Port FastCloneShallowArrayStub to ARM and x64.

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
===================================================================
--- src/x64/codegen-x64.cc	(revision 3834)
+++ src/x64/codegen-x64.cc	(working copy)
@@ -2495,17 +2495,19 @@
   // Load the literals array of the function.
   __ movq(literals.reg(),
           FieldOperand(literals.reg(), JSFunction::kLiteralsOffset));
-  // Literal array.
+
   frame_->Push(&literals);
-  // Literal index.
   frame_->Push(Smi::FromInt(node->literal_index()));
-  // Constant elements.
   frame_->Push(node->constant_elements());
+  int length = node->values()->length();
   Result clone;
   if (node->depth() > 1) {
     clone = frame_->CallRuntime(Runtime::kCreateArrayLiteral, 3);
+  } else if (length > FastCloneShallowArrayStub::kMaximumLength) {
+    clone = frame_->CallRuntime(Runtime::kCreateArrayLiteralShallow, 3);
   } else {
-    clone = frame_->CallRuntime(Runtime::kCreateArrayLiteralShallow, 3);
+    FastCloneShallowArrayStub stub(length);
+    clone = frame_->CallStub(&stub, 3);
   }
   frame_->Push(&clone);
 
@@ -6260,6 +6262,63 @@
 }
 
 
+void FastCloneShallowArrayStub::Generate(MacroAssembler* masm) {
+  // Stack layout on entry:
+  //
+  // [rsp + kPointerSize]: constant elements.
+  // [rsp + (2 * kPointerSize)]: literal index.
+  // [rsp + (3 * kPointerSize)]: literals array.
+
+  // All sizes here are multiples of kPointerSize.
+  int elements_size = (length_ > 0) ? FixedArray::SizeFor(length_) : 0;
+  int size = JSArray::kSize + elements_size;
+
+  // Load boilerplate object into rcx and check if we need to create a
+  // boilerplate.
+  Label slow_case;
+  __ movq(rcx, Operand(rsp, 3 * kPointerSize));
+  __ movq(rax, Operand(rsp, 2 * 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);
+
+  // Allocate both the JS array and the elements array in one big
+  // allocation. This avoids multiple limit checks.
+  __ AllocateInNewSpace(size, rax, rbx, rdx, &slow_case, TAG_OBJECT);
+
+  // Copy the JS array part.
+  for (int i = 0; i < JSArray::kSize; i += kPointerSize) {
+    if ((i != JSArray::kElementsOffset) || (length_ == 0)) {
+      __ movq(rbx, FieldOperand(rcx, i));
+      __ movq(FieldOperand(rax, i), rbx);
+    }
+  }
+
+  if (length_ > 0) {
+    // Get hold of the elements array of the boilerplate and setup the
+    // elements pointer in the resulting object.
+    __ movq(rcx, FieldOperand(rcx, JSArray::kElementsOffset));
+    __ lea(rdx, Operand(rax, JSArray::kSize));
+    __ movq(FieldOperand(rax, JSArray::kElementsOffset), rdx);
+
+    // Copy the elements array.
+    for (int i = 0; i < elements_size; i += kPointerSize) {
+      __ movq(rbx, FieldOperand(rcx, i));
+      __ movq(FieldOperand(rdx, i), rbx);
+    }
+  }
+
+  // Return and remove the on-stack parameters.
+  __ ret(3 * kPointerSize);
+
+  __ bind(&slow_case);
+  ExternalReference runtime(Runtime::kCreateArrayLiteralShallow);
+  __ TailCallRuntime(runtime, 3, 1);
+}
+
+
 void ToBooleanStub::Generate(MacroAssembler* masm) {
   Label false_result, true_result, not_string;
   __ movq(rax, Operand(rsp, 1 * kPointerSize));