[Bug tree-optimization/20702] New: [tcb] ASSERT_EXPRs are not inserted when a certain "if" statement is present.

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

Consider:

typedef struct {
  int code;
} *rtx;

extern void next_active_insn (rtx);

int
can_combine_p (rtx insn, rtx succ, rtx elt)
{
  rtx set = 0;
  if (succ)
    next_active_insn (succ);
  else
    next_active_insn (insn);
  if (insn->code == 3)
    set = insn;
  else if (insn->code == 5)
    {
      set = elt;
      if (set == 0)
	return 0;
    }
  else
    return 0;
  if (set == 0)
    return 1;
  return 0;
}

Here is the dump after inserting ASSERT_EXPRs.

can_combine_p (insn, succ, elt)
{
  struct 
  {
    int code;
  } * set;
  int D.1141;
  int D.1140;

<bb 0>:
  if (succ_4 != 0B) goto <L0>; else goto <L1>;

<L0>:;
  succ_8 = ASSERT_EXPR <succ_4, succ_4 != 0B>;
  next_active_insn (succ_8);
  goto <bb 3> (<L2>);

<L1>:;
  succ_9 = 0B;
  next_active_insn (insn_5);

<L2>:;
  D.1140_6 = insn_5->code;
  if (D.1140_6 == 3) goto <L9>; else goto <L4>;

<L4>:;
  D.1140_10 = D.1140_6;
  if (D.1140_10 == 5) goto <L5>; else goto <L13>;

<L5>:;
  if (elt_12 == 0B) goto <L13>; else goto <L9>;

  # set_1 = PHI <insn_5(3), elt_12(5)>;
<L9>:;
  if (set_1 == 0B) goto <L11>; else goto <L13>;

<L11>:;

  # D.1141_2 = PHI <0(5), 0(4), 1(7), 0(6)>;
<L13>:;
  return D.1141_2;

}

Note that we don't have ASSERT_EXPRs for "if" statements and memory access
that happen later in the function.

I've got a preliminary patch working.

-- 
           Summary: [tcb] ASSERT_EXPRs are not inserted when a certain "if"
                    statement is present.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: dnovillo at redhat dot com,gcc-bugs at gcc dot gnu dot
                    org
 BugsThisDependsOn: 20701


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20702