[Bug tree-optimization/107888] [12/13 Regression] Missed min/max transformation in phiopt due to VRP

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107888

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> which means we fail to optimize a > b ? 1 : b as well, no?

Yes that is correct.

Even for max, "a >= b ? a : 6;" would need to be "reverted" 6 back to b.

  <bb 5> [local count: 1073741824]:
  if (ab_2(D) >= bb_3(D))
    goto <bb 6>; [65.00%]
  else
    goto <bb 7>; [35.00%]

  <bb 6> [local count: 697932184]:

  <bb 7> [local count: 1073741824]:
  # c_1 = PHI <ab_2(D)(6), 6(5)>


The min/max patterns inside match needs to handle CST if the ranges of the two
operands overlap with one/two values.

Even though this is a regression, I don't know if this shows up in real code
and is a small optimization really so I would suspect a P4 for this really as
it requires a bigger change that most likely won't be backported. I filed it as
it was showing up while I was working on the patch for PR 101805 (which won't
be submitted until GCC 14 anyways).