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Re: Question about DRAP register and reserving hard registers
- From: Steve Ellcey <sellcey at imgtec dot com>
- To: Richard Henderson <rth at redhat dot com>
- Cc: <gcc at gcc dot gnu dot org>
- Date: Thu, 9 Jul 2015 09:31:38 -0700
- Subject: Re: Question about DRAP register and reserving hard registers
- Authentication-results: sourceware.org; auth=none
- References: <163e6dcd-b157-47a1-aed3-01eb1b287851 at BAMAIL02 dot ba dot imgtec dot org> <5584148A dot 7040602 at redhat dot com> <1435011263 dot 3099 dot 65 dot camel at ubuntu-sellcey> <55911981 dot 2070901 at redhat dot com>
- Reply-to: <sellcey at imgtec dot com>
On Mon, 2015-06-29 at 11:10 +0100, Richard Henderson wrote:
> > OK, I think I have this part of the code working on MIPS but
> > crtl->drap_reg is used in the epilogue as well as the prologue even if
> > it is not 'live' in between. If I understand the code correctly the x86
> > prologue pushes the drap register on to the stack so that the epilogue
> > can pop it off and use it to restore the stack pointer. Is my
> > understanding correct?
> Yes. Although that saved copy is also used by unwind info.
Do you know how and where this saved copy is used by the unwind info?
I don't see any indication that the unwind library knows if a stack has
been dynamically realigned and I don't see where unwind makes use of