[Arguments] Port fast arguments creation stubs to X64 and ARM.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index f64e338cb35841108701d0c7c51abad456a886f4..5f97f656bf7c91e92afe8050a0a5d46fdbaf15ff 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -1959,133 +1959,378 @@ void ArgumentsAccessStub::GenerateReadElement(MacroAssembler* masm) {
 }
 
 
-void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
-  UNIMPLEMENTED();
-}
+void ArgumentsAccessStub::GenerateNewNonStrictFast(MacroAssembler* masm) {
+  // rsp[0] : return address
+  // rsp[8] : number of parameters (tagged)
+  // rsp[16] : receiver displacement
+  // rsp[24] : function
 
+  Factory* factory = masm->isolate()->factory();
 
-void ArgumentsAccessStub::GenerateNewNonStrictFast(MacroAssembler* masm) {
-  UNIMPLEMENTED();
+  // rbx = parameter count (untagged)

[Lasse Reichstein, 2011/06/07 12:20:19]

I would move this comment to after the code that ensures the condition holds.

[Karl Klose, 2011/06/10 11:32:22]

Done.

+  __ movq(rbx, Operand(rsp, 1 * kPointerSize));
+  __ SmiToInteger64(rbx, rbx);

[Lasse Reichstein, 2011/06/07 12:20:19]

There is a SmiToInteger64(Register,Operand) macro that can do this in one
operation.

[Karl Klose, 2011/06/10 11:32:22]

Done.

+
+  // Check if the calling frame is an arguments adaptor frame.
+  Label runtime;
+  Label adaptor_frame, try_allocate;
+  __ movq(rdx, Operand(rbp, StandardFrameConstants::kCallerFPOffset));
+  __ movq(rcx, Operand(rdx, StandardFrameConstants::kContextOffset));
+  __ Cmp(rcx, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+  __ j(equal, &adaptor_frame);
+
+  // No adaptor, parameter count = argument count.
+  __ movq(rcx, rbx);
+  __ jmp(&try_allocate, Label::kNear);
+
+  // We have an adaptor frame. Patch the parameters pointer.
+  __ bind(&adaptor_frame);
+  __ movq(rcx, Operand(rdx, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ SmiToInteger64(rcx, rcx);

[Lasse Reichstein, 2011/06/07 12:20:19]

Ditto here.

+  __ lea(rdx, Operand(rdx, rcx, times_pointer_size,
+                      StandardFrameConstants::kCallerSPOffset));
+  __ movq(Operand(rsp, 2 * kPointerSize), rdx);
+
+  // rbx = parameter count (untagged)
+  // rcx = argument count (untagged)
+  // rsp[8] = parameter count (tagged)
+  // rsp[16] = address of receiver argument
+  // Compute the mapped parameter count = min(rbx, rcx) in rbx.
+  __ cmpq(rbx, rcx);
+  __ j(less_equal, &try_allocate, Label::kNear);
+  __ movq(rbx, rcx);
+
+  __ bind(&try_allocate);
+
+  // Save mapped parameter count.
+  __ push(rbx);
+
+  // Compute the sizes of backing store, parameter map, and arguments object.
+  // 1. Parameter map, has 2 extra words containing context and backing store.
+  const int kParameterMapHeaderSize =
+      FixedArray::kHeaderSize + 2 * kPointerSize;
+  Label no_parameter_map;
+  __ testq(rbx, rbx);

[Lasse Reichstein, 2011/06/07 12:20:19]

You could get away with using just testl, since rbx is known to be a
sign-extended 32-bit number.
However, that would require a comment that's probably more bother than the extra
byte of code.

[Karl Klose, 2011/06/10 11:32:22]

I will keep the current code.

