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Re: [PATCH, ARM] Use a pseudo for the PIC base
On Wednesday 18 January 2006 00:51, Richard Earnshaw wrote:
> On Tue, 17 Jan 2006 16:04:24 PST, Richard Henderson <rth@redhat.com>
>
> wrote:
> > On Tue, Jan 17, 2006 at 08:29:48PM +0000, Richard Earnshaw wrote:
> > > It seems that contrary to traditional belief no further changes to the
> > > mid-end code are needed.
> >
> > How do you handle constants being spilled to memory during reload,
> > in a block for which the pic pseudo register was not previously live?
>
> I've never seen it happen in any testing, and I've seen a fair number of
> cases where reload was affecting the code. If the pic base can't have a
> hard register it just gets split and reloaded as a normal pseudo. The sum
> of the pic base plus one of the offsets, isn't recorded as a constant, so
> I guess reload would never just throw it away.
Could it be because of the way the Arm backend does its own constant pool
generation? ie. reload never tries to spill constants to a PIC-base relative
address.
Paul