Fix and enable NEW_NON_STRICT_FAST ArgumentsAccess stub on x64.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 24df20ba767bd76df3fe06cbae9109d56afe6512..c3dea0ea8df3c8465ba5f9dac8c0e5ba48bb1cdc 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -222,13 +222,19 @@ void FullCodeGenerator::Generate(CompilationInfo* info) {
            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);