re PR tree-optimization/19038 (tree-ssa causing loops to have more than one BB)

2005-01-20  Daniel Berlin  <dberlin@dberlin.org>

	Fix PR tree-optimization/19038
	* tree-ssa-dom.c (cprop_operand): Don't replace loop invaeriant
	copies with loop variant ones.

From-SVN: r94069

gcc/ChangeLog

+2005-01-20  Daniel Berlin  <dberlin@dberlin.org>
+
+	Fix PR tree-optimization/19038
+	* tree-ssa-dom.c (cprop_operand): Don't replace loop invaeriant
+	copies with loop variant ones.
+
 2005-01-22  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* cfganal.c, real.h, reorg.c, timevar.def, tree-ssa-ccp.c,

gcc/tree-ssa-dom.c

@@ -2819,6 +2819,14 @@ cprop_operand (tree stmt, use_operand_p op_p)
 	 extensions.  */
       else if (!may_propagate_copy (op, val))
 	return false;
+      
+      /* Do not propagate copies if the propagated value is at a deeper loop
+	 depth than the propagatee.  Otherwise, this may move loop variant
+	 variables outside of their loops and prevent coalescing
+	 opportunities.  If the value was loop invariant, it will be hoisted
+	 by LICM and exposed for copy propagation.  */
+      if (loop_depth_of_name (val) > loop_depth_of_name (op))
+	return false;
 
       /* Dump details.  */
       if (dump_file && (dump_flags & TDF_DETAILS))