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Calculate Bit Scan tables at initialization

Browse source 
Instead of hard-coding them.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2011-06-04 08:54:57 +01:00
parent 8647fbd6ed
commit 025d57855a
1 changed files with 23 additions and 23 deletions
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46
src/bitboard.cpp
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@ -24,6 +24,8 @@
#if defined(IS_64BIT)
static const uint64_t DeBruijnMagic = 0x218A392CD3D5DBFULL;
const uint64_t BMult[64] = {
0x0440049104032280ULL, 0x1021023C82008040ULL, 0x0404040082000048ULL,
0x48C4440084048090ULL, 0x2801104026490000ULL, 0x4100880442040800ULL,
@ -90,6 +92,8 @@ const int RShift[64] = {
#else // if !defined(IS_64BIT)
static const uint32_t DeBruijnMagic = 0x783A9B23;
const uint64_t BMult[64] = {
0x54142844C6A22981ULL, 0x710358A6EA25C19EULL, 0x704F746D63A4A8DCULL,
0xBFED1A0B80F838C5ULL, 0x90561D5631E62110ULL, 0x2804260376E60944ULL,
@ -190,6 +194,8 @@ uint8_t BitCount8Bit[256];
namespace {
CACHE_LINE_ALIGNMENT int BSFTable[64];
void init_masks();
void init_step_attacks();
void init_pseudo_attacks();
@ -225,39 +231,22 @@ void print_bitboard(Bitboard b) {
#if defined(IS_64BIT) && !defined(USE_BSFQ)
static CACHE_LINE_ALIGNMENT
const int BitTable[64] = {
0, 1, 2, 7, 3, 13, 8, 19, 4, 25, 14, 28, 9, 34, 20, 40, 5, 17, 26,
38, 15, 46, 29, 48, 10, 31, 35, 54, 21, 50, 41, 57, 63, 6, 12, 18, 24, 27,
33, 39, 16, 37, 45, 47, 30, 53, 49, 56, 62, 11, 23, 32, 36, 44, 52, 55, 61,
22, 43, 51, 60, 42, 59, 58
};
Square first_1(Bitboard b) {
return Square(BitTable[((b & -b) * 0x218a392cd3d5dbfULL) >> 58]);
return Square(BSFTable[((b & -b) * DeBruijnMagic) >> 58]);
}
Square pop_1st_bit(Bitboard* b) {
Bitboard bb = *b;
*b &= (*b - 1);
return Square(BitTable[((bb & -bb) * 0x218a392cd3d5dbfULL) >> 58]);
return Square(BSFTable[((bb & -bb) * DeBruijnMagic) >> 58]);
}
#elif !defined(USE_BSFQ)
static CACHE_LINE_ALIGNMENT
const int BitTable[64] = {
63, 30, 3, 32, 25, 41, 22, 33, 15, 50, 42, 13, 11, 53, 19, 34, 61, 29, 2,
51, 21, 43, 45, 10, 18, 47, 1, 54, 9, 57, 0, 35, 62, 31, 40, 4, 49, 5,
52, 26, 60, 6, 23, 44, 46, 27, 56, 16, 7, 39, 48, 24, 59, 14, 12, 55, 38,
28, 58, 20, 37, 17, 36, 8
};
Square first_1(Bitboard b) {
b ^= (b - 1);
uint32_t fold = int(b) ^ int(b >> 32);
return Square(BitTable[(fold * 0x783a9b23) >> 26]);
uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
return Square(BSFTable[(fold * DeBruijnMagic) >> 26]);
}
// Use type-punning
@ -284,12 +273,12 @@ Square pop_1st_bit(Bitboard* bb) {
if (u.dw.l)
{
ret = Square(BitTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783a9b23) >> 26]);
ret = Square(BSFTable[((u.dw.l ^ (u.dw.l - 1)) * DeBruijnMagic) >> 26]);
u.dw.l &= (u.dw.l - 1);
*bb = u.b;
return ret;
}
ret = Square(BitTable[((~(u.dw.h ^ (u.dw.h - 1))) * 0x783a9b23) >> 26]);
ret = Square(BSFTable[((~(u.dw.h ^ (u.dw.h - 1))) * DeBruijnMagic) >> 26]);
u.dw.h &= (u.dw.h - 1);
*bb = u.b;
return ret;
@ -366,6 +355,17 @@ namespace {
for (Bitboard b = 0; b < 256; b++)
BitCount8Bit[b] = (uint8_t)count_1s<CNT32>(b);
for (int i = 1; i < 64; i++)
if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
{
Bitboard b = 1ULL << i;
b ^= b - 1;
b ^= b >> 32;
BSFTable[uint32_t(b * DeBruijnMagic) >> 26] = i;
}
else
BSFTable[((1ULL << i) * DeBruijnMagic) >> 58] = i;
}
void init_step_attacks() {