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From: "manolis.tsamis at vrull dot eu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/114326] New: Missed optimization for A || B when !B implies A. Date: Wed, 13 Mar 2024 14:19:19 +0000 [thread overview] Message-ID: <bug-114326-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114326 Bug ID: 114326 Summary: Missed optimization for A || B when !B implies A. Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: manolis.tsamis at vrull dot eu Target Milestone: --- The function below doesn't fold to return 0; int cmp1(uint64_t d1, uint64_t d2) { if (((d1 ^ d2) & 0xabcd) == 0 || d1 != d2) return 0; return foo(); } while the following function does: int cmp2(uint64_t d1, uint64_t d2) { if (d1 != d2 || ((d1 ^ d2) & 0xabcd) == 0) return 0; return foo(); } The functions are equivalent since the lhs and rhs of || don't have side effects. In general, there pattern here is a side-effect free expression a || b where !b implies a should be optimized to true. As in the testcase above, a doesn't necessarily imply !b. Something similar could be stated for && expressions. Complementary godbolt link: https://godbolt.org/z/qK5bYf36T
next reply other threads:[~2024-03-13 14:19 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-03-13 14:19 manolis.tsamis at vrull dot eu [this message] 2024-03-13 19:06 ` [Bug tree-optimization/114326] " pinskia at gcc dot gnu.org 2024-03-13 21:18 ` ptomsich at gcc dot gnu.org 2024-03-13 21:41 ` pinskia at gcc dot gnu.org
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