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[algs] 64bit popcount

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This commit is contained in:
Behdad Esfahbod 2023-04-28 12:01:21 -06:00
parent 5b0d818128
commit bd62a91d03
1 changed files with 6 additions and 4 deletions
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10
src/hb-algs.hh
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@ -618,16 +618,18 @@ hb_popcount (T v)
if (sizeof (T) <= 4)
{
/* "HACKMEM 169" */
uint32_t y;
y = (v >> 1) &033333333333;
uint32_t y = (uint32_t) v;
y = (y >> 1) &033333333333;
y = v - y - ((y >>1) & 033333333333);
return (((y + (y >> 3)) & 030707070707) % 077);
}
if (sizeof (T) == 8)
{
unsigned int shift = 32;
return hb_popcount<uint32_t> ((uint32_t) v) + hb_popcount ((uint32_t) (v >> shift));
uint64_t y = (uint64_t) v;
y -= ((y >> 1) & 0x5555555555555555ull);
y = (y & 0x3333333333333333ull) + (y >> 2 & 0x3333333333333333ull);
return ((y + (y >> 4)) & 0xf0f0f0f0f0f0f0full) * 0x101010101010101ull >> 56;
}
if (sizeof (T) == 16)