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

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2004-11-20 17:01 -------
I have the following in the .optimized dump: 
 
flow_bb_inside_loop_p (loop, source_loop) 
{ 
  unsigned char D.1171; 
  struct loop * D.1170; 
  struct loop * * D.1169; 
  struct loop * * D.1168; 
  unsigned int D.1167; 
  unsigned int D.1166; 
  struct loop * * D.1165; 
  int D.1164; 
  int D.1163; 
  int iftmp.0; 
  int D.1161; 
  struct loop * outer; 
  struct loop * loop; 
  unsigned char D.1146; 
  unsigned char D.1145; 
  int iftmp.1; 
  int D.1140; 
  int D.1160; 
 
  # BLOCK 0 
  # PRED: ENTRY [100.0%]  (fallthru,exec) 
  if (loop == source_loop) goto <L8>; else goto <L0>; 
  # SUCC: 6 [10.4%]  (true,exec) 1 [89.6%]  (false,exec) 
 
  # BLOCK 1 
  # PRED: 0 [89.6%]  (false,exec) 
<L0>:; 
  D.1164 = loop->depth; 
  if (source_loop->depth <= D.1164) goto <L4>; else goto <L1>; 
  # SUCC: 4 [50.0%]  (true,exec) 2 [50.0%]  (false,exec) 
 
  # BLOCK 2 
  # PRED: 1 [50.0%]  (false,exec) 
<L1>:; 
  if (loop != *(source_loop->pred + (struct loop * *) ((unsigned int) D.1164 * 
4))) goto <L4>; else goto <L2>; 
  # SUCC: 4 [81.0%]  (true,exec) 3 [19.0%]  (false,exec) 
 
  # BLOCK 3 
  # PRED: 2 [19.0%]  (false,exec) 
<L2>:; 
  iftmp.0 = 1; 
  goto <bb 7> (<L14>); 
  # SUCC: 7 [100.0%]  (fallthru,exec) 
 
  # BLOCK 4 
  # PRED: 1 [50.0%]  (true,exec) 2 [81.0%]  (true,exec) 
<L4>:; 
  iftmp.0 = 0; 
  # SUCC: 7 [100.0%]  (fallthru) 
 
  # BLOCK 7 
  # PRED: 4 [100.0%]  (fallthru) 3 [100.0%]  (fallthru,exec) 
<L14>:; 
  if ((unsigned char) (int) (unsigned char) iftmp.0 != 0) goto <L8>; else goto 
<L7>; 
  # SUCC: 6 [33.0%]  (true,exec) 5 [67.0%]  (false,exec) 
 
  # BLOCK 5 
  # PRED: 7 [67.0%]  (false,exec) 
<L7>:; 
  iftmp.1 = 0; 
  goto <bb 8> (<L15>); 
  # SUCC: 8 [100.0%]  (fallthru,exec) 
 
  # BLOCK 6 
  # PRED: 0 [10.4%]  (true,exec) 7 [33.0%]  (true,exec) 
<L8>:; 
  iftmp.1 = 1; 
  # SUCC: 8 [100.0%]  (fallthru) 
 
  # BLOCK 8 
  # PRED: 6 [100.0%]  (fallthru) 5 [100.0%]  (fallthru,exec) 
<L15>:; 
  return (int) (unsigned char) iftmp.1; 
  # SUCC: EXIT [100.0%] 
} 
 
Control flow graph: 
 
ENTRY 
| 
0 
|\ 
| \ 
1  \ 
|\  \ 
| \  \ 
2  \  \ 
|\ |  | 
| \|  | 
3  4  | 
| /   | 
|/    | 
7     / 
|\   / 
| \ / 
5  6 
| / 
|/ 
8 
| 
EXIT 
 
 
 
Dominator tree: 
 
  0 
 /|\ 
6 8 1 
   /|\ 
  4 7 2 
    | | 
    5 3 
 
 
The problematic part is here: 
 
  # BLOCK 3 
  # PRED: 2 [19.0%]  (false,exec) 
<L2>:; 
  iftmp.0 = 1; 
  goto <bb 7> (<L14>); 
  # SUCC: 7 [100.0%]  (fallthru,exec) 
 
  # BLOCK 4 
  # PRED: 1 [50.0%]  (true,exec) 2 [81.0%]  (true,exec) 
<L4>:; 
  iftmp.0 = 0; 
  # SUCC: 7 [100.0%]  (fallthru) 
 
  # BLOCK 7 
  # PRED: 4 [100.0%]  (fallthru) 3 [100.0%]  (fallthru,exec) 
<L14>:; 
  if ((unsigned char) (int) (unsigned char) iftmp.0 != 0) goto <L8>; else goto 
<L7>; 
  # SUCC: 6 [33.0%]  (true,exec) 5 [67.0%]  (false,exec) 
 
 
Possible causes of the missed jump thread: 
1) Are casts getting in the way? 
2) Do we need that one of edges into the condition we want to 
   thread through dominates the block? 
 
 

-- 


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