rs6000: Add vector count under mask

rs6000: Add vector count under mask

Add support for new vclzdm and vctzdm vector instructions that
count leading and trailing zeros under control of a mask.

[gcc]

2020-05-11  Kelvin Nilsen  <kelvin@gcc.gnu.org>
	    Bill Schmidt  <wschmidt@linux.ibm.com>

	* config/rs6000/altivec.h (vec_clzm): New macro.
	(vec_ctzm): Likewise.
	* config/rs6000/altivec.md (UNSPEC_VCLZDM): New constant.
	(UNSPEC_VCTZDM): Likewise.
	(vclzdm): New insn.
	(vctzdm): Likewise.
	* config/rs6000/rs6000-builtin.def (BU_FUTURE_V_0): New macro.
	(BU_FUTURE_V_1): Likewise.
	(BU_FUTURE_V_2): Likewise.
	(BU_FUTURE_V_3): Likewise.
	(__builtin_altivec_vclzdm): New builtin definition.
	(__builtin_altivec_vctzdm): Likewise.
	* config/rs6000/rs6000-c.c (rs6000_target_modify_macros): Cause
	_ARCH_PWR_FUTURE macro to be defined if OPTION_MASK_FUTURE flag is
	set.
	* config/rs6000/rs6000-call.c (builtin_function_type): Set return
	value and parameter types to be unsigned for VCLZDM and VCTZDM.
	* config/rs6000/rs6000.c (rs6000_builtin_mask_calculate): Add
	support for TARGET_FUTURE flag.
	* config/rs6000/rs6000.h (RS6000_BTM_FUTURE): New macro constant.
	* doc/extend.texi (PowerPC Altivec Built-in Functions Available
	for a Future Architecture): New subsubsection.

[gcc/testsuite]

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

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