80 bit floating point emulation

[Walter Bright]

On 7/9/2022 2:47 AM, JG wrote:
> On Friday, 8 July 2022 at 22:04:38 UTC, Walter Bright wrote:
>> In order for DMD to become a proper cross compiler, it needs to be able to 
>> emulate 80 bit floating point. The full x87 doesn't need to be emulated, just
>> add, sub, mul, div, cmp, neg, tst.
>>
>> [...]
> 
> Thinking of spending a few hours later to get an idea of how long it will take 
> to do. Any specification to work from?

It's IEEE748

You'll mainly need to be aware of sticky bits, guard bits, and unnormals.