re PR bootstrap/36908 (bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution")

2008-11-03  Sebastian Pop  <sebastian.pop@amd.com>

	PR tree-optimization/36908
	* testsuite/gcc.dg/tree-ssa/pr36908.c: New.
	* tree-loop-distribution.c (number_of_rw_in_rdg): New.
	(number_of_rw_in_partition): New.
	(partition_contains_all_rw): New.
	(ldist_gen): Do not distribute when one of the partitions
	contains all the memory operations.

From-SVN: r141550

gcc/ChangeLog

@@ -1,3 +1,13 @@
+2008-11-03  Sebastian Pop  <sebastian.pop@amd.com>
+
+	PR tree-optimization/36908
+	* testsuite/gcc.dg/tree-ssa/pr36908.c: New.
+	* tree-loop-distribution.c (number_of_rw_in_rdg): New.
+	(number_of_rw_in_partition): New.
+	(partition_contains_all_rw): New.
+	(ldist_gen): Do not distribute when one of the partitions
+	contains all the memory operations.
+
 2008-11-03  Sebastian Pop  <sebastian.pop@amd.com>
 
 	* cfghooks.c (split_block): Set BB_IRREDUCIBLE_LOOP and

gcc/testsuite/gcc.dg/tree-ssa/pr36908.c

@@ -0,0 +1,65 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-loop-distribution" } */
+#define NULL ((void *)0)
+
+typedef unsigned int size_t;
+extern void *foo(size_t nelem, size_t elsize);
+extern void bar (char*, ...);
+
+typedef struct alt_state *alt_state_t;
+typedef struct state *state_t;
+
+struct alt_state
+{
+  alt_state_t next_alt_state;
+};
+
+static alt_state_t first_free_alt_state = NULL;
+
+static void
+free_alt_state (alt_state_t alt_state)
+{
+  if (alt_state == NULL)
+    return;
+  alt_state->next_alt_state = first_free_alt_state;
+  first_free_alt_state = alt_state;
+}
+
+/* The function frees list started with node ALT_STATE_LIST.  */
+static void
+free_alt_states (alt_state_t alt_states_list)
+{
+  alt_state_t curr_alt_state;
+  alt_state_t next_alt_state;
+
+  for (curr_alt_state = alt_states_list;
+       curr_alt_state != NULL;
+       curr_alt_state = next_alt_state)
+    {
+      next_alt_state = curr_alt_state->next_alt_state;
+      free_alt_state (curr_alt_state);
+    }
+}
+
+int 
+main (void)
+{
+  int i;
+  alt_state_t state, act_state;
+
+  act_state = state = foo (1, sizeof (struct alt_state));
+  for (i = 0; i < 2; i ++)
+  {
+    act_state->next_alt_state = foo (1, sizeof (struct alt_state));
+    act_state = act_state->next_alt_state;
+  }
+
+  free_alt_states (state);
+
+  for (act_state = first_free_alt_state;
+       act_state != NULL;
+       act_state = act_state->next_alt_state)
+       bar ("going from %p to %p\n", act_state, act_state->next_alt_state);
+
+  return 0;
+}

gcc/tree-loop-distribution.c

@@ -945,6 +945,64 @@ debug_rdg_partitions (VEC (bitmap, heap) *partitions)
   dump_rdg_partitions (stderr, partitions);
 }
 
+/* Returns the number of read and write operations in the RDG.  */
+
+static int
+number_of_rw_in_rdg (struct graph *rdg)
+{
+  int i, res = 0;
+
+  for (i = 0; i < rdg->n_vertices; i++)
+    {
+      if (RDG_MEM_WRITE_STMT (rdg, i))
+	++res;
+
+      if (RDG_MEM_READS_STMT (rdg, i))
+	++res;
+    }
+
+  return res;
+}
+
+/* Returns the number of read and write operations in a PARTITION of
+   the RDG.  */
+
+static int
+number_of_rw_in_partition (struct graph *rdg, bitmap partition)
+{
+  int res = 0;
+  unsigned i;
+  bitmap_iterator ii;
+
+  EXECUTE_IF_SET_IN_BITMAP (partition, 0, i, ii)
+    {
+      if (RDG_MEM_WRITE_STMT (rdg, i))
+	++res;
+
+      if (RDG_MEM_READS_STMT (rdg, i))
+	++res;
+    }
+
+  return res;
+}
+
+/* Returns true when one of the PARTITIONS contains all the read or
+   write operations of RDG.  */
+
+static bool
+partition_contains_all_rw (struct graph *rdg, VEC (bitmap, heap) *partitions)
+{
+  int i;
+  bitmap partition;
+  int nrw = number_of_rw_in_rdg (rdg);
+
+  for (i = 0; VEC_iterate (bitmap, partitions, i, partition); i++)
+    if (nrw == number_of_rw_in_partition (rdg, partition))
+      return true;
+
+  return false;
+}
+
 /* Generate code from STARTING_VERTICES in RDG.  Returns the number of
    distributed loops.  */
 
@@ -992,7 +1050,8 @@ ldist_gen (struct loop *loop, struct graph *rdg,
   BITMAP_FREE (processed);
   nbp = VEC_length (bitmap, partitions);
 
-  if (nbp <= 1)
+  if (nbp <= 1
+      || partition_contains_all_rw (rdg, partitions))
     goto ldist_done;
 
   if (dump_file && (dump_flags & TDF_DETAILS))