[Bug tree-optimization/125672] Jump threading hurts conditional select formation

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125672

--- Comment #7 from Drea Pinski <pinskia at gcc dot gnu.org> ---
(In reply to ktkachov from comment #6)
> Can we teach the threader in tree-ssa-threadbackward.cc profitable_path_p to
> reject paths that are likely to be if-converted i.e. it is a diamond with
> pure operations and no memory ops that ends in a 2-operand PHI of a mode
> that can_conditionally_move_p ? I have a prototype for that that fixes the
> benchmark in question and seems to be relatively clean testsuite-wise

No because a lot of the time those are the ones which you want to be jump
threaded.

E.g.:
If (a) c = 2; else c = 3;
If (c == 3) ....