FLOATING-POINT ADDER WITH OPERAND SHIFTING BASED ON A PREDICTED EXPONENT DIFFERENCE

摘要

Provided are a floating-point adder and methods for implementing a floating-point adder with operand shifting based on a predicted exponent difference when performing an effective subtraction on normal or subnormal numbers. In an aspect, two least significant bits (LSBs) of a first floating-point operand's exponent are compared with two LSBs of a second floating-point operand's exponent to estimate a difference between the two exponents. A first shift of up to one of the first and the second operands is performed, based on the estimated difference. A prospective result is then produced by subtracting the first operand and the second operand. Contemporaneously, one of the first operand's exponent and the second operand's exponent is subtracted from the other of the first operand's exponent and the second operand's exponent to determine if the exponents actually differ by one or less. If the first operand's exponent and the second operand's exponent differ by one or less, the prospective result is provided as the raw difference of the operands.