RFC & patch: Rework MIPS command-line handling

[Thiemo Seufer]

Eric Christopher wrote:
[snip]
> >I'd prefer to select the default ABI at the configure time, from the
> >target triplet ideally.  E.g. I use a local patch that select the 64
> >ABI as the default for binutils if configuring for mips64*-*-linux*. 
> >The same is set in the specs file for gcc for this target.

I'd prefer this, too. My local patch for mips64*-*-linux* uses n32
as default because n64 is only useful for OS kernels and WRT userland
for large memory machines.

> This is only particularly convenient for the hosted toolchains, and I
> don't think I want to get into the habit of splitting things between
> OSes and embedded toolchains.

AFAICS this is done in the target specific code, so it is already
splitted.

[snip]
> This is probably only convenient with hosted toolchains. Also, many
> people are accustomed to the toolchain deciding ABI for them. Also, the
> historical precedent (not always something to look at, but...) of the
> SGI compiler switches ABI based on -mipsX switch as well.

And then they invented the (undocumented) -mabi switch, I assume
because automatic switching didn't work particularily well.

> >Well, the intent seems valid (certain sets of options make
> >non-conforming files to be generated), but the check is incomplete. 
> >Note the ABI setting gets propagated to the ELF header of a generated
> >file, so both the ABI field and the ABI invalidation code like above
> >should probably remain in place.
> 
> Some sort of error checking should be there, that's part of what we get
> with Richard's new patch. The old error checking was well.. error prone
> and not in any way marginally complete.

It was simply a hack to make things a little bit better without breaking
backward compatibility.


Thiemo