[Bug tree-optimization/112626] New: `ABS(a) CMP a` can be optimized

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112626

            Bug ID: 112626
           Summary: `ABS(a) CMP a` can be optimized
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

This assumes, non-wrapping types, non-signed zero types
`abs(a) >= a` -> true
`abs(a) <  a` -> false
`abs(a) <= a` -> `a >= 0`
`abs(a) == a` -> `a >= 0`
`abs(a) != a` -> `a < 0`
`abs(a) >  a` -> `a < 0`


For wrapping types (non-signed zero types) or `((type)absu)`:
`abs(a) >= a` -> `a != TYPE_MIN`
`abs(a) <  a` -> `a == TYPE_MIN`
`abs(a) != a` -> `a <  0 & a != TYPE_MIN`
`abs(a) >  a` -> `a <  0 & a != TYPE_MIN`
`abs(a) == a` -> `a >= 0 | a == TYPE_MIN`
`abs(a) <= a` -> `a >= 0 | a == TYPE_MIN`