re PR middle-end/35204 (crash by too deep recursion in DFS tree-ssa-sccvn.c:1898)

2008-05-20  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/35204
	* tree-ssa-sccvn.c (extract_and_process_scc_for_name): New
	helper, split out from ...
	(DFS): ... here.  Make the DFS walk non-recursive.

From-SVN: r135676

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 65cb134a4616ff20b88d5fb45e6e3d3c2336b538..cdc2b9dd0e0ee48407e0939f5291bf81e161c857 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2008-05-20  Richard Guenther  <rguenther@suse.de>
+
+       PR tree-optimization/35204
+       * tree-ssa-sccvn.c (extract_and_process_scc_for_name): New
+       helper, split out from ...
+       (DFS): ... here.  Make the DFS walk non-recursive.
+
 2008-05-20  Sebastian Pop  <sebastian.pop@amd.com>
            Jan Sjodin  <jan.sjodin@amd.com>
 

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 2bc9cb2e3ef27c48ec967bdcf9c6b6f20bf082be..86777c784f0ea0f6a5f8f2ebac7aad7b19b0156f 100644 (file)
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -1956,6 +1956,53 @@ process_scc (VEC (tree, heap) *scc)
     }
 }
 
+DEF_VEC_O(ssa_op_iter);
+DEF_VEC_ALLOC_O(ssa_op_iter,heap);
+
+/* Pop the components of the found SCC for NAME off the SCC stack
+   and process them.  Returns true if all went well, false if
+   we run into resource limits.  */
+
+static bool
+extract_and_process_scc_for_name (tree name)
+{
+  VEC (tree, heap) *scc = NULL;
+  tree x;
+
+  /* Found an SCC, pop the components off the SCC stack and
+     process them.  */
+  do
+    {
+      x = VEC_pop (tree, sccstack);
+
+      VN_INFO (x)->on_sccstack = false;
+      VEC_safe_push (tree, heap, scc, x);
+    } while (x != name);
+
+  /* Bail out of SCCVN in case a SCC turns out to be incredibly large.  */
+  if (VEC_length (tree, scc)
+      > (unsigned)PARAM_VALUE (PARAM_SCCVN_MAX_SCC_SIZE))
+    {
+      if (dump_file)
+       fprintf (dump_file, "WARNING: Giving up with SCCVN due to "
+                "SCC size %u exceeding %u\n", VEC_length (tree, scc),
+                (unsigned)PARAM_VALUE (PARAM_SCCVN_MAX_SCC_SIZE));
+      return false;
+    }
+
+  if (VEC_length (tree, scc) > 1)
+    sort_scc (scc);
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    print_scc (dump_file, scc);
+
+  process_scc (scc);
+
+  VEC_free (tree, heap, scc);
+
+  return true;
+}
+
 /* Depth first search on NAME to discover and process SCC's in the SSA
    graph.
    Execution of this algorithm relies on the fact that the SCC's are
@@ -1966,10 +2013,13 @@ process_scc (VEC (tree, heap) *scc)
 static bool
 DFS (tree name)
 {
+  VEC(ssa_op_iter, heap) *itervec = NULL;
+  VEC(tree, heap) *namevec = NULL;
+  use_operand_p usep = NULL;
+  tree defstmt, use;
   ssa_op_iter iter;
-  use_operand_p usep;
-  tree defstmt;
 
