+ return true;
+}
+
+/**
+ * returns true if it is assured, that the upper bits of a node are "clean"
+ * which means for a 16 or 8 bit value, that the upper bits in the register
+ * are 0 for unsigned and a copy of the last significant bit for signed
+ * numbers.
+ */
+static bool upper_bits_clean(ir_node *transformed_node, ir_mode *mode)
+{
+ assert(ia32_mode_needs_gp_reg(mode));
+ if (get_mode_size_bits(mode) >= 32)
+ return true;
+
+ if (is_Proj(transformed_node))
+ return upper_bits_clean(get_Proj_pred(transformed_node), mode);
+
+ if (is_ia32_Conv_I2I(transformed_node)
+ || is_ia32_Conv_I2I8Bit(transformed_node)) {
+ ir_mode *smaller_mode = get_ia32_ls_mode(transformed_node);
+ if (mode_is_signed(smaller_mode) != mode_is_signed(mode))
+ return false;
+ if (get_mode_size_bits(smaller_mode) > get_mode_size_bits(mode))
+ return false;
+
+ return true;
+ }
+
+ if (is_ia32_Shr(transformed_node) && !mode_is_signed(mode)) {
+ ir_node *right = get_irn_n(transformed_node, n_ia32_Shr_count);
+ if (is_ia32_Immediate(right) || is_ia32_Const(right)) {
+ const ia32_immediate_attr_t *attr
+ = get_ia32_immediate_attr_const(right);
+ if (attr->symconst == 0
+ && (unsigned) attr->offset >= (32 - get_mode_size_bits(mode))) {
+ return true;
+ }
+ }
+ return upper_bits_clean(get_irn_n(transformed_node, n_ia32_Shr_val), mode);
+ }
+
+ if (is_ia32_And(transformed_node) && !mode_is_signed(mode)) {
+ ir_node *right = get_irn_n(transformed_node, n_ia32_And_right);
+ if (is_ia32_Immediate(right) || is_ia32_Const(right)) {
+ const ia32_immediate_attr_t *attr
+ = get_ia32_immediate_attr_const(right);
+ if (attr->symconst == 0
+ && (unsigned) attr->offset
+ <= (0xffffffff >> (32 - get_mode_size_bits(mode)))) {
+ return true;
+ }
+ }
+ /* TODO recurse? */
+ }
+
+ /* TODO recurse on Or, Xor, ... if appropriate? */
+
+ if (is_ia32_Immediate(transformed_node)
+ || is_ia32_Const(transformed_node)) {
+ const ia32_immediate_attr_t *attr
+ = get_ia32_immediate_attr_const(transformed_node);
+ if (mode_is_signed(mode)) {
+ long shifted = attr->offset >> (get_mode_size_bits(mode) - 1);
+ if (shifted == 0 || shifted == -1)
+ return true;
+ } else {
+ unsigned long shifted = (unsigned long) attr->offset;
+ shifted >>= get_mode_size_bits(mode);
+ if (shifted == 0)
+ return true;
+ }
+ }
+
+ return false;