Re: RFA: MIPS ABI selection

[Andrew Cagney <ac131313 at cygnus dot com>]

> The current state of the world in GCC says: a handful of setups default to
> unique ABIs, but the global default is O32.  The default is also to pass no
> ABI flags to the assembler.
>
> elf64.h, iris6.h, isa3264.h, and r3900.h override this.  Irix defaults to
> N32 and passing -n32 which presumably tags binaries; plus the irix
> configuration in GDB can handle this.  elf64.h does not do pass any flags
> but defaults to O64.  isa3264.h defaults to MEABI and appears not to tag
> binaries.  r3900.h defaults to EABI and untagged binaries.
>
> That's mipsisa32-*-elf*, mips64*-*-elf*, mipstx39*-*-elf*,
> mips-sgi-irix5cross64, and mips-sgi-irix6*.
>
> So what's a debugger to do?  Right now, we try to infer things from our
> header files, but only little details of the ABI.  In particular, we never
> infer O32 correctly.  Better would be to match GCC; that's quite
> straightforward.

> I skipped mipsisa32-*-elf*, because GDB doesn't support MEABI.  So this
> patch fixes the defaults for mips64*-*-elf* and mipstx39*-*-elf*, and a
> little tweaking for IRIX.  It then adds a global O32 default.  In the
> process I found another way that GCC tags binaries with their ABI: a
> ".mdebug.abi32", etc. section.  I handle that too.  All appears to work like
> a charm.  We even get warnings for MEABI etc. binaries.
>
> Andrew, this look OK?
Hmm, this contains several changes:


-- The function mips_find_abi_section() that better identifies the ABI.

Yes.  This is definitly a good idea and approved.


-- Adding the macro MIPS_DEFAULT_ABI to all MIPS targets.

Remember, all the mips/tm-*.h files are going away so this isn't really 
going to help.  Instead, I think a ``(gdb) set mips abi <tab>.. auto o32 
...'' command would be far more useful.  Another place the code could 
look is the ABI from the previous architecture.


-- Some additional MIPS targets

Er, we're trying to get the number of MIPS targets down to zero.


enjoy,
Andrew