* basic-block.h (rediscover_loops_after_threading): Declare.

[thirdparty/gcc.git] / gcc / tree-ssa-dom.c

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 242de47b61089c7e72c28278777c5254109bd8f9..a14356500aa83b9e0f46e774d709b2f228882a60 100644 (file)
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -29,6 +29,7 @@ Boston, MA 02111-1307, USA.  */
 #include "tm_p.h"
 #include "ggc.h"
 #include "basic-block.h"
+#include "cfgloop.h"
 #include "output.h"
 #include "errors.h"
 #include "expr.h"
@@ -368,6 +369,7 @@ tree_ssa_dominator_optimize (void)
 {
   struct dom_walk_data walk_data;
   unsigned int i;
+  struct loops loops_info;
 
   memset (&opt_stats, 0, sizeof (opt_stats));
 
@@ -407,6 +409,17 @@ tree_ssa_dominator_optimize (void)
 
   calculate_dominance_info (CDI_DOMINATORS);
 
+  /* We need to know which edges exit loops so that we can
+     aggressively thread through loop headers to an exit
+     edge.  */
+  flow_loops_find (&loops_info);
+  mark_loop_exit_edges (&loops_info);
+  flow_loops_free (&loops_info);
+
+  /* Clean up the CFG so that any forwarder blocks created by loop
+     canonicalization are removed.  */
+  cleanup_tree_cfg ();
+
   /* If we prove certain blocks are unreachable, then we want to
      repeat the dominator optimization process as PHI nodes may
      have turned into copies which allows better propagation of
@@ -417,6 +430,10 @@ tree_ssa_dominator_optimize (void)
       /* Optimize the dominator tree.  */
       cfg_altered = false;
 
+      /* We need accurate information regarding back edges in the CFG
+        for jump threading.  */
+      mark_dfs_back_edges ();
+
       /* Recursively walk the dominator tree optimizing statements.  */
       walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
 
@@ -445,8 +462,24 @@ tree_ssa_dominator_optimize (void)
        }
 
       if (cfg_altered)
-       free_dominance_info (CDI_DOMINATORS);
+        free_dominance_info (CDI_DOMINATORS);
+
       cfg_altered |= cleanup_tree_cfg ();
+
+      if (rediscover_loops_after_threading)
+       {
+         /* Rerun basic loop analysis to discover any newly
+            created loops and update the set of exit edges.  */
+         rediscover_loops_after_threading = false;
+         flow_loops_find (&loops_info);
+         mark_loop_exit_edges (&loops_info);
+         flow_loops_free (&loops_info);
+
+         /* Remove any forwarder blocks inserted by loop
+            header canonicalization.  */
+         cleanup_tree_cfg ();
+       }
+
       calculate_dominance_info (CDI_DOMINATORS);
 
       rewrite_ssa_into_ssa ();