From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-426609-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 15153 invoked by alias); 24 Jul 2013 11:55:46 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
Received: (qmail 15078 invoked by uid 48); 24 Jul 2013 11:55:42 -0000
From: "amylaar at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/57968] New: MODE_EXIT switches inserted too late
Date: Wed, 24 Jul 2013 11:55:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 4.9.0
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: amylaar at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter
Message-ID: <bug-57968-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2013-07/txt/msg01116.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57968

            Bug ID: 57968
           Summary: MODE_EXIT switches inserted too late
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amylaar at gcc dot gnu.org

I see a miscompilation of ___muldi3 for epiphany-elf; the witch to MODE_EXIT
is done at the start of the exit block, even though it contains instructions
that require a different mode.

The return register on the epiphany is not likely spilled, and a large register
file gives lots of freedom to do optimizations; when optimizig ___muldi3, at
end end the return value is not so much copied as calculated piecemeal.

There is some existing code in compute_pre_exit that is supposed to preserve
computations that need a non-exit mode, but the way it is placed means it is
only active when the immediate result is part of the return register.