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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/110010] New: (a>>N) != (b>>N) is not optimized to (a^b) >= (1<<N) Date: Sun, 28 May 2023 00:31:46 +0000 [thread overview] Message-ID: <bug-110010-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110010 Bug ID: 110010 Summary: (a>>N) != (b>>N) is not optimized to (a^b) >= (1<<N) 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: ``` #define N 5 unsigned f(unsigned a, unsigned b) { return (a>>N) != (b>>N); } ``` This could be optimized down to just `return (a^b) <= (1<<N)`. This shows up in the testsuite as a pr94718-5.c failure when you add the following 2 match patterns: (simplify (negate (convert (lt @0 integer_zerop))) (if (!TYPE_UNSIGNED (TREE_TYPE (@0))) (with { tree type_unsigned = unsigned_type_for (TREE_TYPE (@0)); } (if (types_match (type, TREE_TYPE (@0)) || types_match (type_unsigned, type)) (convert (rshift @0 { build_int_cst (integer_type_node, element_precision (type) - 1); })))))) (simplify (convert (lt @0 integer_zerop)) (if (!TYPE_UNSIGNED (TREE_TYPE (@0))) (with { tree type_unsigned = unsigned_type_for (TREE_TYPE (@0)); } (if (types_match (type, TREE_TYPE (@0)) || types_match (type_unsigned, type)) (convert (rshift (convert:type_unsigned @0) { build_int_cst (integer_type_node, element_precision (type) - 1); }))))))
next reply other threads:[~2023-05-28 0:31 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-28 0:31 pinskia at gcc dot gnu.org [this message] 2023-05-28 0:37 ` [Bug tree-optimization/110010] " pinskia at gcc dot gnu.org 2023-09-04 7:57 ` pinskia at gcc dot gnu.org
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