Strict mode arguments do not share binding with formal parameters.

src/ia32/full-codegen-ia32.cc

Index: src/ia32/full-codegen-ia32.cc
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index 9a7d41ada25f2117859ca644b12d9a5dcc95c946..36238fa126ce867d38ad35dab0ea8ca91a8a7b4e 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -199,10 +199,17 @@ void FullCodeGenerator::Generate(CompilationInfo* info) {
     // stack frame was an arguments adapter frame.
     ArgumentsAccessStub stub(ArgumentsAccessStub::NEW_OBJECT);
     __ CallStub(&stub);
-    __ mov(ecx, eax);  // Duplicate result.
-    Move(arguments->AsSlot(), eax, ebx, edx);
-    Slot* dot_arguments_slot = scope()->arguments_shadow()->AsSlot();
-    Move(dot_arguments_slot, ecx, ebx, edx);
+
+    Variable* arguments_shadow = scope()->arguments_shadow();
+    if (arguments_shadow != NULL) {
+      __ mov(ecx, eax);  // Duplicate result.
+      Move(arguments->AsSlot(), eax, ebx, edx);
+      Move(arguments_shadow->AsSlot(), ecx, ebx, edx);
+    } else {
+      // arguments are allocated without shadow only in strict mode.
+      ASSERT(scope()->is_strict_mode());
+      Move(arguments->AsSlot(), eax, ebx, edx);
+    }
   }
 
   if (FLAG_trace) {