+start_over:
   /* SCC info */
   VN_INFO (name)->dfsnum = next_dfs_num++;
   VN_INFO (name)->visited = true;
@@ -1982,20 +2032,63 @@ DFS (tree name)
   /* Recursively DFS on our operands, looking for SCC's.  */
   if (!IS_EMPTY_STMT (defstmt))
     {
-      FOR_EACH_PHI_OR_STMT_USE (usep, SSA_NAME_DEF_STMT (name), iter,
-                               SSA_OP_ALL_USES)
+      /* Push a new iterator.  */
+      if (TREE_CODE (defstmt) == PHI_NODE)
+       usep = op_iter_init_phiuse (&iter, defstmt, SSA_OP_ALL_USES);
+      else
+       usep = op_iter_init_use (&iter, defstmt, SSA_OP_ALL_USES);
+    }
+  else
+    iter.done = true;
+
+  while (1)
+    {
+      /* If we are done processing uses of a name, go up the stack
+        of iterators and process SCCs as we found them.  */
+      if (op_iter_done (&iter))
        {
-         tree use = USE_FROM_PTR (usep);
+         /* See if we found an SCC.  */
+         if (VN_INFO (name)->low == VN_INFO (name)->dfsnum)
+           if (!extract_and_process_scc_for_name (name))
+             {
+               VEC_free (tree, heap, namevec);
+               VEC_free (ssa_op_iter, heap, itervec);
+               return false;
+             }
 
-         /* Since we handle phi nodes, we will sometimes get
-            invariants in the use expression.  */
-         if (TREE_CODE (use) != SSA_NAME)
-           continue;
+         /* Check if we are done.  */
+         if (VEC_empty (tree, namevec))
+           {
+             VEC_free (tree, heap, namevec);
+             VEC_free (ssa_op_iter, heap, itervec);
+             return true;
+           }
+
+         /* Restore the last use walker and continue walking there.  */
+         use = name;
+         name = VEC_pop (tree, namevec);
+         memcpy (&iter, VEC_last (ssa_op_iter, itervec),
+                 sizeof (ssa_op_iter));
+         VEC_pop (ssa_op_iter, itervec);
+         goto continue_walking;
+       }
 
+      use = USE_FROM_PTR (usep);
+
+      /* Since we handle phi nodes, we will sometimes get
+        invariants in the use expression.  */
+      if (TREE_CODE (use) == SSA_NAME)
+       {
          if (! (VN_INFO (use)->visited))
            {
-             if (!DFS (use))
-               return false;
+             /* Recurse by pushing the current use walking state on
+                the stack and starting over.  */
+             VEC_safe_push(ssa_op_iter, heap, itervec, &iter);
+             VEC_safe_push(tree, heap, namevec, name);
+             name = use;
+             goto start_over;
+
+continue_walking:
              VN_INFO (name)->low = MIN (VN_INFO (name)->low,
                                         VN_INFO (use)->low);
            }
@@ -2006,47 +2099,9 @@ DFS (tree name)
                                         VN_INFO (name)->low);
            }
        }
-    }
-
-  /* See if we found an SCC.  */
-  if (VN_INFO (name)->low == VN_INFO (name)->dfsnum)
-    {
-      VEC (tree, heap) *scc = NULL;
-      tree x;
-
-      /* Found an SCC, pop the components off the SCC stack and
-        process them.  */
-      do
-       {
-         x = VEC_pop (tree, sccstack);
-
-         VN_INFO (x)->on_sccstack = false;
-         VEC_safe_push (tree, heap, scc, x);
-       } while (x != name);
-
-      /* Bail out of SCCVN in case a SCC turns out to be incredibly large.  */
-      if (VEC_length (tree, scc)
-           > (unsigned)PARAM_VALUE (PARAM_SCCVN_MAX_SCC_SIZE))
-       {
-         if (dump_file)
-           fprintf (dump_file, "WARNING: Giving up with SCCVN due to "
-                    "SCC size %u exceeding %u\n", VEC_length (tree, scc),
-                    (unsigned)PARAM_VALUE (PARAM_SCCVN_MAX_SCC_SIZE));
-         return false;
-       }
 
-      if (VEC_length (tree, scc) > 1)
-       sort_scc (scc);
-
-      if (dump_file && (dump_flags & TDF_DETAILS))
-       print_scc (dump_file, scc);
-
-      process_scc (scc);
-
-      VEC_free (tree, heap, scc);
+      usep = op_iter_next_use (&iter);
     }
-
-  return true;
 }
 
 /* Allocate a value number table.  */