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From: "tkoenig at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/21278] New: Move maximum out of a loop Date: Fri, 29 Apr 2005 08:17:00 -0000 [thread overview] Message-ID: <20050429081733.21278.tkoenig@gcc.gnu.org> (raw) This could help in reducing the amount of work for bounds checking. $ cat mymax.c #include <stdlib.h> #include <stdio.h> int main() { char *p; int i,j,n; scanf("%d",&n); j = 0; for (i=0; i<n; i++) { if (j < i) j = i; } printf("%d\n",j); return 0; } $ gcc -g -funroll-all-loops -S -O3 -fdump-tree-optimized mymax.c still does the do loop: <L13>:; j = 0; i = 0; <L0>:; j = MAX_EXPR <j, i>; i = i + 1; if (i != n.10) goto <L0>; else goto <L4>; when the loop could be optimized to if (n <= 0) j = 0; else j = n-1; -- Summary: Move maximum out of a loop Product: gcc Version: 4.1.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P2 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: tkoenig at gcc dot gnu dot org CC: gcc-bugs at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21278
next reply other threads:[~2005-04-29 8:17 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2005-04-29 8:17 tkoenig at gcc dot gnu dot org [this message] 2005-04-30 17:52 ` [Bug tree-optimization/21278] " pinskia at gcc dot gnu dot org
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