Sub(x, Const) -> Add(x, -Const)

[r15660]

diff --git a/ir/ir/iropt.c b/ir/ir/iropt.c
index 5282dbd..7164938 100644 (file)
--- a/ir/ir/iropt.c
+++ b/ir/ir/iropt.c
@@ -2025,6 +2025,7 @@ static ir_node *transform_node_Add(ir_node *n) {
  *   Sub(Sub(x, y), b) -> Sub(x, Add(y,b))
  *   Sub(Add(a, x), x) -> a
  *   Sub(x, Add(x, a)) -> -a
+ *   Sub(x, Const)     -> Add(x, -Const)
  */
 static ir_node *transform_node_Sub(ir_node *n) {
        ir_mode *mode;
@@ -2045,6 +2046,22 @@ restart:
        if (mode_is_float(mode) && (get_irg_fp_model(current_ir_graph) & fp_strict_algebraic))
                return n;
 
+       /* Sub(a, Const) -> Add(a, -Const) */
+       if (is_Const(b)) {
+               tarval *tv = get_Const_tarval(b);
+
+               tv = tarval_neg(tv);
+               if(tv != tarval_bad) {
+                       ir_node  *cnst  = new_Const(get_irn_mode(b), tv);
+                       ir_node  *block = get_nodes_block(n);
+                       dbg_info *dbgi  = get_irn_dbg_info(n);
+                       ir_graph *irg   = get_irn_irg(n);
+                       ir_node  *add   = new_rd_Add(dbgi, irg, block, a, cnst, mode);
+
+                       return add;
+               }
+       }
+
        if (is_Add(a)) {
                if (mode_wrap_around(mode)) {
                        ir_node *left  = get_Add_left(a);