[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Abysmal performance with new gccs
>fxch between a lot of the faddp and fmul instructions. If I remember correctly
>fxch is an inst. to swap registers on the x87 stack (anyone want to correct
>me on this?), which is free if done in the right place.
FXCH is not "free"! It is only free in a way that it uses no functional
unit resources, but it is a real x86
instruction which consumes the same decoding bandwidth as every other
direct path instruction (Athlon
can decode three direct path instructions per cycle).
p.s. Clint, I am back from vacation - more tomorrow (Athlon kernel!)...