[patch, sim] Add isel instruction

[Joel Brobecker]

Abid,

> This patch adds support for isel instruction in the ppc simulator.
> Tested manually by running a small assembly file through the
> simulator. Is this ok?
> 
> Regards,
> Abid
> 
> sim/ChangeLog:
> 2013-04-19  Nathan Froyd  <froydnj@codesourcery.com>
> 
> 	* ppc-instructions (isel): New instruction.

This patch causes the sim build to fail when configured with
--enable-sim-float=spe. The full configure command-line used was:

    % configure --disable-nls --disable-tui --without-zlib --prefix=/[...]/install --enable-sim --enable-sim-float=spe --without-python --with-libexpat-prefix=/[...]/libexpat --target=powerpc-eabispe

The error I get is:

    | ./igen   -E  -F 32,f,o,e500 -CSRI 1024 -N 5  \
    | [...]
    |         expanding ...
    |         -n icache.h
    |         -h 
    |         -c tmp-icache.h
    | gen-icache.c:66: assertion failed - entry->nr_insn == 1
    | make: *** [tmp-igen] Error 1

I am not familiar with this part of the code, so can you please fix
or revert?

Interestingly, no problem with --enable-sim-float=altivec.

Thank you.

> 
> diff --git a/sim/ppc/ppc-instructions b/sim/ppc/ppc-instructions
> index 1b8fd89..d76a765 100644
> --- a/sim/ppc/ppc-instructions
> +++ b/sim/ppc/ppc-instructions
> @@ -3455,6 +3455,19 @@
> void::function::invalid_zero_divide_operation:cpu *processor,
> unsigned_word cia,
>  	PPC_INSN_MFCR(RT_BITMASK);
> 
>  #
> +# I.3.3.15 Fixed-Point Select
> +#
> +
> +0.31,6.RT,11.RA,16.RB,21.BF,26.15,31./:A::isel:Integer Select
> +	unsigned_word a;
> +	if (RA_is_0) a = 0;
> +	else         a = *rA;
> +	if (CR & (1 << (31 - BF)))
> +	  *rT = a;
> +	else
> +	  *rT = *rB;
> +
> +#

-- 
Joel