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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e Date: Mon, 09 Nov 2020 14:19:21 +0000 [thread overview] Message-ID: <bug-97760-4-rVv0sy6j8e@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-97760-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97760 --- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> --- t.c:9:12: note: worklist: examine stmt: i_16 = PHI <i_11(5), 3(2)> t.c:9:12: note: vect_is_simple_use: operand (int) _3, type of def: reduction t.c:9:12: note: reduc-stmt defining reduc-phi in the same nest. t.c:9:12: note: mark relevant 1, live 1: i_11 = (int) _3; so reduc PHI defs are marked live magically - that's obviously wrong here, the live stmt is one in the middle of the reduction path (which _is_ marked live). What happens is that we generate two vectorized epilogues and depending on the order we end up with the wrong result in b. Now, what's _also_ wrong is that we cannot handle this situation since the epilogue of the middle stmt fails to account for the all-but-the-last lane effect of the _not_ live stmt. While the former bug is easy to fix the latter is not. I have a patch.
next prev parent reply other threads:[~2020-11-09 14:19 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-09 2:58 [Bug tree-optimization/97760] New: GCC outputs wrong values when compiling the testcase with -O3 yangyang305 at huawei dot com 2020-11-09 3:01 ` [Bug tree-optimization/97760] " yangyang305 at huawei dot com 2020-11-09 8:13 ` [Bug tree-optimization/97760] [10/11 Regression] GCC outputs wrong values when compiling the testcase with -O3 since r10-4200-gb7ff7cef5005721e marxin at gcc dot gnu.org 2020-11-09 8:17 ` rguenth at gcc dot gnu.org 2020-11-09 13:38 ` rguenth at gcc dot gnu.org 2020-11-09 14:19 ` rguenth at gcc dot gnu.org [this message] 2020-11-10 9:18 ` cvs-commit at gcc dot gnu.org 2020-11-10 9:22 ` [Bug tree-optimization/97760] [10 " rguenth at gcc dot gnu.org 2020-12-01 15:44 ` cvs-commit at gcc dot gnu.org 2020-12-01 15:45 ` rguenth at gcc dot gnu.org
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