re PR middle-end/51389 (GCC uses up to 75GB of virtual memory)

PR middle-end/51389
        * Makefile.in (tree-data-ref.o): Depend on $(PARAMS_H).
        * tree-data-ref.h (find_data_references_in_loop): Remove declaration.
        * tree-data-ref.c (find_data_references_in_loop): Make static.
        (compute_all_dependences): Change return type to bool.  Bail out
        for too many datarefs in a loop.  Move the hunk resetting the data
        dependences vector from ...
        (compute_data_dependences_for_loop): ... here.  Account for
        compute_all_dependences returning false.
        (compute_data_dependences_for_bb): Likewise.
        * params.def (PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS): New param.
        * doc/invoke.texi (loop-max-datarefs-for-datadeps): Document it.

From-SVN: r183624

gcc/ChangeLog

@@ -1,3 +1,18 @@
+2012-01-27  Andrey Belevantsev  <abel@ispras.ru>
+
+	PR middle-end/51389
+	* Makefile.in (tree-data-ref.o): Depend on $(PARAMS_H).
+	* tree-data-ref.h (find_data_references_in_loop): Remove declaration.
+	* tree-data-ref.c (find_data_references_in_loop): Make static.
+	(compute_all_dependences): Change return type to bool.  Bail out
+	for too many datarefs in a loop.  Move the hunk resetting the data
+	dependences vector from ...
+	(compute_data_dependences_for_loop): ... here.  Account for
+	compute_all_dependences returning false.
+	(compute_data_dependences_for_bb): Likewise.
+	* params.def (PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS): New param.
+	* doc/invoke.texi (loop-max-datarefs-for-datadeps): Document it.
+
 2012-01-27  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/51959

gcc/Makefile.in

@@ -2598,7 +2598,7 @@ tree-scalar-evolution.o : tree-scalar-evolution.c $(CONFIG_H) $(SYSTEM_H) \
    $(TREE_PASS_H) $(PARAMS_H) gt-tree-scalar-evolution.h
 tree-data-ref.o : tree-data-ref.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
    gimple-pretty-print.h $(TREE_FLOW_H) $(CFGLOOP_H) $(TREE_DATA_REF_H) \
-   $(TREE_PASS_H) langhooks.h tree-affine.h
+   $(TREE_PASS_H) langhooks.h tree-affine.h $(PARAMS_H)
 sese.o : sese.c sese.h $(CONFIG_H) $(SYSTEM_H) coretypes.h tree-pretty-print.h \
    $(TREE_FLOW_H) $(CFGLOOP_H) $(TREE_DATA_REF_H) tree-pass.h value-prof.h
 graphite.o : graphite.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(DIAGNOSTIC_CORE_H) \

gcc/doc/invoke.texi

@@ -9115,6 +9115,13 @@ with more basic blocks than this parameter won't have loop invariant
 motion optimization performed on them.  The default value of the
 parameter is 1000 for -O1 and 10000 for -O2 and above.
 
+@item loop-max-datarefs-for-datadeps
+Building data dapendencies is expensive for very large loops.  This
+parameter limits the number of data references in loops that are
+considered for data dependence analysis.  These large loops will not
+be handled then by the optimizations using loop data dependencies.
+The default value is 1000.
+
 @item max-vartrack-size
 Sets a maximum number of hash table slots to use during variable
 tracking dataflow analysis of any function.  If this limit is exceeded

gcc/params.def

@@ -820,6 +820,12 @@ DEFPARAM (PARAM_GRAPHITE_MAX_BBS_PER_FUNCTION,
 	  "maximum number of basic blocks per function to be analyzed by Graphite",
 	  100, 0, 0)
 
+/* Avoid data dependence analysis on very large loops.  */
+DEFPARAM (PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS,
+	  "loop-max-datarefs-for-datadeps",
+	  "Maximum number of datarefs in loop for building loop data dependencies",
+	  1000, 0, 0)
+
 /* Avoid doing loop invariant motion on very large loops.  */
 
 DEFPARAM (PARAM_LOOP_INVARIANT_MAX_BBS_IN_LOOP,

gcc/tree-data-ref.c

@@ -85,6 +85,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-pass.h"
 #include "langhooks.h"
 #include "tree-affine.h"
+#include "params.h"
 
 static struct datadep_stats
 {
@@ -4134,9 +4135,10 @@ compute_affine_dependence (struct data_dependence_relation *ddr,
 /* Compute in DEPENDENCE_RELATIONS the data dependence graph for all
    the data references in DATAREFS, in the LOOP_NEST.  When
    COMPUTE_SELF_AND_RR is FALSE, don't compute read-read and self
-   relations.  */
+   relations.  Return true when successful, i.e. data references number
+   is small enough to be handled.  */
 
