+/**
+ * Returns the earliest were a,b are available.
+ * Note that we know that a, b both dominate
+ * the block of the previous operation, so one must dominate the other.
+ *
+ * If the earliest block is the start block, return curr_blk instead
+ */
+static ir_node *earliest_block(ir_node *a, ir_node *b, ir_node *curr_blk) {
+ ir_node *blk_a = get_nodes_block(a);
+ ir_node *blk_b = get_nodes_block(b);
+ ir_node *res;
+
+ /* if blk_a != blk_b, one must dominate the other */
+ if (block_dominates(blk_a, blk_b))
+ res = blk_b;
+ else
+ res = blk_a;
+ if (res == get_irg_start_block(current_ir_graph))
+ return curr_blk;
+ return res;
+} /* earliest_block */
+
+/**
+ * Checks whether a node is a Constant expression.
+ * The following trees are constant expressions:
+ *
+ * Const, SymConst, Const + SymConst
+ *
+ * Handling SymConsts as const might be not a good idea for all
+ * architectures ...
+ */
+static int is_constant_expr(ir_node *irn) {
+ ir_op *op;
+
+ switch (get_irn_opcode(irn)) {
+ case iro_Const:
+ case iro_SymConst:
+ return 1;
+ case iro_Add:
+ op = get_irn_op(get_Add_left(irn));
+ if (op != op_Const && op != op_SymConst)
+ return 0;
+ op = get_irn_op(get_Add_right(irn));
+ if (op != op_Const && op != op_SymConst)
+ return 0;
+ return 1;
+ default:
+ return 0;
+ }
+} /* is_constant_expr */
+
+/**
+ * Apply distributive Law for Mul and Add/Sub
+ */
+static int reverse_rule_distributive(ir_node **node) {
+ ir_node *n = *node;
+ ir_node *left = get_binop_left(n);
+ ir_node *right = get_binop_right(n);
+ ir_node *x, *blk, *curr_blk;
+ ir_node *a, *b, *irn;
+ ir_op *op;
+ ir_mode *mode;
+ dbg_info *dbg;
+
+ op = get_irn_op(left);
+ if (op != get_irn_op(right))
+ return 0;
+
+ if (op == op_Shl) {
+ x = get_Shl_right(left);
+
+ if (x == get_Shl_right(right)) {
+ /* (a << x) +/- (b << x) ==> (a +/- b) << x */
+ a = get_Shl_left(left);
+ b = get_Shl_left(right);
+ goto transform;
+ }
+ } else if (op == op_Mul) {
+ x = get_Mul_left(left);
+
+ if (x == get_Mul_left(right)) {
+ /* (x * a) +/- (x * b) ==> (a +/- b) * x */
+ a = get_Mul_right(left);
+ b = get_Mul_right(right);
+ goto transform;
+ } else if (x == get_Mul_right(right)) {
+ /* (x * a) +/- (b * x) ==> (a +/- b) * x */
+ a = get_Mul_right(left);
+ b = get_Mul_left(right);
+ goto transform;
+ }
+
+ x = get_Mul_right(left);
+
+ if (x == get_Mul_right(right)) {
+ /* (a * x) +/- (b * x) ==> (a +/- b) * x */
+ a = get_Mul_left(left);
+ b = get_Mul_left(right);
+ goto transform;
+ } else if (x == get_Mul_left(right)) {
+ /* (a * x) +/- (x * b) ==> (a +/- b) * x */
+ a = get_Mul_left(left);
+ b = get_Mul_right(right);
+ goto transform;
+ }
+ }
+ return 0;
+
+transform:
+ curr_blk = get_nodes_block(n);
+
+ blk = earliest_block(a, b, curr_blk);
+
+ dbg = get_irn_dbg_info(n);
+ mode = get_irn_mode(n);
+
+ if (is_Add(n))
+ irn = new_rd_Add(dbg, current_ir_graph, blk, a, b, mode);
+ else
+ irn = new_rd_Sub(dbg, current_ir_graph, blk, a, b, mode);
+
+ blk = earliest_block(irn, x, curr_blk);
+
+ if (op == op_Mul)
+ irn = new_rd_Mul(dbg, current_ir_graph, blk, irn, x, mode);
+ else
+ irn = new_rd_Shl(dbg, current_ir_graph, blk, irn, x, mode);
+
+ exchange(n, irn);
+ *node = irn;
+ return 1;
+} /* reverse_rule_distributive */
+
+/**
+ * Move Constants towards the root.
