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From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/95836] New: Failure to remove strchr converted to bool with string literal when bit magic would be much more efficient (and sometimes smaller) Date: Tue, 23 Jun 2020 09:41:53 +0000 [thread overview] Message-ID: <bug-95836-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95836 Bug ID: 95836 Summary: Failure to remove strchr converted to bool with string literal when bit magic would be much more efficient (and sometimes smaller) Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: gabravier at gmail dot com Target Milestone: --- bool f(char c) { return strchr("1234567890", c); } This (and a lot of other similar strchr calls with string literals) can be optimized to using a few bitwise operations (here, to something like `return ((unsigned)c < 64) & ((((uint64_t)1 << c) & 287948901175001089) != 0);`). This transformation is done by LLVM, but not by GCC.
next reply other threads:[~2020-06-23 9:41 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-23 9:41 gabravier at gmail dot com [this message] 2020-06-23 9:48 ` [Bug tree-optimization/95836] " jakub at gcc dot gnu.org 2020-06-23 15:55 ` gabravier at gmail dot com 2020-06-23 16:43 ` jakub at gcc dot gnu.org
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