From: Michael Matz <matz@suse.de>
To: Richard Guenther <richard.guenther@gmail.com>
Cc: Steven Bosscher <stevenb.gcc@gmail.com>,
Ulrich Weigand <uweigand@de.ibm.com>,
gcc-patches@gcc.gnu.org, tom@codesourcery.com
Subject: Re: Tree tail merging breaks __builtin_unreachable optimization
Date: Thu, 05 Jul 2012 13:17:00 -0000 [thread overview]
Message-ID: <alpine.LNX.2.00.1207051447570.16308@wotan.suse.de> (raw)
In-Reply-To: <CAFiYyc1OHhD7SOXB_D3RN0_zkEo3k39+vJDnBDEy-MuVnceGRA@mail.gmail.com>
Hi,
On Thu, 5 Jul 2012, Richard Guenther wrote:
> >> On Wed, Jul 4, 2012 at 7:02 PM, Ulrich Weigand <uweigand@de.ibm.com>
> >> wrote:
> >> > Any suggestions how to fix this? Should tail merging detect
> >> > __builtin_unreachable and not merge such block?
> >>
> >> That seems to be the most straight-forward thing to do. I don't think
> >> there are any other passes that do this kind of code merging.
> >
> > What do we gain by delaying to remove these blocks until RTL? AFAICS
> > not much if anything. So removing those on the tree level would make
> > more sense.
>
> The gain is to derive assertions from the conditional guarding these
> blocks and optimize using that knowledge.
I know that we derive assertions, but that's no reason why we couldn't
remove the BBs (or move it's sideeffects) in e.g. pass_fold_builtins. It
runs late enough that we don't make use of assertions afterwards.
Ciao,
Michael.
next prev parent reply other threads:[~2012-07-05 13:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-04 17:02 Ulrich Weigand
2012-07-04 18:09 ` Andrew Pinski
2012-07-04 18:17 ` Steven Bosscher
2012-07-05 12:44 ` Michael Matz
2012-07-05 12:46 ` Richard Guenther
2012-07-05 13:17 ` Michael Matz [this message]
2012-07-05 12:49 ` Tom de Vries
2012-07-05 13:18 ` Richard Guenther
2012-07-05 13:30 ` Michael Matz
2012-07-05 18:46 ` Tom de Vries
2012-07-06 11:02 ` Richard Guenther
2012-07-06 16:37 ` Tom de Vries
2012-07-09 8:10 ` Richard Guenther
2012-07-16 13:56 ` [RFC] 4.7 backport crashes (was: Re: Tree tail merging breaks __builtin_unreachable optimization) Ulrich Weigand
2012-07-16 14:11 ` Richard Guenther
2012-07-09 20:36 ` Tree tail merging breaks __builtin_unreachable optimization Ulrich Weigand
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