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From: "kazu at cs dot umass dot edu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/21090] New: VRP does not notice nonzero-ness from a PHI node Date: Mon, 18 Apr 2005 17:39:00 -0000 [thread overview] Message-ID: <20050418173921.21090.kazu@cs.umass.edu> (raw) Consider: int g, h; int foo (int a) { int *p; if (a) p = &g; else p = &h; if (p != 0) return 1; else return 0; } With -O2 -fno-dominator-opts, VRP does not optimize away the "if" statement. This is because VRP does not run the propagator when it does not insert any ASSERT_EXPR. Even if I force it to run the propagator by forcing vrp_initialize to return true, the meet function decides that the lattice value of p at the second "if" statement is VARYING. I guess we can teach the meet function to generate ~[0, 0] when we meet &g and &h. -- Summary: VRP does not notice nonzero-ness from a PHI node Product: gcc Version: unknown Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P2 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: kazu at cs dot umass dot edu CC: dnovillo at redhat dot com,gcc-bugs at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21090
next reply other threads:[~2005-04-18 17:39 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2005-04-18 17:39 kazu at cs dot umass dot edu [this message] 2005-04-18 19:13 ` [Bug tree-optimization/21090] " pinskia at gcc dot gnu dot org 2005-06-02 2:59 ` cvs-commit at gcc dot gnu dot org 2005-06-02 3:07 ` dnovillo at gcc dot gnu dot org 2005-06-02 18:47 ` pinskia at gcc dot gnu dot org
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