From: Marco Costalba <mcostalba@gmail.com>
Date: Tue, 3 Feb 2009 14:41:04 +0000 (+0100)
Subject: Revert previous commit.
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=c32904f0a049491585a043f95716f5b2c2678825

Revert previous commit.
Optimization is correct but slightly slower
so it is a pessimization :-)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/bitboard.h b/src/bitboard.h
index da467cd8..1aefd8ad 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -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);