Strict mode arguments do not share binding with formal parameters.

src/x64/codegen-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 593 matching lines @@
     LoadFromSlotCheckForArguments(variable->AsSlot(), INSIDE_TYPEOF);
   } else {
     // Anything else can be handled normally.
     Load(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;
 }
 
 
 Result CodeGenerator::StoreArgumentsObject(bool initial) {
   ArgumentsAllocationMode mode = ArgumentsMode();
   ASSERT(mode != NO_ARGUMENTS_ALLOCATION);
 
   Comment cmnt(masm_, "[ store arguments object");
   if (mode == LAZY_ARGUMENTS_ALLOCATION && initial) {
     // When using lazy arguments allocation, we store the arguments marker value
     // as a sentinel indicating that the arguments object hasn't been
     // allocated yet.
     frame_->Push(Factory::arguments_marker());
   } else {
     ArgumentsAccessStub stub(ArgumentsAccessStub::NEW_OBJECT);
     frame_->PushFunction();
     frame_->PushReceiverSlotAddress();
     frame_->Push(Smi::FromInt(scope()->num_parameters()));
     Result result = frame_->CallStub(&stub, 3);
     frame_->Push(&result);
   }
 
   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) {
     // We have to skip storing into the arguments slot if it has
     // already been written to. This can happen if the a function
     // has a local variable named 'arguments'.
     LoadFromSlot(arguments->AsSlot(), NOT_INSIDE_TYPEOF);
     Result probe = frame_->Pop();
     if (probe.is_constant()) {
       // We have to skip updating the arguments object if it has
       // been assigned a proper value.
       skip_arguments = !probe.handle()->IsArgumentsMarker();
     } else {
       __ CompareRoot(probe.reg(), Heap::kArgumentsMarkerRootIndex);
       probe.Unuse();
       done.Branch(not_equal);
     }
   }
   if (!skip_arguments) {
     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();
 }
 
 //------------------------------------------------------------------------------
 // CodeGenerator implementation of variables, lookups, and stores.
 
 Reference::Reference(CodeGenerator* cgen,
                      Expression* expression,
                      bool  persist_after_get)
     : cgen_(cgen),
@@ skipping 8146 matching lines @@
 }
 
 #endif
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64