[Bug tree-optimization/127292] `(a > 1) != a` should be optimized to `a != 0`

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127292

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot 
gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-09-09
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
The general rule here for

(a CMP CST) != a
(a CMP CST) ? 1 != a : 0 != a


So

(simplify
 (cmp1:c @0 (convert (cmp2@2 @0 CST@1)))
 (convert (cond! @2 (cmp1 @0 {one;}) (cmp1 @ {zero;})))

The problem here is we don't have comparisons combiners for cond here.

So we need to expansion of `a ? b : c` into `(a & b) | (!a & c)` or `(a & b) |
(a < c)`.  I am not sure it will always simplify so I will need some `!` on the
bit_and/lt/bit_ior I think.

Let me see what I can do.