+  __ j(zero, &no_parameter_map, Label::kNear);
+  __ lea(rbx, Operand(rbx, times_pointer_size, kParameterMapHeaderSize));
+  __ bind(&no_parameter_map);
+
+  // 2. Backing store.
+  __ lea(rbx, Operand(rbx, rcx, times_pointer_size, FixedArray::kHeaderSize));
+
+  // 3. Arguments object.
+  __ addq(rbx, Immediate(Heap::kArgumentsObjectSize));
+
+  // Do the allocation of all three objects in one go.
+  __ AllocateInNewSpace(rbx, rax, rdx, rdi, &runtime, TAG_OBJECT);
+
+  // rax = address of new object(s) (tagged)
+  // rcx = argument count (untagged)
+  // rsp[0] = mapped parameter count (tagged)
+  // rsp[16] = parameter count (tagged)
+  // rsp[24] = address of receiver argument
+  // Get the arguments boilerplate from the current (global) context into rdi.
+  Label has_mapped_parameters, copy;
+  __ movq(rdi, Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
+  __ movq(rdi, FieldOperand(rdi, GlobalObject::kGlobalContextOffset));
+  __ movq(rbx, Operand(rsp, 0 * kPointerSize));
+  __ SmiToInteger64(rbx, rbx);

[Lasse Reichstein, 2011/06/07 12:20:19]

And another 64-bit load.

[Karl Klose, 2011/06/10 11:32:22]

Done.

+  __ testq(rbx, rbx);
+  __ j(not_zero, &has_mapped_parameters, Label::kNear);
+
+  const int kIndex = Context::ARGUMENTS_BOILERPLATE_INDEX;
+  __ movq(rdi, Operand(rdi, Context::SlotOffset(kIndex)));
+  __ jmp(&copy, Label::kNear);
+
+  const int kAliasedIndex = Context::ALIASED_ARGUMENTS_BOILERPLATE_INDEX;
+  __ bind(&has_mapped_parameters);
+  __ movq(rdi, Operand(rdi, Context::SlotOffset(kAliasedIndex)));
+  __ bind(&copy);
+
+  // rax = address of new object (tagged)
+  // rbx = mapped parameter count (untagged)
+  // rcx = argument count (untagged)
+  // rdi = address of boilerplate object (tagged)
+  // rsp[0] = mapped parameter count (tagged)
+  // rsp[16] = parameter count (tagged)
+  // rsp[24] = address of receiver argument
+  // Copy the JS object part.
+  for (int i = 0; i < JSObject::kHeaderSize; i += kPointerSize) {
+    __ movq(rdx, FieldOperand(rdi, i));
+    __ movq(FieldOperand(rax, i), rdx);
+  }
+
+  // Setup the callee in-object property.
+  STATIC_ASSERT(Heap::kArgumentsCalleeIndex == 1);
+  __ movq(rdx, Operand(rsp, 4 * kPointerSize));
+  __ movq(FieldOperand(rax, JSObject::kHeaderSize +
+                       Heap::kArgumentsCalleeIndex * kPointerSize),
+          rdx);
+
+  // Use the length (smi tagged) and set that as an in-object property too.
+  // Note: rcx is tagged from here on.
+  STATIC_ASSERT(Heap::kArgumentsLengthIndex == 0);
+  __ Integer64PlusConstantToSmi(rcx, rcx, 0);

[Lasse Reichstein, 2011/06/07 12:20:19]

Just use Integer32ToSmi when the costant is zero. The macro will truncate the
value to a signed 32-bit value after addition anyway.
It probably should check for the constant being zero.
It really is a stupid macro which doesn't provide any good optimizations with
the current smi implementation.

[Karl Klose, 2011/06/10 11:32:22]

Done.

