[Bug tree-optimization/18576] New: missing jump threading because of type changes

[pinskia at gcc dot gnu dot org]

struct loop
{
  int depth;
  struct loop **pred;
};

static __inline__ unsigned char
flow_loop_nested_p (const struct loop *outer, const struct loop *loop)
{
  return (loop->depth > outer->depth
  && loop->pred[outer->depth] == outer);
}

unsigned char
flow_bb_inside_loop_p (const struct loop *loop, const struct loop *source_loop)
{
  return loop == source_loop || flow_loop_nested_p (loop, source_loop);
}

In .64.final_cleanup:
<L2>:;
  iftmp.0 = 1;
  goto <bb 5> (<L14>);

<L4>:;
  iftmp.0 = 0;

<L14>:;
  if ((unsigned char) (int) (unsigned char) iftmp.0 != 0) goto <L8>; else goto 
<L7>;

See miss this jump threading (in fact we miss it on the RTL level also).
We do get better code already on the tree-cleanup-branch but that is because of 
my rewrite of PHI-OPT
for that branch we get:
<L12>:;
  iftmp.0 = 0;
  goto <bb 5> (<L4>);

<L1>:;
  iftmp.0 = (int) !(loop != *(source_loop->pred + (struct loop * *) ((unsigned 
int) D.1160 * 4)));

<L4>:;
  iftmp.1 = (int) ((unsigned char) (int) (unsigned char) iftmp.0 != 0);

-- 
           Summary: missing jump threading because of type changes
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18576