[PATCH] [mips] Add the SoftFloat MipsSubtarget feature.

[Matthew Fortune]

> I've got a few comments but nothing major. LGTM with those.
> 
> 
> ================
> Comment at: lib/Target/Mips/AsmParser/MipsAsmParser.cpp:90
> @@ -90,1 +89,3 @@
> +      Mips::FeatureFP64Bit | Mips::FeatureGP64Bit |
> Mips::FeatureNaN2008 |
> +      Mips::FeatureSoftFloat;
> 
> ----------------
> I don't think soft-float is an arch related feature. Does '.set mips32'
> and similar reset it?

In general the .set options are supposed to be as independent as possible
there is unfortunate historic entanglement in binutils which means that
we have to allow .set mips<blah> to automatically set gp and fp defaults.
However, with fp=xx I believe the behaviour is that .set mips<blah>
does not force a specific fp setting when the current value is xx. The
other .set options only update one feature even if that produces a
slightly unusual overall configuration.

Thanks,
Matthew