http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59429
--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
My idea was to have sth like tree-affine for conditions and that condition
optimizing passes (like ifcombine or ifcvt or phiopt) build an on-the-side
representation for this, also catching straight-line code
a = b < 0;
c = d > 1;
d = a | c;
if (d)
...
the tree-affine like condition can be normalized and simplified on-the-side
and you'd do simplifications/lookup using that machinery, only emitting
changed computes in a transform stage. Basically you collect BB or edge
predicates (like ifcvt does) but with a more elaborate machinery that
allows for simplification (ifcombine has its own as well).
I wouldn't try to tackle this testcase from a pattern matching side.
In principle comment#4 looks like sth for phiopt.
