re PR tree-optimization/34683 (SSA rewriting in the loop unroller causes quadratic behavior)

2008-01-10  Richard Guenther  <rguenther@suse.de>

	PR middle-end/34683
	* tree-cfg.c (tree_merge_blocks): Do not go through the
	full-blown folding and stmt updating path if we just deal
	with virtual operands.
	* tree-ssa-copy.c (may_propagate_copy): Do not short-cut
	test for abnormal SSA_NAMEs.

From-SVN: r131446

gcc/ChangeLog

+2008-01-10  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/34683
+	* tree-cfg.c (tree_merge_blocks): Do not go through the
+	full-blown folding and stmt updating path if we just deal
+	with virtual operands.
+	* tree-ssa-copy.c (may_propagate_copy): Do not short-cut
+	test for abnormal SSA_NAMEs.
+
 2008-01-10  Andreas Krebbel  <krebbel1@de.ibm.com>
 
 	PR middle-end/34641

gcc/tree-cfg.c

@@ -1322,7 +1322,21 @@ tree_merge_blocks (basic_block a, basic_block b)
 	}
       else
         {
-          replace_uses_by (def, use);
+	  /* If we deal with a PHI for virtual operands, we can simply
+	     propagate these without fussing with folding or updating
+	     the stmt.  */
+	  if (!is_gimple_reg (def))
+	    {
+	      imm_use_iterator iter;
+	      use_operand_p use_p;
+	      tree stmt;
+
+	      FOR_EACH_IMM_USE_STMT (stmt, iter, def)
+		FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+		  SET_USE (use_p, use);
+	    }
+	  else
+            replace_uses_by (def, use);
           remove_phi_node (phi, NULL, true);
         }
     }

gcc/tree-ssa-copy.c

@@ -62,6 +62,17 @@ may_propagate_copy (tree dest, tree orig)
   tree type_d = TREE_TYPE (dest);
   tree type_o = TREE_TYPE (orig);
 
+  /* If ORIG flows in from an abnormal edge, it cannot be propagated.  */
+  if (TREE_CODE (orig) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig))
+    return false;
+
+  /* If DEST is an SSA_NAME that flows from an abnormal edge, then it
+     cannot be replaced.  */
+  if (TREE_CODE (dest) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest))
+    return false;
+
   /* For memory partitions, copies are OK as long as the memory symbol
      belongs to the partition.  */
   if (TREE_CODE (dest) == SSA_NAME
@@ -164,17 +175,6 @@ may_propagate_copy (tree dest, tree orig)
       return false;
     }
 
-  /* If ORIG flows in from an abnormal edge, it cannot be propagated.  */
-  if (TREE_CODE (orig) == SSA_NAME
-      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig))
-    return false;
-
-  /* If DEST is an SSA_NAME that flows from an abnormal edge, then it
-     cannot be replaced.  */
-  if (TREE_CODE (dest) == SSA_NAME
-      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest))
-    return false;
-
   /* Anything else is OK.  */
   return true;
 }