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Rename first_1 / last_1 in lsb / msb

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It seems more accurate: lsb is clear while 'first
bit' depends from where you look at the bitboard.

And fix compile in case of 64 bits platforms that
do not use BSFQ intrinsics.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2012-07-08 08:30:37 +01:00
parent 67d91dfd50
commit 6b5322ce00
12 changed files with 66 additions and 70 deletions
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29
src/bitboard.cpp
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@@ -69,40 +69,35 @@ namespace {
Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
}
/// first_1() finds the least significant nonzero bit in a nonzero bitboard.
/// pop_1st_bit() finds and clears the least significant nonzero bit in a
/// nonzero bitboard.
/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard.
/// pop_lsb() finds and clears the least significant bit in a nonzero bitboard.
#if defined(IS_64BIT) && !defined(USE_BSFQ)
#if !defined(USE_BSFQ)
Square first_1(Bitboard b) {
return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
}
Square lsb(Bitboard b) {
Square pop_1st_bit(Bitboard* b) {
Bitboard bb = *b;
*b &= (*b - 1);
return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
}
if (Is64Bit)
return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
#elif !defined(USE_BSFQ)
Square first_1(Bitboard b) {
b ^= (b - 1);
uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
}
Square pop_1st_bit(Bitboard* b) {
Square pop_lsb(Bitboard* b) {
Bitboard bb = *b;
*b = bb & (bb - 1);
if (Is64Bit)
return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
bb ^= (bb - 1);
uint32_t fold = unsigned(bb) ^ unsigned(bb >> 32);
return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
}
Square last_1(Bitboard b) {
Square msb(Bitboard b) {
unsigned b32;
int result = 0;