tree-optimization/112961 - include latch in if-conversion CSE
The following makes sure to also process the (empty) latch when
performing CSE on the if-converted loop body. That's important
to get all uses of copies propagated out on the backedge as well.
To avoid CSE on the PHI nodes itself which is prohibitive
(see PR90402) this temporarily adds a fake entry edge to the loop.
PR tree-optimization/112961
* tree-if-conv.cc (tree_if_conversion): Instead of excluding
the latch block from VN, add a fake entry edge.
* g++.dg/vect/pr112961.cc: New testcase.