Jacek Caban : msvcp: Use BitScanReverse in log2i.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 03b4bffbbbb9fbe0ea19f59662a6877867929e72
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=03b4bffbbbb9fbe0ea19f59662a6877867929e72

Author: Jacek Caban <jacek at codeweavers.com>
Date:   Wed Jun 10 14:22:00 2020 +0200

msvcp: Use BitScanReverse in log2i.

Signed-off-by: Jacek Caban <jacek at codeweavers.com>
Signed-off-by: Piotr Caban <piotr at codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard at winehq.org>

---

 dlls/msvcp90/misc.c | 31 +++----------------------------
 1 file changed, 3 insertions(+), 28 deletions(-)

diff --git a/dlls/msvcp90/misc.c b/dlls/msvcp90/misc.c
index 4fb7ab24c1..563086c074 100644
--- a/dlls/msvcp90/misc.c
+++ b/dlls/msvcp90/misc.c
@@ -1889,37 +1889,12 @@ typedef struct compact_block
     int size_check;
 }compact_block;
 
-/* based on wined3d_log2i from wined3d.h */
 /* Return the integer base-2 logarithm of (x|1). Result is 0 for x == 0. */
 static inline unsigned int log2i(unsigned int x)
 {
-#if defined(__GNUC__) && ((__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 3)))
-    return __builtin_clz(x|1) ^ 0x1f;
-#else
-    static const unsigned int l[] =
-    {
-        ~0u, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
-          4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
-          5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
-          5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
-          6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
-          6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
-          6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
-          6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-          7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
-    };
-    unsigned int i;
-
-    x |= 1;
-    return (i = x >> 16) ? (x = i >> 8) ? l[x] + 24 : l[i] + 16 : (i = x >> 8) ? l[i] + 8 : l[x];
-#endif
+    unsigned int index;
+    BitScanReverse(&index, x|1);
+    return index;
 }
 
 /* ?_Segment_index_of at _Concurrent_vector_base_v4@details at Concurrency@@KAII at Z */