From: Eric Botcazou <ebotcazou@adacore.com>
To: Steven Bosscher <stevenb.gcc@gmail.com>
Cc: gcc-patches@gcc.gnu.org, Paolo Bonzini <bonzini@gnu.org>,
Jan Hubicka <hubicka@ucw.cz>
Subject: Re: Fix twolf -funroll-loops -O3 miscompilation (a semi-latent web.c bug)
Date: Sun, 14 Oct 2012 21:35:00 -0000 [thread overview]
Message-ID: <11595999.ttxDvgfuv1@polaris> (raw)
In-Reply-To: <CABu31nM8G7_vy_1prSFWF+9b1Gg52Hvcu+yVA=QMeUvD=CDcVw@mail.gmail.com>
> I don't think we want to do that. A REG_EQUAL/REG_EQUIV note can use a
> pseudo that isn't live and still be valid. Consider a simple example
> like this:
>
> a = b + 3
> // b dies here
> c = a {REG_EQUAL b+3}
>
> The REG_EQUAL note is valid and may help optimization. Removing it
> just because b is dead at that point would be unnecessarily
> pessimistic.
But if you have a REG_DEAD note for b on the first insn, then you cannot
rematerialize the REG_EQUAL note after it, otherwise bad things can happen.
See PR rtl-optimization/51505 for an example.
--
Eric Botcazou
next prev parent reply other threads:[~2012-10-14 21:27 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-12 20:14 Jan Hubicka
2012-10-12 20:36 ` Markus Trippelsdorf
2012-10-12 20:44 ` Steven Bosscher
2012-10-12 21:16 ` Jan Hubicka
2012-10-12 21:19 ` Steven Bosscher
2012-10-12 21:31 ` Jan Hubicka
2012-10-12 22:41 ` Steven Bosscher
2012-10-14 9:13 ` Paolo Bonzini
2012-10-14 21:27 ` Steven Bosscher
2012-10-14 21:35 ` Eric Botcazou [this message]
2012-10-14 21:45 ` Steven Bosscher
2012-10-15 8:14 ` Paolo Bonzini
2012-10-15 8:23 ` Steven Bosscher
2012-10-15 8:35 ` Paolo Bonzini
2012-10-15 8:38 ` Steven Bosscher
2012-10-15 10:49 ` Steven Bosscher
2012-10-15 12:28 ` Paolo Bonzini
2012-10-15 13:19 ` Steven Bosscher
2012-10-15 13:29 ` Paolo Bonzini
2012-10-15 13:49 ` Steven Bosscher
2012-10-16 10:35 ` Steven Bosscher
2012-10-16 11:05 ` Steven Bosscher
2012-10-16 11:42 ` Paolo Bonzini
2012-10-16 22:57 ` Steven Bosscher
2012-10-19 5:14 ` Bin.Cheng
2012-10-12 21:05 ` Steven Bosscher
2012-11-18 23:15 Dominique Dhumieres
2012-11-19 9:50 ` Steven Bosscher
2012-11-19 11:27 ` Eric Botcazou
2012-11-19 20:35 ` Steven Bosscher
2012-11-19 21:20 ` Steven Bosscher
2012-11-19 21:52 ` Eric Botcazou
2012-11-19 22:03 ` Steven Bosscher
2012-11-19 22:44 ` Eric Botcazou
2012-11-19 22:48 ` Steven Bosscher
2012-11-23 22:46 ` Steven Bosscher
2012-11-24 1:10 ` Steven Bosscher
2012-11-25 20:44 ` Steven Bosscher
2012-11-25 22:38 ` Steven Bosscher
2012-11-26 14:38 ` Dominique Dhumieres
2012-11-26 15:46 ` Steven Bosscher
2012-11-27 9:58 ` Eric Botcazou
2012-11-27 10:35 ` Steven Bosscher
2012-11-27 12:01 ` Steven Bosscher
2012-11-27 12:29 ` Steven Bosscher
2012-11-27 13:04 ` Steven Bosscher
2012-11-27 14:25 ` Dominique Dhumieres
2012-11-27 14:49 ` Steven Bosscher
2012-11-27 13:48 ` Dominique Dhumieres
2012-11-27 14:33 ` Paolo Bonzini
2012-11-27 16:59 ` Eric Botcazou
2012-11-27 23:29 ` Steven Bosscher
2012-11-27 23:50 ` Eric Botcazou
2012-11-27 23:54 ` Steven Bosscher
2012-11-27 23:59 ` Steven Bosscher
2012-11-28 0:43 ` Steven Bosscher
2012-11-28 7:46 ` Eric Botcazou
2012-11-28 15:57 ` Steven Bosscher
2012-11-28 22:12 ` Eric Botcazou
2012-11-28 23:54 ` Steven Bosscher
2012-12-01 14:57 ` Eric Botcazou
2012-12-01 16:45 ` Steven Bosscher
2012-12-03 18:26 ` Eric Botcazou
2012-12-03 20:20 ` Steven Bosscher
2012-12-03 21:12 ` Eric Botcazou
2012-12-03 23:28 ` Steven Bosscher
2012-12-03 20:15 ` Paolo Bonzini
2012-11-19 21:29 ` Eric Botcazou
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