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Rewrite bsfq management

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Use compiler intrinsics when possible to
avoid writing platform specific asm code.

Tested on Windows 7 with MSVC 2013 and mingw 4.8.3 (32 and 64 bit)
and on Linux Mint with g++ 4.8.4 and clang 3.4 (32 and 64 bit).

No functional change

Resolves #609
This commit is contained in:
Marco Costalba
2016-03-28 10:08:06 +02:00
committed by Joona Kiiski
parent 24dac5ccd3
commit db4b0d8b7d
4 changed files with 11 additions and 52 deletions
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40
src/bitboard.h
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@@ -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__)
#else
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 // ifdef(USE_BSFQ)
#define NO_BSF // Fallback on software implementation for other cases
Square lsb(Bitboard b);
Square msb(Bitboard b);