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Merge pull request #2939 from janisozaur/perf 

Use GCC's __builtin_ffs for bitscanforward impl
This commit is contained in:
Ted John 2016-02-14 23:24:40 +00:00
parent f15d8bc5e4 016d26976e
commit 9fd24651f9
1 changed files with 7 additions and 0 deletions
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7
src/util/util.c
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@ -158,7 +158,14 @@ int bitscanforward(int source)
#if _MSC_VER >= 1400 // Visual Studio 2005
uint8 success = _BitScanForward(&i, source);
return success != 0 ? i : -1;
#elif __GNUC__
int success = __builtin_ffs(source);
return success - 1;
#else
#pragma message "Falling back to iterative bitscan forward, consider using intrinsics"
// This is a low-hanging optimisation boost, check if your compiler offers
// any intrinsic.
// cf. https://github.com/OpenRCT2/OpenRCT2/pull/2093
for (i = 0; i < 32; i++)
if (source & (1u << i))
return i;