rs6000: Put CR0 first in REG_ALLOC_ORDER

rs6000: Put CR0 first in REG_ALLOC_ORDER

IRA and LRA prefer to use CR7 (which is first in REG_ALLOC_ORDER) over
CR0, although the latter often is cheaper ("x" vs. "y" constraints).
We should figure out why this is and fix it; but until that is done,
this patch makes CR0 the first allocated register: it improves the
current code, and it is required for later patches to be effective.

(It changes two testcases to no longer look at what CR field is
allocated).

	* config/rs6000/rs6000.h (REG_ALLOC_ORDER): Move 68 (that is, CR0) to
	be the first CR field allocated.

gcc/testsuite/
	* gcc.target/powerpc/safe-indirect-jump-2.c: Do not check assigned CR
	field number.
	* gcc.target/powerpc/safe-indirect-jump-3.c: Ditto.

From-SVN: r265318