-void
+bool
 compute_all_dependences (VEC (data_reference_p, heap) *datarefs,
 			 VEC (ddr_p, heap) **dependence_relations,
 			 VEC (loop_p, heap) *loop_nest,
@@ -4146,6 +4148,18 @@ compute_all_dependences (VEC (data_reference_p, heap) *datarefs,
   struct data_reference *a, *b;
   unsigned int i, j;
 
+  if ((int) VEC_length (data_reference_p, datarefs)
+      > PARAM_VALUE (PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS))
+    {
+      struct data_dependence_relation *ddr;
+
+      /* Insert a single relation into dependence_relations:
+	 chrec_dont_know.  */
+      ddr = initialize_data_dependence_relation (NULL, NULL, loop_nest);
+      VEC_safe_push (ddr_p, heap, *dependence_relations, ddr);
+      return false;
+    }
+
   FOR_EACH_VEC_ELT (data_reference_p, datarefs, i, a)
     for (j = i + 1; VEC_iterate (data_reference_p, datarefs, j, b); j++)
       if (DR_IS_WRITE (a) || DR_IS_WRITE (b) || compute_self_and_rr)
@@ -4164,6 +4178,8 @@ compute_all_dependences (VEC (data_reference_p, heap) *datarefs,
         if (loop_nest)
    	  compute_affine_dependence (ddr, VEC_index (loop_p, loop_nest, 0));
       }
+
+  return true;
 }
 
 /* Stores the locations of memory references in STMT to REFERENCES.  Returns
@@ -4338,7 +4354,7 @@ find_data_references_in_bb (struct loop *loop, basic_block bb,
    TODO: This function should be made smarter so that it can handle address
    arithmetic as if they were array accesses, etc.  */
 
-tree
+static tree
 find_data_references_in_loop (struct loop *loop,
 			      VEC (data_reference_p, heap) **datarefs)
 {
@@ -4427,19 +4443,10 @@ compute_data_dependences_for_loop (struct loop *loop,
      dependences.  */
   if (!loop
       || !find_loop_nest (loop, loop_nest)
-      || find_data_references_in_loop (loop, datarefs) == chrec_dont_know)
+      || find_data_references_in_loop (loop, datarefs) == chrec_dont_know
-    {
+      || !compute_all_dependences (*datarefs, dependence_relations, *loop_nest,
-      struct data_dependence_relation *ddr;
+				   compute_self_and_read_read_dependences))
-
+    res = false;
-      /* Insert a single relation into dependence_relations:
-	 chrec_dont_know.  */
-      ddr = initialize_data_dependence_relation (NULL, NULL, *loop_nest);
-      VEC_safe_push (ddr_p, heap, *dependence_relations, ddr);
-      res = false;
-    }
-  else
-    compute_all_dependences (*datarefs, dependence_relations, *loop_nest,
-			     compute_self_and_read_read_dependences);
 
   if (dump_file && (dump_flags & TDF_STATS))
     {
@@ -4507,9 +4514,8 @@ compute_data_dependences_for_bb (basic_block bb,
   if (find_data_references_in_bb (NULL, bb, datarefs) == chrec_dont_know)
     return false;
 
-  compute_all_dependences (*datarefs, dependence_relations, NULL,
+  return compute_all_dependences (*datarefs, dependence_relations, NULL,
-                           compute_self_and_read_read_dependences);
+				  compute_self_and_read_read_dependences);
-  return true;
 }
 
 /* Entry point (for testing only).  Analyze all the data references

gcc/tree-data-ref.h

@@ -394,8 +394,6 @@ extern bool compute_data_dependences_for_loop (struct loop *, bool,
 extern bool compute_data_dependences_for_bb (basic_block, bool,
                                              VEC (data_reference_p, heap) **,
                                              VEC (ddr_p, heap) **);
-extern tree find_data_references_in_loop (struct loop *,
-                                          VEC (data_reference_p, heap) **);
 extern void print_direction_vector (FILE *, lambda_vector, int);
 extern void print_dir_vectors (FILE *, VEC (lambda_vector, heap) *, int);
 extern void print_dist_vectors (FILE *, VEC (lambda_vector, heap) *, int);
@@ -426,7 +424,7 @@ extern bool find_loop_nest (struct loop *, VEC (loop_p, heap) **);
 extern struct data_dependence_relation *initialize_data_dependence_relation
      (struct data_reference *, struct data_reference *, VEC (loop_p, heap) *); 
 extern void compute_self_dependence (struct data_dependence_relation *);
-extern void compute_all_dependences (VEC (data_reference_p, heap) *,
+extern bool compute_all_dependences (VEC (data_reference_p, heap) *,
 				     VEC (ddr_p, heap) **, VEC (loop_p, heap) *,
 				     bool);
 extern tree find_data_references_in_bb (struct loop *, basic_block,