From: Richard Biener <richard.guenther@gmail.com>
To: Jeff Law <jeffreyalaw@gmail.com>
Cc: Aldy Hernandez <aldyh@redhat.com>, GCC patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Add debug counters to back threader.
Date: Tue, 2 Nov 2021 14:27:28 +0100 [thread overview]
Message-ID: <CAFiYyc30_zjPQeOUL0Fj5-Zfav=4KObAVORT4+H0xfJrjY0pkw@mail.gmail.com> (raw)
In-Reply-To: <c6ce5313-d209-d7cd-5b4b-91db46f73ff1@gmail.com>
On Mon, Nov 1, 2021 at 2:03 PM Jeff Law via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
>
> On 11/1/2021 3:54 AM, Aldy Hernandez wrote:
> > Chasing down stage3 miscomparisons is never fun, and having no way to
> > distinguish between jump threads registered by a particular
> > pass, is even harder. This patch adds debug counters for the individual
> > back threading passes. I've left the ethread pass alone, as that one is
> > usually benign, but we could easily add it if needed.
> >
> > The fact that we can only pass one boolean argument to the passes
> > infrastructure has us do all sorts of gymnastics to differentiate
> > between the various back threading passes.
> >
> > Tested on x86-64 Linux.
> >
> > OK?
> >
> > gcc/ChangeLog:
> >
> > * dbgcnt.def: Add debug counter for back_thread[12] and
> > back_threadfull[12].
> > * passes.def: Pass "first" argument to each back threading pass.
> > * tree-ssa-threadbackward.c (back_threader::back_threader): Add
> > first argument.
> > (back_threader::debug_counter): New.
> > (back_threader::maybe_register_path): Call debug_counter.
> OK
But it's ugly. Very. Why isn't a single debug-counter good enough?
You should be able to reduce to a single threading pass via
-fdisable-tree-xyz and then bisect with the debug counter.
Alternatively at least store the debug counter to query somewhere
so you can have the "hot" path query a single one. So instead of
if (!dbg_cnt (back_thread1))
do
if (!dbg_cnt (curr_cnt))
and compute curr_cnt somewhere.
Richard.
> jeff
>
next prev parent reply other threads:[~2021-11-02 13:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 9:54 Aldy Hernandez
2021-11-01 13:02 ` Jeff Law
2021-11-02 13:27 ` Richard Biener [this message]
2021-11-02 13:35 ` Aldy Hernandez
2021-11-02 14:12 ` Richard Biener
2021-11-06 15:53 ` Aldy Hernandez
2021-11-08 12:22 ` Martin Liška
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