+  __ movq(FieldOperand(rax, JSObject::kHeaderSize +
+                       Heap::kArgumentsLengthIndex * kPointerSize),
+          rcx);
+
+  // Setup the elements pointer in the allocated arguments object.
+  // If we allocated a parameter map, edi will point there, otherwise to the
+  // backing store.
+  __ lea(rdi, Operand(rax, Heap::kArgumentsObjectSize));
+  __ movq(FieldOperand(rax, JSObject::kElementsOffset), rdi);
+
+  // rax = address of new object (tagged)
+  // rbx = mapped parameter count (untagged)
+  // rcx = argument count (tagged)
+  // rdi = address of parameter map or backing store (tagged)
+  // rsp[0] = mapped parameter count (tagged)
+  // rsp[16] = parameter count (tagged)
+  // rsp[24] = address of receiver argument
+  // Free a register.
+  __ push(rax);
+
+  // Initialize parameter map. If there are no mapped arguments, we're done.
+  Label skip_parameter_map;
+  __ testq(rbx, rbx);
+  __ j(zero, &skip_parameter_map);
+
+  __ LoadRoot(kScratchRegister, Heap::kNonStrictArgumentsElementsMapRootIndex);
+  // rbx contains the untagged argument count. Add 2 and tag to write.
+  __ movq(FieldOperand(rdi, FixedArray::kMapOffset), kScratchRegister);
+  __ Integer64PlusConstantToSmi(rax, rbx, 2);
+  __ movq(FieldOperand(rdi, FixedArray::kLengthOffset), rax);
+  __ movq(FieldOperand(rdi, FixedArray::kHeaderSize + 0 * kPointerSize), rsi);
+  __ lea(rax, Operand(rdi, rbx, times_pointer_size, kParameterMapHeaderSize));
+  __ movq(FieldOperand(rdi, FixedArray::kHeaderSize + 1 * kPointerSize), rax);
+
+  // Copy the parameter slots and the holes in the arguments.
+  // We need to fill in mapped_parameter_count slots. They index the context,
+  // where parameters are stored in reverse order, at
+  //   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;
+  __ push(rcx);
+  // Load tagged parameter count into rax.
+  __ movq(rax, Operand(rsp, 2 * kPointerSize));
+  __ Move(rbx, Smi::FromInt(Context::MIN_CONTEXT_SLOTS));
+  __ addq(rbx, Operand(rsp, 4 * kPointerSize));
+  __ subq(rbx, rax);
+  __ Move(rcx, factory->the_hole_value());
+  __ movq(rdx, rdi);
+  __ SmiToInteger64(kScratchRegister, rax);
+  __ lea(rdi, Operand(rdi, kScratchRegister,
+                      times_pointer_size,
+                      kParameterMapHeaderSize));
+  // rax = loop variable (tagged)
+  // rbx = mapping index (tagged)
+  // rcx = the hole value
+  // rdx = address of parameter map (tagged)
+  // rdi = address of backing store (tagged)
+  // rsp[0] = argument count (tagged)
+  // rsp[8] = address of new object (tagged)
+  // rsp[16] = mapped parameter count (tagged)
+  // rsp[32] = parameter count (tagged)
+  // rsp[40] = address of receiver argument
+  __ jmp(&parameters_test, Label::kNear);
+
+  __ bind(&parameters_loop);
+  __ SmiSubConstant(rax, rax, Smi::FromInt(1));
+  __ SmiToInteger64(kScratchRegister, rax);
+  __ movq(FieldOperand(rdx, kScratchRegister,
+                       times_pointer_size,
+                       kParameterMapHeaderSize),
+          rbx);
+  __ movq(FieldOperand(rdi, kScratchRegister,
+                       times_pointer_size,
+                       FixedArray::kHeaderSize),
+          rcx);
+  __ SmiAddConstant(rbx, rbx, Smi::FromInt(1));
+  __ bind(&parameters_test);
+  __ testq(rax, rax);

[Lasse Reichstein, 2011/06/07 12:20:19]

If rax is a smi, use SmiTest(rax); for readability.
It'll do the same thing :)

[Karl Klose, 2011/06/10 11:32:22]

Done.

+  __ j(not_zero, &parameters_loop, Label::kNear);
+  __ pop(rcx);
+
+  __ bind(&skip_parameter_map);
+
+  // rcx = argument count (tagged)
+  // rdi = address of backing store (tagged)
+  // rsp[0] = address of new object (tagged)
+  // rsp[8] = mapped parameter count (tagged)
+  // rsp[24] = parameter count (tagged)
+  // rsp[32] = address of receiver argument
+  // Copy arguments header and remaining slots (if there are any).
+  __ Move(FieldOperand(rdi, FixedArray::kMapOffset),
+          factory->fixed_array_map());
+  __ movq(FieldOperand(rdi, FixedArray::kLengthOffset), rcx);
+
+  Label arguments_loop, arguments_test;
+  __ movq(rbx, Operand(rsp, 1 * kPointerSize));
+  __ movq(rdx, Operand(rsp, 4 * kPointerSize));
+  // Untag rcx and rbx for the loop below.
+  __ SmiToInteger64(rcx, rcx);
+  __ SmiToInteger64(rbx, rbx);
+  __ lea(kScratchRegister, Operand(rbx, times_pointer_size, 0));
+  __ subq(rdx, kScratchRegister);
+  __ jmp(&arguments_test, Label::kNear);
+
+  __ bind(&arguments_loop);
+  __ subq(rdx, Immediate(kPointerSize));
+  __ movq(rax, Operand(rdx, 0));
+  __ movq(FieldOperand(rdi, rbx,
+                       times_pointer_size,
+                       FixedArray::kHeaderSize),
+          rax);
+  __ addq(rbx, Immediate(1));
+
+  __ bind(&arguments_test);
+  __ cmpq(rbx, rcx);
+  __ j(less, &arguments_loop, Label::kNear);
+
+  // Restore.
+  __ pop(rax);  // Address of arguments object.
+  __ pop(rbx);  // Parameter count.
+
+  // Return and remove the on-stack parameters.
+  __ ret(3 * kPointerSize);
+
+  // Do the runtime call to allocate the arguments object.
+  // rcx = argument count (untagged)
+  __ bind(&runtime);
+  __ pop(rax);  // Remove saved parameter count.
+  __ Integer64PlusConstantToSmi(rcx, rcx, 0);

