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Big-endian compatible pop_1st_bit() 

Thanks to Eric Mullins we have now endian friendly
pop_1st_bit() and also is removed the need to use
-fno-strict-aliasing compiler option with GCC.

Speed is almost as fast, very small difference if any in
perft test, so I assume almost no difference in real games.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
sf_2.3.1_base
Marco Costalba 2009-11-05 19:29:26 +01:00
parent a9e536a7eb
commit dc286d2673
3 changed files with 120 additions and 104 deletions
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6
Readme.txt
View File

@ -52,9 +52,9 @@ UCI parameter "Book File".
On Unix-like systems, it should usually be possible to compile
Stockfish directly from the source code with the included Makefile.
The exception is computer with big-endian CPUs, like PowerPC
Macintoshes. Some of the bitboard routines in the current version of
Stockfish are endianness-sensitive, and won't work on a big-endian CPU.
For big-endian machines like Power PC you need to enable the proper
flag changing from -DNBIGENDIAN to -DBIGENDIAN in the Makefile.
Stockfish has POPCNT instruction runtime detection and support. This can
give an extra speed on Core i7 or similar systems. To enable this feature

14
src/Makefile
View File

@ -39,6 +39,14 @@ ICCFLAGS += -DNDEBUG
ICCFLAGS-OSX += -DNDEBUG
### ==========================================================================
### Enable/disable compile for a big-endian CPU, disabled by default
### ==========================================================================
GCCFLAGS += -DNBIGENDIAN
ICCFLAGS += -DNBIGENDIAN
ICCFLAGS-OSX += -DNBIGENDIAN
### ==========================================================================
### Run built-in benchmark for pgo-builds with: 32MB hash 1 thread 10 depth
### These settings are generally fast, but may be changed experimentally
@ -47,9 +55,9 @@ PGOBENCH = ./$(EXE) bench 32 1 10 default depth
### General compiler settings. Do not change
GCCFLAGS += -g -Wall -fno-exceptions -fno-rtti -fno-strict-aliasing
ICCFLAGS += -g -Wall -fno-exceptions -fno-rtti -fno-strict-aliasing -wd383,869,981,10187,10188,11505,11503
ICCFLAGS-OSX += -g -Wall -fno-exceptions -fno-rtti -fno-strict-aliasing -wd383,869,981,10187,10188,11505,11503
GCCFLAGS += -g -Wall -fno-exceptions -fno-rtti
ICCFLAGS += -g -Wall -fno-exceptions -fno-rtti -wd383,869,981,10187,10188,11505,11503
ICCFLAGS-OSX += -g -Wall -fno-exceptions -fno-rtti -wd383,869,981,10187,10188,11505,11503
### General linker settings. Do not change

34
src/bitboard.cpp
View File

@ -317,8 +317,8 @@ Square pop_1st_bit(Bitboard* b) {
#elif !defined(USE_BSFQ)
CACHE_LINE_ALIGNMENT
static const int BitTable[64] = {
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,
@ -336,26 +336,34 @@ union b_union {
Bitboard b;
struct {
#if defined (BIGENDIAN)
uint32_t h;
uint32_t l;
#else
uint32_t l;
uint32_t h;
#endif
} dw;
};
// WARNING: Needs -fno-strict-aliasing compiler option
Square pop_1st_bit(Bitboard* bb) {
b_union u;
b_union u;
Square ret;
u.b = *bb;
u.b = *bb;
if (u.dw.l)
{
*((uint32_t*)bb) = u.dw.l & (u.dw.l - 1);
return Square(BitTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783a9b23) >> 26]);
}
*((uint32_t*)bb+1) = u.dw.h & (u.dw.h - 1); // Little endian only?
return Square(BitTable[((~(u.dw.h ^ (u.dw.h - 1))) * 0x783a9b23) >> 26]);
if (u.dw.l)
{
ret = Square(BitTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783a9b23) >> 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]);
u.dw.h &= (u.dw.h - 1);
*bb = u.b;
return ret;
}
#endif