Implement code stub for object literal creation.

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 a30d62f96551e8d16edf21a3e3f8f8afdaa9c8c5..b8f820d7f5581e9727731f61fa8481a751258aa0 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -354,6 +354,49 @@ void FastCloneShallowArrayStub::Generate(MacroAssembler* masm) {
 }
 
 
+void FastCloneShallowObjectStub::Generate(MacroAssembler* masm) {
+  // Stack layout on entry:
+  //
+  // [rsp + kPointerSize]: object literal flags.
+  // [rsp + (2 * kPointerSize)]: constant properties.
+  // [rsp + (3 * kPointerSize)]: literal index.
+  // [rsp + (4 * kPointerSize)]: literals array.
+
+  // Load boilerplate object into ecx and check if we need to create a
+  // boilerplate.
+  Label slow_case;
+  __ movq(rcx, Operand(rsp, 4 * kPointerSize));
+  __ movq(rax, Operand(rsp, 3 * kPointerSize));
+  SmiIndex index = masm->SmiToIndex(rax, rax, kPointerSizeLog2);
+  __ movq(rcx,
+          FieldOperand(rcx, index.reg, index.scale, FixedArray::kHeaderSize));
+  __ CompareRoot(rcx, Heap::kUndefinedValueRootIndex);
+  __ j(equal, &slow_case);
+
+  // Check that the boilerplate contains only fast properties and we can
+  // statically determine the instance size.
+  int size = JSObject::kHeaderSize + length_ * kPointerSize;
+  __ movq(rax, FieldOperand(rcx, HeapObject::kMapOffset));
+  __ movzxbq(rax, FieldOperand(rax, Map::kInstanceSizeOffset));
+  __ cmpq(rax, Immediate(size >> kPointerSizeLog2));
+  __ j(not_equal, &slow_case);
+
+  // Allocate the JS object and copy header together with all in-object
+  // properties from the boilerplate.
+  __ AllocateInNewSpace(size, rax, rbx, rdx, &slow_case, TAG_OBJECT);
+  for (int i = 0; i < size; i += kPointerSize) {
+    __ movq(rbx, FieldOperand(rcx, i));
+    __ movq(FieldOperand(rax, i), rbx);
+  }
+
+  // Return and remove the on-stack parameters.
+  __ ret(4 * kPointerSize);
+
+  __ bind(&slow_case);
+  __ TailCallRuntime(Runtime::kCreateObjectLiteralShallow, 4, 1);
+}
+
+
 // The stub expects its argument on the stack and returns its result in tos_:
 // zero for false, and a non-zero value for true.
 void ToBooleanStub::Generate(MacroAssembler* masm) {