[Bug tree-optimization/19832] don't remove an if when we know the value is the same as with the if (subtraction)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19832

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot 
gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I will implement this match pattern since that is all that is needed now with
phiopt using match.

Something like:
(simplify
 (cond (ne @0 @1) (minus@2 @0 @1) (zerop@3))
 (@2))
Should work.

Note there might be need to be a check for HONOR_SIGNED_ZEROS and maybe
HONOR_NANS missing.