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Re: rs6000 stack_tie mishap again
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Olivier Hainque <hainque at adacore dot com>
- Cc: Alan Modra <amodra at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Richard Henderson <rth at redhat dot com>
- Date: Thu, 14 Apr 2016 17:42:07 -0500
- Subject: Re: rs6000 stack_tie mishap again
- Authentication-results: sourceware.org; auth=none
- References: <DC6B501A-B999-41EC-B3D9-2D04E0A472CD at adacore dot com> <20160324041034 dot GB31470 at bubble dot grove dot modra dot org> <56F96CE2 dot 9020001 at redhat dot com> <888A9BC7-458D-46DE-BEC1-8AC000C6849D at adacore dot com>
On Mon, Apr 11, 2016 at 12:15:10PM +0200, Olivier Hainque wrote:
>
> > On Mar 28, 2016, at 19:41 , Richard Henderson <rth@redhat.com> wrote:
> >
> > But I expect for stage4, the best solution is to strengthen the stack_tie pattern to block all memory. Early scheduling of the stack frame deallocation (a simple logic insn) can't really be that important to performance.
>
> Something like the attached patch, at least for next stage1 until the
> more general issue is sorted out ?
It's a bit heavy; as a workaround, we may want this clobber in the stack
deallocation in the epilogue, but not in all other places stack_tie is
used.
And for stage 1 we do not really want a workaround, we want to fix the
actual problem ;-)
Segher