rs6000: Add vcfuged instruction

rs6000: Add vcfuged instruction

Add the new vector centrifuge-doubleword instruction and built-in
function access.

[gcc]

2020-05-11  Kelvin Nilsen  <kelvin@gcc.gnu.org>

	* config/rs6000/altivec.h (vec_cfuge): New #define.
	* config/rs6000/altivec.md (UNSPEC_VCFUGED): New constant.
	(vcfuged): New insn.
	* config/rs6000/rs6000-builtin.def (__builtin_altivec_vcfuged):
	New built-in function.
	* config/rs6000/rs6000-call.c (builtin_function_type): Add
	handling for FUTURE_BUILTIN_VCFUGED case.
	* doc/extend.texi (PowerPC AltiVec Built-in Functions Available
	for a Future Architecture): Add description of vec_cfuge built-in
	function.

[gcc/testsuite]

2020-05-11  Kelvin Nilsen  <kelvin@gcc.gnu.org>

	* gcc.target/powerpc/vec-cfuged-0.c: New test.
	* gcc.target/powerpc/vec-cfuged-1.c: New test.