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[Bug optimization/13299] New: Unsafe treatment of extended givs


Loops of the form:

    void f (unsigned int *x)
    {
      unsigned char i;
      int j;

      i = 0x10;
      for (j = 0; j < 0x10; j++)
        {
          i += 0xe8;
          x[i] = 0;
          i -= 0xe7;
        }
    }

are miscompiled on x86 with -freduce-all-givs.  Complete gcc.dg-style
testcase attached.

-- 
           Summary: Unsafe treatment of extended givs
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rsandifo at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13299


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