[gcc/devel/omp/gcc-12] graphite: Adjust scop loop-nest choice

[gcc/devel/omp/gcc-12] graphite: Adjust scop loop-nest choice

[Kwok Yeung]

https://gcc.gnu.org/g:b1e894b815ebf8d8a757cf324c93f17582b62b86

commit b1e894b815ebf8d8a757cf324c93f17582b62b86
Author: Frederik Harwath <frederik@codesourcery.com>
Date:   Tue Nov 16 16:21:57 2021 +0100

    graphite: Adjust scop loop-nest choice
    
    The find_common_loop function is used in Graphite to obtain a common
    super-loop of all loops inside a SCoP.  The function is applied to the
    loop of the destination block of the edge that leads into the SESE
    region and the loop of the source block of the edge that exits the
    region.  The exit block is usually introduced by the canonicalization
    of the loop structure that Graphite does to support its code
    generation. If it is empty, it may happen that it belongs to the outer
    fake loop.  This way, build_alias_set may end up analysing
    data-references with respect to this loop although there may exist a
    proper super-loop of the SCoP loops.  This does not seem to be correct
    in general and it leads to problems with runtime alias check creation
    which fails if executed on a loop without niter information.
    
    gcc/ChangeLog:
    
            * graphite-scop-detection.cc (scop_context_loop): New function.
            (build_alias_set): Use scop_context_loop instead of find_common_loop.
            * graphite-isl-ast-to-gimple.cc (graphite_regenerate_ast_isl): Likewise.
            * graphite.h (scop_context_loop): New declaration.

Diff:
---
 gcc/ChangeLog.omp                 |  7 +++++++
 gcc/graphite-isl-ast-to-gimple.cc |  4 +---
 gcc/graphite-scop-detection.cc    | 21 ++++++++++++++++++---
 gcc/graphite.h                    |  1 +
 4 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/gcc/ChangeLog.omp b/gcc/ChangeLog.omp
index 955e3a2222f..8773233b4d9 100644
--- a/gcc/ChangeLog.omp
+++ b/gcc/ChangeLog.omp
@@ -1,3 +1,10 @@
+2021-11-16  Frederik Harwath  <frederik@codesourcery.com>
+
+	* graphite-scop-detection.cc (scop_context_loop): New function.
+	(build_alias_set): Use scop_context_loop instead of find_common_loop.
+	* graphite-isl-ast-to-gimple.cc (graphite_regenerate_ast_isl): Likewise.
+	* graphite.h (scop_context_loop): New declaration.
+
 2021-11-16  Frederik Harwath  <frederik@codesourcery.com>
 
 	* graphite-optimize-isl.cc (optimize_isl): Adjust
diff --git a/gcc/graphite-isl-ast-to-gimple.cc b/gcc/graphite-isl-ast-to-gimple.cc
index 9350f5ead41..49cbb9d5cfe 100644
--- a/gcc/graphite-isl-ast-to-gimple.cc
+++ b/gcc/graphite-isl-ast-to-gimple.cc
@@ -1539,9 +1539,7 @@ graphite_regenerate_ast_isl (scop_p scop)
 	 conditional if aliasing can be ruled out at runtime and the original
 	 version of the SCoP, otherwise. */
 
-      loop_p loop
-	  = find_common_loop (scop->scop_info->region.entry->dest->loop_father,
-			      scop->scop_info->region.exit->src->loop_father);
+      loop_p loop = scop_context_loop (scop);
       tree cond = generate_alias_cond (scop->unhandled_alias_ddrs, loop);
       tree non_alias_cond = build1 (TRUTH_NOT_EXPR, boolean_type_node, cond);
       set_ifsese_condition (region->if_region, non_alias_cond);
diff --git a/gcc/graphite-scop-detection.cc b/gcc/graphite-scop-detection.cc
index 8656e4b1e99..f4dba010bde 100644
--- a/gcc/graphite-scop-detection.cc
+++ b/gcc/graphite-scop-detection.cc
@@ -297,6 +297,23 @@ single_pred_cond_non_loop_exit (basic_block bb)
   return NULL;
 }
 
+
+/* Return the innermost loop that encloses all loops in SCOP. */
+
+loop_p
+scop_context_loop (scop_p scop)
+{
+  edge scop_entry = scop->scop_info->region.entry;
+  edge scop_exit = scop->scop_info->region.exit;
+  basic_block exit_bb = scop_exit->src;
+
+  while (sese_trivially_empty_bb_p (exit_bb) && single_pred_p (exit_bb))
+    exit_bb = single_pred (exit_bb);
+
+  loop_p entry_loop = scop_entry->dest->loop_father;
+  return find_common_loop (entry_loop, exit_bb->loop_father);
+}
+
 namespace
 {
 
@@ -1774,9 +1791,7 @@ build_alias_set (scop_p scop)
   int i, j;
   int *all_vertices;
 
-  struct loop *nest
-    = find_common_loop (scop->scop_info->region.entry->dest->loop_father,
-			scop->scop_info->region.exit->src->loop_father);
+  struct loop *nest = scop_context_loop (scop);
 
   gcc_checking_assert (nest);
 
diff --git a/gcc/graphite.h b/gcc/graphite.h
index 69d5579c78a..42599e80893 100644
--- a/gcc/graphite.h
+++ b/gcc/graphite.h
@@ -480,4 +480,5 @@ extern tree cached_scalar_evolution_in_region (const sese_l &, loop_p, tree);
 extern void dot_all_sese (FILE *, vec<sese_l> &);
 extern void dot_sese (sese_l &);
 extern void dot_cfg ();
+extern loop_p scop_context_loop (scop_p);
 #endif