Limit the number of parameters per SCoP.

2010-03-09  Sebastian Pop  <sebastian.pop@amd.com>

	* graphite-sese-to-poly.c (build_poly_scop): Limit scops following
	the number of parameters in the scop.  Use as an upper bound
	PARAM_GRAPHITE_MAX_NB_SCOP_PARAMS.
	* params.def (PARAM_GRAPHITE_MAX_NB_SCOP_PARAMS): Declared.
	* doc/invoke.texi: Document it.

From-SVN: r157431

gcc/ChangeLog.graphite

+2010-03-09  Sebastian Pop  <sebastian.pop@amd.com>
+
+	* graphite-sese-to-poly.c (build_poly_scop): Limit scops following
+	the number of parameters in the scop.  Use as an upper bound
+	PARAM_GRAPHITE_MAX_NB_SCOP_PARAMS.
+	* params.def (PARAM_GRAPHITE_MAX_NB_SCOP_PARAMS): Declared.
+	* doc/invoke.texi: Document it.
+
 2010-03-05  Sebastian Pop  <sebastian.pop@amd.com>
 
 	* graphite-sese-to-poly.c (add_param_constraints): Use

gcc/doc/invoke.texi

@@ -8492,6 +8492,10 @@ parameters only when their cumulative size is less or equal to
 @option{ipa-sra-ptr-growth-factor} times the size of the original
 pointer parameter.
 
+@item graphite-max-nb-scop-params
+To avoid exponential effects in the Graphite loop transforms, the
+number of parameters in a SCoP is bounded by 10.
+
 @end table
 @end table
 

gcc/graphite-sese-to-poly.c

@@ -2937,6 +2937,7 @@ build_poly_scop (scop_p scop)
 {
   sese region = SCOP_REGION (scop);
   sbitmap reductions = sbitmap_alloc (last_basic_block * 2);
+  graphite_dim_t max_dim;
 
   sbitmap_zero (reductions);
   rewrite_commutative_reductions_out_of_ssa (region, reductions);
@@ -2960,6 +2961,10 @@ build_poly_scop (scop_p scop)
   build_sese_conditions (region);
   find_scop_parameters (scop);
 
+  max_dim = PARAM_VALUE (PARAM_GRAPHITE_MAX_NB_SCOP_PARAMS);
+  if (scop_nb_params (scop) > max_dim)
+    return false;
+
   build_scop_iteration_domain (scop);
   build_scop_context (scop);
 

gcc/params.def

@@ -745,6 +745,13 @@ DEFPARAM (PARAM_LOOP_BLOCK_TILE_SIZE,
 	  "size of tiles for loop blocking",
 	  51, 0, 0)
 
+/* Maximal number of parameters that we allow in a SCoP.  */
+
+DEFPARAM (PARAM_GRAPHITE_MAX_NB_SCOP_PARAMS,
+	  "graphite-max-nb-scop-params",
+	  "maximal number of parameters in a SCoP",
+	  10, 0, 0)
+
 /* Avoid doing loop invariant motion on very large loops.  */
 
 DEFPARAM (PARAM_LOOP_INVARIANT_MAX_BBS_IN_LOOP,