2007-12-13 Richard Guenther <rguenther@suse.de>

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-sccvn.c

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 8edd03b..a14c2a7 100644 (file)
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "bitmap.h"
 #include "langhooks.h"
 #include "cfgloop.h"
+#include "params.h"
 #include "tree-ssa-propagate.h"
 #include "tree-ssa-sccvn.h"
 
@@ -1837,9 +1838,11 @@ process_scc (VEC (tree, heap) *scc)
 /* 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
-   popped off the stack in topological order.  */
+   popped off the stack in topological order.
+   Returns true if successful, false if we stopped processing SCC's due
+   to ressource constraints.  */
 
-static void
+static bool
 DFS (tree name)
 {
   ssa_op_iter iter;
@@ -1870,7 +1873,8 @@ DFS (tree name)
 
          if (! (VN_INFO (use)->visited))
            {
-             DFS (use);
+             if (!DFS (use))
+               return false;
              VN_INFO (name)->low = MIN (VN_INFO (name)->low,
                                         VN_INFO (use)->low);
            }
@@ -1899,6 +1903,17 @@ DFS (tree name)
          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);
 
@@ -1909,6 +1924,8 @@ DFS (tree name)
 
       VEC_free (tree, heap, scc);
     }
+
+  return true;
 }
 
 static void
@@ -2074,7 +2091,10 @@ free_scc_vn (void)
     }
 }
 
-void
+/* Do SCCVN.  Returns true if it finished, false if we bailed out
+   due to ressource constraints.  */
+
+bool
 run_scc_vn (void)
 {
   size_t i;
@@ -2100,7 +2120,11 @@ run_scc_vn (void)
       if (name
          && VN_INFO (name)->visited == false
          && !has_zero_uses (name))
-       DFS (name);
+       if (!DFS (name))
+         {
+           free_scc_vn ();
+           return false;
+         }
     }
 
   if (dump_file && (dump_flags & TDF_DETAILS))
@@ -2123,4 +2147,6 @@ run_scc_vn (void)
            }
        }
     }
+
+  return true;
 }