[Bug target/82403] New: [openacc, nvptx] Optimize binary shuffle tree

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82403

            Bug ID: 82403
           Summary: [openacc, nvptx] Optimize binary shuffle tree
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

In nvptx_goacc_reduction_fini we find the following todo:
...
  if (level == GOMP_DIM_VECTOR)
    {
      /* Emit binary shuffle tree.  TODO. Emit this as an actual loop,          
         but that requires a method of emitting a unified jump at the           
         gimple level.  */
...

A fix for this was committed to the gomp4 branch in august 2016 (submitted
here: https://gcc.gnu.org/ml/gcc-patches/2016-08/msg02147.html ), but it's not
yet present on trunk.