From: tm <tm@mail.kloo.net>
To: law@redhat.com
Cc: kkojima@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: PATCH: reorg branch displacement fix
Date: Fri, 01 Nov 2002 11:35:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.21.0211011127060.4789-100000@mail.kloo.net> (raw)
In-Reply-To: <200211011445.gA1Ej8sA030186@porcupine.cygnus.com>
On Fri, 1 Nov 2002, Jeff Law wrote:
> In message <Pine.LNX.4.21.0210311508160.3016-100000@mail.kloo.net>, tm writes:
> >
> >This fixes the problem mentioned in:
> >
> >http://gcc.gnu.org/ml/gcc-bugs/2002-06/msg00896.html
> >
> >When a conditional branch jumps to an unconditional branch, reorg will
> >thread the branch without checking if the conditional branch has enough
> >displacement bits to branch to the target.
> >
> >This patch uses MD_CAN_REDIRECT_BRANCH (as suggested by Joern in followup
> >messages to original message) to implement the substitution checking.
> >
> >Please review and if correct, commit as I don't have CVS access.
> >
> >Toshi
> >
> >Thu Oct 31 Toshiyasu Morita <toshiyasu.morita@hsa.hitachi.com>
> >
> > * reorg.c (relax_delay_slots): Don't thread conditional jump
> > through unconditional jump if the conditional jump can't reach
> > the branch target on this processor target.
> This is wrong. reorg does not and should not be checking branch displacements.
> That is a problem for shorten-branches and the backend.
>
> jeff
Aha! I see now. I will try disabling that chunk of code, and testing.
Incidentially, MD_CAN_REDIRECT_BRANCH is already used in reorg in one
other place, in steal_delay_list_from_target():
#ifdef MD_CAN_REDIRECT_BRANCH
/* On some targets, branches with delay slots can have a limited
displacement. Give the back end a chance to tell us we can't do
this. */
if (! MD_CAN_REDIRECT_BRANCH (insn, XVECEXP (seq, 0, 0)))
return delay_list;
#endif
This should probably be fixed as well.
Toshi
next prev parent reply other threads:[~2002-11-01 19:35 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-31 15:25 tm
2002-11-01 6:34 ` Jeff Law
2002-11-01 11:35 ` tm [this message]
2002-11-03 12:34 ` Jeff Law
2002-11-01 14:55 ` tm
2002-11-01 15:07 ` Jeff Law
2002-11-01 14:13 Joern Rennecke
2002-11-01 14:49 ` Jeff Law
2002-11-01 14:52 ` tm
2002-11-01 15:21 ` Joern Rennecke
2002-11-01 15:37 ` Jeff Law
2002-11-01 14:51 ` tm
2002-11-01 15:05 ` Jeff Law
2002-11-04 15:16 ` Joern Rennecke
2002-11-04 17:40 ` Hans-Peter Nilsson
2002-11-05 11:45 ` tm
2002-11-06 12:18 ` Joern Rennecke
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