Re: [Dri-devel] Mesa Defaults in 4.0.2 Build

[Nathan H. <na...@ma...>]

On Mon, Jan 01, 2001 at 12:14:27PM +0100, Damon LoCascio wrote:
> Hey all,
> 
> 	Just answered a question on the Dri-Users list about building the
> mga_hal driver. In doing this I came across something that I thought
> everyone should know about in order that silly questions are not asked
> twice. Having said that, if someone could tell me WHY -DUSE_KATMAI_ASM is
> the default????

Because the GL code has assembly paths for all the common CPUs and
dynamically hooks in the appropriate paths at runtime. This allows
for a single binary that is optimised on all CPUs.

The most likely problem is that the user has compiled their kernel
for P3 support when they don't have a P3. I'm no expert on how the
katmai detection works though. I think Gareth would know.

You might like to find out where in check_os_katmai_support you're
bombing out. Easiest way to do this is to remote attach a debugger
to the X server. Failing that, use printf()/fflush() in the code.

> >From my mail:
> 
> CAVEATS: 1)
> 
> I am going to mention this on the developer list as well but it's worth
> saying it twice because I got burned myself. It seems that the Xfree86-
> 4.0.2 tree when building the GL libriaries defaults to using the
> USE_KATMAI_ASM macro as well as any mmx or 3dnow extensions your CPU may
> support. This was fatal on my machine, an AMD K6-III, and any object
> compiled against that libGL.so lib or even trying to use it dynamically
> would core dump with an illegal instruction. If you are using an Intel
> Processor the chances are you won't even notice and perhaps get a bit of
> speed increase.
> 
>         To disable this macro if you need to, define
> 
>  MesaUseKatmai NO
> 
> in the same place as the Matrox macro. And it will compile it with out
> that particular type of asm.