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                                SoftFloat

This provides a software implementation of functions performing floating point

operations according to the IEEE 754 standard.

It is used in or1ksim due to problems arising when using the simulator host

machine's floating point unit to perform single precision floating point

calculations (or even double, in some cases.) Typically the host machine's FPU

will support extended (80-bit), or higher, precision, resulting in values which

can differ from those which are calculated on a true single or double precision

floating point unit (very small differences when in rounding and generating

status flags.)

Although using a software implementation is slow, it ensures an accurate

simulation of a single or double precision floating point unit.

This software was sourced from the author's (John Hauser) site:

http://www.jhauser.us/arithmetic/SoftFloat.html

Note that the code cannot be compiled with -O0 for debugging purpose, because

of the approach used to code inlining. Additional macros have been added to

ease this problem. For debugging purposes, Or1ksim should be configured adding

CFLAGS="-O0 -DINLINE=static -DNO_SOFTFLOAT_UNUSED" to the configure line.

Julius Baxter, August 1, 2010

Jeremy Bennett, August 4, 2010 (-O0 compilation)