Strict mode arguments do not share binding with formal parameters.

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
diff --git a/src/arm/codegen-arm.cc b/src/arm/codegen-arm.cc
index d32b009109ae8b9b95baac5c41ae58ab64ee6f1e..4f243eab015081234b7797d168d1fa16321e4e73 100644
--- a/src/arm/codegen-arm.cc
+++ b/src/arm/codegen-arm.cc
@@ -577,11 +577,13 @@ void CodeGenerator::LoadGlobalReceiver(Register scratch) {
 
 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;
 }
@@ -615,7 +617,9 @@ void 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;
   if (mode == LAZY_ARGUMENTS_ALLOCATION && !initial) {
     // We have to skip storing into the arguments slot if it has
@@ -629,7 +633,9 @@ void 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);
+  }
 }