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Re: [discuss] When is RBX used for base pointer?
> On Feb 13, 2008 2:49 PM, Michael Matz <matz@suse.de> wrote:
> > Hi,
> >
> > On Wed, 13 Feb 2008, H.J. Lu wrote:
> >
> > > Our proposal is at
> > >
> > > http://gcc.gnu.org/ml/gcc/2007-12/msg00567.html
> > >
> > > For most cases, we can align stack with RBP/RSP. But
> > > we need an extra register when there is dynamic stack
> > > allocation or nested functions. It has to be callee-saved
> > > to work with setjmp/longjmp.
> >
> > I'm probably missing something, but why does it have to be a fixed
> > register at all? Why not simply saying "a free callee-saved register"?
> >
>
> We allocate this register when expanding prologue. Joey, Xuepeng,
> will "a free callee-saved register" work here?
See code around ix86_select_alt_pic_regnum. You can play similar
tricks.
Honza
>
> H.J.
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