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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/52589] New: VRP missed optimization
Date: Wed, 14 Mar 2012 16:13:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52589

             Bug #: 52589
           Summary: VRP missed optimization
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org


extern void link_error (void);

void
foo (unsigned int s)
{
  if (s + 0x70000000 < 0xf0000000U)
    {
      if (s >= 0x80000000U && s < 0x90000000U)
        link_error ();
    }
}

void
bar (unsigned int s)
{
  if (s + 0x70000000 >= 0xf0000000U)
    {
      if (s < 0x80000000U || s >= 0x90000000U)
        link_error ();
    }
}

In the above testcase, bar is optimized fine (VRP adds an ASSERT_EXPR with
range [0x80000000, 0x8fffffff] and optimizes away the test), but in foo it
isn't - the range there is ~[0x80000000, 0x8ffffffff] and we don't handle the
VR_ANTI_RANGE somewhere where we should.
I've noticed this while working on PR52267 - the vrp65.c testcase that I'm
bootstrapping there right now needs to have 4 tests commented out (well,
replaced by checks of a few selected values from the range which VRP optimizes
out properly).