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Re: [PATCH 6/13] mips musl support


On Tue, Apr 21, 2015 at 01:58:02PM +0000, Matthew Fortune wrote:
> Szabolcs Nagy <szabolcs.nagy@arm.com> writes:
> > Set up dynamic linker name for mips.
> > 
> > gcc/Changelog:
> > 
> > 2015-04-16  Gregor Richards  <gregor.richards@uwaterloo.ca>
> > 
> > 	* config/mips/linux.h (MUSL_DYNAMIC_LINKER): Define.
> 
> I understand that mips musl is o32 only currently is that correct?

This is correct. Other ABIs if/when we support them will have
different names.

> There does however appear to be both soft and hard float variants
> listed in the musl docs. Do you plan on using the same dynamic linker
> name for both float variants? No problem if so but someone must have
> decided to have unique names for big and little endian so I thought
> it worth checking.

No, it's supposed to be different (-sf suffix for soft float; see
arch/mips/reloc.h in musl source). If this didn't make it into the
patches it's an omission, probably because we didn't officially
support the sf ABI at all for a long time.

> Also, are you aware of the two nan encoding formats that MIPS has
> and the support present in glibc's dynamic linker to deal with it?

I am aware but somewhat skeptical of treating it as yet another
dimension to ABI and the resulting ABI combinatorics. The vast
majority of programs couldn't care less which is which and whether a
NAN is quiet or signaling. Officially we just use the classic mips ABI
(with qnan/snan swapped vs other archs) but there's no harm in
somebody doing the opposite if they really know what they're doing.

> I wonder if it would be wise to refuse to target musl unless the
> ABI is known to be supported so that we can avoid compatibility
> issues when different ABI variants are added in musl.

Possibly, though this might make bootstrapping new ABIs harder.

Rich


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