For conversion to signed long long, we can almost just use SANE's FX2C call to convert it to comp. But LLONG_MIN corresponds to the bit pattern of the comp NaN, so it has to be treated specially. (You might think SANE would return the comp NaN when converting out-of-range values, which would give the value we want, but somewhat strangely it does not.)
For conversion to unsigned long long, we check if the value is greater than LLONG_MAX (which is also the max comp value). If so, we subtract LLONG_MAX+1 from the floating-point value before conversion and add it back in to the integer afterward.
The new m16.int64 file contains a new "negate8" macro (for 64-bit negation), as well as an improved version of "ph8". These have been added to the individual *.macros files, but if those are regenerated, m16.int64 should be used as an input to macgen ahead of m16.ORCA (which contains the original version of ph8).
SANE does not have built in operations for this, but all the values are exactly representable in the SANE extended format, so we just do the conversion ourselves based on the definition of the extended format.
This file will be expanded with more support routines as needed.
The unsigned multiply routine uses the core multiplication loop from the 64-bit signed multiply routine in SysLib, with new entry/exit code for the unsigned version.
Stephen Heumann