METHOD AND APPARATUS FOR PERFORMING ALIGNMENT SHIFTING IN A FLOATING-POINT UNIT

An apparatus for performing alignment shifting in a floating-point unit is disclosed. An alignment shifter includes a shift amount calculator, a set of first level shifters and a set of second level shifter. The shift amount calculator generates one shift amount under a double-precision mode and two shift amounts under a single-precision mode. The first level shifters can concurrently receive two double-precision mantissas under the double-precision mode or two single-precision mantissas under the single-precision mode. The first level of shifts performs small shifts concurrently on the two double-precision mantissas according to the single shift amount, or on the two single-precision mantissas according to the two shift amounts. The second level shifters performs large shifts on outputs from the first level shifters to generate one double-precision floating-point result or two single-precision floating-point results.