Improve the AM folding heuristics: Do not fold AM if at least one of the AM operands...

[r16324]

diff --git a/ir/be/ia32/ia32_address_mode.c b/ir/be/ia32/ia32_address_mode.c
index 79b6546..ac876fc 100644 (file)
--- a/ir/be/ia32/ia32_address_mode.c
+++ b/ir/be/ia32/ia32_address_mode.c
@@ -465,8 +465,8 @@ static void mark_non_address_nodes(ir_node *node, void *env)
                left  = get_binop_left(node);
                right = get_binop_right(node);
 
-               /* live end: we won't save a register by AM folding */
-               if(be_is_live_end(lv, block, left) || be_is_live_end(lv, block, right))
+               /* If both are live end not folding AM costs a register */
+               if(be_is_live_end(lv, block, left) && be_is_live_end(lv, block, right))
                        return;
 
                /* if multiple nodes in this block use left/right values, then we
@@ -475,17 +475,19 @@ static void mark_non_address_nodes(ir_node *node, void *env)
                 * calculations. */
                foreach_out_edge(left, edge) {
                        ir_node *user = get_edge_src_irn(edge);
-                       if(user != node && get_nodes_block(user) == block)
-                               return;
-               }
-               foreach_out_edge(right, edge) {
-                       ir_node *user = get_edge_src_irn(edge);
-                       if(user != node && get_nodes_block(user) == block)
-                               return;
+                       if(user != node && get_nodes_block(user) == block) {
+                               foreach_out_edge(right, edge) {
+                                       ir_node *user = get_edge_src_irn(edge);
+                                       if(user != node && get_nodes_block(user) == block)
+                                               return;
+                               }
+                               break;
+                       }
                }
 
-               /* noone-else in this block is using left/right so we'll reduce register
-                * pressure if we don't fold the node */
+               /* At least one of left and right are not used by anyone else, so it is
+                * beneficial for the register pressure (if both are unused otherwise,
+                * else neutral) and ALU use to not fold AM. */
                bitset_set(non_address_mode_nodes, get_irn_idx(node));
                break;