[Bug tree-optimization/85692] New: Two source permute not used for vector initialization

[linux at carewolf dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85692

            Bug ID: 85692
           Summary: Two source permute not used for vector initialization
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: linux at carewolf dot com
  Target Milestone: ---

If a vector initialization is using elements from only a single vector source,
it will be optimized as a shuffle, but if it is using elements from two, it
will not be attempted.

This appears to be a missing case in
tree-ssa-forwprop.c:simplify_vector_constructor