[Lasse Reichstein, 2011/06/07 12:20:19]

Integer32ToSmi.

[Karl Klose, 2011/06/10 11:32:22]

Done.

+  __ movq(Operand(rsp, 1 * kPointerSize), rcx);  // Patch argument count.
+  __ TailCallRuntime(Runtime::kNewStrictArgumentsFast, 3, 1);
 }
 
 
 void ArgumentsAccessStub::GenerateNewNonStrictSlow(MacroAssembler* masm) {
+  // esp[0] : return address
+  // esp[8] : number of parameters
+  // esp[16] : receiver displacement
+  // esp[24] : function
+
+  // Check if the calling frame is an arguments adaptor frame.
+  Label runtime;
+  __ movq(rdx, Operand(rbp, StandardFrameConstants::kCallerFPOffset));
+  __ movq(rcx, Operand(rdx, StandardFrameConstants::kContextOffset));
+  __ Cmp(rcx, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+  __ j(not_equal, &runtime);
+
+  // Patch the arguments.length and the parameters pointer.
+  __ movq(rcx, Operand(rdx, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ movq(Operand(rsp, 1 * kPointerSize), rcx);
+  __ SmiToInteger64(rcx, rcx);
+  __ lea(rdx, Operand(rdx, rcx, times_pointer_size,
+              StandardFrameConstants::kCallerSPOffset));
+  __ movq(Operand(rsp, 2 * kPointerSize), rdx);
+
+  __ bind(&runtime);
+  __ TailCallRuntime(Runtime::kNewArgumentsFast, 3, 1);
+}
+
+
+void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
   // rsp[0] : return address
   // rsp[8] : number of parameters
   // rsp[16] : receiver displacement
   // rsp[24] : function
 
-  // The displacement is used for skipping the return address and the
-  // frame pointer on the stack. It is the offset of the last
-  // parameter (if any) relative to the frame pointer.
-  static const int kDisplacement = 2 * kPointerSize;
-
   // Check if the calling frame is an arguments adaptor frame.
   Label adaptor_frame, try_allocate, runtime;
   __ movq(rdx, Operand(rbp, StandardFrameConstants::kCallerFPOffset));
-  __ Cmp(Operand(rdx, StandardFrameConstants::kContextOffset),
-         Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+  __ movq(rcx, Operand(rdx, StandardFrameConstants::kContextOffset));
+  __ Cmp(rcx, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
   __ j(equal, &adaptor_frame);
 
   // Get the length from the frame.
-  __ SmiToInteger32(rcx, Operand(rsp, 1 * kPointerSize));
+  __ movq(rcx, Operand(rsp, 1 * kPointerSize));
+  __ SmiToInteger64(rcx, rcx);
   __ jmp(&try_allocate);
 
   // Patch the arguments.length and the parameters pointer.
   __ bind(&adaptor_frame);
-  __ SmiToInteger32(rcx,
-                    Operand(rdx,
-                            ArgumentsAdaptorFrameConstants::kLengthOffset));
-  // Space on stack must already hold a smi.
-  __ Integer32ToSmiField(Operand(rsp, 1 * kPointerSize), rcx);
-  // Do not clobber the length index for the indexing operation since
-  // it is used compute the size for allocation later.
-  __ lea(rdx, Operand(rdx, rcx, times_pointer_size, kDisplacement));
+  __ movq(rcx, Operand(rdx, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ movq(Operand(rsp, 1 * kPointerSize), rcx);
+  __ SmiToInteger64(rcx, rcx);
+  __ lea(rdx, Operand(rdx, rcx, times_pointer_size,
+                      StandardFrameConstants::kCallerSPOffset));
   __ movq(Operand(rsp, 2 * kPointerSize), rdx);
 
