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.c (scop_context_loop): New function.
        (build_alias_set): Use scop_context_loop instead of find_common_loop.
        * graphite-isl-ast-to-gimple.c (graphite_regenerate_ast_isl): Likewise.
        * graphite.h (scop_context_loop): New declaration.

diff --git a/gcc/graphite-isl-ast-to-gimple.c b/gcc/graphite-isl-ast-to-gimple.c
index bdabe588c3d85f4e633236878cf0487a97307eae..ec055a358f39c582b25a9356ed8bf944cbaa74b4 100644 (file)
--- a/gcc/graphite-isl-ast-to-gimple.c
+++ b/gcc/graphite-isl-ast-to-gimple.c
@@ -1543,9 +1543,7 @@ 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.c b/gcc/graphite-scop-detection.c
index afc955cc97eb96e3e1c388ee3b275c526f3d861f..99e906a5d1208c9405c931d44a39be0ca39087c3 100644 (file)
--- a/gcc/graphite-scop-detection.c
+++ b/gcc/graphite-scop-detection.c
@@ -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
 {
 
@@ -1776,9 +1793,7 @@ 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 9c508f31109fef82111f11d2554256491ccdf0a6..dacb27a9073cf0b0b2a14fc2a22ba0094c3caa6d 100644 (file)
--- 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