Re: [gentoo-dev] make.conf optimization flags for k6, athlon

[Dan Armak]

On Sunday 15 July 2001 03:54, you wrote:
> A few comments I've been meaning to make.
>
> 1.  According to the GCC documentation you shouldn't be using -m<processor>
> any more. It's been depreciated in favor of -mcpu<processor>.
I know that. The mpentium etc. flags wre in the originl make.conf, the things 
I added were -march=x -mcpu=x. I'll change mpentium for march=pentium if I 
haven't already.

>
> 2.  You don't need to use -mcpu usually with -march as -march sets -mcpu
> for you.  I say usually 'cause there's an AMD processor (can't remember
> which) that uses a different instruction set than the default set by the
> -march it uses.
I think you're wrong. If I say march=i486 mcpu=i586 this means the binary 
will run on any 486 or better, but is optimized for the 586.


>
> 3.  The usage of processor names has been depreciated as well.  Should
> use i586, etc. instead.
For intel processors maybe. However AMD's k6, though a 586, is better than a 
Pentium, and the Athlon, though a 686, is better than a Pentium3.

Although it really would be better if gcc allowed for flags of instruction 
sets etc. so that you could define your 'custom processor' by saying, use 
MMX+3DNow!2+sse. Than we'd know exactly what optimization it was doing.


Dan Armak