From: Jeff Law <jeffreyalaw@gmail.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: "H.J. Lu" <hjl.tools@gmail.com>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Ignore debug insns with CONCAT and CONCATN for insn scheduling
Date: Mon, 26 Sep 2022 19:40:24 -0600 [thread overview]
Message-ID: <54413b00-89a6-4289-8f29-ea381750058e@gmail.com> (raw)
In-Reply-To: <YzI5MCDHlmbMbYhk@tucnak>
On 9/26/22 17:43, Jakub Jelinek wrote:
> On Mon, Sep 26, 2022 at 05:23:45PM -0600, Jeff Law via Gcc-patches wrote:
>> On 9/26/22 13:52, H.J. Lu wrote:
>>> On Sat, Sep 24, 2022 at 1:37 PM Jeff Law <jeffreyalaw@gmail.com> wrote:
>>>> On 9/21/22 16:11, H.J. Lu wrote:
>>>>> On Wed, Sep 7, 2022 at 10:03 AM Jeff Law via Gcc-patches
>>>>> <gcc-patches@gcc.gnu.org> wrote:
>>>>>> On 9/2/2022 8:36 AM, H.J. Lu via Gcc-patches wrote:
>>>>>>> CONCAT and CONCATN never appear in the insn chain. They are only used
>>>>>>> in debug insn. Ignore debug insns with CONCAT and CONCATN for insn
>>>>>>> scheduling to avoid different insn orders with and without debug insn.
>>>>>>>
>>>>>>> gcc/
>>>>>>>
>>>>>>> PR rtl-optimization/106746
>>>>>>> * sched-deps.cc (sched_analyze_2): Ignore debug insns with CONCAT
>>>>>>> and CONCATN.
>>>>>> Shouldn't we be ignoring everything in a debug insn? I don't see why
>>>>>> CONCAT/CONCATN are special here.
>>>>> Debug insns are processed by insn scheduling. I think it is to improve debug
>>>>> experiences. It is just that there are no matching usages of CONCAT/CONCATN
>>>>> in non-debug insns.
>>>> But from a dependency standpoint ISTM all debug insn can be ignored. I
>>>> still don't see why concat/concatn should be special here.
>>>>
>>> I tried to ignore everything in a debug insn. It caused many regressions in
>>> the GCC testsuite.
>> Not terribly useful -- what failed and why?
> I think the design for debug insns in the scheduler is that they do affect
> scheduling decisions, but what is in debug insns should only affect actual
> scheduling of the debug insns and not the rest.
> So it wouldn't surprise me if ignoring everything in a debug insn broke a
> lot. But I admit I never fully understood how it works, hopefully Alex or
> Vlad do.
But if we look at debug insns in scheduling decisions, wouldn't that
likely trigger a variety of compare-debug failures. Something here
doesn't make sense.
jeff
prev parent reply other threads:[~2022-09-27 1:40 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-02 14:36 H.J. Lu
2022-09-07 17:02 ` Jeff Law
2022-09-21 22:11 ` H.J. Lu
2022-09-24 20:37 ` Jeff Law
2022-09-26 19:52 ` H.J. Lu
2022-09-26 23:23 ` Jeff Law
2022-09-26 23:43 ` Jakub Jelinek
2022-09-27 1:40 ` Jeff Law [this message]
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