[Bug tree-optimization/126143] phiopt does not flatten predicate-uniform multi-PHI diamonds: argmax-style scalar loops keep unpredictable branches at -O2

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126143

--- Comment #5 from ptomsich at gcc dot gnu.org ---
Created attachment 64981
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64981&action=edit
b381e58ccc2.patch

Here is the proposed change to handle this in ifcvt.
This extends the usage of the cond_inverted fallback (added in
r13-5962-g7d5a935070e) to cover our case.

It provides the full benefit on the workload.