Move platform abstraction to base library

src/x64/cpu-x64.cc

 // 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.
 
 // CPU specific code for x64 independent of OS goes here.
 
 #if defined(__GNUC__) && !defined(__MINGW64__)
 #include "src/third_party/valgrind/valgrind.h"
 #endif
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
-#include "src/cpu.h"
+#include "src/assembler.h"
 #include "src/macro-assembler.h"
 
 namespace v8 {
 namespace internal {
 
-void CPU::FlushICache(void* start, size_t size) {
+void CpuFeatures::FlushICache(void* start, size_t size) {
   // No need to flush the instruction cache on Intel. On Intel instruction
   // cache flushing is only necessary when multiple cores running the same
   // code simultaneously. V8 (and JavaScript) is single threaded and when code
   // is patched on an intel CPU the core performing the patching will have its
   // own instruction cache updated automatically.
 
   // If flushing of the instruction cache becomes necessary Windows has the
   // API function FlushInstructionCache.
 
   // By default, valgrind only checks the stack for writes that might need to
   // invalidate already cached translated code.  This leads to random
   // instability when code patches or moves are sometimes unnoticed.  One
   // solution is to run valgrind with --smc-check=all, but this comes at a big
   // performance cost.  We can notify valgrind to invalidate its cache.
 #ifdef VALGRIND_DISCARD_TRANSLATIONS
   unsigned res = VALGRIND_DISCARD_TRANSLATIONS(start, size);
   USE(res);
 #endif
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64