From: Jeff Law <jeffreyalaw@gmail.com>
To: Claudiu Zissulescu Ianculescu <claziss@gmail.com>,
Eric Botcazou <botcazou@adacore.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Possible regression in DF analysis
Date: Fri, 16 Dec 2022 17:33:40 -0700 [thread overview]
Message-ID: <8de37756-4b6f-48fc-e878-40a966db61b0@gmail.com> (raw)
In-Reply-To: <CAL0iMy2P1-MrEs=4mE7-fFH5UAmE8JqeznKMtnWxyE-msT0o9g@mail.gmail.com>
On 12/8/22 04:51, Claudiu Zissulescu Ianculescu via Gcc wrote:
> Hi Eric,
> 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
But simply inserting an instruction that clobbers CC can't be a valid
thing to do. You have to verify that the register isn't live at the
point where you want to do the insertion.
Or is that the core of the problem -- that life analysis is inaccurate
or unavailable?
Jeff
next prev parent reply other threads:[~2022-12-17 0:33 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
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 [this message]
[not found] ` <CAL0iMy1ad0PmprQdu6BMhHdivPz--1Yq72+n02Lj-SmxhZmxQQ@mail.gmail.com>
2022-12-20 12:34 ` Fwd: " Claudiu Zissulescu Ianculescu
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