[runtime] Implement %_ToLength via ToLengthStub.

src/arm64/code-stubs-arm64.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_ARM64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 3896 matching lines @@
   __ B(ne, &not_oddball);
   __ Ldr(x0, FieldMemOperand(x0, Oddball::kToNumberOffset));
   __ Ret();
   __ Bind(&not_oddball);
 
   __ Push(x0);  // Push argument.
   __ TailCallRuntime(Runtime::kToNumber, 1, 1);
 }
 
 
+void ToLengthStub::Generate(MacroAssembler* masm) {
+  // The ToLength stub takes one argument in x0.
+  Label not_smi;
+  __ JumpIfNotSmi(x0, &not_smi);
+  STATIC_ASSERT(kSmiTag == 0);
+  __ Tst(x0, x0);
+  __ Csel(x0, x0, Operand(0), ge);
+  __ Ret();
+  __ Bind(&not_smi);
+
+  __ Push(x0);  // Push argument.
+  __ TailCallRuntime(Runtime::kToLength, 1, 1);
+}
+
+
 void ToStringStub::Generate(MacroAssembler* masm) {
   // The ToString stub takes one argument in x0.
   Label is_number;
   __ JumpIfSmi(x0, &is_number);
 
   Label not_string;
   __ JumpIfObjectType(x0, x1, x1, FIRST_NONSTRING_TYPE, &not_string, hs);
   // x0: receiver
   // x1: receiver instance type
   __ Ret();
@@ skipping 2062 matching lines @@
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64