[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

--- Comment #9 from Andrew Pinski  ---
in GCC 13+ we get now (for the testcase in comment #0) at -O3:
```
   [local count: 452984831]:
  # i_lsm.4_2 = PHI 
  if (i_lsm.4_2 == 5)
goto ; [25.00%]
  else
goto ; [75.00%]

   [local count: 452984832]:
  goto ; [100.00%]
```
This is an infinite no matter which branch is taken ...
Coming in we get either `3->4->4->5` or `3->4->5` no matter what we end up in 5
always.

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

--- Comment #8 from Andrew Pinski  ---
Note I noticed gimple loop code invariant motion is causing comment #0 to be
really bad.

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

Richard Biener  changed:

   What|Removed |Added

 Status|NEW |ASSIGNED

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

--- Comment #7 from Andrew Pinski  ---
(In reply to Andrew Pinski from comment #2)
> Two things, we just don't jump thread.

The testcase in comment #2 works correctly on the trunk:
   [15.0%]:
  i_lsm.3_8 = i;
  switch (i_lsm.3_8)  [15.0%], case 5:  [85.0%]>

 [85.0%]:
  i = 4;

 [15.0%]:
  return 0;


That is no loop.

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[aldot at gcc dot gnu dot org]

--- Comment #6 from aldot at gcc dot gnu dot org  2007-12-14 15:00 ---
Still present on current trunk (20071214).
This used to work with 3.4.6:
.L14:
cmpl$5, %eax
ja  .L14
.ident  GCC: (GNU) 3.4.6 (Debian 3.4.6-6)

Not quite optimal though since this would be even better:
.L14:
cmpl $5,%eax
ja .L4711
.L4711:
jmp .L4711
(or something to that effect).


-- 

aldot at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||aldot at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu dot org]

--- Comment #5 from pinskia at gcc dot gnu dot org  2006-09-17 07:59 ---
(In reply to comment #2)
 Two things, we just don't jump thread.
The testcase mentioned in comment #2 is fixed but we still don't make an
infinite loop for the orginal case:
L9:;
  switch (i_lsm.25)
{
  case 0 ... 1: goto L1;
  case 2 ... 3: goto L12;
  case 5: goto L5;
  default : goto L9;
}
L5:;
  i_lsm.25 = 4;
  goto bb 3 (L9);
...
Which is obvious an infinite loop but we still go through the switch every
time.


-- 

pinskia at gcc dot gnu dot org changed:

   What|Removed |Added

   Last reconfirmed|2006-01-21 03:00:56 |2006-09-17 07:59:49
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[steven at gcc dot gnu dot org]

--- Additional Comments From steven at gcc dot gnu dot org  2005-05-06 
08:50 ---
Can someone explain what is expected here?  I get the following .optimized 
dump: 
 
main () 
{ 
  int lsm_tmp.1; 
  int D.1572; 
  int D.1571; 
  int i.0; 
 
L8:; 
  lsm_tmp.1 = i; 
  goto bb 2 (L10); 
 
L9:; 
 
L10:; 
  switch (lsm_tmp.1) 
{ 
  case 0 ... 1: goto L1; 
  case 2 ... 3: goto L13; 
  case 5: goto L5; 
  default : goto L9; 
} 
 
L1:; 
  i = lsm_tmp.1; 
  D.1571 = 1; 
  goto bb 6 (L7); 
 
L5:; 
  lsm_tmp.1 = 4; 
  goto bb 1 (L9); 
 
L13:; 
  i = lsm_tmp.1; 
  D.1571 = 0; 
 
L7:; 
  return D.1571; 
 
} 
 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-06 
13:39 ---
(In reply to comment #3)
 Can someone explain what is expected here?  I get the following .optimized 

This is what it should look like instead:
main () 
{ 
  int lsm_tmp.1; 
  int D.1572; 
  int D.1571; 
  int i.0; 
 
L8:; 
  lsm_tmp.1 = i; 
  goto bb 2 (L10); 
 
L9:; 
  goto L9;
 
L10:; 
  switch (lsm_tmp.1) 
{ 
  case 0 ... 1: goto L1; 
  case 2 ... 3: goto L13; 
  case 5: goto L5; 
  default : goto L9; 
} 
 
L1:; 
  i = lsm_tmp.1; 
  D.1571 = 1; 
  goto bb 6 (L7); 
 
L5:; 
  lsm_tmp.1 = 4; 
  goto bb 1 (L9); 
 
L13:; 
  i = lsm_tmp.1; 
  D.1571 = 0; 
 
L7:; 
  return D.1571; 
 
} 

So we should get an infinite loop for L9 because there is no way lsm_tmp.1 can 
change.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-04-13 
18:30 ---
Two things, we just don't jump thread.
Another testcase:
int i;
int main()
{
  for (;;)
  {
switch (i)
{
  case 5:
i = 4;
break;
  default:
return 0;
}
  }
}

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514

[Bug tree-optimization/20514] hoisting of label out of jumptable would take place at cse, should happen at trees

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-17 
17:23 ---
Confirmed.

-- 
   What|Removed |Added

   Severity|normal  |enhancement
 Status|UNCONFIRMED |NEW
 Ever Confirmed||1
   Keywords||missed-optimization, TREE
   Last reconfirmed|-00-00 00:00:00 |2005-03-17 17:23:27
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20514