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

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 69b1c970c6a8759fa79dc2be821ad74a39afbf6a..2bc78010e7076142efbd64a2e322ba7f46170511 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1954,7 +1954,11 @@ LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
   LOperand* context = info()->IsStub()
       ? UseFixed(instr->context(), esi)
       : NULL;
-  return new(zone()) LReturn(UseFixed(instr->value(), eax), context);
+  LOperand* parameter_count = instr->has_constant_parameter_count()
+      ? NULL
+      : UseRegister(instr->parameter_count());

[mvstanton, 2013/03/07 13:30:13]

Hi Danno, is UseRegister the best predicate?

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

As commented elsewhere, UseRegisterOrConstant, but don't allow a NULL operand

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

Done.

+  return new(zone()) LReturn(UseFixed(instr->value(), eax), context,
+                             parameter_count);
 }