[Bug other/68500] New: Remove in_loop_pipeline usage

["vries at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68500

            Bug ID: 68500
           Summary: Remove in_loop_pipeline usage
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Consider pass_slp_vectorize::execute
...
pass_slp_vectorize::execute (function *fun)
{
  basic_block bb;

  bool in_loop_pipeline = scev_initialized_p ();
  if (!in_loop_pipeline)
    {
      loop_optimizer_init (LOOPS_NORMAL);
      scev_initialize ();
    }

  ...

  if (!in_loop_pipeline)
    {
      scev_finalize ();
      loop_optimizer_finalize ();
    } 
...

It uses an in_loop_pipeline variable, initialized using scev_initialized_p to
detect whether the pass is run in the loop pipeline, to allow different
behaviour inside and outside the loop pipeline.

We want a cleaner way to allow passes to run correctly inside and outside the
loop pipeline.