powerpc switches

[Aldy Hernandez]

> I've just had a confusing time investigating why a ppc compiler
> accepted -mcpu=8540 and -mabi=spe, yet refused to recognise the builtins.
> Turned out it was configured wrongly and TARGET_SPE and TARGET_SPE_ABI
> were hardwired to false.

He he.  That was Zack and David's doing for reducing the size of the
compiler on configurations that wouldn't need spe/altivec/etc.

I'm ok with this patch, but I don't agree with this:

>     if (rs6000_cpu == PROCESSOR_PPC8540)
> !     rs6000_isel = 1;
>   
>     /* If we are optimizing big endian systems for space, use the load/store
>        multiple and string instructions.  */
> --- 575,585 ----
>       }
>   
>     if (rs6000_cpu == PROCESSOR_PPC8540)
> !     {
> !       rs6000_isel = 1;
> !       if (!TARGET_SPE)
> ! 	warning ("not configured for spe extensions");
> !     }

Motorola has said future (non SPE) chips may have the isel
instruction, so this patch wouldn't permit us to do -misel=yes on such
a target.

Aldy