[Bug gcov-profile/100145] missed optimization for dead code elimination at -O3 (vs. -O2)

2023-06-09 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100145

--- Comment #4 from Andrew Pinski  ---
(In reply to Richard Biener from comment #2)
> So we get optimize_edge_for_size_p () returning OPTIMIZE_SIZE_BALANCED and
> thus optimize_edge_for_speed_p which is
> 
> 340 bool
> 341 optimize_edge_for_speed_p (edge e)
> 342 {
> 343   return !optimize_edge_for_size_p (e);
> 344 }
> 
> return false.  And that's likely because this is 'main'. 

Yes it is.
If we do s/main/c123/
And then add:
```
int main()
{
return c123();
}
```
The -O3 issue goes away.

[Bug gcov-profile/100145] missed optimization for dead code elimination at -O3 (vs. -O2)

2021-05-20 Thread rguenth at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100145

--- Comment #3 from Richard Biener  ---
Note after inlining we still have a backedge into BB 3:

   [local count: 1073741824]:
  c = 0;
  b.1_7 = b;
  if (b.1_7 != 0)
goto ; [34.00%]
  else
goto ; [66.00%]

   [local count: 3318838410]:
  _9 = 1;
  _10 = 0;
  _11 = _9 & _10;
  if (_11 != 0)
goto ; [50.00%]
  else
goto ; [50.00%]

   [local count: 1659419208]:
  _12 = 0;
  _13 = _10 & _12;
  if (_13 != 0)
goto ; [50.00%]
  else
goto ; [50.00%]

   [local count: 829709603]:
  iftmp.0_14 = 1;

   [local count: 3318838410]:
  # iftmp.0_15 = PHI <0(3), 0(4), iftmp.0_14(5)>
  _19 = iftmp.0_15;
  _8 = _19;
  c = _8;
  if (_8 != 0)
goto ; [11.00%]
  else
goto ; [89.00%]

   [local count: 1073741824]:

but that's quickly elided by CCP after inlining producing

   [local count: 1073741824]:
  c = 0;
  b.1_7 = b;
  if (b.1_7 != 0)
goto ; [34.00%]
  else
goto ; [66.00%]

   [local count: 3318838410]:
  if (0 != 0)
goto ; [50.00%]
  else
goto ; [50.00%]

   [local count: 1659419208]:
  if (0 != 0)
goto ; [50.00%]
  else
goto ; [50.00%]

   [local count: 829709603]:

   [local count: 3318838410]:
  c = 1;
  if (1 != 0)
goto ; [11.00%]
  else
goto ; [89.00%]

   [local count: 1073741824]:

and the CFG cleanup ends up with the following:

   [local count: 1073741824]:
  c = 0;
  b.1_7 = b;
  if (b.1_7 != 0)
goto ; [34.00%]
  else
goto ; [66.00%]

   [local count: 3318838410]:
  c = 1;

   [local count: 1073741824]:
  d = 1;
  _1 = c;
  if (_1 > 100)
goto ; [33.00%]
  else
goto ; [67.00%]

   [local count: 354334800]:
  foo ();

   [local count: 1073741824]:
  return 0;

[Bug gcov-profile/100145] missed optimization for dead code elimination at -O3 (vs. -O2)

2021-04-20 Thread rguenth at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100145

Richard Biener  changed:

   What|Removed |Added

  Component|ipa |gcov-profile

--- Comment #2 from Richard Biener  ---
So we get optimize_edge_for_size_p () returning OPTIMIZE_SIZE_BALANCED and
thus optimize_edge_for_speed_p which is

340 bool
341 optimize_edge_for_speed_p (edge e)
342 {
343   return !optimize_edge_for_size_p (e);
344 }

return false.  And that's likely because this is 'main'.  At -O2 BB counts
are broken:

   [local count: 1073741824]:
  c = 0;
  b.1_7 = b;
  if (b.1_7 != 0)
goto ; [34.00%]
  else
goto ; [66.00%]

   [local count: 708669600]:
  goto ; [100.00%]

   [local count: 3318838410]:
  c = 1;

   [local count: 1073741824]:
  d = 1;

here 3->4 artificially appears 'hot'.  The bogus counts appear during IPA
inlining of g() into main.