[PATCH][GRAPHITE] Allow --param graphite-max-arrays-per-scop=0

[Richard Biener <rguenther at suse dot de>]

The following is to allow making --param graphite-max-arrays-per-scop
unbounded.  That's a little tricky because the bound is used when
computing "alias-sets" for scalar constraints.  There's an easy way
out though as we know the maximum alias-set assigned in the SCOP,
we only have to remember it.  The advantage (if it matters at all)
is that we avoid a constraint coefficient gap between that last
used alias-set and the former PARAM_GRAPHITE_MAX_ARRAYS_PER_SCOP.

Bootstrap and regtest running on x86_64-unknown-linux-gnu, SPEC CPU 2006
tested.  Will apply after testing finished.

Richard.

2017-09-27  Richard Biener  <rguenther@suse.de>

	* graphite.h (scop::max_alias_set): New member.
	* graphite-scop-detection.c: Remove references to non-existing
	--param in comments.
	(build_alias_sets): Record the maximum alias set used for drs.
	(build_scops): Support zero as unlimited for
	--param graphite-max-arrays-per-scop.
	* graphite-sese-to-poly.c (add_scalar_version_numbers): Remove
	and inline into ...
	(build_poly_sr_1): ... here.  Compute alias set based on the
	maximum alias set used for drs rather than
	PARAM_GRAPHITE_MAX_ARRAYS_PER_SCOP

Index: gcc/graphite-scop-detection.c
===================================================================
--- gcc/graphite-scop-detection.c	(revision 253226)
+++ gcc/graphite-scop-detection.c	(working copy)
@@ -389,10 +389,7 @@ public:
 
   void remove_intersecting_scops (sese_l s1);
 
-  /* Return true when a statement in SCOP cannot be represented by Graphite.
-     The assumptions are that L1 dominates L2, and SCOP->entry dominates L1.
-     Limit the number of bbs between adjacent loops to
-     PARAM_SCOP_MAX_NUM_BBS_BETWEEN_LOOPS.  */
+  /* Return true when a statement in SCOP cannot be represented by Graphite.  */
 
   bool harmful_loop_in_region (sese_l scop) const;
 
@@ -760,10 +757,7 @@ scop_detection::add_scop (sese_l s)
   DEBUG_PRINT (dp << "[scop-detection] Adding SCoP: "; print_sese (dump_file, s));
 }
 
-/* Return true when a statement in SCOP cannot be represented by Graphite.
-   The assumptions are that L1 dominates L2, and SCOP->entry dominates L1.
-   Limit the number of bbs between adjacent loops to
-   PARAM_SCOP_MAX_NUM_BBS_BETWEEN_LOOPS.  */
+/* Return true when a statement in SCOP cannot be represented by Graphite.  */
 
 bool
 scop_detection::harmful_loop_in_region (sese_l scop) const
@@ -1531,7 +1525,8 @@ build_alias_set (scop_p scop)
   for (i = 0; i < num_vertices; i++)
     all_vertices[i] = i;
 
-  graphds_dfs (g, all_vertices, num_vertices, NULL, true, NULL);
+  scop->max_alias_set
+    = graphds_dfs (g, all_vertices, num_vertices, NULL, true, NULL) + 1;
   free (all_vertices);
 
   for (i = 0; i < g->n_vertices; i++)
@@ -1755,7 +1750,8 @@ build_scops (vec<scop_p> *scops)
 	}
 
       unsigned max_arrays = PARAM_VALUE (PARAM_GRAPHITE_MAX_ARRAYS_PER_SCOP);
-      if (scop->drs.length () >= max_arrays)
+      if (max_arrays > 0
+	  && scop->drs.length () >= max_arrays)
 	{
 	  DEBUG_PRINT (dp << "[scop-detection-fail] too many data references: "
 		       << scop->drs.length ()
Index: gcc/graphite-sese-to-poly.c
===================================================================
--- gcc/graphite-sese-to-poly.c	(revision 253225)
+++ gcc/graphite-sese-to-poly.c	(working copy)
@@ -491,25 +491,6 @@ pdr_add_alias_set (isl_map *acc, dr_info
   return isl_map_add_constraint (acc, c);
 }
 
-/* Add a constrain to the ACCESSES polyhedron for the alias set of
-   data reference DR.  ACCESSP_NB_DIMS is the dimension of the
-   ACCESSES polyhedron, DOM_NB_DIMS is the dimension of the iteration
-   domain.  */
-
-static isl_map *
-add_scalar_version_numbers (isl_map *acc, tree var)
-{
-  isl_constraint *c = isl_equality_alloc
-      (isl_local_space_from_space (isl_map_get_space (acc)));
-  int max_arrays = PARAM_VALUE (PARAM_GRAPHITE_MAX_ARRAYS_PER_SCOP);
-  /* Each scalar variables has a unique alias set number starting from
-     max_arrays.  */
-  c = isl_constraint_set_constant_si (c, -max_arrays - SSA_NAME_VERSION (var));
-  c = isl_constraint_set_coefficient_si (c, isl_dim_out, 0, 1);
-
-  return isl_map_add_constraint (acc, c);
-}
-
 /* Assign the affine expression INDEX to the output dimension POS of
    MAP and return the result.  */
 
@@ -684,13 +665,21 @@ static void
 build_poly_sr_1 (poly_bb_p pbb, gimple *stmt, tree var, enum poly_dr_type kind,
 		 isl_map *acc, isl_set *subscript_sizes)
 {
-  int max_arrays = PARAM_VALUE (PARAM_GRAPHITE_MAX_ARRAYS_PER_SCOP);
+  scop_p scop = PBB_SCOP (pbb);
   /* Each scalar variables has a unique alias set number starting from
-     max_arrays.  */
+     the maximum alias set assigned to a dr.  */
+  int alias_set = scop->max_alias_set + SSA_NAME_VERSION (var);
   subscript_sizes = isl_set_fix_si (subscript_sizes, isl_dim_set, 0,
-				    max_arrays + SSA_NAME_VERSION (var));
+				    alias_set);
+
+  /* Add a constrain to the ACCESSES polyhedron for the alias set of
+     data reference DR.  */
+  isl_constraint *c
+    = isl_equality_alloc (isl_local_space_from_space (isl_map_get_space (acc)));
+  c = isl_constraint_set_constant_si (c, -alias_set);
+  c = isl_constraint_set_coefficient_si (c, isl_dim_out, 0, 1);
 
-  new_poly_dr (pbb, stmt, kind, add_scalar_version_numbers (acc, var),
+  new_poly_dr (pbb, stmt, kind, isl_map_add_constraint (acc, c),
 	       subscript_sizes);
 }
 
Index: gcc/graphite.h
===================================================================
--- gcc/graphite.h	(revision 253225)
+++ gcc/graphite.h	(working copy)
@@ -379,6 +379,9 @@ struct scop
   /* Number of parameters in SCoP.  */
   graphite_dim_t nb_params;
 
+  /* The maximum alias set as assigned to drs by build_alias_sets.  */
+  unsigned max_alias_set;
+
   /* All the basic blocks in this scop that contain memory references
      and that will be represented as statements in the polyhedral
      representation.  */