80 bit floating point emulator

[kinke]

On Sunday, 6 February 2022 at 13:29:23 UTC, Ola Fosheim Grøstad 
wrote:
> But WHY would you compute compile time in only 80-bit?

For `log(0.1L)` at CTFE, the compiler must when targeting a 
platform with x87 real.

 From https://dlang.org/spec/float.html#fp_const_folding:
> 1. Regardless of the type of the operands, floating-point 
> constant folding is done in real or greater precision. It is 
> always done following IEEE-754 rules and round-to-nearest is 
> used.