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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/109893] [14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r14-160-gf828503eeb79ad1f1ada6db7deccc5abcc2f3ca3 Date: Fri, 12 Jan 2024 12:53:10 +0000 [thread overview] Message-ID: <bug-109893-4-1ZZsbdjXcA@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-109893-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109893 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org --- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- This is a failure to jump-thread because of size limits. If we'd limit the backward threader the same way as the forward threader we'd optimize this (--param fsm-scale-path-stmts=1). --param max-jump-thread-duplication-stmts is 15 --param fsm-scale-path-stmts is 2 but for "true" FSM paths we allow --param max-fsm-thread-path-insns == 100 For non-loop FSM threads we only allow 7 stmts (and we lack the forward thread estimation of the number of stmts we likely eliminate). Increasing --param max-jump-thread-duplication-stmts to 17 also works to resolve the regression. But IMHO the scale param should simply go - we have the other limit for paths across a backedge when threading multi-way branches. The argument for the scaling is /* The generic copier used by the backthreader does not re-use an existing threading path to reduce code duplication. So for that case, drastically reduce the number of statements we are allowed to copy. */ that sounds more like limiting overall threading rather than individual ones. I'll adjust fsm-scale-path-stmts to be more finely tunable.
next prev parent reply other threads:[~2024-01-12 12:53 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-17 15:15 [Bug tree-optimization/109893] New: " theodort at inf dot ethz.ch 2023-05-17 15:29 ` [Bug tree-optimization/109893] " pinskia at gcc dot gnu.org 2023-08-09 6:33 ` pinskia at gcc dot gnu.org 2024-01-12 12:53 ` rguenth at gcc dot gnu.org [this message] 2024-03-08 15:36 ` law at gcc dot gnu.org 2024-05-07 7:40 ` [Bug tree-optimization/109893] [14/15 " rguenth at gcc dot gnu.org
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