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Support MSVC intrinsic in MostSignificantBit() (#270)

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Arkady Shapkin 2017-10-27 02:09:59 +03:00 committed by Ondrej Stava
parent 0ec5ed3380
commit c5a7054091
1 changed files with 8 additions and 0 deletions
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8
src/draco/core/bit_utils.h
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@ -21,6 +21,10 @@
#include <stdint.h> #include <stdint.h>
#if defined(_MSC_VER)
#include <intrin.h>
#endif // defined(_MSC_VER)
namespace draco { namespace draco {
namespace bits { namespace bits {
@ -54,6 +58,10 @@ inline void CopyBits32(uint32_t *dst, int dst_offset, uint32_t src,
inline int MostSignificantBit(uint32_t n) { inline int MostSignificantBit(uint32_t n) {
#if defined(__GNUC__) #if defined(__GNUC__)
return 31 ^ __builtin_clz(n); return 31 ^ __builtin_clz(n);
#elif defined(_MSC_VER)
unsigned long where;
_BitScanReverse(&where, n);
return (int)where;
#else #else
// TODO(fgalligan): Optimize this code. // TODO(fgalligan): Optimize this code.
int msb = -1; int msb = -1;