Author: Vincent Diepeveen
Date: 16:48:04 05/18/02
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On May 18, 2002 at 13:38:02, Matthias Gemuh wrote:
>
>Hi Experts,
>I want to speed up my chess engine and need assembler versions of these
>functions. These below seem to be pentium-specific. I need something general
>and don't understand assembler.
they are general functions, but indeed they are very slow
functions. 2 very slow jnz instructions are there. Not the instruction
is that slow, but if it gets wrong predicted then the branch is
giving loads of penalties.
If i remember well some time ago a way faster version for the K7
was posted, which also seems to work for the P3 (p4 i do not know),
though that is not garantueed.
>int FirstBit(BITBOARD a)
>{
> __asm {
> bsr edx, dword ptr a+4
> mov eax, 31
> jnz l6
> bsr edx, dword ptr a
> mov eax, 63
> jnz l6
> mov edx, -1
> l6: sub eax, edx
> }
>}
>
>int LastBit(BITBOARD a)
>{
> __asm {
> bsf edx, dword ptr a
> mov eax, 63
> jnz l7
> bsf edx, dword ptr a+4
> mov eax, 31
> jnz l7
> mov edx, -33
> l7: sub eax, edx
> }
>}
>
>Please, help me.
>
>Thanks,
>Matthias.
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