rs6000-c: Add support for built-in function vector unsigned short vec_pack_to_short_f...

rs6000-c: Add support for built-in function vector unsigned short vec_pack_to_short_fp32...

gcc/ChangeLog:

2017-07-07 Carl Love  <cel@us.ibm.com>

	* config/rs6000/rs6000-c: Add support for built-in function
	vector unsigned short vec_pack_to_short_fp32 (vector float,
						      vector float).
	* config/rs6000/rs6000-builtin.def (CONVERT_4F32_8I16): Add
	BU_P9V_AV_2 and BU_P9V_OVERLOAD_2 definitions.
	* config/rs6000/altivec.h (vec_pack_to_short_fp32): Add define.
	* config/rs6000/altivec.md(UNSPEC_CONVERT_4F32_8I16): Add UNSPEC.
	(convert_4f32_8i16): Add define_expand.
	* doc/extend.texi: Update the built-in documentation file for the
	new built-in function.

gcc/testsuite/ChangeLog:

2017-07-07  Carl Love  <cel@us.ibm.com>

	* gcc.target/powerpc/builtins-1-p9-runnable.c: Add new test
	file for built-ins.

From-SVN: r250051