This does not answer the originally posed question, but if you are a programmer working with similar issues, this answer might help you. I really don’t see where the perceived difficulty is. Providing strict IEEE-754 binary64 semantics while being limited to 80387 floating-point math, and retaining 80-bit long double computation, seems to follow well-specified C99 … Read more
Ad 1. Those types are designed to work with numbers with huge dynamic range. The long double is implemented in a native way in the x87 FPU. The 128b double I suspect would be implemented in software mode on modern x86s, as there’s no hardware to do the computations in hardware. The funny thing is … Read more
I think it may be possible to implement BigNum with SIMD efficiently but not in the way you suggest. Instead of implementing a single BigNum using a SIMD register (or with an array of SIMD registers) you should process multiple BigNums at once. Let’s consider 128-bit addition. Let 128-bit integers be defined by a pair … Read more