History of Berkeley SoftFloat, to Release 3

John R. Hauser
2015 February 16

Complete rewrite, funded by the University of California, Berkeley, and consequently having a different use license than earlier releases. Major changes included renaming most types and functions, upgrading some algorithms, restructuring the source files, and making SoftFloat into a true library.
Added functions to convert between floating-point and unsigned integers, both 32-bit and 64-bit (uint32_t and uint64_t).
Added functions for fused multiply-add, for all supported floating-point formats except 80-bit double-extended-precision.
Added support for a fifth rounding mode, near_maxMag (round to nearest, with ties to maximum magnitude, away from zero).
Dropped the timesoftfloat program (now part of the Berkeley TestFloat package).

Fixed mistakes affecting some 64-bit processors.
Further improved the documentation and the wording for the legal restrictions on using SoftFloat releases through 2c (not applicable to Release 3 or later).

Made minor updates to the documentation, including improved wording for the legal restrictions on using SoftFloat.

Added functions to convert between 64-bit integers (int64) and all supported floating-point formats.
Fixed a bug in all 64-bit-version square root functions except float32_sqrt that caused the result sometimes to be off by 1 unit in the last place (1 ulp) from what it should be. (Bug discovered by Paul Donahue.)
Improved the Makefiles.

Created the 64-bit (bits64) version, adding the floatx80 and float128 formats.
Changed the source directory structure, splitting the sources into a bits32 and a bits64 version. Renamed environment.h to milieu.h to avoid confusion with environment variables.
Fixed a small error that caused float64_round_to_int often to round the wrong way in nearest/even mode when the operand was between 2²⁰ and 2²¹ and halfway between two integers.

Corrected a mistake that caused borderline underflow cases not to raise the underflow flag when they should have. (Problem reported by Doug Priest.)
Added the float_detect_tininess variable to control whether tininess is detected before or after rounding.

Original release, based on work done for the International Computer Science Institute (ICSI) in Berkeley, California.