From: Claudiu Zissulescu Ianculescu <claziss@gmail.com>
To: Eric Botcazou <botcazou@adacore.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Possible regression in DF analysis
Date: Tue, 13 Dec 2022 14:30:37 +0200 [thread overview]
Message-ID: <CAL0iMy17-H3h-LfaPcKJyZVhpF7LL9TM30HxWGMFBzyozqg=8w@mail.gmail.com> (raw)
In-Reply-To: <4447258.LvFx2qVVIh@fomalhaut>
It looks like that. The df_analyze_loop is only looking at the loop
BBs, and it is not clear for me if df_analyze_loop is required to have
all the df_live_outs correctly computed or not. Do you know if it is
true?
If the df_analyze_loop is not supposed to compute all the df_live_outs
correctly, then the error resides in how loop-doloop is using the
iv_analysis_loop_init().
Thank you for your help,
Claudiu
On Tue, Dec 13, 2022 at 10:41 AM Eric Botcazou <botcazou@adacore.com> wrote:
>
> > The problem shows in loop-doloop.c when I introduce a loop end pattern
> > that replaces the first jump instruction (JUMP_INSN 15) with a pattern
> > that clobbers CC reg. However, the DF doesn't look like it works as
> > the doloop step cannot find the CC reg alive. Please see
> > loop-doloop.c:766. Hence, it introduces the doloop_end patterns, and
> > renders the compare instruction (INSN 14) dead code. leading to
> > errors.
>
> So df_get_live_out does not contain the CC register? iv_analysis_loop_init
> only performs a local update of the DF information, maybe it does not cover
> the basic block containing insn 14 and 15?
>
> --
> Eric Botcazou
>
>
next prev parent reply other threads:[~2022-12-13 12:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-08 10:40 Claudiu Zissulescu Ianculescu
2022-12-08 11:33 ` Eric Botcazou
2022-12-08 11:51 ` Claudiu Zissulescu Ianculescu
2022-12-13 8:41 ` Eric Botcazou
2022-12-13 12:30 ` Claudiu Zissulescu Ianculescu [this message]
2022-12-13 16:53 ` Claudiu Zissulescu Ianculescu
2022-12-13 17:01 ` Richard Biener
2022-12-13 17:38 ` Claudiu Zissulescu Ianculescu
2022-12-14 10:37 ` Claudiu Zissulescu Ianculescu
2022-12-14 11:06 ` Richard Biener
2022-12-14 11:30 ` Claudiu Zissulescu Ianculescu
2022-12-14 12:39 ` Richard Biener
2022-12-17 0:33 ` Jeff Law
[not found] ` <CAL0iMy1ad0PmprQdu6BMhHdivPz--1Yq72+n02Lj-SmxhZmxQQ@mail.gmail.com>
2022-12-20 12:34 ` Fwd: " Claudiu Zissulescu Ianculescu
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