[Bug tree-optimization/126689] Missed removal of nested copysigns

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126689

--- Comment #2 from ktkachov at gcc dot gnu.org ---
(In reply to Richard Biener from comment #1)
> A backprop thing?

In the general case I guess, but a straightforward match.pd pattern first?