Add x - (a+x) = -a

[r15540]

diff --git a/ir/ir/iropt.c b/ir/ir/iropt.c
index 698ba03..22df826 100644 (file)
--- a/ir/ir/iropt.c
+++ b/ir/ir/iropt.c
@@ -2023,6 +2023,8 @@ static ir_node *transform_node_Add(ir_node *n) {
  *   Sub(0,a)          -> Minus(a)
  *   Sub(Mul(a, x), a) -> Mul(a, x-1)
  *   Sub(Sub(x, y), b) -> Sub(x, Add(y,b))
+ *   Sub(Add(a, x), x) -> a
+ *   Sub(x, Add(x, a)) -> -a
  */
 static ir_node *transform_node_Sub(ir_node *n) {
        ir_mode *mode;
@@ -2048,7 +2050,7 @@ restart:
                        ir_node *left  = get_Add_left(a);
                        ir_node *right = get_Add_right(a);
 
-                       /* FIXME: Does the Conv's word only for two complement or generally? */
+                       /* FIXME: Does the Conv's work only for two complement or generally? */
                        if (left == b) {
                                if (mode != get_irn_mode(right)) {
                                        /* This Sub is an effective Cast */
@@ -2065,6 +2067,32 @@ restart:
                                DBG_OPT_ALGSIM1(oldn, a, b, n, FS_OPT_ADD_SUB);
                        }
                }
+       } else if (is_Add(b)) {
+               if (mode_wrap_around(mode)) {
+                       ir_node *left  = get_Add_left(b);
+                       ir_node *right = get_Add_right(b);
+
+                       /* FIXME: Does the Conv's work only for two complement or generally? */
+                       if (left == a) {
+                               ir_mode *r_mode = get_irn_mode(right);
+
+                               n = new_r_Minus(get_irn_irg(n), get_irn_n(n, -1), right, r_mode);
+                               if (mode != r_mode) {
+                                       /* This Sub is an effective Cast */
+                                       n = new_r_Conv(get_irn_irg(n), get_irn_n(n, -1), n, mode);
+                               }
+                               DBG_OPT_ALGSIM1(oldn, a, b, n, FS_OPT_ADD_SUB);
+                       } else if (right == a) {
+                               ir_mode *l_mode = get_irn_mode(left);
+
+                               n = new_r_Minus(get_irn_irg(n), get_irn_n(n, -1), left, l_mode);
+                               if (mode != l_mode) {
+                                       /* This Sub is an effective Cast */
+                                       n = new_r_Conv(get_irn_irg(n), get_irn_n(n, -1), n, mode);
+                               }
+                               DBG_OPT_ALGSIM1(oldn, a, b, n, FS_OPT_ADD_SUB);
+                       }
+               }
        } else if (mode_is_int(mode) && is_Conv(a) && is_Conv(b)) {
                ir_mode *mode = get_irn_mode(a);