rs6000-c.c (P8V_BUILTIN_VEC_REVB): Add power 8 definitions.

rs6000-c.c (P8V_BUILTIN_VEC_REVB): Add power 8 definitions.

gcc/ChangeLog:

2017-11-06  Carl Love  <cel@us.ibm.com>

	* config/rs6000/rs6000-c.c (P8V_BUILTIN_VEC_REVB): Add power 8
	definitions.
	(P9V_BUILTIN_VEC_REVB): Remove the power 9 instance definitions.
	* config/rs6000/altivec.h (vec_revb): Change the #define from power 9
	to power 8.
	* config/rs6000/r6000-protos.h (swap_endian_selector_for_mode): Add new
	extern declaration.
	* config/rs6000/rs6000.c (swap_endian_selector_for_mode): Add function.
	* config/rs6000/rs6000-builtin.def (BU_P8V_VSX_1, BU_P8V_OVERLOAD_1):
	Add power 8 macro expansions.
	(BU_P9V_OVERLOAD_1): Remove power 9 overload expansion.
	* config/rs6000/vsx.md (revb_<mode>): Add define_expand to generate
	power 8 instructions.  (VSX_XXBR): Add iterator.

gcc/testsuite/ChangeLog:

2017-11-06  Carl Love  <cel@us.ibm.com>

	* gcc.target/powerpc/builtins-revb-runnable.c: New runnable test file.

From-SVN: r254464