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From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/32075] New: can't determine dependence between p->a[x+i] and p->a[x+i+1] where x is invariant but defined in the function Date: Thu, 24 May 2007 21:56:00 -0000 [thread overview] Message-ID: <bug-32075-6528@http.gcc.gnu.org/bugzilla/> (raw) While looking into some failures on the pointer plus branch after fixing up forwprop, I noticed that we would get a failure in the vectorizer testsuite and the reason is because we no longer could determine dependence for the two data accesses. Here is the testcase which is a modified version of vect-102.c which gets us the same IR as what the pointer plus branch gives: /* { dg-require-effective-target vect_int } */ #include <stdlib.h> #include <stdarg.h> #include "tree-vect.h" #define N 9 struct extraction { int a[N]; int b[N]; }; static int a[N] = {1,2,3,4,5,6,7,8,9}; static int b[N] = {2,3,4,5,6,7,8,9,9}; int main1 (int x, int y) { int i; unsigned x1 = x; struct extraction *p; p = (struct extraction *) malloc (sizeof (struct extraction)); for (i = 0; i < N; i++) { p->a[i] = a[i]; if (x == 135) abort (); /* to avoid vectorization */ } /* Not vectorizable: distance 1. */ for (i = 0; i < N - 1; i++) { p->a[x1 + i] = p->a[x1 + i + 1]; } /* check results: */ for (i = 0; i < N; i++) { if (p->a[i] != b[i]) abort(); } return 0; } int main (void) { check_vect (); return main1 (0, N); } /* { dg-final { scan-tree-dump-times "vectorized 1 loops" 0 "vect" } } */ /* { dg-final { scan-tree-dump-times "possible dependence between data-refs" 1 "vect" } } */ /* { dg-final { cleanup-tree-dump "vect" } } */ -------------------------- cut --------------- if you change the 1 to 8, we should be able to vectorize that loop too. Note I was wrong in PR 31995, that we got the same IR for that testcase as we got for this bug, I had missed the cast in the IR. Anyways this is represenative of what the IR looks like for the testcase on the pointer plus branch. -- Summary: can't determine dependence between p->a[x+i] and p- >a[x+i+1] where x is invariant but defined in the function Product: gcc Version: 4.3.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P3 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: pinskia at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32075
next reply other threads:[~2007-05-24 21:56 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-05-24 21:56 pinskia at gcc dot gnu dot org [this message] 2007-05-25 1:06 ` [Bug tree-optimization/32075] " pinskia at gcc dot gnu dot org 2007-06-18 11:04 ` dorit at il dot ibm dot com 2007-06-20 16:57 ` spop at gcc dot gnu dot org 2007-06-20 23:42 ` spop at gcc dot gnu dot org 2007-06-20 23:45 ` spop at gcc dot gnu dot org 2007-06-21 21:05 ` ubizjak at gmail dot com 2007-06-24 4:07 ` pinskia at gcc dot gnu dot org
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