From 3b906ffc2765856948f1baac5ceb5209fe4380e2 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Mon, 13 Feb 2012 09:52:58 +0100 Subject: [PATCH] Micro-optimize pop_1st_bit() for 32 bits Small perft speed-up of 2% and also a code simplification. No functional change. Signed-off-by: Marco Costalba --- src/bitboard.cpp | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-) diff --git a/src/bitboard.cpp b/src/bitboard.cpp index bdde9161..84e576c6 100644 --- a/src/bitboard.cpp +++ b/src/bitboard.cpp @@ -112,7 +112,7 @@ Square first_1(Bitboard b) { // Use type-punning union b_union { - Bitboard b; + Bitboard dummy; struct { #if defined (BIGENDIAN) uint32_t h; @@ -121,27 +121,21 @@ union b_union { uint32_t l; uint32_t h; #endif - } dw; + } b; }; -Square pop_1st_bit(Bitboard* bb) { - - b_union u; - Square ret; +Square pop_1st_bit(Bitboard* b) { - u.b = *bb; + const b_union u = *((b_union*)b); - if (u.dw.l) + if (u.b.l) { - ret = Square(BSFTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783A9B23) >> 26]); - u.dw.l &= (u.dw.l - 1); - *bb = u.b; - return ret; + ((b_union*)b)->b.l = u.b.l & (u.b.l - 1); + return Square(BSFTable[((u.b.l ^ (u.b.l - 1)) * 0x783A9B23) >> 26]); } - ret = Square(BSFTable[((~(u.dw.h ^ (u.dw.h - 1))) * 0x783A9B23) >> 26]); - u.dw.h &= (u.dw.h - 1); - *bb = u.b; - return ret; + + ((b_union*)b)->b.h = u.b.h & (u.b.h - 1); + return Square(BSFTable[((~(u.b.h ^ (u.b.h - 1))) * 0x783A9B23) >> 26]); } #endif // !defined(USE_BSFQ) -- 2.39.2