1 // Copyright 2006-2008 the V8 project authors. All rights reserved.
2 // Redistribution and use in source and binary forms, with or without
3 // modification, are permitted provided that the following conditions are
4 // met:
5 //
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9 // copyright notice, this list of conditions and the following
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11 // with the distribution.
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15 //
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27
28 #ifndef V8_COMPILER_INTRINSICS_H_
29 #define V8_COMPILER_INTRINSICS_H_
30
31 namespace v8 {
32 namespace internal {
33
34 class 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__
CountTrailingZeros(uint32_t value)46 int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
47 return __builtin_ctz(value);
48 }
49
CountLeadingZeros(uint32_t value)50 int 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
CountTrailingZeros(uint32_t value)59 int 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
CountLeadingZeros(uint32_t value)65 int 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