Vc  1.2.0
SIMD Vector Classes for C++
bitscanintrinsics.h
1 /* This file is part of the Vc library. {{{
2 Copyright © 2011-2015 Matthias Kretz <kretz@kde.org>
3 All rights reserved.
4 
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27 }}}*/
28 
29 #ifndef VC_COMMON_BITSCANINTRINSICS_H_
30 #define VC_COMMON_BITSCANINTRINSICS_H_
31 
32 #if defined(Vc_GCC) || defined(Vc_CLANG)
33 # if Vc_GCC >= 0x40500
34  // GCC 4.5.0 introduced _bit_scan_forward / _bit_scan_reverse
35 # include <x86intrin.h>
36 # else
37  // GCC <= 4.4 and clang have x86intrin.h, but not the required functions
38 # define _bit_scan_forward(x) __builtin_ctz(x)
39 #include "macros.h"
40 static Vc_ALWAYS_INLINE Vc_CONST int _Vc_bit_scan_reverse_asm(unsigned int x) {
41  int r;
42  __asm__("bsr %1,%0" : "=r"(r) : "X"(x));
43  return r;
44 }
45 # define _bit_scan_reverse(x) _Vc_bit_scan_reverse_asm(x)
46 # endif
47 #elif defined(Vc_ICC)
48 // for all I know ICC supports the _bit_scan_* intrinsics
49 #elif defined(Vc_OPEN64)
50 // TODO
51 #elif defined(Vc_MSVC)
52 #include "windows_fix_intrin.h"
53 #pragma intrinsic(_BitScanForward)
54 #pragma intrinsic(_BitScanReverse)
55 static inline __forceinline unsigned long _bit_scan_forward(unsigned long x) {
56  unsigned long index;
57  _BitScanForward(&index, x);
58  return index;
59 }
60 static inline __forceinline unsigned long _bit_scan_reverse(unsigned long x) {
61  unsigned long index;
62  _BitScanReverse(&index, x);
63  return index;
64 }
65 #else
66 // just assume the compiler can do it
67 #endif
68 
69 
70 #endif // VC_COMMON_BITSCANINTRINSICS_H_