr(r1, FieldMemOperand(r1, ExternalString::kResourceDataOffset));
   __ bind(&second_prepared);
 
   Label non_ascii_string_add_flat_result;
-  // r7: first character of first string
+  // r6: first character of first string
   // r1: first character of second string
   // r2: length of first string.
   // r3: length of second string.
-  // r6: sum of lengths.
   // Both strings have the same encoding.
   STATIC_ASSERT(kTwoByteStringTag == 0);
   __ tst(r5, Operand(kStringEncodingMask));
   __ b(eq, &non_ascii_string_add_flat_result);
 
-  __ AllocateAsciiString(r0, r6, r4, r5, r9, &call_runtime);
-  __ add(r6, r0, Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
+  __ add(r2, r2, Operand(r3));
+  __ AllocateAsciiString(r0, r2, r4, r5, r9, &call_runtime);
+  __ sub(r2, r2, Operand(r3));
+  __ add(r5, r0, Operand(SeqOneByteString::kHeaderSize - kHeapObjectTag));
   // r0: result string.
-  // r7: first character of first string.
+  // r6: first character of first string.
   // r1: first character of second string.
   // r2: length of first string.
   // r3: length of second string.
-  // r6: first character of result.
-  StringHelper::GenerateCopyCharacters(masm, r6, r7, r2, r4, true);
-  // r6: next character of result.
-  StringHelper::GenerateCopyCharacters(masm, r6, r1, r3, r4, true);
+  // r5: first character of result.
+  StringHelper::GenerateCopyCharacters(masm, r5, r6, r2, r4, true);
+  // r5: next character of result.
+  StringHelper::GenerateCopyCharacters(masm, r5, r1, r3, r4, true);
   __ IncrementCounter(counters->string_add_native(), 1, r2, r3);
   __ add(sp, sp, Operand(2 * kPointerSize));
   __ Ret();
 
   __ bind(&non_ascii_string_add_flat_result);
-  __ AllocateTwoByteString(r0, r6, r4, r5, r9, &call_runtime);
-  __ add(r6, r0, Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
+  __ add(r2, r2, Operand(r3));
+  __ AllocateTwoByteString(r0, r2, r4, r5, r9, &call_runtime);
+  __ sub(r2, r2, Operand(r3));
+  __ add(r5, r0, Operand(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
   // r0: result string.
-  // r7: first character of first string.
+  // r6: first character of first string.
   // r1: first character of second string.
   // r2: length of first string.
   // r3: length of second string.
-  // r6: first character of result.
-  StringHelper::GenerateCopyCharacters(masm, r6, r7, r2, r4, false);
-  // r6: next character of result.
-  StringHelper::GenerateCopyCharacters(masm, r6, r1, r3, r4, false);
+  // r5: first character of result.
+  StringHelper::GenerateCopyCharacters(masm, r5, r6, r2, r4, false);
+  // r5: next character of result.
+  StringHelper::GenerateCopyCharacters(masm, r5, r1, r3, r4, false);
   __ IncrementCounter(counters->string_add_native(), 1, r2, r3);
   __ add(sp, sp, Operand(2 * kPointerSize));
   __ Ret();
 
   // Just jump to runtime to add the two strings.
   __ bind(&call_runtime);
   if ((flags_ & STRING_ADD_ERECT_FRAME) != 0) {
     GenerateRegisterArgsPop(masm);
     // Build a frame
     {
@@ skipping 680 matching lines @@
 struct AheadOfTimeWriteBarrierStubList {
   Register object, value, address;
   RememberedSetAction action;
 };
 
 
 #define REG(Name) { kRegister_ ## Name ## _Code }
 
 static const AheadOfTimeWriteBarrierStubList kAheadOfTime[] = {
   // Used in RegExpExecStub.
-  { REG(r6), REG(r4), REG(r7), EMIT_REMEMBERED_SET },
+  { REG(r6), REG(r4), REG(r3), EMIT_REMEMBERED_SET },
   // Used in CompileArrayPushCall.
   // Also used in StoreIC::GenerateNormal via GenerateDictionaryStore.
   // Also used in KeyedStoreIC::GenerateGeneric.
   { REG(r3), REG(r4), REG(r5), EMIT_REMEMBERED_SET },
   // Used in CompileStoreGlobal.
   { REG(r4), REG(r1), REG(r2), OMIT_REMEMBERED_SET },
   // Used in StoreStubCompiler::CompileStoreField via GenerateStoreField.
   { REG(r1), REG(r2), REG(r3), EMIT_REMEMBERED_SET },
   { REG(r3), REG(r2), REG(r1), EMIT_REMEMBERED_SET },
   // Used in KeyedStoreStubCompiler::CompileStoreField via GenerateStoreField.
   { REG(r2), REG(r1), REG(r3), EMIT_REMEMBERED_SET },
   { REG(r3), REG(r1), REG(r2), EMIT_REMEMBERED_SET },
   // KeyedStoreStubCompiler::GenerateStoreFastElement.
   { REG(r3), REG(r2), REG(r4), EMIT_REMEMBERED_SET },
   { REG(r2), REG(r3), REG(r4), EMIT_REMEMBERED_SET },
   // ElementsTransitionGenerator::GenerateMapChangeElementTransition
   // and ElementsTransitionGenerator::GenerateSmiToDouble
   // and ElementsTransitionGenerator::GenerateDoubleToObject
   { REG(r2), REG(r3), REG(r9), EMIT_REMEMBERED_SET },
   { REG(r2), REG(r3), REG(r9), OMIT_REMEMBERED_SET },
   // ElementsTransitionGenerator::GenerateDoubleToObject
   { REG(r6), REG(r2), REG(r0), EMIT_REMEMBERED_SET },
   { REG(r2), REG(r6), REG(r9), EMIT_REMEMBERED_SET },
   // StoreArrayLiteralElementStub::Generate
   { REG(r5), REG(r0), REG(r6), EMIT_REMEMBERED_SET },
   // FastNewClosureStub::Generate
   { REG(r2), REG(r4), REG(r1), EMIT_REMEMBERED_SET },
   // StringAddStub::Generate
-  { REG(r7), REG(r1), REG(r4), EMIT_REMEMBERED_SET },
-  { REG(r7), REG(r0), REG(r4), EMIT_REMEMBERED_SET },
+  { REG(r3), REG(r1), REG(r4), EMIT_REMEMBERED_SET },
+  { REG(r3), REG(r0), REG(r4), EMIT_REMEMBERED_SET },
   // Null termination.
   { REG(no_reg), REG(no_reg), REG(no_reg), EMIT_REMEMBERED_SET}
 };
 
 #undef REG
 
 
 bool RecordWriteStub::IsPregenerated() {
   for (const AheadOfTimeWriteBarrierStubList* entry = kAheadOfTime;
        !entry->object.is(no_reg);
@@ skipping 668 matching lines @@
   __ bind(&fast_elements_case);
   GenerateCase(masm, FAST_ELEMENTS);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM