Improve the performance of bit set searches with a compiler intrinsic.

runtime/platform/utils.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef PLATFORM_UTILS_H_
 #define PLATFORM_UTILS_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 
@@ skipping 61 matching lines @@
   }
 
   template<typename T>
   static inline T* RoundUp(T* x, int n) {
     return reinterpret_cast<T*>(RoundUp(reinterpret_cast<uword>(x), n));
   }
 
   static uint32_t RoundUpToPowerOfTwo(uint32_t x);
   static int CountOneBits(uint32_t x);
 
+  static int CountTrailingZeros(uint32_t x);
+  static int CountTrailingZeros(uint64_t x);
+
   // Computes a hash value for the given string.
   static uint32_t StringHash(const char* data, int length);
 
   // Computes a hash value for the given word.
   static uint32_t WordHash(word key);
 
   // Check whether an N-bit two's-complement representation can hold value.
   template<typename T>
   static inline bool IsInt(int N, T value) {
     ASSERT((0 < N) &&
@@ skipping 71 matching lines @@
                                 intptr_t length) {
     return offset >= 0 &&
            count >= 0 &&
            length >= 0 &&
            count <= (length - offset);
   }
 };
 
 }  // namespace dart
 
+#if defined(TARGET_OS_LINUX)
+#include "platform/utils_linux.h"
+#elif defined(TARGET_OS_MACOS)
+#include "platform/utils_macos.h"
+#elif defined(TARGET_OS_WINDOWS)
+#include "platform/utils_win.h"
+#else
+#error Unknown target os.
+#endif
+
 #endif  // PLATFORM_UTILS_H_