hint?

[Henio Paszczak <blurrpp@xxxxxxxxx>]

Hi.
I've read hint in some magazine that if you are not
using the same registers in following lines new
procesor ( my is quite old PIII(coppermine)600Mhz )
can make commands syumyltaniously ie:

mov %eax,%ebx
mov %ecx,%edx

can be does allmost in the same time. i've check it by
using extremly simple example:

movl $3,%ebx
movl $3,%edx
movl $0b111111111111111111111111111,%ecx

loop:
sall $2,%eax
orl  %ebx,%eax
sall $2,%edi
orl  %edx,%edi
   loop loop

it works ( agains theorem from magazine ) faster then

movl $3,%ebx
movl $3,%edx
movl $0b111111111111111111111111111,%ecx

loop:
sall $2,%eax
sall $2,%edi
orl  %ebx,%eax
orl  %edx,%edi
   loop loop

so what is real answer ?
Secund i'he allways trying not to use moemory becouse
its extremly slow .

nut again if i exchange walue between registers with
using temporary memory:

movl %eax,temp
movl %ebx,%eax,
movl temp,%ebx

it works faster than:

movl %eax,%edx
movl %ebx,%eax,
movl %edx,%ebx

WHY? maybe linux is doing something in the mean time
... ?

amaizing hink is that 

xchgl %eax,%ebx

works slowest :) WHY ?

I realy need time in my programs thats why i'm looking
for any optimalization...

Lukas
 

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