Specialize GenericUnaryStub so that it knows whether it needs to...

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
===================================================================
--- src/x64/full-codegen-x64.cc	(revision 5015)
+++ src/x64/full-codegen-x64.cc	(working copy)
@@ -2807,9 +2807,11 @@
 
     case Token::SUB: {
       Comment cmt(masm_, "[ UnaryOperation (SUB)");
-      bool overwrite =
+      bool can_overwrite =
           (expr->expression()->AsBinaryOperation() != NULL &&
            expr->expression()->AsBinaryOperation()->ResultOverwriteAllowed());
+      UnaryOverwriteMode overwrite =
+          can_overwrite ? UNARY_OVERWRITE : UNARY_NO_OVERWRITE;
       GenericUnaryOpStub stub(Token::SUB, overwrite);
       // GenericUnaryOpStub expects the argument to be in the
       // accumulator register rax.
@@ -2821,9 +2823,11 @@
 
     case Token::BIT_NOT: {
       Comment cmt(masm_, "[ UnaryOperation (BIT_NOT)");
-      bool overwrite =
+      bool can_overwrite =
           (expr->expression()->AsBinaryOperation() != NULL &&
            expr->expression()->AsBinaryOperation()->ResultOverwriteAllowed());
+      UnaryOverwriteMode overwrite =
+          can_overwrite ? UNARY_OVERWRITE : UNARY_NO_OVERWRITE;
       GenericUnaryOpStub stub(Token::BIT_NOT, overwrite);
       // GenericUnaryOpStub expects the argument to be in the
       // accumulator register rax.