Changing the MIPS ISA definition for the Loongson 3A from MIPS64 to MIPS64r2

[Richard Sandiford]

Heiher <r@hev.cc> writes:
> Hi, Andrew
>
> Thank you for your attention, There have an Arch Linux MIPS n32
> abi port for Loongson3 that compiled by patched binutils and gcc with
> -march=mips64r2 -mtune =loongson3a. I did not find complatible problem
> running it on Lemote Yeloong 8133(Loonson3a) notebook.
>
> Arch Linux Mips mirrors:
> USA: http://mirrors.hev.cc/
> China: http://mirror.lemote.com/archls/
>
> May be help your testing.

Thanks for the note.  Although changing it to MIPS64r2 might seem
obvious, the danger is that the support for the MIPS64r2 and Loongson
extensions might interact badly, especially on the GCC side.  So I think
we'd need to test specifically with -march=loongson3a rather than
-march=mips64r2 -mtune=loongson3a.  (The patch doesn't change the
behaviour of -mtune=loongson3a.)

If you've also tested the patched GCC and binutils in the same way
with -march=loongson3a rather than -march=mips64r2 -mtune=loongson3a
then that's plenty of testing, thanks.

Richard