From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10877 invoked by alias); 22 Dec 2010 16:23:43 -0000 Received: (qmail 10867 invoked by uid 22791); 22 Dec 2010 16:23:42 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 22 Dec 2010 16:23:37 +0000 From: "ibolton at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/45051] [4.6 Regression]: gcc.c-torture/execute/builtins/abs-2.c and abs-3.c due to "track subwords of DImode allocnos" 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: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: ibolton at gcc dot gnu.org X-Bugzilla-Status: REOPENED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Status CC Resolution 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 Date: Wed, 22 Dec 2010 16:23:00 -0000 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: 2010-12/txt/msg02501.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45051 Ian Bolton changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED CC| |ibolton at gcc dot gnu.org Resolution|FIXED | --- Comment #7 from Ian Bolton 2010-12-22 16:23:21 UTC --- (In reply to comment #5) > Assuming fixed and closing. Please reopen if you still have a problem. This patch has caused SpecCPU2000 Ammp to fail for ARM -O3 thumb. I assume the patch was meant to prevent deletions that shouldn't occur. This might be what happens for the original symptomatic test, but I am now seeing extra deletions that shouldn't happen for Ammp. For example, without this patch, you get these insns somewhere in the ira dump for mm_fv_update_nonbon() from rectmm.c: (insn 3163 3161 3164 107 rectmm.c:1041 (set (reg:SI 1 r1) (plus:SI (reg:SI 1 r1) (const_int 280 [0x118]))) 4 {*arm_addsi3} (nil)) (insn 3164 3163 1730 107 rectmm.c:1041 (set (reg:SI 3 r3) (reg:SI 1 r1)) 586 {*thumb2_movsi_vfp} (nil)) With the patch, you lose the add and just get this: (insn 3164 3161 1730 107 rectmm.c:1041 (set (reg:SI 3 r3) (reg:SI 1 r1)) 586 {*thumb2_movsi_vfp} (nil)) The incrementing of r1 is perfectly legitimate and useful and removing it is a bug. Other increments of r9, ip, r0 and r3 are also lost. I think the issue might be that reg_mentioned_p() considers output registers to have been "mentioned", whereas the refers_to_regno_p() does not consider an output register to have been "referred to". I can see the problem with only using reg_mentioned_p() because it doesn't handle subregs, but there is also a problem with only using refers_to_regno_p(), as we can see with this segfault in Ammp. I therefore wonder if the fix might be this: Index: gcc/reload1.c =================================================================== --- gcc/reload1.c (revision 168082) +++ gcc/reload1.c (working copy) @@ -8395,7 +8395,8 @@ delete_output_reload (rtx insn, int j, i if (NOTE_INSN_BASIC_BLOCK_P (i1)) return; if ((NONJUMP_INSN_P (i1) || CALL_P (i1)) - && refers_to_regno_p (regno, regno + nregs, PATTERN (i1), NULL)) + && (refers_to_regno_p (regno, regno + nregs, PATTERN (i1), NULL) + || reg_mentioned_p (reg, PATTERN (i1)))) { /* If this is USE in front of INSN, we only have to check that there are no more references than accounted for by inheritance. */ I am heading off for Christmas vacation shortly, so cannot look into this any further, but I wanted to record my findings so far publicly. Apologies if there is missing information. I return to work Jan 4th.