X87: silence C++ compiler warnings.

src/x87/lithium-codegen-x87.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_X87_LITHIUM_CODEGEN_X87_H_
 #define V8_X87_LITHIUM_CODEGEN_X87_H_
 
 #include <map>
 #include "src/x87/lithium-x87.h"
 
@@ skipping 390 matching lines @@
     void Free(X87Register reg);
     void PrepareToWrite(X87Register reg);
     void CommitWrite(X87Register reg);
     void FlushIfNecessary(LInstruction* instr, LCodeGen* cgen);
     void LeavingBlock(int current_block_id, LGoto* goto_instr, LCodeGen* cgen);
     int depth() const { return stack_depth_; }
     int GetLayout();
     int st(X87Register reg) { return st2idx(ArrayIndex(reg)); }
     void pop() {
       DCHECK(is_mutable_);
+      USE(is_mutable_);
       stack_depth_--;
     }
     void push(X87Register reg) {
       DCHECK(is_mutable_);
       DCHECK(stack_depth_ < X87Register::kMaxNumAllocatableRegisters);
       stack_[stack_depth_] = reg;
       stack_depth_++;
     }
 
     MacroAssembler* masm() const { return masm_; }
@@ skipping 81 matching lines @@
   Label exit_;
   Label* external_exit_;
   Label done_;
   int instruction_index_;
   LCodeGen::X87Stack x87_stack_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X87_LITHIUM_CODEGEN_X87_H_