===================================================================
@@ -2639,6 +2639,33 @@ get_lhs_or_phi_result (gimple stmt)
gcc_unreachable ();
}
+/* Return the loop depth of the basic block of the defining statement of X.
+ This number should not be treated as absolutely correct because the loop
+ information may not be completely up-to-date when dom runs. However, it
+ will be relatively correct, and as more passes are taught to keep loop info
+ up to date, the result will become more and more accurate. */
+
+static int
+loop_depth_of_name (tree x)
+{
+ gimple defstmt;
+ basic_block defbb;
+
+ /* If it's not an SSA_NAME, we have no clue where the definition is. */
+ if (TREE_CODE (x) != SSA_NAME)
+ return 0;
+
+ /* Otherwise return the loop depth of the defining statement's bb.
+ Note that there may not actually be a bb for this statement, if the
+ ssa_name is live on entry. */
+ defstmt = SSA_NAME_DEF_STMT (x);
+ defbb = gimple_bb (defstmt);
+ if (!defbb)
+ return 0;
+
+ return bb_loop_depth (defbb);
+}
+
/* Propagate RHS into all uses of LHS (when possible).
RHS and LHS are derived from STMT, which is passed in solely so
@@ -2654,7 +2681,8 @@ static void
propagate_rhs_into_lhs (gimple stmt, tree lhs, tree rhs, bitmap interesting_names)
{
/* First verify that propagation is valid. */
- if (may_propagate_copy (lhs, rhs))
+ if (may_propagate_copy (lhs, rhs)
+ && loop_depth_of_name (lhs) >= loop_depth_of_name (rhs))
{
use_operand_p use_p;
imm_use_iterator iter;