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blockfilter: Optimization on compilers with int128 support.

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Jim Posen 2018-05-13 12:00:02 -07:00
parent 97b64d67da
commit f33b717a85
1 changed files with 4 additions and 0 deletions
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src/blockfilter.cpp
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@ -52,6 +52,9 @@ static uint64_t GolombRiceDecode(BitStreamReader<IStream>& bitreader, uint8_t P)
// See: https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
static uint64_t MapIntoRange(uint64_t x, uint64_t n)
{
#ifdef __SIZEOF_INT128__
return (static_cast<unsigned __int128>(x) * static_cast<unsigned __int128>(n)) >> 64;
#else
// To perform the calculation on 64-bit numbers without losing the
// result to overflow, split the numbers into the most significant and
// least significant 32 bits and perform multiplication piece-wise.
@ -70,6 +73,7 @@ static uint64_t MapIntoRange(uint64_t x, uint64_t n)
uint64_t mid34 = (bd >> 32) + (bc & 0xFFFFFFFF) + (ad & 0xFFFFFFFF);
uint64_t upper64 = ac + (bc >> 32) + (ad >> 32) + (mid34 >> 32);
return upper64;
#endif
}
uint64_t GCSFilter::HashToRange(const Element& element) const