[Bug tree-optimization/44976] reductions with short variables do not get vectorized

[rguenth at gcc dot gnu dot org]

--- Comment #2 from rguenth at gcc dot gnu dot org  2010-07-20 14:48 ---
t.c:6: note: reduction: not commutative/associative: sum_13 = (short int)
D.2726_12;

this is because

  sum = (short)((int)sum + (int)a[i]);

cannot be folded to

  sum = sum + a[i];

as that exposes new undefined overflow.  Instead we fold it to

  sum = (short)((unsigned short)sum + (unsigned short)a[i]);

which the pattern detection does not handle explicitly.


-- 

rguenth at gcc dot gnu dot org changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
  GCC build triplet|elf |
   GCC host triplet|linux   |
 GCC target triplet|ia64|
   Keywords||missed-optimization
   Last reconfirmed|-00-00 00:00:00 |2010-07-20 14:48:32
   date||
Summary|short variables do not get  |reductions with short
   |vectorized  |variables do not get
   ||vectorized


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44976

[Bug tree-optimization/44976] reductions with short variables do not get vectorized

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44976

Richard Biener  changed:

   What|Removed |Added

  Known to work||10.1.0
 Resolution|--- |FIXED
 Status|NEW |RESOLVED

--- Comment #4 from Richard Biener  ---
Fixed in GCC 10.

[Bug tree-optimization/44976] reductions with short variables do not get vectorized

[amylaar at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44976

Jorn Wolfgang Rennecke  changed:

   What|Removed |Added

 CC||amylaar at gcc dot gnu.org

--- Comment #3 from Jorn Wolfgang Rennecke  ---
Ironically, this is a case where -fwrapv improves optimization.