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Re: [PATCH] Improve alloca alignment
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Eric Botcazou <ebotcazou at adacore dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>, Rainer Orth <ro at cebitec dot uni-bielefeld dot de>, nd <nd at arm dot com>
- Date: Thu, 5 Oct 2017 11:16:28 +0200
- Subject: Re: [PATCH] Improve alloca alignment
- Authentication-results: sourceware.org; auth=none
- References: <DB6PR0801MB2053EFC180A8360BC943BEB883B90@DB6PR0801MB2053.eurprd08.prod.outlook.com> <3900952.9QGmdsGrcf@polaris> <a7ad8524-da61-a146-fa54-c97d487b703f@redhat.com> <14087494.rKko7M8Fzl@polaris> <bc29fb11-917d-ceef-351b-31b945e6c94d@redhat.com>
On Thu, Oct 5, 2017 at 1:07 AM, Jeff Law <law@redhat.com> wrote:
> On 10/04/2017 08:53 AM, Eric Botcazou wrote:
>>> This seems like a SPARC target problem to me -- essentially it's
>>> claiming a higher STACK_BOUNDARY than it really has.
>>
>> No, it is not, I can guarantee you that the stack pointer is always aligned to
>> 64-bit boundaries on SPARC, otherwise all hell would break loose...
> Then something is inconsistent somehwere. Either the stack is aligned
> prior to that code or it is not. If it is aligned, then Wilco's patch
> ought to keep it aligned. If is not properly aligned, then well, that's
> the problem ISTM.
>
> Am I missing something here?
What I got from the discussion and the PR is that the stack hardregister
is properly aligned but what GCC maps to it (virtual or frame or whatever)
might not be at all points.
allocate_dynamic_stack_space uses virtual_stack_dynamic_rtx and I'm not
sure STACK_BOUNDARY applies to it?
Not that I know anything about this here ;)
Richard.
> jeff