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Revert previous commit.

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Optimization is correct but slightly slower
so it is a pessimization :-)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-02-03 15:41:04 +01:00
parent 6cfb661ca5
commit c32904f0a0
1 changed files with 8 additions and 4 deletions
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12
src/bitboard.h
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@ -395,8 +395,10 @@ inline int count_1s_max_15(Bitboard b) {
inline int count_1s(Bitboard b) {
unsigned w = unsigned(b >> 32), v = unsigned(b);
v -= ((v >> 1) & 0x77777777) + ((v >> 2) & 0x33333333) + ((v & 0x88888888) >> 3); // 0-4 in 4 bits
w -= ((w >> 1) & 0x77777777) + ((w >> 2) & 0x33333333) + ((w & 0x88888888) >> 3);
v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
w -= (w >> 1) & 0x55555555;
v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
v *= 0x01010101; // mul is fast on amd procs
@ -405,8 +407,10 @@ inline int count_1s(Bitboard b) {
inline int count_1s_max_15(Bitboard b) {
unsigned w = unsigned(b >> 32), v = unsigned(b);
v -= ((v >> 1) & 0x77777777) + ((v >> 2) & 0x33333333) + ((v & 0x88888888) >> 3); // 0-4 in 4 bits
w -= ((w >> 1) & 0x77777777) + ((w >> 2) & 0x33333333) + ((w & 0x88888888) >> 3);
v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
w -= (w >> 1) & 0x55555555;
v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
v += w; // 0-8 in 4 bits
v *= 0x11111111;
return int(v >> 28);