[Bug tree-optimization/23622] Dom jump threading at -O1 confuses branch prediction

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-29 
12:57 -------
Hmm, in dom1 we get:
<bb 0>:
  goto <bb 4> (<L3>);

  # i_4 = PHI <i_1(2), i_2(4)>;
<L0>:;
  something ();
  i_3 = i_4 + 1;

  # i_1 = PHI <i_3(1)>;
<L1>:;
  if (i_1 <= 99) goto <L0>; else goto <L2>;

<L2>:;
  return;

  # i_2 = PHI <0(0)>;
<L3>:;
  goto <bb 1> (<L0>);

In PHI-OPT we get:
  # i_4 = PHI <i_3(1), 0(0)>;
<L0>:;
  something ();
  i_3 = i_4 + 1;
  if (i_3 <= 99) goto <L0>; else goto <L2>;

Becuase we run a cfg cleanup.  I don't see anything wrong here now.

This is the same for -O2 also.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23622