romcc and EPIA

[SONE Takeshi]

I noticed romcc has support for MMX/SSE registers and epia/Config.lb
does not use it. Is there any problem using MMX registers on a C3?
I also wonder why -mcpu=p3 is required to enable MMX support of romcc.
IIRC, MMX has been supported since Pentium MMX and up, and Pentium III
adds SSE.
Isn't it better to have options like -mmmx and -msse, instead of
-mcpu=<name>. There are too many CPUs.

[Stefan Reinauer]

* SONE Takeshi  [031003 10:47]:
> I noticed romcc has support for MMX/SSE registers and epia/Config.lb
> does not use it. Is there any problem using MMX registers on a C3?
> I also wonder why -mcpu=p3 is required to enable MMX support of romcc.
> IIRC, MMX has been supported since Pentium MMX and up, and Pentium III
> adds SSE.

On CPUs prior to PIII the mmx registers were shared with the floating
point unit. Switching between those was extremely slow. Don't know
whether this is an issue, since LinuxBIOS does not use fp

Stefan

Stefan Reinauer  writes:
> SONE Takeshi  [031003 10:47]:
> > I noticed romcc has support for MMX/SSE registers and epia/Config.lb
> > does not use it. Is there any problem using MMX registers on a C3?
> > I also wonder why -mcpu=p3 is required to enable MMX support of romcc.
> > IIRC, MMX has been supported since Pentium MMX and up, and Pentium III
> > adds SSE.

The current set of options to romcc are mostly something I hacked together
one day.

-mmmx or -msse sound like a better mapping.  The only advantage to doing
by cpu is it is easier to remember which cpu you have, but there are
other ways to achieve that effect.

Patches welcome if someone wants to change the options.
> On CPUs prior to PIII the mmx registers were shared with the floating
> point unit. Switching between those was extremely slow. Don't know
> whether this is an issue, since LinuxBIOS does not use fp

mmx registers are architecturally if not practically shared with
the floating point registers.

Eric

[SONE Takeshi]

On Fri, Oct 03, 2003 at 09:32:30AM -0600, Eric W. Biederman wrote:
> Patches welcome if someone wants to change the options.

Attached patch changes romcc to internally have a set of features,
instead of CPU name. CPU name sets the feature set for the CPU,
and users can also set individual feature bits.