On Sat, 12 Dec 2020, Jakub Jelinek via Gcc-patches wrote:
This patch adds the ~(X - Y) -> ~X + Y simplification requested in the PR (plus also ~(X + C) -> ~X + (-C) for constants C that can be safely negated.
Would it have been wrong to produce ~X - C without caring about negating (and then extending it to non-constants)?
I wonder if this makes /* ~(~X - Y) -> X + Y and ~(~X + Y) -> X - Y. */ useless. -- Marc Glisse
