Method and apparatus for performing multiple types of multiplication including signed and unsigned multiplication

A multiplier capable of performing both signed and unsigned multiplication comprising:

• an effective sign generator configured to receive a sign-in bit and a most significant bit from a multiplicand operand as an inputs, wherein said effective sign generator is configured to output an effective sign bit corresponding to said multiplicand operand;
• a partial product generator coupled to receive said multiplicand operand and said effective sign bit, wherein said multiplicand operand is in scalar or packed vector format, wherein said partial product generator is configured to generate a plurality of partial product values using said multiplicand operand and said effective sign bit;
• selection logic coupled to said partial product generator, wherein said selection logic is coupled to receive a multiplier operand, wherein said multiplier operand is in scalar or packed vector format, wherein said selection logic is configured to select a number of partial products from said partial product generator based upon said multiplier operand;
• and
• an adder coupled to said selection logic unit, wherein said adder is configured to sum the partial products selected by said selection unit to form a product.

A method for operating a multiplier within a microprocessor comprising:

• receiving a multiplier operand, a multiplicand operand, and a sign-in signal as inputs from functional units within the microprocessor, wherein said multiplier operand is in scalar or packed vector format, wherein said multiplicand operand is in scalar or packed vector format;
• generating an effective sign bit for said multiplicand operand from said sign-in signal and the most significant bit of said multiplicand operand using an AND gate;
• calculating a number of partial products from said effective sign bit and said multiplicand operand using inverters and shifting logic;
• selecting partial products according to said multiplier operand;
• summing the selected partial products;
• and
• outputting the results.