Saving to 32 bits of GPRs in signal context

[Steve Munroe]

Steven J. Munroe
Linux on Power Toolchain Architect
IBM Corporation, Linux Technology Center


Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote on 05/30/2007
07:58:12 AM:

> On Wed, 2007-05-30 at 21:48 +0900, Hiroyuki Machida wrote:
> >
> > I think same framework as proposed at follwoing URLs,  works.
> > http://penguinppc.org/dev/glibc/glibc-powerpc-cpu-addon.html

This is about keeping the cpu-specific code separated out in the glibc
build system. The appropriat code can be selected by configuring
--with=cpu=<cpu-type>

> > http://sources.redhat.com/ml/libc-alpha/2006-01/msg00094.html
>

This is about selecting whole cpu-tuned libraries dynamically (at load
time) that separated in the directory structure.

> Yeah, it would make sense to define a new feature bit to trigger
> automatic loading of optimized libs...
>
For dynamic library selection the primary selection is based on
AT_PLATFORM. Specific bits from AT_WHCAP can qualify the search path. For
example /lib/power4 is searched on POWER4 systems based on AT_PLATFORM. The
directory /lib/ppc970/altivec is searched on 970s from AT_PLATFORM=ppc970
and AT_HWCAP=PPC_FEATURE_HAS_ALTIVEC.

Not all bits in the AT_HWCAP effect the search, controls be the
HWCAP_IMPORTANT mask. Current only optional ISA features are includes in
the mask at this time (PPC_FEATURE_HAS_ALTIVEC and PPC_FEATURE_HAS_DFP).

> Steve, how hard do you think it would be to extend AT_HWCAP ? Like
> adding an AT_HWCAP2 or something like that ?
>
If needed, I dont think we are there yet.


Steven J. Munroe
Linux on Power Toolchain Architect
IBM Corporation, Linux Technology Center