Move wtf/BitwiseOperations.h into base/bits.h.

third_party/WebKit/Source/wtf/BitwiseOperations.h

Index: third_party/WebKit/Source/wtf/BitwiseOperations.h
diff --git a/third_party/WebKit/Source/wtf/BitwiseOperations.h b/third_party/WebKit/Source/wtf/BitwiseOperations.h
index 2e6d2774fe1a002f2e97f16275c70394b6758efa..e07227a15d2e19a4f841544f2713766823d9d97c 100644
--- a/third_party/WebKit/Source/wtf/BitwiseOperations.h
+++ b/third_party/WebKit/Source/wtf/BitwiseOperations.h
@@ -28,72 +28,23 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+// TODO(palmer): The only caller of this code in Blink is PartitionAlloc. When
+// PA is moved to base, we can remove this file.
+// https://bugs.chromium.org/p/chromium/issues/detail?id=632441
+
 #ifndef WTF_BitwiseOperations_h
 #define WTF_BitwiseOperations_h
 
-// DESCRIPTION
-// countLeadingZeros() is a bitwise operation that counts the number of leading
-// zeros in a binary value, starting with the most significant bit. C does not
-// have an operator to do this, but fortunately the various compilers have
-// built-ins that map to fast underlying processor instructions.
-
+#include "base/bits.h"
 #include "wtf/CPU.h"
-#include "wtf/Compiler.h"
-#include <cstddef>
-#include <stdint.h>
-
-#if COMPILER(MSVC)
-#include <intrin.h>
-#endif
 
 namespace WTF {
 
-#if COMPILER(MSVC)
-
-ALWAYS_INLINE uint32_t countLeadingZeros32(uint32_t x) {
-  unsigned long index;
-  return LIKELY(_BitScanReverse(&index, x)) ? (31 - index) : 32;
-}
+using base::bits::CountLeadingZeroBits32;
+using base::bits::CountLeadingZeroBitsSizeT;
 
 #if CPU(64BIT)
-
-// MSVC only supplies _BitScanForward64 when building for a 64-bit target.
-ALWAYS_INLINE uint64_t countLeadingZeros64(uint64_t x) {
-  unsigned long index;
-  return LIKELY(_BitScanReverse64(&index, x)) ? (63 - index) : 64;
-}
-
-#endif
-
-#elif COMPILER(GCC)
-
-// This is very annoying. __builtin_clz has undefined behaviour for an input of
-// 0, even though these's clearly a return value that makes sense, and even
-// though nascent processor clz instructions have defined behaviour for 0.
-// We could drop to raw __asm__ to do better, but we'll avoid doing that unless
-// we see proof that we need to.
-ALWAYS_INLINE uint32_t countLeadingZeros32(uint32_t x) {
-  return LIKELY(x) ? __builtin_clz(x) : 32;
-}
-
-ALWAYS_INLINE uint64_t countLeadingZeros64(uint64_t x) {
-  return LIKELY(x) ? __builtin_clzll(x) : 64;
-}
-
-#endif
-
-#if CPU(64BIT)
-
-ALWAYS_INLINE size_t countLeadingZerosSizet(size_t x) {
-  return countLeadingZeros64(x);
-}
-
-#else
-
-ALWAYS_INLINE size_t countLeadingZerosSizet(size_t x) {
-  return countLeadingZeros32(x);
-}
-
+using base::bits::CountLeadingZeroBits64;
 #endif
 
 }  // namespace WTF