Re: [GCC PATCH] powerpc64 musl libc support for IEEE binary128 long double

[Szabolcs Nagy <nsz@port70.net>]

* Samuel Holland <samuel@sholland.org> [2019-06-30 19:59:28 -0500]:
> >> -#define RS6000_DEFAULT_LONG_DOUBLE_SIZE 128
> >> +#define RS6000_DEFAULT_LONG_DOUBLE_SIZE (OPTION_MUSL ? 64 : 128)
> > 
> > configuring 32bit ppc with 128bit long double is unsupported in musl
> > 
> > i think reporting an error in config.gcc is better than trying to fix
> > it up later.
> 
> I don't think that's possible, but I'm happy to be proven wrong. gcc accepts a
> single gcc_cv_target_ldbl128, which is applied everywhere with
> multilib/multiarch/--enable-targets=all. So even if --with-long-double-128 was
> made an error for powerpc-linux-musl, the logic still has to work for
> powerpc64-linux-musl, where it can't be an error.
> 
> > OPTION_MUSL can handle -mmusl cflag, not just the configured libc, but
> > i think that's unreliable for other reasons anyway.
> 
> That also has to work: --target=powerpc-linux-gnu --with-long-double-128, and
> then powerpc-linux-gnu-gcc -mmusl, will do the wrong thing unless it's fixed up
> at runtime.

what i'm saying is that this is not a supportable usage so there
is no point adding musl specific hacks to gcc internals which
wont work anyway.

if somebody uses -mmusl on a toolchain with default 128bit ldbl
then it's their responsibility to pass correct abi flags.
but it still wont work if the target libs like libgcc depend on
those abi flags: there will be no target libs with the right abi.

> > otherwise keep it with some easy to remember ordering for the extension
> > suffixes (e.g. alphabetical)
> 
> Should there be a dash between "ieee128" and "sf"?

well you defined the extension as -foo, i prefer using _foo
not to confuse target triplet parsers, but since -sf is already
there -foo is probably better.