Re: [RFA] W.I.P. AltiVec ppc registers support.

[Kevin Buettner <kevinb at redhat dot com>]

On Nov 29,  4:09pm, Daniel Jacobowitz wrote:

> On Thu, Nov 29, 2001 at 12:04:22PM -0500, Andrew Cagney wrote:
> > >
> > >Wait, I knew I was forgetting something important.
> > >
> > >There is no kernel support for this feature in any public PowerPC
> > >kernel tree, and to my knowledge there has been no suggested patch for
> > >it on any of the public LinuxPPC forums.  As such, the interface to it
> > >is still up in the air.  I've discussed this with other kernel folk at
> > >various times, and the general consensus is that, instead of adding
> > >them to the user area and using PEEKUSR, someone should simply
> > >implement PTRACE_GETFPXREGS (perhaps just PTRACE_GETXREGS, as the FP
> > >does not really apply, but consistency...).  We almost never want to
> > >fetch just one altivec register, excepting maybe VRSAVE, and GETFPXREGS
> > >takes negligibly more time than a single PEEKUSR call.
> > 
> > So if the tweek to ppc-linux-nat.c that does the register fetch was 
> > omitted, it would be ok?
> 
> It would be (somewhat trivial, but) OK, yes.  I have nothing against
> the implementation, just the interface.

If Elena makes the changes that I have in mind, the AltiVec specific
code which affects the interface will collapse down to 5 lines or so. 
Of course, if PTRACE_GETFPXREGS (or the like) ends up being used,
ppc-linux-nat.c need to be substantially rewritten anyway.  But the
point is that the five lines (or so) that I have in mind can then just
be deleted.

Kevin