Optimized fused-multiply-add method and system

摘要

A fused-multiply-add system is disclosed. The fused-multiply-add system includes a multiplier to multiply first and second operands and to provide at least one product. The fused-multiply-add system also includes an alignment shifter for aligning a third operand with the at least one product to provide an aligned third operand. The fused-multiply-add system also includes an adder and a subtractor coupled to the multiplier and the alignment shifter for performing two asymmetrical additions in parallel paths. The fused-multiply-add system also includes at least one leading zero counter for counting a number of leading zero bits provided by at least one of the adder and the subtractor to provide at least one normalization shift amount. Finally, the fused-multiply-add system includes a multiplexer coupled to the adder and the subtractor for providing an appropriate output based upon a sign bit.

主权项

1. A fused-multiply-add (FMA) system comprising:
a multiplier multiplying a first operand and a second operand and providing at least one product of the first and second operands; an alignment shifter aligning a third operand with the at least one product and providing an aligned third operand; an adder and a subtractor coupled to the multiplier and the alignment shifter, the adder and the subtractor in parallel paths; at least one leading zero counter providing at least one normalization shift amount by counting a number of leading zero bits provided by at least one of the adder and the subtractor; and a multiplexer having a first multiplexer input coupled to an adder output of the adder and a second multiplexer input coupled to a subtractor output of the subtractor and, based upon a control signal input of the multiplexer, providing the first multiplexer input or the second multiplexer input as an output of the multiplexer.