Rewrite bsfq management

[stockfish] / src / bitboard.h

diff --git a/src/bitboard.h b/src/bitboard.h
index 967a68f59f8f8247397bb62e24eb8a7a3a569b7a..2ad8773634dce967e6cc6b223e68eeb3d4d66f05 100644 (file)
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -259,9 +259,12 @@ inline Bitboard attacks_bb(Piece pc, Square s, Bitboard occupied) {
 
 /// lsb() and msb() return the least/most significant bit in a non-zero bitboard
 
-#ifdef USE_BSFQ
+#if defined(__GNUC__)
 
-#  if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
+inline Square lsb(Bitboard b) { return Square(__builtin_ctzll(b)); }
+inline Square msb(Bitboard b) { return Square(63 - __builtin_clzll(b)); }
+
+#elif defined(_WIN64) && defined(_MSC_VER)
 
 inline Square lsb(Bitboard b) {
   unsigned long idx;
@@ -275,38 +278,9 @@ inline Square msb(Bitboard b) {
   return (Square) idx;
 }
 
-#  elif defined(__arm__)
-
-inline int lsb32(uint32_t v) {
-  __asm__("rbit %0, %1" : "=r"(v) : "r"(v));
-  return __builtin_clz(v);
-}
-
-inline Square msb(Bitboard b) {
-  return (Square) (63 - __builtin_clzll(b));
-}
-
-inline Square lsb(Bitboard b) {
-  return (Square) (uint32_t(b) ? lsb32(uint32_t(b)) : 32 + lsb32(uint32_t(b >> 32)));
-}
-
-#  else // Assumed gcc or compatible compiler
-
-inline Square lsb(Bitboard b) { // Assembly code by Heinz van Saanen
-  Bitboard idx;
-  __asm__("bsfq %1, %0": "=r"(idx): "rm"(b) );
-  return (Square) idx;
-}
-
-inline Square msb(Bitboard b) {
-  Bitboard idx;
-  __asm__("bsrq %1, %0": "=r"(idx): "rm"(b) );
-  return (Square) idx;
-}
-
-#  endif
+#else
 
-#else // ifdef(USE_BSFQ)
+#define NO_BSF // Fallback on software implementation for other cases
 
 Square lsb(Bitboard b);
 Square msb(Bitboard b);