Abstract: A novel method and apparatus of performing data bit moving functions on a data word using two barrel shifters: a left shifter and a right shifter. The present invention is able to handle both shift and rotate functions using one shifter unit. Specifically, for shift functions, only one of the two shifters is used to perform the shifting function. On the other hand, for rotate functions, both shifters are needed for shifting the data word. The amounts of the right shift and left shift depend on the number defined by the count operand and the specific shift/rotate instruction requested.

Abstract: A single chip microprocessor has at least two parallel pipelines that each have multiple processing stages, one of which is an instruction execution stage with a full functioned arithmetic logic unit (ALU). The ALU of one pipeline includes an adder that has the usual two input ports while the adder of the ALU of the other pipeline has at least one extra input port. Two successive arithmetically data dependent instructions are executed by the larger adder alone, while the smaller adder is used as part of a logic circuit that determines the carry bit for the instruction execution result obtained from the larger adder. The smaller adder is thus efficiently used, in an operation where it would otherwise be idle. The additional logic circuitry necessary to determine the carry bit is thus minimized.

Abstract: A novel method and apparatus is disclosed for locating the first most, or least, significant set bit in a bit-string. The present invention breaks down the bit-string into a plurality of shorter sub-strings so that boolean operations can be performed directly to the shorter sub-strings for determining the location of the most/least significant set bit. Furthermore, this method can be repeatedly used to reduce the length of the shorter sub-string after the most/least significant sub-string is located. Particularly, this method of repeatedly dividing the bit-string greatly increases the speed of locating the set bit.