[Bug optimization/14495] New: [tree-ssa] Propagate range info into a switch statement

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

Consider:

void bar0 (void);
void bar1 (void);
void bar2 (void);
void bar3 (void);

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

  switch (a)
    {
    case  99: bar0 (); return;
    case 100: bar1 (); return;
    case 101: bar2 (); return;
    case 102: bar3 (); return;
    }
}

case 99 won't trigger, but I still get:

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

<L0>:;
  return;

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

<L2>:;
  return;

<L3>:;
  switch (a)
    {
      case 99: goto <L4>;
      case 100: goto <L5>;
      case 101: goto <L6>;
      case 102: goto <L7>;
      default : goto <L8>;
    }

<L4>:;
  bar0 () [tail call];
  return;

<L5>:;
  bar1 () [tail call];
  return;

<L6>:;
  bar2 () [tail call];
  return;

<L7>:;
  bar3 () [tail call];
  return;

<L8>:;
  return;

}

-- 
           Summary: [tree-ssa] Propagate range info into a switch statement
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Keywords: pessimizes-code
          Severity: normal
          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=14495