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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/113632] New: Range info for a^CST could be improved Date: Sun, 28 Jan 2024 06:23:30 +0000 [thread overview] Message-ID: <bug-113632-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113632 Bug ID: 113632 Summary: Range info for a^CST could be improved Product: gcc Version: 14.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: pinskia at gcc dot gnu.org Target Milestone: --- Take: ``` void dummy(); _Bool f(unsigned long a) { _Bool cmp = a > 8192; if (cmp) goto then; else goto e; then: unsigned long t = __builtin_clzl(a); // [0,50] t^=63; // [13,63] return t >= 13; e: dummy(); return 0; } ``` Currently after the t^=63; we get: ``` # RANGE [irange] int [1, 63] MASK 0x3f VALUE 0x0 _7 = _1 ^ 63; ``` But this could/should be improved to [13,63]. If we change to using minus instead: ``` t = 63 - t; ``` We get the better range and the comparison (t >= 13) is optimized away. ``` Folding statement: t_10 = 63 - t_9; Global Exported: t_10 = [irange] long unsigned int [13, 63] MASK 0x3f VALUE 0x0 Not folded ``` Yes this should up in real code, see the LLVM issue for more information on that.
next reply other threads:[~2024-01-28 6:23 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-01-28 6:23 pinskia at gcc dot gnu.org [this message] 2024-01-28 6:25 ` [Bug tree-optimization/113632] Range info for a^CSTP2-1 could be improved in some cases pinskia at gcc dot gnu.org 2024-03-04 14:53 ` amacleod at redhat dot com
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