[Bug optimization/14490] New: [tree-ssa] Simplify "a - 10 > 150" into "a > 160"

["kazu at cs dot umass dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

Consider:

void bar (void);

void
foo (int a)
{
  if (a < 100)
    return;
  if (200 < a)
    return;

  if (a - 10 > 150)
    bar ();
}

We know that "a" is between 100 and 200 after the first two ifs.
So we should be able to simplify "a - 10 > 150" into "a > 160".
Here is what I get:

foo (a)
{
  int T.0;

<bb 0>:
  if (a <= 99) goto <L0>; else goto <L1>;

<L0>:;
  return;

<L1>:;
  if (a > 200) goto <L2>; else goto <L3>;

<L2>:;
  return;

<L3>:;
  if (a - 10 > 150) goto <L4>; else goto <L5>;

<L4>:;
  bar () [tail call];

<L5>:;
  return;

}

-- 
           Summary: [tree-ssa] Simplify "a - 10 > 150" into "a > 160"
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14490