Optimize ~~(expr) in optimized code.

src/ia32/lithium-ia32.cc

 // Copyright 2012 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 1312 matching lines @@
     LArithmeticT* result =
         new(zone()) LArithmeticT(instr->op(), context, left, right);
     return MarkAsCall(DefineFixed(result, eax), instr);
   }
 }
 
 
 LInstruction* LChunkBuilder::DoBitNot(HBitNot* instr) {
   ASSERT(instr->value()->representation().IsInteger32());
   ASSERT(instr->representation().IsInteger32());
+  if (instr->HasNoUses()) return NULL;
   LOperand* input = UseRegisterAtStart(instr->value());
   LBitNotI* result = new(zone()) LBitNotI(input);
   return DefineSameAsFirst(result);
 }
 
 
 LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
   if (instr->representation().IsDouble()) {
     return DoArithmeticD(Token::DIV, instr);
   } else if (instr->representation().IsInteger32()) {
@@ skipping 1098 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32