Implement SDL_MostSignificantBitIndex32 using MSVC intrinsics

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