1// Copyright 2006-2008 the V8 project authors. All rights reserved.
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27
28#ifndef V8_COMPILER_INTRINSICS_H_
29#define V8_COMPILER_INTRINSICS_H_
30
31namespace v8 {
32namespace internal {
33
34class CompilerIntrinsics {
35 public:
36  // Returns number of zero bits preceding least significant 1 bit.
37  // Undefined for zero value.
38  INLINE(static int CountTrailingZeros(uint32_t value));
39
40  // Returns number of zero bits following most significant 1 bit.
41  // Undefined for zero value.
42  INLINE(static int CountLeadingZeros(uint32_t value));
43};
44
45#ifdef __GNUC__
46int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
47  return __builtin_ctz(value);
48}
49
50int CompilerIntrinsics::CountLeadingZeros(uint32_t value) {
51  return __builtin_clz(value);
52}
53
54#elif defined(_MSC_VER)
55
56#pragma intrinsic(_BitScanForward)
57#pragma intrinsic(_BitScanReverse)
58
59int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
60  unsigned long result;  //NOLINT
61  _BitScanForward(&result, static_cast<long>(value));  //NOLINT
62  return static_cast<int>(result);
63}
64
65int CompilerIntrinsics::CountLeadingZeros(uint32_t value) {
66  unsigned long result;  //NOLINT
67  _BitScanReverse(&result, static_cast<long>(value));  //NOLINT
68  return 31 - static_cast<int>(result);
69}
70
71#else
72#error Unsupported compiler
73#endif
74
75} }  // namespace v8::internal
76
77#endif  // V8_COMPILER_INTRINSICS_H_
78