Fixed dca transfer function for Add, Sub, Minus, Mul and Shl.

We have to consider that less significant bits of the operands
can affect more significant bits of the operation itself.

This fixes opt/occult2.c and 177.mesa.

ir/ana/dca.c

@@ -56,6 +56,20 @@ static void care_for(ir_node *irn, ir_tarval *care, pdeq *q)
 	}
 }
 
+/* Creates a bit mask that have the msb and all less significant bits set. */
+static ir_tarval *create_msb_mask(ir_tarval *tv)
+{
+	ir_mode   *mode         = get_tarval_mode(tv);
+	ir_tarval *shift_amount = get_tarval_one(mode);
+
+	for (int msb = get_tarval_highest_bit(tv); msb != 0; msb /= 2) {
+		tv           = tarval_or(tv, tarval_shr(tv, shift_amount));
+		shift_amount = tarval_add(shift_amount, shift_amount);
+	}
+
+	return tv;
+}
+
 /* Compute cared for bits in predecessors of irn. */
 static void dca_transfer(ir_node *irn, pdeq *q)
 {
@@ -171,18 +185,19 @@ static void dca_transfer(ir_node *irn, pdeq *q)
 			return;
 		case iro_Add:
 		case iro_Sub: {
-			ir_node *left  = get_binop_left(irn);
-			ir_node *right = get_binop_right(irn);
-			care_for(right, care, q);
-			care_for(left, care, q);
+			ir_node   *left      = get_binop_left(irn);
+			ir_node   *right     = get_binop_right(irn);
+			ir_tarval *care_mask = create_msb_mask(care);
+			care_for(right, care_mask, q);
+			care_for(left, care_mask, q);
 
-			/* Carry. */
-			care_for(irn, tarval_shr(care, get_tarval_one(mode)), q);
 			return;
 		}
 		case iro_Minus:
+			care_for(get_Minus_op(irn), create_msb_mask(care), q);
+			return;
 		case iro_Not:
-			care_for(get_irn_n(irn, 0), care, q);
+			care_for(get_Not_op(irn), care, q);
 			return;
 		case iro_Shrs:
 		case iro_Shr: {
@@ -212,29 +227,30 @@ static void dca_transfer(ir_node *irn, pdeq *q)
 			if (is_Const(right))
 				care_for(left, tarval_shr(care, get_Const_tarval(right)), q);
 			else
-				care_for(left, care, q);
+				care_for(left, create_msb_mask(care), q);
 
 			care_for(right, 0, q);
 
 			return;
 		}
 		case iro_Mul: {
-			ir_node *left  = get_Mul_left(irn);
-			ir_node *right = get_Mul_right(irn);
+			ir_node   *left      = get_Mul_left(irn);
+			ir_node   *right     = get_Mul_right(irn);
+			ir_tarval *care_mask = create_msb_mask(care);
 
 			if (is_Const(right))
 				care_for(
 					left,
 					tarval_shr(
-						care,
+						care_mask,
 						new_tarval_from_long(
 							get_tarval_lowest_bit(
 								get_Const_tarval(right)), mode)),
 					q);
 			else
-				care_for(left, care, q);
+				care_for(left, care_mask, q);
 
-			care_for(right, 0, q);
+			care_for(right, care_mask, q);
 			return;
 		}
 		}