Strict mode arguments do not share binding with formal parameters.

src/ia32/codegen-ia32.cc

Index: src/ia32/codegen-ia32.cc
diff --git a/src/ia32/codegen-ia32.cc b/src/ia32/codegen-ia32.cc
index 3a2753d27c8451e9254e09171e2abe3d84aa5c1c..fcb06d2f590001d7a6ea179bae743fdb22ec3790 100644
--- a/src/ia32/codegen-ia32.cc
+++ b/src/ia32/codegen-ia32.cc
@@ -729,11 +729,14 @@ void CodeGenerator::LoadTypeofExpression(Expression* expr) {
 
 ArgumentsAllocationMode CodeGenerator::ArgumentsMode() {
   if (scope()->arguments() == NULL) return NO_ARGUMENTS_ALLOCATION;
-  ASSERT(scope()->arguments_shadow() != NULL);
+
+  // In strict mode there is no need for shadow arguments.
+  ASSERT(scope()->arguments_shadow() != NULL || scope()->is_strict_mode());
+
   // We don't want to do lazy arguments allocation for functions that
   // have heap-allocated contexts, because it interfers with the
   // uninitialized const tracking in the context objects.
-  return (scope()->num_heap_slots() > 0)
+  return (scope()->num_heap_slots() > 0 || scope()->is_strict_mode())
       ? EAGER_ARGUMENTS_ALLOCATION
       : LAZY_ARGUMENTS_ALLOCATION;
 }
@@ -760,8 +763,11 @@ Result CodeGenerator::StoreArgumentsObject(bool initial) {
 
   Variable* arguments = scope()->arguments();
   Variable* shadow = scope()->arguments_shadow();
+
   ASSERT(arguments != NULL && arguments->AsSlot() != NULL);
-  ASSERT(shadow != NULL && shadow->AsSlot() != NULL);
+  ASSERT((shadow != NULL && shadow->AsSlot() != NULL) ||
+         scope()->is_strict_mode());
+
   JumpTarget done;
   bool skip_arguments = false;
   if (mode == LAZY_ARGUMENTS_ALLOCATION && !initial) {
@@ -784,7 +790,9 @@ Result CodeGenerator::StoreArgumentsObject(bool initial) {
     StoreToSlot(arguments->AsSlot(), NOT_CONST_INIT);
     if (mode == LAZY_ARGUMENTS_ALLOCATION) done.Bind();
   }
-  StoreToSlot(shadow->AsSlot(), NOT_CONST_INIT);
+  if (shadow != NULL) {
+    StoreToSlot(shadow->AsSlot(), NOT_CONST_INIT);
+  }
   return frame_->Pop();
 }