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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/114502] New: Missed sccp final value with `a = -a` Date: Wed, 27 Mar 2024 21:02:31 +0000 [thread overview] Message-ID: <bug-114502-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114502 Bug ID: 114502 Summary: Missed sccp final value with `a = -a` Product: gcc Version: 14.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: pinskia at gcc dot gnu.org Target Milestone: --- Inspired by PR 114485 and PR 114476. I noticed that SCCP is not figuring out what happens when just doing negative of the value. These days we do handle `^&|` so handling unary - should be in a similar way I suspect. Testcase: ``` [[gnu::noipa]] unsigned f(unsigned c) { for (int i = 0; i < 1024; i ++) { c *= -1; } return c; } ``` Note non-constant loop bounds handling is in a different bug report even. The above should be optimized to just `return -c;` for -O2; We do optimize it at -O3 but that is because the complete loop unroller figures out the cost for the loop is nothing.
next reply other threads:[~2024-03-27 21:02 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-03-27 21:02 pinskia at gcc dot gnu.org [this message] 2024-03-27 21:07 ` [Bug tree-optimization/114502] " pinskia at gcc dot gnu.org
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