[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

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> I will implement this match pattern since that is all that is needed now
> with phiopt using match.

Funny I came up with the same match patterns twice now.