Fix and enable NEW_NON_STRICT_FAST ArgumentsAccess stub on x64.

src/x64/full-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 204 matching lines @@
     } else {
       __ push(Operand(rbp, JavaScriptFrameConstants::kFunctionOffset));
     }
     // The receiver is just before the parameters on the caller's stack.
     int num_parameters = info->scope()->num_parameters();
     int offset = num_parameters * kPointerSize;
     __ lea(rdx,
            Operand(rbp, StandardFrameConstants::kCallerSPOffset + offset));
     __ push(rdx);
     __ Push(Smi::FromInt(num_parameters));
-    // Arguments to ArgumentsAccessStub:
+    // Arguments to ArgumentsAccessStub and/or New...:

[fschneider, 2012/01/16 14:25:07]

What's "New..."? I think the comment was fine as it was.

     //   function, receiver address, parameter count.
     // The stub will rewrite receiver and parameter count if the previous
     // stack frame was an arguments adapter frame.
-    ArgumentsAccessStub stub(
-        is_classic_mode() ? ArgumentsAccessStub::NEW_NON_STRICT_SLOW
-                          : ArgumentsAccessStub::NEW_STRICT);
+    ArgumentsAccessStub::Type type;
+    if (!is_classic_mode()) {
+      type = ArgumentsAccessStub::NEW_STRICT;
+    } else if (function()->has_duplicate_parameters()) {
+      type = ArgumentsAccessStub::NEW_NON_STRICT_SLOW;
+    } else {
+      type = ArgumentsAccessStub::NEW_NON_STRICT_FAST;
+    }
+    ArgumentsAccessStub stub(type);
     __ CallStub(&stub);
 
     SetVar(arguments, rax, rbx, rdx);
   }
 
   if (FLAG_trace) {
     __ CallRuntime(Runtime::kTraceEnter, 0);
   }
 
   // Visit the declarations and body unless there is an illegal
@@ skipping 4104 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64