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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/107107] [10/11/12/13 Regression] Wrong codegen from TBAA when stores to distinct same-mode types are collapsed? Date: Thu, 06 Oct 2022 09:22:18 +0000 [thread overview] Message-ID: <bug-107107-4-tL6YLI8x0q@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-107107-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107107 --- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> --- The issue is how we value-number for tail-merging. We do Processing block 1: BB4 Value numbering stmt = MEM[(long int *)_3] = 2; RHS 2 simplified to 2 No store match Value numbering store MEM[(long int *)_3] to 2 Setting value number of .MEM_12 to .MEM_12 (changed) marking outgoing edge 4 -> 5 executable Processing block 2: BB3 Value numbering stmt = *_3 = 2; RHS 2 simplified to 2 Setting value number of .MEM_11 to .MEM_12 (changed) marking outgoing edge 3 -> 5 executable Processing block 3: BB5 Value numbering stmt = .MEM_10 = PHI <.MEM_11(3), .MEM_12(4)> Setting value number of .MEM_10 to .MEM_12 (changed) Value numbering stmt = _9 = *p_5(D); Setting value number of _9 to 1 (changed) oops. So we figure that the two stores from '2' are "redundant" which causes us to only consider one (the wrong one) when later looking up *p_5(D). That's if (!resultsame) { /* Only perform the following when being called from PRE which embeds tail merging. */ if (default_vn_walk_kind == VN_WALK) { assign = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, op); vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult, false); if (vnresult) { VN_INFO (vdef)->visited = true; return set_ssa_val_to (vdef, vnresult->result_vdef); } that's a case I never understood fully (and that seems wrong). That visited flag set is also odd. I'm testing a patch.
next prev parent reply other threads:[~2022-10-06 9:22 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-09-30 21:34 [Bug middle-end/107107] New: " bugdal at aerifal dot cx 2022-10-01 2:25 ` [Bug middle-end/107107] " bugdal at aerifal dot cx 2022-10-01 2:59 ` pinskia at gcc dot gnu.org 2022-10-01 3:02 ` pinskia at gcc dot gnu.org 2022-10-01 3:05 ` [Bug tree-optimization/107107] [10/11/12/13 Regression] " pinskia at gcc dot gnu.org 2022-10-01 3:05 ` pinskia at gcc dot gnu.org 2022-10-01 17:08 ` amonakov at gcc dot gnu.org 2022-10-01 20:01 ` bugdal at aerifal dot cx 2022-10-06 9:02 ` rguenth at gcc dot gnu.org 2022-10-06 9:22 ` rguenth at gcc dot gnu.org [this message] 2022-10-06 10:07 ` cvs-commit at gcc dot gnu.org 2022-10-06 10:08 ` [Bug tree-optimization/107107] [10/11/12 " rguenth at gcc dot gnu.org 2022-10-17 13:10 ` cvs-commit at gcc dot gnu.org 2022-12-12 16:33 ` [Bug tree-optimization/107107] [10/11 " cvs-commit at gcc dot gnu.org 2023-01-26 13:05 ` [Bug tree-optimization/107107] [10 " cvs-commit at gcc dot gnu.org 2023-01-26 13:06 ` rguenth at gcc dot gnu.org
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