supporting --with-cpu=default32 option for x86_64

[Nitin Gupta]

Hi,

I noticed that ppc64 has this support for building biarch compiler
defaulting to 32-bit. x86_64 does not suport that as of now. I am
trying to follow ppc64 to add this support for x86_64. I saw that
following lines were added in config.gcc in order to recognise
--with-cpu=default32. But I dont understand , how it was actually made
to default to 32-bit.
If anyone gets it, please explain.
	

snippet from config.gcc

powerpc*-*-* | rs6000-*-*)
		supported_defaults="cpu float tune"

		for which in cpu tune; do
			eval "val=\$with_$which"
			case ${val} in
>			default32 | default64)
>				with_which="with_$which"
>				eval $with_which=
>				;;
			"" | common \
			| power | power2 | power3 | power4 \
			| powerpc | powerpc64 \
			| rios | rios1 | rios2 | rsc | rsc1 | rs64a \
			| 401 | 403 | 405 | 405fp | 440 | 440fp | 505 \
			| 601 | 602 | 603 | 603e | ec603e | 604 \
			| 604e | 620 | 630 | 740 | 750 | 7400 | 7450 \
			| 8540 | 801 | 821 | 823 | 860 | 970 | G3 | G4 | G5)
				# OK
				;;
			*)
				echo "Unknown cpu used in --with-$which=$val." 1>&2
				exit 1
				;;
			esac
		done
		;;