Hans-Kristian Arntzen : vkd3d: Add MSVC path for vkd3d_log2i.

[Alexandre Julliard]

Module: vkd3d
Branch: master
Commit: 69660ca5c908fe17ab0ad717454fcd01fce93e0a
URL:    https://source.winehq.org/git/vkd3d.git/?a=commit;h=69660ca5c908fe17ab0ad717...

Author: Hans-Kristian Arntzen 
Date:   Tue Oct  1 12:33:39 2019 +0200

vkd3d: Add MSVC path for vkd3d_log2i.

Signed-off-by: Hans-Kristian Arntzen 
Signed-off-by: Henri Verbeet 
Signed-off-by: Alexandre Julliard

---

include/private/vkd3d_common.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/private/vkd3d_common.h b/include/private/vkd3d_common.h
index ba4b68a..d8fb361 100644
--- a/include/private/vkd3d_common.h
+++ b/include/private/vkd3d_common.h
@@ -84,7 +84,13 @@ static inline bool vkd3d_bitmask_is_contiguous(unsigned int mask)
 /* Undefined for x == 0. */
 static inline unsigned int vkd3d_log2i(unsigned int x)
 {
-#ifdef HAVE_BUILTIN_CLZ
+#ifdef _MSC_VER
+    /* _BitScanReverse returns the index of the highest set bit,
+     * unlike clz which is 31 - index. */
+    unsigned long result;
+    _BitScanReverse(&result, x);
+    return (unsigned int)result;
+#elif defined(HAVE_BUILTIN_CLZ)
     return __builtin_clz(x) ^ 0x1f;
 #else
     static const unsigned int l[] =