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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/101481] [11/12 Regression]
 -ftree-loop-distribute-patterns can slow down and increases size of code
Date: Sat, 17 Jul 2021 03:36:06 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101481

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
           Keywords|                            |missed-optimization
   Target Milestone|---                         |11.2
   Last reconfirmed|                            |2021-07-17
            Summary|-ftree-loop-distribute-patt |[11/12 Regression]
                   |erns can slow down and      |-ftree-loop-distribute-patt
                   |increases size of code      |erns can slow down and
                   |                            |increases size of code
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.  The ranges should be figured out that the max size is 4.

In fact GCC knows the range really (note I think it is really [0,2] but tha=
t is
a different issue) and the loop bounds is max 4.

;;   basic block 6, loop depth 1, count 805306369 (estimated locally), maybe
hot
;;    prev block 8, next block 9, flags: (NEW, REACHABLE, VISITED)
;;    pred:       9 [always]  count:603979777 (estimated locally)
(FALLTHRU,DFS_BACK)
;;                8 [always]  count:201326592 (estimated locally) (FALLTHRU)
  # RANGE [-1, 2]
  # i_17 =3D PHI <i_16(9), i_11(8)>
  # .MEM_21 =3D PHI <.MEM_15(9), .MEM_9(D)(8)>
  # RANGE [1, 3] NONZERO 3
  _4 =3D i_17 + 1;
  # VUSE <.MEM_21>
  _5 =3D a_10(D)->chunksD.1943[i_17];
  # .MEM_15 =3D VDEF <.MEM_21>
  a_10(D)->chunksD.1943[_4] =3D _5;
  # RANGE [-1, 1]
  i_16 =3D i_17 + -1;
  if (i_16 >=3D _20)
    goto <bb 9>; [75.00%]
  else
    goto <bb 7>; [25.00%]
;;    succ:       9 [75.0% (guessed)]  count:603979777 (estimated locally)
(TRUE_VALUE,EXECUTABLE)
;;                7 [25.0% (guessed)]  count:201326592 (estimated locally)
(FALSE_VALUE,EXECUTABLE)

;;   basic block 9, loop depth 1, count 603979777 (estimated locally), maybe
hot
;;    prev block 6, next block 7, flags: (NEW)
;;    pred:       6 [75.0% (guessed)]  count:603979777 (estimated locally)
(TRUE_VALUE,EXECUTABLE)
  goto <bb 6>; [100.00%]
;;    succ:       6 [always]  count:603979777 (estimated locally)
(FALLTHRU,DFS_BACK)=