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util: Use win32 intrinsics for util_last_bit if present.

Browse source 
v2: Split into two patches.
v3: Fix off by one problem.

Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Reviewed-by: Brian Paul <brianp@vmware.com>
Tested-by: Brian Paul <brianp@vmware.com>
This commit is contained in:
Mathias Fröhlich 2016-08-06 07:26:51 +02:00 • committed by Mathias Fröhlich
parent 3f100b77f9
commit 0ce5ec8ece
1 changed files with 12 additions and 0 deletions
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12
src/util/bitscan.h
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@ -157,6 +157,12 @@ util_last_bit(unsigned u)
{
#if defined(HAVE___BUILTIN_CLZ)
return u == 0 ? 0 : 32 - __builtin_clz(u);
#elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
unsigned long index;
if (_BitScanReverse(&index, u))
return index + 1;
else
return 0;
#else
unsigned r = 0;
while (u) {
@ -177,6 +183,12 @@ util_last_bit64(uint64_t u)
{
#if defined(HAVE___BUILTIN_CLZLL)
return u == 0 ? 0 : 64 - __builtin_clzll(u);
#elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM || _M_IA64)
unsigned long index;
if (_BitScanReverse64(&index, u))
return index + 1;
else
return 0;
#else
unsigned r = 0;
while (u) {