X87: [runtime] Implement %_ToLength via ToLengthStub.

    port e678a0f9 (r31358)

    original commit message:
    Use %_ToLength for TO_LENGTH, implemented via a ToLengthStub
    that supports a fast path for small integers. Everything else is still
    handled in the runtime.

BUG=

Review URL: https://codereview.chromium.org/1421803002

Cr-Commit-Position: refs/heads/master@{#31542}

src/x87/code-stubs-x87.cc

@@ -2902,6 +2902,25 @@ 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;

src/x87/interface-descriptors-x87.cc

@@ -105,6 +105,10 @@ void ToNumberDescriptor::InitializePlatformSpecific(
 }
 
 
+// static
+const Register ToLengthDescriptor::ReceiverRegister() { return eax; }
+
+
 // static
 const Register ToStringDescriptor::ReceiverRegister() { return eax; }