Introduce least_significant_square_bb()

Introducing least_significant_square_bb(). It is a function that returns a value equal
to square_bb(lsb(bb)), but it uses fewer instruction. It should speed up more on older
processors like armv7-a Clang.

Passed STC:
LLR: 2.93 (-2.94,2.94) {-0.25,1.25}
Total: 213200 W: 19171 L: 18753 D: 175276
Ptnml(0-2): 680, 14513, 75831, 14861, 715
https://tests.stockfishchess.org/tests/view/604bc7632433018de7a38982

Closes https://github.com/official-stockfish/Stockfish/pull/3391

No functional change
This commit is contained in:
bmc4
2021-03-16 20:51:31 +01:00
committed by Stéphane Nicolet
parent f3b296c2e2
commit 939395729c
2 changed files with 12 additions and 5 deletions
+7
View File
@@ -414,6 +414,13 @@ inline Square msb(Bitboard b) {
#endif
/// least_significant_square_bb() returns the bitboard of the least significant
/// square of a non-zero bitboard. It is equivalent to square_bb(lsb(bb)).
inline Bitboard least_significant_square_bb(Bitboard b) {
assert(b);
return b & -b;
}
/// pop_lsb() finds and clears the least significant bit in a non-zero bitboard