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

src/x64/full-codegen-x64.cc

 // Copyright 2010 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 2789 matching lines @@
       __ j(is_smi, &no_conversion);
       __ push(result_register());
       __ InvokeBuiltin(Builtins::TO_NUMBER, CALL_FUNCTION);
       __ bind(&no_conversion);
       Apply(context_, result_register());
       break;
     }
 
     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.
       VisitForValue(expr->expression(), kAccumulator);
       __ CallStub(&stub);
       Apply(context_, rax);
       break;
     }
 
     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.
       VisitForValue(expr->expression(), kAccumulator);
       // Avoid calling the stub for Smis.
       Label smi, done;
       Condition is_smi = masm_->CheckSmi(result_register());
       __ j(is_smi, &smi);
       // Non-smi: call stub leaving result in accumulator register.
       __ CallStub(&stub);
@@ skipping 404 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64