NetBSD amd64: which way is the best for supporting 80 bits real/double?

[Dominikus Dittes Scherkl via Digitalmars-d]

On Thursday, 11 May 2017 at 10:07:32 UTC, Joakim wrote:
> On Thursday, 11 May 2017 at 02:05:11 UTC, Nikolay wrote:
>> I am porting LDC to NetBSD amd64, and I ask advice how to 
>> handle real type. NetBSD has limited support for this type.
>
> What is long double on NetBSD/amd64, 64-bit or full 80-bit?  We 
> were talking about this when I was porting to Android/x86, 
> where long double is 64-bit but the FPU should support 80-bit.  
> Iain suggested just sticking to the ABI, ie using 64-bit if 
> that's how long double is defined (see next three comments 
> after linked comment):
>
> https://github.com/dlang/phobos/pull/2150#issuecomment-42731651
>
>> This type exists, but standard library does not provide full 
>> set of math functions for it (e.g. sinus, cosinus, and etc). 
>> Currently I just forward all function calls to 64 bits version 
>> counterparts, but in this case a set of unit tests are 
>> failing. I see following approaches to handle this issue:
>>    - Totally remove 80 bit real type from NetBSD port (make 
>> real==double)
>>    - Change tests and skip asserts for NetBSD
>>
>> There is one additional approach: implement these functions in 
>> druntime, but it is too big/massive work for me.
>
> I wouldn't worry about it too much.  If someone really needs 
> this, they will have to chip in.  Dmd uses compiler intrinsics 
> for those trig functions, and I notice that they seem to just 
> call the native x86 asm instructions:

I hate it if D doesn't fully support the hardware just to be 
compatible to some bad designed C library.
Hey, it's a system language! I want to be able to use the 
hardware I have to its fullest!
And for calling C functions you always have to fing the fitting 
D-type by checking "mantdig" and map accordingly. Thats really 
not so difficult.