To fully support hydrogen code stubs which accept a variable number of arguments,

src/ia32/lithium-ia32.h

Index: src/ia32/lithium-ia32.h
diff --git a/src/ia32/lithium-ia32.h b/src/ia32/lithium-ia32.h
index 087eb74ecae2d928dec5cfe28157a30ee98e77e4..0c879352b68003567da1b65313e166b7aa2f7b38 100644
--- a/src/ia32/lithium-ia32.h
+++ b/src/ia32/lithium-ia32.h
@@ -1391,14 +1391,28 @@ class LArithmeticT: public LTemplateInstruction<1, 3, 0> {
 };
 
 
-class LReturn: public LTemplateInstruction<0, 2, 0> {
+class LReturn: public LTemplateInstruction<0, 3, 0> {
  public:
-  explicit LReturn(LOperand* value, LOperand* context) {
+  explicit LReturn(LOperand* value, LOperand* context,
+                   LOperand* parameter_count) {
     inputs_[0] = value;
     inputs_[1] = context;
+    inputs_[2] = parameter_count;
+  }
+
+  bool has_constant_parameter_count() const {
+    return hydrogen()->has_constant_parameter_count();

[danno, 2013/03/07 15:11:14]

You can implement these in terms of calls on the parameter_count LOperand*,
maybe allowing you to keep some of the
has_constant_parameter_count/constant_parameter_count abstraction that you count
on in lithium-codegen-ia32.cc

[mvstanton, 2013/03/07 16:48:49]

Done.

+  }
+  int constant_parameter_count() const {
+    return hydrogen()->constant_parameter_count();
+  }
+  LOperand* parameter_count() {
+    ASSERT(!has_constant_parameter_count());
+    return inputs_[2];
   }
 
   DECLARE_CONCRETE_INSTRUCTION(Return, "return")
+  DECLARE_HYDROGEN_ACCESSOR(Return)
 };