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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/52254] New: VRP does not fold (~a) & N to a ^ N if a has range [0, N] Date: Wed, 15 Feb 2012 00:21:00 -0000 [thread overview] Message-ID: <bug-52254-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52254 Bug #: 52254 Summary: VRP does not fold (~a) & N to a ^ N if a has range [0, N] Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: pinskia@gcc.gnu.org While working on moving fold-const.c bit expression optimizations to a SSA based optimization, I found that if we optimize (a^N)&N to ~a & N, VRP does not change that to just a ^ N. Simple example: /* { dg-do compile } */ /* { dg-options "-O2 -fno-tree-ccp -fdump-tree-vrp1" } */ int f(int x) { if (x >= 0 && x <= 3) { x = (x ^ 3) & 3; } return x; } /* { dg-final { scan-tree-dump-times " & 3;" 0 "vrp1" { xfail *-*-* } } } */ /* { dg-final { cleanup-tree-dump "vrp1" } } */
next reply other threads:[~2012-02-15 0:21 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-02-15 0:21 pinskia at gcc dot gnu.org [this message] 2012-02-15 0:23 ` [Bug tree-optimization/52254] " pinskia at gcc dot gnu.org 2012-02-15 11:25 ` rguenth at gcc dot gnu.org 2012-02-16 3:05 ` pinskia at gcc dot gnu.org 2021-06-03 0:40 ` pinskia at gcc dot gnu.org
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