Author: Dezhi Zhao
Date: 03:37:38 06/12/98
Go up one level in this thread
On June 12, 1998 at 03:41:43, Vincent Diepeveen wrote:
>Now what's more likely: BSF/R to become faster in future or mispredicted
>branches becoming faster :)
Yes. It only takes 1 or 2 cycles on PII if the 2 operands are both in
registers.
However there some problems with BSF/R instructions.
1. They are machine dependent.
2. There are no (BSF/R) operators in C or C++ compliers. You have to
use them as asm inline.
eg:
int bit_string;
int index_first1;
_asm index_first1, bit_string
After you disassembly the above, you will find the compiler
generated code is far from optimal. Compiler will treat index_first1
and bit_string as memory operands, and reload them each time
it encounter them. The memory reloads also harms the optimization
of the inline c/c++ neighbor codes.
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