Clean up the usage of V8_TARGET_ARCH_${arch} and V8_HOST_ARCH_${arch}

src/platform-tls-mac.h

 // Copyright 2011 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 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_PLATFORM_TLS_MAC_H_
 #define V8_PLATFORM_TLS_MAC_H_
 
 #include "globals.h"
 
 namespace v8 {
 namespace internal {
 
-#if defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_X64)
+#if V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64
 
 #define V8_FAST_TLS_SUPPORTED 1
 
 extern intptr_t kMacTlsBaseOffset;
 
 INLINE(intptr_t InternalGetExistingThreadLocal(intptr_t index));
 
 inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
   intptr_t result;
-#if defined(V8_HOST_ARCH_IA32)
+#if V8_HOST_ARCH_IA32
   asm("movl %%gs:(%1,%2,4), %0;"
       :"=r"(result)  // Output must be a writable register.
       :"r"(kMacTlsBaseOffset), "r"(index));
 #else
   asm("movq %%gs:(%1,%2,8), %0;"
       :"=r"(result)
       :"r"(kMacTlsBaseOffset), "r"(index));
 #endif
   return result;
 }
 
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_TLS_MAC_H_