Let fp-vrp optimize Minus nodes.

diff --git a/ir/opt/fp-vrp.c b/ir/opt/fp-vrp.c
index 3bee116..5a06aa5 100644 (file)
--- a/ir/opt/fp-vrp.c
+++ b/ir/opt/fp-vrp.c
@@ -746,6 +746,24 @@ exchange_only:
                        break;
                }
 
+               case iro_Minus: {
+                       ir_mode *mode = get_irn_mode(irn);
+
+                       /* If all bits except the highest bit are zero the Minus is superfluous. */
+                       if (get_mode_arithmetic(mode) == irma_twos_complement) {
+                               ir_node         *const op  = get_Minus_op(irn);
+                               bitinfo   const *const b   = get_bitinfo(op);
+                               ir_tarval       *const min = get_mode_min(mode);
+
+                               if (tarval_is_all_one(tarval_or(min, tarval_not(b->z)))) {
+                                       DB((dbg, LEVEL_2, "%+F(%+F) is superfluous\n", irn, op));
+                                       exchange(irn, op);
+                                       env->modified = 1;
+                               }
+                       }
+                       break;
+               }
+
                case iro_Or: {
                        ir_node*       const l  = get_Or_left(irn);
                        ir_node*       const r  = get_Or_right(irn);