International Business Machines Corporation
Floating point unit for exponential function implementation

Abstract:

A computer-implemented method for performing an exponential calculation using only two fully-pipelined instructions in a floating point unit that includes. The method includes computing an intermediate value y' by multiplying an input operand with a predetermined constant value. The input operand is received in floating point representation. The method further includes computing an exponential result for the input operand by executing a fused instruction. The fused instructions includes converting the intermediate value y' to an integer representation z represented by v most significant bits (MSB), and w least significant bits (LSB). The fused instruction further includes determining exponent bits of the exponential result based on the v MSB from the integer representation z. The method further includes determining mantissa bits of the exponential result according to a piece-wise linear mapping function using a predetermined number of segments based on the w LSB from the integer representation z.