{"id":2225651,"url":"http://patchwork.ozlabs.org/api/patches/2225651/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260421111416.6E5524BA23F9@sourceware.org/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260421111416.6E5524BA23F9@sourceware.org>","list_archive_url":null,"date":"2026-04-21T11:13:48","name":"tree-optimization/124947 - IVOPTs emits uninit use","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"476956f8dc93528700ec085e2fecc9a57588d882","submitter":{"id":4338,"url":"http://patchwork.ozlabs.org/api/people/4338/?format=json","name":"Richard Biener","email":"rguenther@suse.de"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260421111416.6E5524BA23F9@sourceware.org/mbox/","series":[{"id":500781,"url":"http://patchwork.ozlabs.org/api/series/500781/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500781","date":"2026-04-21T11:13:48","name":"tree-optimization/124947 - IVOPTs emits uninit use","version":1,"mbox":"http://patchwork.ozlabs.org/series/500781/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2225651/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2225651/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=suse.de header.i=@suse.de header.a=rsa-sha256\n header.s=susede2_rsa header.b=X8fiOV/u;\n\tdkim=pass header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=3dEHhPp5;\n\tdkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de\n header.a=rsa-sha256 header.s=susede2_rsa header.b=X8fiOV/u;\n\tdkim=neutral header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=3dEHhPp5;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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charset=US-ASCII","X-Spamd-Result":"default: False [-1.80 / 50.00]; BAYES_HAM(-3.00)[100.00%];\n MISSING_MID(2.50)[]; NEURAL_HAM_LONG(-1.00)[-0.998];\n NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain];\n TO_MATCH_ENVRCPT_ALL(0.00)[]; RCPT_COUNT_ONE(0.00)[1];\n MISSING_XM_UA(0.00)[]; FROM_EQ_ENVFROM(0.00)[];\n TO_DN_NONE(0.00)[]; ARC_NA(0.00)[]; RCVD_COUNT_ZERO(0.00)[0];\n FUZZY_RATELIMITED(0.00)[rspamd.com];\n DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519];\n MIME_TRACE(0.00)[0:+]; FROM_HAS_DN(0.00)[]","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org","Message-Id":"<20260421111416.6E5524BA23F9@sourceware.org>"},"content":"The following prevents IVOPTs from rewriting a compare using an IV\nthat involves undefined SSA vars.\n\nBootstrapped and tested on x86_64-unknown-linux-gnu, queued for stage1.\n\n\tPR tree-optimization/124947\n\t* tree-ssa-loop-ivopts.cc (may_eliminate_iv): Do not use\n\ta candidate that involves undefs.\n\n\t* gcc.dg/pr124947.c: New testcase.\n---\n gcc/testsuite/gcc.dg/pr124947.c | 19 +++++++++++++++++++\n gcc/tree-ssa-loop-ivopts.cc | 5 +++++\n 2 files changed, 24 insertions(+)\n create mode 100644 gcc/testsuite/gcc.dg/pr124947.c","diff":"diff --git a/gcc/testsuite/gcc.dg/pr124947.c b/gcc/testsuite/gcc.dg/pr124947.c\nnew file mode 100644\nindex 00000000000..5e64d29a943\n--- /dev/null\n+++ b/gcc/testsuite/gcc.dg/pr124947.c\n@@ -0,0 +1,19 @@\n+/* { dg-options \"-O -fdump-tree-ivopts\" } */\n+\n+long *BN_uadd_ap;\n+\n+void\n+BN_uadd (int dif, long t1)\n+{\n+ volatile long *rp;\n+ while (dif)\n+ {\n+ dif--;\n+ t1 = *BN_uadd_ap;\n+ *rp++ = t1;\n+ if (t1)\n+ break;\n+ }\n+}\n+\n+/* { dg-final { scan-tree-dump-times \"rp_\\[0-9\\]+\\\\\\(D\\\\\\)\" 1 \"ivopts\" } } */\ndiff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc\nindex 6ecf5bef7b4..dfec607fd2e 100644\n--- a/gcc/tree-ssa-loop-ivopts.cc\n+++ b/gcc/tree-ssa-loop-ivopts.cc\n@@ -5382,6 +5382,11 @@ may_eliminate_iv (struct ivopts_data *data,\n aff_tree bnd;\n class tree_niter_desc *desc = NULL;\n \n+ /* If the IV candidate involves undefs do not attempt to use it to\n+ express a condition. */\n+ if (cand->involves_undefs)\n+ return false;\n+\n if (TREE_CODE (cand->iv->step) != INTEGER_CST)\n return false;\n \n","prefixes":[]}