[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |8.0

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The original testcase in comment #0 is fixed in GCC 8, I don't know what caused
the improvement though.

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|8.0                         |---

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #7)
> The original testcase in comment #0 is fixed in GCC 8, I don't know what
> caused the improvement though.

Well actually if you use the C++ front-end, it still fails.

for f2_signed, we start out as:
  _1 = MAX_EXPR <a3_4(D), a2_5(D)>;
  if (_1 >= a1_6(D))
    goto <bb 3>; [INV]
  else
    goto <bb 6>; [INV]

  <bb 3> :
  if (a3_4(D) < a2_5(D))
    goto <bb 6>; [INV]
  else
    goto <bb 4>; [INV]

  <bb 4> :

  <bb 6> :
  # iftmp.5_2 = PHI <a3_4(D)(4), a1_6(D)(2), a2_5(D)(3)>
  return iftmp.5_2;

phiopt1 transforms it to:
  _1 = MAX_EXPR <a3_4(D), a2_5(D)>;
  if (_1 >= a1_6(D))
    goto <bb 3>; [INV]
  else
    goto <bb 4>; [INV]

  <bb 3> :
  _3 = MAX_EXPR <a3_4(D), a2_5(D)>;

  <bb 4> :
  # iftmp.12_2 = PHI <_3(3), a1_6(D)(2)>

Which is perfect.
But then we don't exactly patch that _1 and _3 are the same though we do try to
simplify it at least on the trunk:
phiopt match-simplify trying:
        _1 >= a1_6(D) ? _3 : a1_6(D)

phiopt match-simplify trying:
        _1 < a1_6(D) ? a1_6(D) : _3

What happens afterwards is fre (or is it pre) figures out _1 and _3 are the
same and get:
  if (_1 >= a1_6(D))
    goto <bb 3>; [INV]
  else
    goto <bb 4>; [INV]

  <bb 3> :

  <bb 4> :
  # iftmp.12_2 = PHI <_1(3), a1_6(D)(2)>

Which then phiopt2 is able to simplify.
So if we iterate phiopt and fre we should able to handle all of these but that
is NOT a reasonable solution.
I have to think of a good way of solving these really.

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
One thing I noticed is that:
  _2 = MAX_EXPR <_6, a3_7(D)>;
  _3 = MAX_EXPR <_2, a3_7(D)>;

Is not optimized at all.

(for minmax (min max)
 (simplify
  (minmax:c (minmax:c@2 @0 @1) @0)
  @2))

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #9)
> One thing I noticed is that:
>   _2 = MAX_EXPR <_6, a3_7(D)>;
>   _3 = MAX_EXPR <_2, a3_7(D)>;
> 
> Is not optimized at all.
> 
> (for minmax (min max)
>  (simplify
>   (minmax:c (minmax:c@2 @0 @1) @0)
>   @2))

Submitted the patch for that as
https://gcc.gnu.org/pipermail/gcc-patches/2023-July/625135.html .
Note after that patch we get decent code for the original testcases but it is
not fully optimized at the gimple level.

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Andrew Pinski <pinskia@gcc.gnu.org>:

https://gcc.gnu.org/g:6d449531a60b56ed0f4aeb640aa9e46e4ec35208

commit r14-2698-g6d449531a60b56ed0f4aeb640aa9e46e4ec35208
Author: Andrew Pinski <apinski@marvell.com>
Date:   Thu Jul 20 17:36:29 2023 -0700

    MATCH: Add Max<Max<a,b>,a> -> Max<a,b> simplifcation

    This adds a simple match pattern to simplify
    `max<max<a,b>,a>` to `max<a,b>`.  Reassociation handles
    this already (r0-77700-ge969dbde29bfd396259357) but
    seems like we should be able to handle this even before
    reassociation.

    This fixes part of PR tree-optimization/80574 but more
    work is needed fix it the rest of the way. The original
    testcase there is fixed but the RTL level is what fixes
    it the rest of the way.

    OK? Bootstrapped and tested on x86_64-linux-gnu.

    gcc/ChangeLog:

            * match.pd (minmax<minmax<a,b>,a>->minmax<a,b>): New
            transformation.

    gcc/testsuite/ChangeLog:

            * gcc.dg/tree-ssa/reassoc-12.c: Disable all of
            the passes that enables match-and-simplify.
            * gcc.dg/tree-ssa/minmax-23.c: New test.

[Bug tree-optimization/80574] GCC fail to optimize nested ternary

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80574

--- Comment #12 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note the original example in comment #0 is now optimized for GCC 14 but only at
the RTL level rather than the gimple level.