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From: "tobi at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/31313] New: consecutive strcmps are not merged Date: Thu, 22 Mar 2007 15:12:00 -0000 [thread overview] Message-ID: <bug-31313-8513@http.gcc.gnu.org/bugzilla/> (raw) I just ran into some code which did something like int strcmp(const char *, const char *); int f (const char *c) { return (strcmp (c, "aaa") == 0 || strcmp (c, "aab") == 0); } It would be possible to optimize this into something like (hopefully I get it right) int f (const char *c) { if (strncmp (c, "aa", 2)) return 0; return ((c[2] == 'a' || c[2] == 'b') && !c[3]); } Instead, we scan through the whole string twice, as can be seen in the assembly. Likewise, more complicated combinations of comparisons could be reduced into an optimal matching sequence. Putting this into component rtl-optimization, because the strcmp calls survive all of the tree optimizers unchanged. -- Summary: consecutive strcmps are not merged Product: gcc Version: 4.3.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: rtl-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: tobi at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31313
next reply other threads:[~2007-03-22 15:12 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-03-22 15:12 tobi at gcc dot gnu dot org [this message] 2007-03-22 15:28 ` [Bug tree-optimization/31313] " pinskia at gcc dot gnu dot org 2007-04-29 6:47 ` pinskia at gcc dot gnu dot org
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