-/**
- * 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 *node, ir_mode *mode)
-{
- switch ((ir_opcode)get_irn_opcode(node)) {
- case iro_And:
- if (!mode_is_signed(mode)) {
- return upper_bits_clean(get_And_left(node), mode)
- || upper_bits_clean(get_And_right(node), mode);
- }
- /* FALLTHROUGH */
- case iro_Or:
- case iro_Eor:
- return upper_bits_clean(get_binop_left(node), mode)
- && upper_bits_clean(get_binop_right(node), mode);
-
- case iro_Shr:
- if (mode_is_signed(mode)) {
- return false; /* TODO */
- } else {
- ir_node *right = get_Shr_right(node);
- if (is_Const(right)) {
- ir_tarval *tv = get_Const_tarval(right);
- long val = get_tarval_long(tv);
- if (val >= 32 - (long)get_mode_size_bits(mode))
- return true;
- }
- return upper_bits_clean(get_Shr_left(node), mode);
- }
-
- case iro_Shrs:
- return upper_bits_clean(get_Shrs_left(node), mode);
-
- case iro_Const: {
- ir_tarval *tv = get_Const_tarval(node);
- long val = get_tarval_long(tv);
- if (mode_is_signed(mode)) {
- long shifted = val >> (get_mode_size_bits(mode)-1);
- return shifted == 0 || shifted == -1;
- } else {
- unsigned long shifted = (unsigned long)val;
- shifted >>= get_mode_size_bits(mode)-1;
- shifted >>= 1;
- return shifted == 0;
- }
- }
-
- case iro_Conv: {
- ir_mode *dest_mode = get_irn_mode(node);
- ir_node *op = get_Conv_op(node);
- ir_mode *src_mode = get_irn_mode(op);
- unsigned src_bits = get_mode_size_bits(src_mode);
- unsigned dest_bits = get_mode_size_bits(dest_mode);
- /* downconvs are a nop */
- if (src_bits <= dest_bits)
- return upper_bits_clean(op, mode);
- if (dest_bits <= get_mode_size_bits(mode)
- && mode_is_signed(dest_mode) == mode_is_signed(mode))
- return true;
- return false;
- }
-
- case iro_Proj: {
- ir_node *pred = get_Proj_pred(node);
- switch (get_irn_opcode(pred)) {
- case iro_Load: {
- ir_mode *load_mode = get_Load_mode(pred);
- unsigned load_bits = get_mode_size_bits(load_mode);
- unsigned bits = get_mode_size_bits(mode);
- if (load_bits > bits)
- return false;
- if (mode_is_signed(mode) != mode_is_signed(load_mode))
- return false;
- return true;
- }
- default:
- break;
- }
- }
- default:
- break;
- }
- return false;
-}
-