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Implement SDL_MostSignificantBitIndex32 using MSVC intrinsics

This commit is contained in:
Cameron Gutman 2021-01-03 14:02:55 -06:00
parent 014f507c40
commit 91a831e2d0
1 changed files with 6 additions and 0 deletions
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6
include/SDL_bits.h
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@ -73,6 +73,12 @@ SDL_MostSignificantBitIndex32(Uint32 x)
return -1; return -1;
} }
return 31 - _SDL_clz_watcom(x); return 31 - _SDL_clz_watcom(x);
#elif defined(_MSC_VER)
unsigned long index;
if (_BitScanReverse(&index, x)) {
return index;
}
return -1;
#else #else
/* Based off of Bit Twiddling Hacks by Sean Eron Anderson /* Based off of Bit Twiddling Hacks by Sean Eron Anderson
* <seander@cs.stanford.edu>, released in the public domain. * <seander@cs.stanford.edu>, released in the public domain.