[MIPS] Re-enable ABI->ISA inference

[Moore, Catherine]

> -----Original Message-----
> From: Matthew Fortune [mailto:Matthew.Fortune@imgtec.com]
> Sent: Monday, January 05, 2015 6:09 PM
> To: Moore, Catherine
> Cc: 'gcc-patches@gcc.gnu.org' (gcc-patches@gcc.gnu.org)
> Subject: [MIPS] Re-enable ABI->ISA inference
> 
> The R6 patch introduced MIPS_ISA_LEVEL_SPEC into DRIVER_SELF_SPECS for
> all configurations. One part of MIPS_ISA_LEVEL_SPEC is however
> incompatible with those configurations which infer an ISA from an ABI
> without specifically setting the default ISAs using --with-arch-[32|64].
> 
> I.e. a generic mips-linux (--enable-targets=all) and mips64-linux would fail to
> build the n32/n64 multilibs as -mips1 would be introduced by
> DRIVER_SELF_SPECS.
> 
> I have therefore split MIPS_ISA_LEVEL_SPEC into two. One part is suitable
> for all confgurations and one part is only suitable for configurations that infer
> an ABI from an ISA (these tend to be cross-compiler vendor configurations)
> 
> I have built and checked the driver generated options for all relevant
> configurations and everything appears to work.
> 
> Let me know if you can see any problems with this?
> 
> Thanks,
> Matthew
> 
> gcc/
> 
>      * config/mips/mips.h (MIPS_ISA_LEVEL_SPEC): Only infer an ISA
>      level from an ARCH; do not inject the default.
>      (MIPS_DEFAULT_ISA_LEVEL_SPEC): New macro split out from
>      MIPS_ISA_LEVEL_SPEC.
>      (MIPS_ISA_NAN2008_SPEC): Update comment.
>      (BASE_DRIVER_SELF_SPECS): Likewise.
>      * config/mips/elfoabi.h (DRIVER_SELF_SPECS): Add
>      MIPS_DEFAULT_ISA_LEVEL_SPEC.
>      * config/mips/mti-elf.h (DRIVER_SELF_SPECS): Likewise.
>      * config/mips/mti-linux.h (DRIVER_SELF_SPECS): Likewise.
>      * config/mips/sde.h (DRIVER_SELF_SPECS): Likewise.
> ---

This looks OK.