fix PR68693: Check for loop structure when extending the SCoP

fix PR68693: Check for loop structure when extending the SCoP

The check for dominance while extending the scop assumed that
multiple successors meant a loop which is not true in case of
conditionals around the loop.

Improved pretty printers for better debugging.

	PR tree-optimization/68693
        * graphite-scop-detection.c (dot_all_sese): New
        (dot_all_scops_1): Renamed to dot_all_sese.
        (dot_all_scops): Removed.
        (dot_sese): New.
        (dot_cfg): New.
        (scop_detection::get_nearest_dom_with_single_entry): Check that preds are from different loop levels.
        (scop_detection::get_nearest_pdom_with_single_exit): Check that succs are from different loop levels.
        (scop_detection::print_sese): Inlined.
        (scop_detection::print_edge): New.
        (scop_detection::merge_sese): Added dumps.
        * graphite.h: Add declarations.

gcc/testsuite/ChangeLog:

        * gfortran.dg/graphite/pr68693.f90: New test.

Co-Authored-By: Sebastian Pop <s.pop@samsung.com>
From-SVN: r231309