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Rewrite count_1s() to be similar to 64bit counterpart

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No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-01-11 17:15:18 +01:00
parent 14c1fd4d27
commit 3e6e57231e
1 changed files with 11 additions and 11 deletions
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22
src/bitboard.h
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@@ -395,23 +395,23 @@ inline int count_1s_max_15(Bitboard b) {
inline int count_1s(Bitboard b) { inline int count_1s(Bitboard b) {
unsigned w = unsigned(b >> 32), v = unsigned(b); unsigned w = unsigned(b >> 32), v = unsigned(b);
v = v - ((v >> 1) & 0x55555555); v -= (v >> 1) & 0x55555555;
w = w - ((w >> 1) & 0x55555555); w -= (w >> 1) & 0x55555555;
v += w; v += w;
v = (v & 0x33333333) + ((v >> 2) & 0x33333333); v = ((v >> 2) & 0x33333333) + (v & 0x33333333);
v = (v + (v >> 4)) & 0x0F0F0F0F; v = ((v >> 4) + v) & 0x0F0F0F0F;
v = (v * 0x01010101) >> 24; // mul is fast on amd procs v *= 0x01010101; // mul is fast on amd procs
return int(v); return int(v >> 24);
} }
inline int count_1s_max_15(Bitboard b) { inline int count_1s_max_15(Bitboard b) {
unsigned w = unsigned(b >> 32), v = unsigned(b); unsigned w = unsigned(b >> 32), v = unsigned(b);
v = v - ((v >> 1) & 0x55555555); v -= (v >> 1) & 0x55555555;
w = w - ((w >> 1) & 0x55555555); w -= (w >> 1) & 0x55555555;
v += w; v += w;
v = (v & 0x33333333) + ((v >> 2) & 0x33333333); v = ((v >> 2) & 0x33333333) + (v & 0x33333333);
v = (v * 0x11111111) >> 28; v *= 0x11111111;
return int(v); return int(v >> 28);
} }
#elif defined(BITCOUNT_SWAR_64) #elif defined(BITCOUNT_SWAR_64)