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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/55157] New: Missing VRP
Date: Wed, 31 Oct 2012 21:51:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55157

             Bug #: 55157
           Summary: Missing VRP
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pinskia@gcc.gnu.org
            Blocks: 55155


Testcase:
void gg(void);
int f(unsigned t)
{
  unsigned g = t*16;
  if (g==0)  return 1;
  gg();
  gg();
  gg();
  gg();
  gg();
  gg();
  if (g<=4)  return 1;
  return 0;
}

In the end there should only be one check for t == 0.
Yes this shows up in real code (well with the autovectorizer); See PR 55155