tree-cfg.c (tree_forwarder_block_p): Reorder checks so that common cases will be…

tree-cfg.c (tree_forwarder_block_p): Reorder checks so that common cases will be caught earlier than others.

	* tree-cfg.c (tree_forwarder_block_p): Reorder checks so that
	common cases will be caught earlier than others.

From-SVN: r88752

gcc/ChangeLog

+2004-10-08  Kazu Hirata  <kazu@cs.umass.edu>
+
+	* tree-cfg.c (tree_forwarder_block_p): Reorder checks so that
+	common cases will be caught earlier than others.
+
 2004-10-08  Michael Matz  <matz@suse.de>
 
 	* loop-doloop.c (doloop_optimize): Extend count.

gcc/tree-cfg.c

@@ -3694,7 +3694,10 @@ tree_make_forwarder_block (edge fallthru)
 
 /* Return true if basic block BB does nothing except pass control
    flow to another block and that we can safely insert a label at
-   the start of the successor block.  */
+   the start of the successor block.
+
+   As a precondition, we require that BB be not equal to
+   ENTRY_BLOCK_PTR.  */
 
 static bool
 tree_forwarder_block_p (basic_block bb)
@@ -3708,17 +3711,25 @@ tree_forwarder_block_p (basic_block bb)
   if (! bb_ann (bb)->forwardable)
     return false;
 
-  /* BB must have a single outgoing normal edge.  Otherwise it can not be
-     a forwarder block.  */
+  /* BB must have a single outgoing edge.  */
   if (EDGE_COUNT (bb->succs) != 1
+      /* BB can not have any PHI nodes.  This could potentially be
+	 relaxed early in compilation if we re-rewrote the variables
+	 appearing in any PHI nodes in forwarder blocks.  */
+      || phi_nodes (bb)
+      /* BB may not be a predecessor of EXIT_BLOCK_PTR.  */
       || EDGE_SUCC (bb, 0)->dest == EXIT_BLOCK_PTR
-      || (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL)
-      || bb == ENTRY_BLOCK_PTR)
+      /* BB may not have an abnormal outgoing edge.  */
+      || (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL))
     {
       bb_ann (bb)->forwardable = 0;
       return false; 
     }
 
+#if ENABLE_CHECKING
+  gcc_assert (bb != ENTRY_BLOCK_PTR);
+#endif
+
   /* Successors of the entry block are not forwarders.  */
   FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
     if (e->dest == bb)
@@ -3727,15 +3738,6 @@ tree_forwarder_block_p (basic_block bb)
 	return false;
       }
 
-  /* BB can not have any PHI nodes.  This could potentially be relaxed
-     early in compilation if we re-rewrote the variables appearing in
-     any PHI nodes in forwarder blocks.  */
-  if (phi_nodes (bb))
-    {
-      bb_ann (bb)->forwardable = 0;
-      return false; 
-    }
-
   /* Now walk through the statements.  We can ignore labels, anything else
      means this is not a forwarder block.  */
   for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))