[musl] ld128 math function support

[musl] ld128 math function support

[gzh2233]

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Hi, all


I am trying to use ld128 in x86_64 musl and i have some problems.


Long double format is defined in arch/x86_64/bits/float.h and i am trying to
change long double relevant macros. However, many long double functions
still use double implementions(mostly "xxhl" functions). This is just a way to
make musl compile and can be a problem in some cases. Simply changing
the long double relevant macros can change ld80 into ld128 but this
problem still exists. 


Is there any official support for long double math functions?

Regards,
Zhihao Gu.


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Re: [musl] ld128 math function support

[Szabolcs Nagy]

* gzh2233 <gzh1754344759@163.com> [2022-12-08 15:56:35 +0800]:
> I am trying to use ld128 in x86_64 musl and i have some problems.

that has multiple issues.

> Long double format is defined in arch/x86_64/bits/float.h and i am trying to
> change long double relevant macros. However, many long double functions
> still use double implementions(mostly "xxhl" functions). This is just a way to
> make musl compile and can be a problem in some cases. Simply changing
> the long double relevant macros can change ld80 into ld128 but this
> problem still exists. 
> 
> 
> Is there any official support for long double math functions?

musl does not support long double == float128 on x86_64.
this is part of the abi.

if you add a new abi variant where long double is float128,
that works but many float128 math functions have low quality
currently as you noticed. fixing this is significant effort.
i don't have immediate plans to fix this.

another option is to keep long double as is but add _Float128
support and f128 math functions (on all targets). such support
would require additional work and increase the size of libc.so.