From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15187 invoked by alias); 7 Dec 2012 00:14:42 -0000 Received: (qmail 15057 invoked by uid 48); 7 Dec 2012 00:14:14 -0000 From: "aoliva at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/52573] [4.6/4.7/4.8 regression] regrename creates overlapping register allocations for output operands Date: Fri, 07 Dec 2012 00:14:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: rtl-optimization X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: aoliva at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.6.4 X-Bugzilla-Changed-Fields: Status Last reconfirmed CC Ever Confirmed Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-12/txt/msg00622.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52573 Alexandre Oliva changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2012-12-07 CC| |aoliva at gcc dot gnu.org, | |zadeck at naturalbridge dot | |com Ever Confirmed|0 |1 --- Comment #5 from Alexandre Oliva 2012-12-07 00:14:12 UTC --- I've looked a bit into this. The code in df-problems.c (see bug 32749) is at least inconsistent. df_note_bb_compute is supposed to set do_not_gen at the def, so that we emit the REG_UNUSED but not the REG_DEAD. However, it does not set do_not_gen for clobbers (may or must), even though it emits the note. Oh, and it only emits the note if it's not a call;for calls, the REG_UNUSED note is not emitted for clobbers (I wonder why that is), and we still fail to set do_not_gen, so we emit the REG_DEAD for the parallel use anyway. Kenny, it seems to me that we should set do_not_gen regardless of any clobber flags, because the whole (documented) point of do_not_gen is to avoid emitting a REG_DEAD for a parallel use, and we should make the REG_UNUSED note emission consistently conditional on clobbers. Does it sound like this would work?