[PATCH] MIPS: gas: alter 64 or 32 for r6 triples if march is implicit

[Richard Sandiford]

YunQiang Su <syq@debian.org> writes:
> Let's be back to the problem of this patch: what should we do for
>      mipsisa32rXel-*-as -64
> and
>     mipsisa64rXel-*-as -32
> We have several options:
> 1. Keep current, aka issue an error message and exit for 32-64 combination.
> 2. set the default arch to mips64r6 only for mipsisa32r6, aka not for
> mipsisa32r[1-5].
>     set the default arch to mips32r6 only for mipsisa64r6, aka not for
> mipsisa32r[1-5].
>     That's what I did in this patch.
> 3. set the default arch to mips64rN for mipsisa32rN
>     set the default arch to mips32rN for mipsisa64rN
>     but do nothing for any other triples, such as
>        mipstx39* or mips64vr,
>     Since it's hard to determine which arches are best for them.

Personally, I think we should do this one, similarly to your
9171de358f230b64646bbb525a74e5f8e3dbe0dc.  IMO it's better to think
of mipsr6+ as a separate ISA group from pre-r6, since no pair of ISAs
from either group is binary compatible in either direction.

So for mipsr6+ toolchains (those with a mipsr6+ triplet), from-abi
should select the appropriate r6 ISA rather than mips1 or mips3.

Thanks,
Richard

> 4. Set the default 32/64 arch for all triples.