From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16556 invoked by alias); 29 Nov 2013 10:34:10 -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 Received: (qmail 16521 invoked by uid 48); 29 Nov 2013 10:34:07 -0000 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/59163] [4.8/4.9 Regression] program compiled with g++ -O3 segfaults Date: Fri, 29 Nov 2013 10:34:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 4.8.2 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub 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: 4.8.3 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc Message-ID: In-Reply-To: References: 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: 2013-11/txt/msg02994.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59163 Jakub Jelinek changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |uros at gcc dot gnu.org --- Comment #5 from Jakub Jelinek --- Looks like it, yes. In *.jump we still have (IMHO correct): (insn 2 4 3 2 (set (reg/v/f:DI 89 [ a ]) (reg:DI 5 di [ a ])) pr59163-2.C:13 85 {*movdi_internal} (nil)) (note 3 2 6 2 NOTE_INSN_FUNCTION_BEG) (insn 6 3 7 2 (set (reg:TI 90) (mem:TI (reg/v/f:DI 89 [ a ]) [3 MEM[(const struct A &)a_4(D)]+0 S16 A32])) pr59163-2.C:15 84 {*movti_internal} (nil)) (insn 7 6 8 2 (set (mem/c:TI (plus:DI (reg/f:DI 20 frame) (const_int -16 [0xfffffffffffffff0])) [3 c+0 S16 A128]) (reg:TI 90)) pr59163-2.C:15 84 {*movti_internal} (nil)) ... (insn 9 8 10 2 (set (reg:V4SF 91 [ vect__7.10 ]) (mult:V4SF (reg:V4SF 92) (mem/c:V4SF (plus:DI (reg/f:DI 20 frame) (const_int -16 [0xfffffffffffffff0])) [2 MEM[(float *)&c]+0 S16 A128]))) pr59163-2.C:17 1269 {*mulv4sf3} (nil)) movti_internal handles unaligned loads properly. Then *.dse1 transforms this into: (insn 6 3 18 2 (set (reg:TI 90 [ MEM[(const struct A &)a_4(D)] ]) (mem:TI (reg/v/f:DI 89 [ a ]) [3 MEM[(const struct A &)a_4(D)]+0 S16 A32])) pr59163-2.C:15 84 {*movti_internal} (nil)) (insn 18 6 8 2 (set (reg:V4SF 94) (subreg:V4SF (reg:TI 90 [ MEM[(const struct A &)a_4(D)] ]) 0)) pr59163-2.C:15 -1 (expr_list:REG_DEAD (reg:TI 90 [ MEM[(const struct A &)a_4(D)] ]) (nil))) ... (insn 9 8 19 2 (set (reg:V4SF 91 [ vect__7.10 ]) (mult:V4SF (reg:V4SF 92) (reg:V4SF 94))) pr59163-2.C:17 1269 {*mulv4sf3} (expr_list:REG_DEAD (reg:V4SF 94) (expr_list:REG_DEAD (reg:V4SF 92) (nil)))) which also looks ok to me. But then combine combines it into: (insn 9 8 19 2 (set (reg:V4SF 91 [ vect__7.10 ]) (mult:V4SF (reg:V4SF 92) (mem:V4SF (reg/v/f:DI 89 [ a ]) [3 MEM[(const struct A &)a_4(D)]+0 S16 A32]))) pr59163-2.C:17 1269 {*mulv4sf3} (expr_list:REG_DEAD (reg:V4SF 92) (nil))) which is wrong (for pre-AVX), because mulv4sf3 can't accept unaligned memory. Likely the SSEx pre-AVX predicates assume that an unaligned vector load will be done using UNSPEC and thus not really mergeable here, and don't count with the fact that the load could be done using integral mode and just subreged into vector mode. Perhaps we need new predicates for this that would fail for exactly this situation (disallow unaligned scalar load subregged into vector mode for pre-AVX) and use them everywhere where SSE? doesn't accept unaligned loads?