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Bug 1182370 - _BitScan* does not modify *pIndex if input is zero. - r=waldo

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This commit is contained in:
Jeff Gilbert 2015-07-17 10:24:30 -07:00
parent f1efb68004
commit 0616f41059
1 changed files with 8 additions and 4 deletions
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12
mfbt/MathAlgorithms.h
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@ -170,7 +170,8 @@ inline uint_fast8_t
CountLeadingZeroes32(uint32_t aValue)
{
unsigned long index;
_BitScanReverse(&index, static_cast<unsigned long>(aValue));
if (!_BitScanReverse(&index, static_cast<unsigned long>(aValue)))
return 32;
return uint_fast8_t(31 - index);
}
@ -179,7 +180,8 @@ inline uint_fast8_t
CountTrailingZeroes32(uint32_t aValue)
{
unsigned long index;
_BitScanForward(&index, static_cast<unsigned long>(aValue));
if (!_BitScanForward(&index, static_cast<unsigned long>(aValue)))
return 32;
return uint_fast8_t(index);
}
@ -202,7 +204,8 @@ CountLeadingZeroes64(uint64_t aValue)
{
#if defined(MOZ_BITSCAN_WINDOWS64)
unsigned long index;
_BitScanReverse64(&index, static_cast<unsigned __int64>(aValue));
if (!_BitScanReverse64(&index, static_cast<unsigned __int64>(aValue)))
return 64;
return uint_fast8_t(63 - index);
#else
uint32_t hi = uint32_t(aValue >> 32);
@ -218,7 +221,8 @@ CountTrailingZeroes64(uint64_t aValue)
{
#if defined(MOZ_BITSCAN_WINDOWS64)
unsigned long index;
_BitScanForward64(&index, static_cast<unsigned __int64>(aValue));
if (!_BitScanForward64(&index, static_cast<unsigned __int64>(aValue)))
return 64;
return uint_fast8_t(index);
#else
uint32_t lo = uint32_t(aValue);