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Micro optimize count_1s_max_15() for 32 bit system

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Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-01-11 17:05:29 +01:00
parent 4b53bb02f6
commit 14c1fd4d27
1 changed files with 4 additions and 5 deletions
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9
src/bitboard.h
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@@ -397,11 +397,10 @@ inline int count_1s(Bitboard b) {
unsigned w = unsigned(b >> 32), v = unsigned(b);
v = v - ((v >> 1) & 0x55555555);
w = w - ((w >> 1) & 0x55555555);
v += w;
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
v = (v + (v >> 4)) & 0x0F0F0F0F;
w = (w + (w >> 4)) & 0x0F0F0F0F;
v = ((v+w) * 0x01010101) >> 24; // mul is fast on amd procs
v = (v * 0x01010101) >> 24; // mul is fast on amd procs
return int(v);
}
@@ -409,9 +408,9 @@ inline int count_1s_max_15(Bitboard b) {
unsigned w = unsigned(b >> 32), v = unsigned(b);
v = v - ((v >> 1) & 0x55555555);
w = w - ((w >> 1) & 0x55555555);
v += w;
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
w = (w & 0x33333333) + ((w >> 2) & 0x33333333);
v = ((v+w) * 0x11111111) >> 28;
v = (v * 0x11111111) >> 28;
return int(v);
}