Author: Bo Persson
Date: 07:00:51 01/16/99
Go up one level in this thread
This is my solution for VC6, not perfect but working!
// warning C4035: 'BSF' : no return value
#pragma warning(disable : 4035)
inline unsigned BSF(unsigned Bits)
{
__asm mov eax,[Bits]
__asm bsf eax,eax
}
#pragma warning(default : 4035)
inline SQUARE BitBoard::GetLowMember()
{
if (Half[0] != 0)
{
const unsigned BitFound = BSF(Half[0]);
Half[0] ^= (1 << BitFound);
return static_cast<SQUARE>(BitFound);
}
else
{
const unsigned BitFound = BSF(Half[1]);
Half[1] ^= (1 << BitFound);
return static_cast<SQUARE>(BitFound + 4 * FILES);
}
} /* GetLowMember */
VC6 still puts the argument 'Bits' on the stack and reloads it, so you loose a
few instructions but still come out faster *on a PII*.
Compared to a 16-bit table lookup, the BSF is faster on a PII, makes no
difference on an AMD K6 and is actually *slower* on a Pentium 133!
BTW, you don't have to invent new operators for C/C++ to improve inlining. Many
years ago I used the TopSpeed C++ that solved regsiter assignment with special
pragmas, like:
#pragma call(reg_param=>(cx,dx), reg_return=>ax)
Worked fine!
Bo Persson
bop@malmo.mail.telia.com
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