[runtime] Implement %_ToLength via ToLengthStub.

src/x64/code-stubs-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 3104 matching lines @@
   __ Ret();
   __ bind(&not_oddball);
 
   __ PopReturnAddressTo(rcx);     // Pop return address.
   __ Push(rax);                   // Push argument.
   __ PushReturnAddressFrom(rcx);  // Push return address.
   __ TailCallRuntime(Runtime::kToNumber, 1, 1);
 }
 
 
+void ToLengthStub::Generate(MacroAssembler* masm) {
+  // The ToLength stub takes on argument in rax.
+  Label not_smi, positive_smi;
+  __ JumpIfNotSmi(rax, &not_smi, Label::kNear);
+  STATIC_ASSERT(kSmiTag == 0);
+  __ testp(rax, rax);
+  __ j(greater_equal, &positive_smi, Label::kNear);
+  __ xorl(rax, rax);
+  __ bind(&positive_smi);
+  __ Ret();
+  __ bind(&not_smi);
+
+  __ PopReturnAddressTo(rcx);     // Pop return address.
+  __ Push(rax);                   // Push argument.
+  __ PushReturnAddressFrom(rcx);  // Push return address.
+  __ TailCallRuntime(Runtime::kToLength, 1, 1);
+}
+
+
 void ToStringStub::Generate(MacroAssembler* masm) {
   // The ToString stub takes one argument in rax.
   Label is_number;
   __ JumpIfSmi(rax, &is_number, Label::kNear);
 
   Label not_string;
   __ CmpObjectType(rax, FIRST_NONSTRING_TYPE, rdi);
   // rax: receiver
   // rdi: receiver map
   __ j(above_equal, &not_string, Label::kNear);
@@ skipping 2441 matching lines @@
                            kStackSpace, nullptr, return_value_operand, NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64