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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/103325] 1 << -1 is never reduced to a constant during gimple Date: Fri, 19 Nov 2021 07:48:36 +0000 [thread overview] Message-ID: <bug-103325-4-tpUghRr89E@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-103325-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103325 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2021-11-19 Ever confirmed|0 |1 --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- I think we used to constant fold this as 1<<1. GCC 7 does > gcc-7 -S t.c -fdump-tree-original t.c: In function 'main': t.c:2:12: warning: right shift count is negative [-Wshift-count-negative] return 1 >> (-1); ^~ > cat t.c.003t.original ;; Function main (null) ;; enabled by -tree-original { return 2; } return 0; but IIRC that behavior was removed from {int_const,wide}_int_binop at some point, maybe also to enable sanitization. gimple-ssa-isolate-paths.c would be one place to turn such code into unreachable or traps (see other PRs to make the behavior configurable).
next prev parent reply other threads:[~2021-11-19 7:48 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-19 1:35 [Bug tree-optimization/103325] New: " pinskia at gcc dot gnu.org 2021-11-19 1:36 ` [Bug tree-optimization/103325] " pinskia at gcc dot gnu.org 2021-11-19 7:48 ` rguenth at gcc dot gnu.org [this message] 2021-11-19 12:14 ` pinskia at gcc dot gnu.org 2023-05-28 4:21 ` pinskia at gcc dot gnu.org
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