+ */
+static int move_consts_up(ir_node **node) {
+ ir_node *n = *node;
+ ir_op *op;
+ ir_node *l, *r, *a, *b, *c, *blk, *irn, *in[2];
+ ir_mode *mode, *ma, *mb;
+ dbg_info *dbg;
+
+ l = get_binop_left(n);
+ r = get_binop_right(n);
+
+ /* check if one is already a constant expression */
+ if (is_constant_expr(l) || is_constant_expr(r))
+ return 0;
+
+ dbg = get_irn_dbg_info(n);
+ op = get_irn_op(n);
+ if (get_irn_op(l) == op) {
+ /* (a .op. b) .op. r */
+ a = get_binop_left(l);
+ b = get_binop_right(l);
+
+ if (is_constant_expr(a)) {
+ /* (C .op. b) .op. r ==> (r .op. b) .op. C */
+ c = a;
+ a = r;
+ blk = get_nodes_block(l);
+ dbg = dbg == get_irn_dbg_info(l) ? dbg : NULL;
+ goto transform;
+ } else if (is_constant_expr(b)) {
+ /* (a .op. C) .op. r ==> (a .op. r) .op. C */
+ c = b;
+ b = r;
+ blk = get_nodes_block(l);
+ dbg = dbg == get_irn_dbg_info(l) ? dbg : NULL;
+ goto transform;
+ }
+ } else if (get_irn_op(r) == op) {
+ /* l .op. (a .op. b) */
+ a = get_binop_left(r);
+ b = get_binop_right(r);
+
+ if (is_constant_expr(a)) {
+ /* l .op. (C .op. b) ==> (l .op. b) .op. C */
+ c = a;
+ a = l;
+ blk = get_nodes_block(r);
+ dbg = dbg == get_irn_dbg_info(r) ? dbg : NULL;
+ goto transform;
+ } else if (is_constant_expr(b)) {
+ /* l .op. (a .op. C) ==> (a .op. l) .op. C */
+ c = b;
+ b = l;
+ blk = get_nodes_block(r);
+ dbg = dbg == get_irn_dbg_info(r) ? dbg : NULL;
+ goto transform;
+ }
+ }
+ return 0;
+
+transform:
+ /* In some cases a and b might be both of different integer mode, and c a SymConst.
+ * in that case we could either
+ * 1.) cast into unsigned mode
+ * 2.) ignore
+ * we implement the second here
+ */
+ ma = get_irn_mode(a);
+ mb = get_irn_mode(b);
+ if (ma != mb && mode_is_int(ma) && mode_is_int(mb))
+ return 0;
+
+ /* check if (a .op. b) can be calculated in the same block is the old instruction */
+ if (! block_dominates(get_nodes_block(a), blk))
+ return 0;
+ if (! block_dominates(get_nodes_block(b), blk))
+ return 0;
+ /* ok */
+ in[0] = a;
+ in[1] = b;
+
+ mode = get_mode_from_ops(a, b);
+ in[0] = irn = optimize_node(new_ir_node(dbg, current_ir_graph, blk, op, mode, 2, in));
+
+ /* beware: optimize_node might have changed the opcode, check again */
+ if (is_Add(irn) || is_Sub(irn)) {
+ reverse_rule_distributive(&in[0]);
+ }
+ in[1] = c;
+
+ mode = get_mode_from_ops(in[0], in[1]);
+ irn = optimize_node(new_ir_node(dbg, current_ir_graph, blk, op, mode, 2, in));
+
+ exchange(n, irn);
+ *node = irn;
+ return 1;
+} /* move_consts_up */
+
+/**
+ * Apply the rules in reverse order, removing code that was not collapsed
+ */
+static void reverse_rules(ir_node *node, void *env) {
+ walker_t *wenv = env;
+ ir_mode *mode = get_irn_mode(node);
+ int res;
+
+ /* for FP these optimizations are only allowed if fp_strict_algebraic is disabled */
+ if (mode_is_float(mode) && get_irg_fp_model(current_ir_graph) & fp_strict_algebraic)
+ return;
+
+ do {
+ ir_op *op = get_irn_op(node);
+
+ res = 0;
+ if (is_op_commutative(op)) {
+ wenv->changes |= res = move_consts_up(&node);
+ }
+ /* beware: move_consts_up might have changed the opcode, check again */
+ if (is_Add(node) || is_Sub(node)) {
+ wenv->changes |= res = reverse_rule_distributive(&node);
+ }
+ } while (res);
+}
+