[Bug tree-optimization/27441] New: VAR - 1 not identified as the same as VAR + -1

[dann at godzilla dot ics dot uci dot edu]

It seems that neither FRE nor PRE can determine that stride.115 - 1 is the same
as stride.115 + -1 in the example below (taken from the comm3 function in mgrid
from SPEC2000). (Or am I missing something?)

<bb 2>:
  stride.115 = *n;
  stride.117 = stride.115 * stride.115;
  offset.118 = ~stride.115 - stride.117;
  D.1969 = stride.115 - 1;
  if (D.1969 > 1) goto <L68>; else goto <L24>;

<L68>:;
  pretmp.221 = stride.115 + -1;
  pretmp.228 = offset.118 + pretmp.221;
  pretmp.236 = offset.118 + stride.115;
  i3 = 2;


-- 
           Summary: VAR - 1 not identified as the same as VAR + -1
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dann at godzilla dot ics dot uci dot edu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27441