cvs commit: src/sys/i386/i386 pmap.c

[Jeff Roberson]

On Sun, 26 Oct 2003, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote:

> Peter Wemm <peter at wemm.org> writes:
> > Massively deep pipelines help get the MHz up, and careful optimization =
can
> > stop it affecting frame rates.  But it blows chunks if you mispredict a
> > branch in typical gcc generated code.  Or take our libc syscall stubs..
> > every single one will be mispredicted because the usual case (no errors=
)
> > has an opposite direction branch to what intel's static branch predicti=
on
> > expects.
>
> Is there any way to teach (or trick) gcc to generate a branch which
> the p4 will predict correctly?

I doubt the effect would be measurable.  We could simply rearrange the
code.  I do not know why it is arranged the way it is now but you would
expect that there is some good reason.

>
> DES
> --
> Dag-Erling Sm=F8rgrav - des at des.no
>