[Bug tree-optimization/97008] New: [openacc] Remove invariant that IFN_UNIQUE is last stmt in bb

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97008

            Bug ID: 97008
           Summary: [openacc] Remove invariant that IFN_UNIQUE is last
                    stmt in bb
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

[ spin-off of PR97000 comment 9. ]

There's an invariant that says IFN_UNIQUE needs to be the last stmt in a bb.
The rationale given is that it speeds up lookup.

This is somewhat of a hack, and potentially inhibits various
optimizations/cleanups.

So, can we drop this invariant?

This patch (PR97000 comment 2) is probably needed, possibly more.