IR_BIT_MASK
int reg = ir->ir_bits_map[31 ^ idx] & ~IR_BIT_MASK;
#define IR_BIT_USED_P(x) (((x) & IR_BIT_MASK) != IR_BIT_MASK)
#define IR_BIT_NESTED_P(x) (((x) & IR_BIT_MASK) == IR_BIT_MASK)
#define IR_BIT_UNUSED_P(x) ((x) == IR_BIT_MASK)
#define IR_BIT_REG(x) (IR_BIT_MASK | (x))