Re: [musl] Considering x86-64 fenv.s to C

[Damian McGuckin <damianm@esi.com.au>]

On Mon, 20 Jan 2020, Rich Felker wrote:

> If you don't feel ready to do unification or work on archs you're 
> unfamiliar with, I think it's okay to either (1) only do the x86 work 
> now, with no unification, or (2) start the unification in src/fenv/*.c, 
> but with the arch files left in place in src/fenv/*/*.[csS] for all the 
> archs that haven't been converted yet. I don't want to block improvement 
> of the x86 versions just because the bigger task is too big.

I will revisit the abstraction without the i386/x86-?? architecture.
I think that would work.

> Another really stupid but perhaps very efficient idea we could do is
> just emulating the flags. Add a TLS slot for an fexcept_t value, move
> exceptions there as needed, and or it onto the result when reading
> back current exceptions. This would also make it dirt cheap for the
> math library to raise any exception it wants, without needing
> arithmetic, and it would make it possible to have the math library
> return errors via exception flags even on softfloat archs.

That makes a lot of sense.

That just leaves rounding and, even on the X86, the abstraction of 
getting/setting the register can be made generic.

Regards - Damian

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