public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/101009] [12 Regression] wrong code with "-O3 -fno-tree-sra" Date: Fri, 11 Jun 2021 07:19:39 +0000 [thread overview] Message-ID: <bug-101009-4-SS2lHCYWv0@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-101009-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101009 --- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> --- So interestingly we do compute a distance vector of zero but we fail to add it, instead we end up returning true from build_classic_dist_vector_1 without setting *init_b to true (the access fns are not POLYNOMIAL_CHREC but are equal). Then in build_classic_dist_vector we skip /* Save the distance vector if we initialized one. */ if (init_b) .. and run into /* There is a distance of 1 on all the outer loops: Example: there is a dependence of distance 1 on loop_1 for the array A. | loop_1 | A[5] = ... | endloop */ add_outer_distances (ddr, dist_v, lambda_vector_first_nz (dist_v, DDR_NB_LOOPS (ddr), 0)); which ends up pushing a distance vector (1) as "outer distance". But in the skipped if () case we'd only ever do that if DDR_NB_LOOPS > 1. Both @@ -5435,7 +5437,7 @@ build_classic_dist_vector (struct data_dependence_relation *ddr, save_dist_v (ddr, save_v); } } - else + else if (DDR_NB_LOOPS (ddr) > 1) { /* There is a distance of 1 on all the outer loops: Example: there is a dependence of distance 1 on loop_1 for the array A. and @@ -5121,6 +5121,8 @@ build_classic_dist_vector_1 (struct data_dependence_relati on *ddr, non_affine_dependence_relation (ddr); return false; } + else + *init_b = true; } return true; fix the miscompilation. For the first patch we end up with no distance vector in ddr->dist_vects and for the second with a single { 0 } distance vector. IMHO the second looks more correct to me but maybe it is intended that non-affine but constant indexes do not get a distance vector. Anybody with some insights here?
next prev parent reply other threads:[~2021-06-11 7:19 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-10 8:17 [Bug tree-optimization/101009] New: " suochenyao at 163 dot com 2021-06-10 9:28 ` [Bug tree-optimization/101009] [12 Regression] " rguenth at gcc dot gnu.org 2021-06-10 9:40 ` rguenth at gcc dot gnu.org 2021-06-10 13:38 ` jakub at gcc dot gnu.org 2021-06-11 6:08 ` rguenth at gcc dot gnu.org 2021-06-11 6:23 ` rguenth at gcc dot gnu.org 2021-06-11 6:41 ` rguenth at gcc dot gnu.org 2021-06-11 7:19 ` rguenth at gcc dot gnu.org [this message] 2021-06-11 7:21 ` [Bug tree-optimization/101009] [10/11/12 " rguenth at gcc dot gnu.org 2021-06-11 7:33 ` rguenth at gcc dot gnu.org 2021-06-11 9:15 ` jakub at gcc dot gnu.org 2021-06-11 9:26 ` cvs-commit at gcc dot gnu.org 2021-06-11 9:27 ` [Bug tree-optimization/101009] [10/11 " rguenth at gcc dot gnu.org 2021-06-16 13:12 ` cvs-commit at gcc dot gnu.org 2021-09-06 10:18 ` [Bug tree-optimization/101009] [10 " cvs-commit at gcc dot gnu.org 2021-09-06 10:18 ` rguenth at gcc dot gnu.org
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=bug-101009-4-SS2lHCYWv0@http.gcc.gnu.org/bugzilla/ \ --to=gcc-bugzilla@gcc.gnu.org \ --cc=gcc-bugs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).