From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by sourceware.org (Postfix) with ESMTPS id 234323858D3C for ; Mon, 22 Aug 2022 06:16:51 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 234323858D3C Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 4DA975C5D5 for ; Mon, 22 Aug 2022 06:16:49 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3AF011332D for ; Mon, 22 Aug 2022 06:16:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id J/IzDVEfA2OZCAAAMHmgww (envelope-from ) for ; Mon, 22 Aug 2022 06:16:49 +0000 Date: Mon, 22 Aug 2022 08:16:48 +0200 (CEST) From: Richard Biener To: gcc-patches@gcc.gnu.org Subject: [PATCH][RFC] tree-optimization/105646 - re-interpret always executed in uninit diag MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Message-Id: <20220822061649.3AF011332D@imap2.suse-dmz.suse.de> X-Spam-Status: No, score=-11.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Aug 2022 06:16:52 -0000 The following fixes PR105646, not diagnosing int f1(); int f3(){ auto const & a = f1(); bool v3{v3}; return a; } with optimization because the early uninit diagnostic pass only diagnoses always executed cases. The patch does this by re-interpreting what always executed means and choosing to ignore exceptional and abnormal control flow for this. At the same time it improves things as suggested in a comment - when the value-numbering run done without optimizing figures there's a fallthru path, consider blocks on it as always executed. Bootstrapped and tested on x86_64-unknown-linux-gnu. OK? Thanks, Richard. PR tree-optimization/105646 * tree-ssa-uninit.cc (warn_uninitialized_vars): Pre-compute the set of fallthru reachable blocks from function entry and use that to determine wlims.always_executed. * g++.dg/uninit-pr105646.C: New testcase. --- gcc/testsuite/g++.dg/uninit-pr105646.C | 17 +++++++++ gcc/tree-ssa-uninit.cc | 53 +++++++++++++++++++++----- 2 files changed, 61 insertions(+), 9 deletions(-) create mode 100644 gcc/testsuite/g++.dg/uninit-pr105646.C diff --git a/gcc/testsuite/g++.dg/uninit-pr105646.C b/gcc/testsuite/g++.dg/uninit-pr105646.C new file mode 100644 index 00000000000..48ceb986ec6 --- /dev/null +++ b/gcc/testsuite/g++.dg/uninit-pr105646.C @@ -0,0 +1,17 @@ +// { dg-do compile } +// { dg-require-effective-target c++11 } +// { dg-options "-O2 -Wuninitialized" } + +int f1(); +int f2(){ + bool v2{v2}; // { dg-warning "is used uninitialized" } + auto const & a = f1(); + return a; +} +int f3(){ + auto const & a = f1(); + // Diagnose the following when optimizing and as unconditional + // uninitialized use despite f1 possibly throwing + bool v3{v3}; // { dg-warning "is used uninitialized" } + return a; +} diff --git a/gcc/tree-ssa-uninit.cc b/gcc/tree-ssa-uninit.cc index 7074c9117b2..b687e24a7e6 100644 --- a/gcc/tree-ssa-uninit.cc +++ b/gcc/tree-ssa-uninit.cc @@ -987,10 +987,49 @@ warn_uninitialized_vars (bool wmaybe_uninit) wlimits wlims = { }; wlims.wmaybe_uninit = wmaybe_uninit; - gimple_stmt_iterator gsi; - basic_block bb; + auto_bb_flag ft_reachable (cfun); + + /* Mark blocks that are always executed when we ignore provably + not executed and EH and abnormal edges. */ + basic_block bb = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)); + while (!(bb->flags & ft_reachable)) + { + bb->flags |= ft_reachable; + edge e = find_fallthru_edge (bb->succs); + if (e && e->flags & EDGE_EXECUTABLE) + { + bb = e->dest; + continue; + } + /* Find a single executable edge. */ + edge_iterator ei; + edge ee = NULL; + FOR_EACH_EDGE (e, ei, bb->succs) + if (e->flags & EDGE_EXECUTABLE) + { + if (!ee) + ee = e; + else + { + ee = NULL; + break; + } + } + if (ee) + bb = ee->dest; + else + { + bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb); + if (!bb || bb->index == EXIT_BLOCK) + break; + } + } + FOR_EACH_BB_FN (bb, cfun) { + wlims.always_executed = (bb->flags & ft_reachable); + bb->flags &= ~ft_reachable; + edge_iterator ei; edge e; FOR_EACH_EDGE (e, ei, bb->preds) @@ -1001,14 +1040,10 @@ warn_uninitialized_vars (bool wmaybe_uninit) if (!e) continue; - basic_block succ = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)); - /* ??? This could be improved when we use a greedy walk and have - some edges marked as not executable. */ - wlims.always_executed = dominated_by_p (CDI_POST_DOMINATORS, succ, bb); - if (wlims.always_executed) warn_uninit_phi_uses (bb); + gimple_stmt_iterator gsi; for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple *stmt = gsi_stmt (gsi); @@ -1029,7 +1064,7 @@ warn_uninitialized_vars (bool wmaybe_uninit) FOR_EACH_SSA_USE_OPERAND (use_p, stmt, op_iter, SSA_OP_USE) { /* BIT_INSERT_EXPR first operand should not be considered - a use for the purpose of uninit warnings. */ + a use for the purpose of uninit warnings. */ if (gassign *ass = dyn_cast (stmt)) { if (gimple_assign_rhs_code (ass) == BIT_INSERT_EXPR @@ -1040,7 +1075,7 @@ warn_uninitialized_vars (bool wmaybe_uninit) if (wlims.always_executed) warn_uninit (OPT_Wuninitialized, use, SSA_NAME_VAR (use), stmt); - else if (wmaybe_uninit) + else if (wlims.wmaybe_uninit) warn_uninit (OPT_Wmaybe_uninitialized, use, SSA_NAME_VAR (use), stmt); } -- 2.35.3