[Bug tree-optimization/110327] [12/13/14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r12-4790-g4b3a325f07a

2024-03-08 Thread law at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110327

--- Comment #3 from Jeffrey A. Law  ---
Two block copies isn't fatal when the second one is the one with the actual
jump thread.  But costing does get more complex.  

Basically we copy 8 so that we can isolate its two incoming paths which thread
differently in bb10.  That's pretty standard stuff.

It looks like that particular threading possibility is hidden until after DOM3
is complete.  Prior to and during DOM3, there's another block in the way.


  # c.3_16 = PHI <0(3), 2(5)>
  _9 = h;
  _10 = *_9;
  _11 = *_10; 
  _12 = *_11; 
  _13 = (char) _12;
  if (_13 != -28)
goto ; [0.00%]
  else
goto ; [100.00%]
;;succ:   8
;;9

;;   basic block 8, loop depth 0
;;pred:   7
  __builtin_unreachable ();
;;succ:

;;   basic block 9, loop depth 1
;;pred:   7
  if (_12 <= 4)
goto ; [50.00%]
  else
goto ; [50.00%]
;;succ:   10
;;15

;;   basic block 10, loop depth 1
;;pred:   9
  _15 = d;
  *_10 = _15;
  if (c.3_16 <= 0)
goto ; [5.50%]
  else
goto ; [94.50%]

Note bb9.

[Bug tree-optimization/110327] [12/13/14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r12-4790-g4b3a325f07a

2024-03-08 Thread law at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110327

Jeffrey A. Law  changed:

   What|Removed |Added

   Priority|P3  |P2
 CC||law at gcc dot gnu.org

[Bug tree-optimization/110327] [12/13/14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r12-4790-g4b3a325f07a

2023-11-23 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110327

Andrew Pinski  changed:

   What|Removed |Added

 Ever confirmed|0   |1
 Status|UNCONFIRMED |NEW
 CC||pinskia at gcc dot gnu.org
   Last reconfirmed||2023-11-24

--- Comment #2 from Andrew Pinski  ---
Confirmed.

[Bug tree-optimization/110327] [12/13/14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r12-4790-g4b3a325f07a

2023-06-24 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110327

--- Comment #1 from Andrew Pinski  ---
What is interesting is that the call to foo is still there on the gimple level
in GCC 11, it is only on the RTL level it is able to be removed 

What I see missing on the gimple level on the trunk is a jump threading
opportunity (but might be too complex to do):
   [local count: 12528922893]:
  # c.3_16 = PHI <0(4), 2(7)>
  _9 = h;
  _10 = *_9;
  _11 = *_10;
  _12 = *_11;
  if (_12 <= 4)
goto ; [50.00%]
  else
goto ; [50.00%]

...

   [local count: 6264461501]:
  _15 = d;
  *_10 = _15;
  if (c.3_16 == 0)
goto ; [5.50%]
  else
goto ; [94.50%]

   [local count: 5919916023]:
  if (a.11_30 != 0)
goto ; [33.00%]
  else
goto ; [67.00%]

The threading is:
4->8->10->11
7->8->10->12

This requires copying bb 8 and 10. I am not saying it is the right thing to do
but rather that is how to optimize this out I think.


There is also this one too:
   [local count: 12528922784]:
  # a.11_30 = PHI <_18(14), -28(2)>
  c.0_3 = c;
  if (a.11_30 != 0)
goto ; [5.50%]
  else
goto ; [94.50%]


2->3->4
14->3

But as I said I have not looked into more than that.

[Bug tree-optimization/110327] [12/13/14 Regression] Missed Dead Code Elimination when using __builtin_unreachable since r12-4790-g4b3a325f07a

2023-06-21 Thread rguenth at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110327

Richard Biener  changed:

   What|Removed |Added

   Target Milestone|--- |12.4
   Keywords||missed-optimization