Remove broken _WIN64 checks.

src/compiler/x64/instruction-selector-x64.cc

 // Copyright 2014 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.
 
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
-#ifndef _WIN64
-
 // Adds X64-specific methods for generating operands.
 class X64OperandGenerator V8_FINAL : public OperandGenerator {
  public:
   explicit X64OperandGenerator(InstructionSelector* selector)
       : OperandGenerator(selector) {}
 
   InstructionOperand* TempRegister(Register reg) {
     return new (zone()) UnallocatedOperand(UnallocatedOperand::FIXED_REGISTER,
                                            Register::ToAllocationIndex(reg));
   }
@@ skipping 688 matching lines @@
   }
 
   // Caller clean up of stack for C-style calls.
   if (descriptor->kind() == CallDescriptor::kCallAddress &&
       buffer.pushed_count > 0) {
     DCHECK(deoptimization == NULL && continuation == NULL);
     Emit(kPopStack | MiscField::encode(buffer.pushed_count), NULL);
   }
 }
 
-#endif
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8