Revert new OS and CC detection and related changes since r15923.

src/misc-intrinsics.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 21 matching lines @@
 #include "globals.h"
 
 namespace v8 {
 namespace internal {
 
 // Returns the index of the leading 1 bit, counting the least significant bit at
 // index 0.  (1 << IntegerLog2(x)) is a mask for the most significant bit of x.
 // Result is undefined if input is zero.
 int IntegerLog2(uint32_t value);
 
-#if V8_CC_GNU
+#if defined(__GNUC__)
 
 inline int IntegerLog2(uint32_t value) {
   return 31 - __builtin_clz(value);
 }
 
-#elif V8_CC_MSVC
+#elif defined(_MSC_VER)
 
 #pragma intrinsic(_BitScanReverse)
 
 inline int IntegerLog2(uint32_t value) {
   unsigned long result;             // NOLINT: MSVC intrinsic demands this type.
   _BitScanReverse(&result, value);
   return result;
 }
 
 #else
@@ skipping 21 matching lines @@
 
   result |= (value >> 1);
 
   return result;
 }
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_MISC_INTRINSICS_H_