   // Try the new space allocation. Start out with computing the size of
   // the arguments object and the elements array.
   Label add_arguments_object;
   __ bind(&try_allocate);
-  if (type_ == NEW_NON_STRICT_SLOW || type_ == NEW_NON_STRICT_FAST) {
-    __ TailCallRuntime(Runtime::kNewArgumentsFast, 3, 1);
-  } else {
-    __ testl(rcx, rcx);
-    __ j(zero, &add_arguments_object);
-    __ leal(rcx, Operand(rcx, times_pointer_size, FixedArray::kHeaderSize));
-    __ bind(&add_arguments_object);
-    __ addl(rcx, Immediate(Heap::kArgumentsObjectSize));
-
-    // Do the allocation of both objects in one go.
-    __ AllocateInNewSpace(rcx, rax, rdx, rbx, &runtime, TAG_OBJECT);
-
-    // Get the arguments boilerplate from the current (global) context.
-    __ movq(rdi, Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
-    __ movq(rdi, FieldOperand(rdi, GlobalObject::kGlobalContextOffset));
-    __ movq(rdi, Operand(rdi, Context::SlotOffset(
-        Context::STRICT_MODE_ARGUMENTS_BOILERPLATE_INDEX)));
-
-    // Copy the JS object part.
-    STATIC_ASSERT(JSObject::kHeaderSize == 3 * kPointerSize);
-    __ movq(kScratchRegister, FieldOperand(rdi, 0 * kPointerSize));
-    __ movq(rdx, FieldOperand(rdi, 1 * kPointerSize));
-    __ movq(rbx, FieldOperand(rdi, 2 * kPointerSize));
-    __ movq(FieldOperand(rax, 0 * kPointerSize), kScratchRegister);
-    __ movq(FieldOperand(rax, 1 * kPointerSize), rdx);
-    __ movq(FieldOperand(rax, 2 * kPointerSize), rbx);
-
-    if (type_ == NEW_NON_STRICT_SLOW || type_ == NEW_NON_STRICT_FAST) {
-      // Setup the callee in-object property.
-      ASSERT(Heap::kArgumentsCalleeIndex == 1);
-      __ movq(kScratchRegister, Operand(rsp, 3 * kPointerSize));
-      __ movq(FieldOperand(rax, JSObject::kHeaderSize +
-                           Heap::kArgumentsCalleeIndex * kPointerSize),
-              kScratchRegister);
-    }
+  __ testq(rcx, rcx);
+  __ j(zero, &add_arguments_object, Label::kNear);
+  __ lea(rcx, Operand(rcx, times_pointer_size, FixedArray::kHeaderSize));
+  __ bind(&add_arguments_object);
+  __ addq(rcx, Immediate(Heap::kArgumentsObjectSizeStrict));
+
+  // Do the allocation of both objects in one go.
+  __ AllocateInNewSpace(rcx, rax, rdx, rbx, &runtime, TAG_OBJECT);
+
+  // Get the arguments boilerplate from the current (global) context.
+  __ movq(rdi, Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
+  __ movq(rdi, FieldOperand(rdi, GlobalObject::kGlobalContextOffset));
+  const int offset =
+      Context::SlotOffset(Context::STRICT_MODE_ARGUMENTS_BOILERPLATE_INDEX);
+  __ movq(rdi, Operand(rdi, offset));
+
+  // Copy the JS object part.
+  for (int i = 0; i < JSObject::kHeaderSize; i += kPointerSize) {
+    __ movq(rbx, FieldOperand(rdi, i));
+    __ movq(FieldOperand(rax, i), rbx);
+  }
 
