tree-ssa-threadedge.c (thread_around_empty_blocks): New argument backedge_seen_p.

	* tree-ssa-threadedge.c (thread_around_empty_blocks): New
	argument backedge_seen_p.  Set, use and pass it to children
	appropriately.
	(thread_through_normal_block): Similarly.
	(thread_across_edge): Similarly.

From-SVN: r204724

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4b7209e..2c0554b 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 2013-11-12  Jeff Law  <law@redhat.com>
 
+       * tree-ssa-threadedge.c (thread_around_empty_blocks): New
+       argument backedge_seen_p.  Set, use and pass it to children
+       appropriately.
+       (thread_through_normal_block): Similarly.
+       (thread_across_edge): Similarly.
+
        * gimple-ssa-isolate-paths.c (check_loadstore): Mark discovered
        memory references as volatile.
        (insert_trap_and_remove_trailing_statements): Fix comment.

diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
index cd2b34a..0c9dcda 100644 (file)
--- a/gcc/tree-ssa-threadedge.c
+++ b/gcc/tree-ssa-threadedge.c
@@ -760,7 +760,8 @@ thread_around_empty_blocks (edge taken_edge,
                            bool handle_dominating_asserts,
                            tree (*simplify) (gimple, gimple),
                            bitmap visited,
-                           vec<jump_thread_edge *> *path)
+                           vec<jump_thread_edge *> *path,
+                           bool *backedge_seen_p)
 {
   basic_block bb = taken_edge->dest;
   gimple_stmt_iterator gsi;
@@ -795,19 +796,20 @@ thread_around_empty_blocks (edge taken_edge,
       if (single_succ_p (bb))
        {
          taken_edge = single_succ_edge (bb);
-         if ((taken_edge->flags & EDGE_DFS_BACK) == 0
-             && !bitmap_bit_p (visited, taken_edge->dest->index))
+         if (!bitmap_bit_p (visited, taken_edge->dest->index))
            {
              jump_thread_edge *x
                = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
              path->safe_push (x);
              bitmap_set_bit (visited, taken_edge->dest->index);
+             *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
              return thread_around_empty_blocks (taken_edge,
                                                 dummy_cond,
                                                 handle_dominating_asserts,
                                                 simplify,
                                                 visited,
-                                                path);
+                                                path,
+                                                backedge_seen_p);
            }
        }
 
@@ -841,13 +843,15 @@ thread_around_empty_blocks (edge taken_edge,
       jump_thread_edge *x
        = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
       path->safe_push (x);
+      *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
 
       thread_around_empty_blocks (taken_edge,
                                  dummy_cond,
                                  handle_dominating_asserts,
                                  simplify,
                                  visited,
-                                 path);
+                                 path,
+                                 backedge_seen_p);
       return true;
     }
 
@@ -889,17 +893,16 @@ thread_through_normal_block (edge e,
                             vec<tree> *stack,
                             tree (*simplify) (gimple, gimple),
                             vec<jump_thread_edge *> *path,
-                            bitmap visited)
+                            bitmap visited,
+                            bool *backedge_seen_p)
 {
-  /* If E is a backedge, then we want to verify that the COND_EXPR,
+  /* If we have crossed a backedge, then we want to verify that the COND_EXPR,
      SWITCH_EXPR or GOTO_EXPR at the end of e->dest is not affected
      by any statements in e->dest.  If it is affected, then it is not
      safe to thread this edge.  */
-  if (e->flags & EDGE_DFS_BACK)
-    {
-      if (cond_arg_set_in_bb (e, e->dest))
-       return false;
-    }
+  if (*backedge_seen_p
+      && cond_arg_set_in_bb (e, e->dest))
+    return false;
 
   /* PHIs create temporary equivalences.  */
   if (!record_temporary_equivalences_from_phis (e, stack))
@@ -931,20 +934,24 @@ thread_through_normal_block (edge e,
 
          /* DEST could be NULL for a computed jump to an absolute
             address.  */
-         if (dest == NULL || dest == e->dest || bitmap_bit_p (visited, dest->index))
+         if (dest == NULL
+             || dest == e->dest
+             || bitmap_bit_p (visited, dest->index))
            return false;
 
           jump_thread_edge *x
            = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
          path->safe_push (x);
+         *backedge_seen_p |= ((e->flags & EDGE_DFS_BACK) != 0);
 
          x = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_BLOCK);
          path->safe_push (x);
+         *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
 
          /* See if we can thread through DEST as well, this helps capture
             secondary effects of threading without having to re-run DOM or
             VRP.  */
-         if ((e->flags & EDGE_DFS_BACK) == 0
+         if (!*backedge_seen_p
               || ! cond_arg_set_in_bb (taken_edge, e->dest))
            {
              /* We don't want to thread back to a block we have already
@@ -956,7 +963,8 @@ thread_through_normal_block (edge e,
                                          handle_dominating_asserts,
                                          simplify,
                                          visited,
-                                         path);
+                                         path,
+                                         backedge_seen_p);
            }
          return true;
        }
@@ -999,6 +1007,7 @@ thread_across_edge (gimple dummy_cond,
                    tree (*simplify) (gimple, gimple))
 {
   bitmap visited = BITMAP_ALLOC (NULL);
+  bool backedge_seen;
 
   stmt_count = 0;
 
@@ -1006,8 +1015,10 @@ thread_across_edge (gimple dummy_cond,
   bitmap_clear (visited);
   bitmap_set_bit (visited, e->src->index);
   bitmap_set_bit (visited, e->dest->index);
+  backedge_seen = ((e->flags & EDGE_DFS_BACK) != 0);
   if (thread_through_normal_block (e, dummy_cond, handle_dominating_asserts,
-                                  stack, simplify, path, visited))
+                                  stack, simplify, path, visited,
+                                  &backedge_seen))
     {
       propagate_threaded_block_debug_into (path->last ()->e->dest,
                                           e->dest);
@@ -1067,14 +1078,17 @@ thread_across_edge (gimple dummy_cond,
         x = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_JOINER_BLOCK);
        path->safe_push (x);
        found = false;
-       if ((e->flags & EDGE_DFS_BACK) == 0
+       backedge_seen = ((e->flags & EDGE_DFS_BACK) != 0);
+       backedge_seen |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+       if (!backedge_seen
            || ! cond_arg_set_in_bb (path->last ()->e, e->dest))
          found = thread_around_empty_blocks (taken_edge,
                                              dummy_cond,
                                              handle_dominating_asserts,
                                              simplify,
                                              visited,
-                                             path);
+                                             path,
+                                             &backedge_seen);
 
        /* If we were able to thread through a successor of E->dest, then
           record the jump threading opportunity.  */