[runtime] Implement %_ToLength via ToLengthStub.

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 4431944c1fe5facc5c5329776b42083ee2d7befa..2f2929f5cffa13a72e30f1cc52969a91aed73fe9 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -3192,6 +3192,25 @@ void ToNumberStub::Generate(MacroAssembler* masm) {
 }
 
 
+void ToLengthStub::Generate(MacroAssembler* masm) {
+  // The ToLength stub takes on argument in eax.
+  Label not_smi, positive_smi;
+  __ JumpIfNotSmi(eax, &not_smi, Label::kNear);
+  STATIC_ASSERT(kSmiTag == 0);
+  __ test(eax, eax);
+  __ j(greater_equal, &positive_smi, Label::kNear);
+  __ xor_(eax, eax);
+  __ bind(&positive_smi);
+  __ Ret();
+  __ bind(&not_smi);
+
+  __ pop(ecx);   // Pop return address.
+  __ push(eax);  // Push argument.
+  __ push(ecx);  // Push return address.
+  __ TailCallRuntime(Runtime::kToLength, 1, 1);
+}
+
+
 void ToStringStub::Generate(MacroAssembler* masm) {
   // The ToString stub takes one argument in eax.
   Label is_number;