-    // Get the length (smi tagged) and set that as an in-object property too.
-    ASSERT(Heap::kArgumentsLengthIndex == 0);
-    __ movq(rcx, Operand(rsp, 1 * kPointerSize));
-    __ movq(FieldOperand(rax, JSObject::kHeaderSize +
-                         Heap::kArgumentsLengthIndex * kPointerSize),
-            rcx);
+  // Get the length (smi tagged) and set that as an in-object property too.
+  STATIC_ASSERT(Heap::kArgumentsLengthIndex == 0);
+  __ movq(rcx, Operand(rsp, 1 * kPointerSize));
+  __ movq(FieldOperand(rax, JSObject::kHeaderSize +
+                       Heap::kArgumentsLengthIndex * kPointerSize),
+          rcx);
 
-    // If there are no actual arguments, we're done.
-    Label done;
-    __ SmiTest(rcx);
-    __ j(zero, &done);
-
-    // Get the parameters pointer from the stack and untag the length.
-    __ movq(rdx, Operand(rsp, 2 * kPointerSize));
-
-    // Setup the elements pointer in the allocated arguments object and
-    // initialize the header in the elements fixed array.
-    __ lea(rdi, Operand(rax, Heap::kArgumentsObjectSize));
-    __ movq(FieldOperand(rax, JSObject::kElementsOffset), rdi);
-    __ LoadRoot(kScratchRegister, Heap::kFixedArrayMapRootIndex);
-    __ movq(FieldOperand(rdi, FixedArray::kMapOffset), kScratchRegister);
-    __ movq(FieldOperand(rdi, FixedArray::kLengthOffset), rcx);
-    __ SmiToInteger32(rcx, rcx);  // Untag length for the loop below.
-
-    // Copy the fixed array slots.
-    Label loop;
-    __ bind(&loop);
-    // -1 ~ skip the receiver.
-    __ movq(kScratchRegister, Operand(rdx, -1 * kPointerSize));
-    __ movq(FieldOperand(rdi, FixedArray::kHeaderSize), kScratchRegister);
-    __ addq(rdi, Immediate(kPointerSize));
-    __ subq(rdx, Immediate(kPointerSize));
-    __ decl(rcx);
-    __ j(not_zero, &loop);
-
-    // Return and remove the on-stack parameters.
-    __ bind(&done);
-    __ ret(3 * kPointerSize);
+  // If there are no actual arguments, we're done.
+  Label done;
+  __ testq(rcx, rcx);
+  __ j(zero, &done);
 
-    // Do the runtime call to allocate the arguments object.
-    __ bind(&runtime);
-    __ TailCallRuntime(Runtime::kNewStrictArgumentsFast, 3, 1);
-  }
+  // Get the parameters pointer from the stack.
+  __ movq(rdx, Operand(rsp, 2 * kPointerSize));
+
+  // Setup the elements pointer in the allocated arguments object and
+  // initialize the header in the elements fixed array.
+  __ lea(rdi, Operand(rax, Heap::kArgumentsObjectSizeStrict));
+  __ movq(FieldOperand(rax, JSObject::kElementsOffset), rdi);
+  __ LoadRoot(kScratchRegister, Heap::kFixedArrayMapRootIndex);
+  __ movq(FieldOperand(rdi, FixedArray::kMapOffset), kScratchRegister);
+
+
+  __ movq(FieldOperand(rdi, FixedArray::kLengthOffset), rcx);
+  // Untag the length for the loop below.
+  __ SmiToInteger64(rcx, rcx);

[Lasse Reichstein, 2011/06/07 12:20:19]

It seems rcx could be just a 32-bit value here. It's only used as a counter, not
as a part of an address calculation.

+
+  // Copy the fixed array slots.
+  Label loop;
+  __ bind(&loop);
+  __ movq(rbx, Operand(rdx, -1 * kPointerSize));  // Skip receiver.
+  __ movq(FieldOperand(rdi, FixedArray::kHeaderSize), rbx);
+  __ addq(rdi, Immediate(kPointerSize));
+  __ subq(rdx, Immediate(kPointerSize));
+  __ decq(rcx);
+  __ j(not_zero, &loop);
+
+  // Return and remove the on-stack parameters.
+  __ bind(&done);
+  __ ret(3 * kPointerSize);
+
+  // Do the runtime call to allocate the arguments object.
+  __ bind(&runtime);
+  __ TailCallRuntime(Runtime::kNewStrictArgumentsFast, 3, 1);
 }