rs6000, Add vector replace builtin support GCC maintainers:

rs6000, Add vector replace builtin support GCC maintainers:

The following patch adds support for builtins vec_replace_elt and
vec_replace_unaligned.

The patch has been compiled and tested on

  powerpc64le-unknown-linux-gnu (Power 8 LE)
  powerpc64le-unknown-linux-gnu (Power 9 LE)

and mambo with no regression errors.

Please let me know if this patch is acceptable for the mainline
branch.  Thanks.

                         Carl Love

-------------------------------------------------------

gcc/ChangeLog

	    2020-08-04 Carl Love  <cel@us.ibm.com>

	* config/rs6000/altivec.h: Add define for vec_replace_elt and
	vec_replace_unaligned.
	* config/rs6000/vsx.md (UNSPEC_REPLACE_ELT, UNSPEC_REPLACE_UN): New
	unspecs.
	(REPLACE_ELT): New mode iterator.
	(REPLACE_ELT_char, REPLACE_ELT_sh, REPLACE_ELT_max): New mode attributes.
	(vreplace_un_<mode>, vreplace_elt_<mode>_inst): New.
	* config/rs6000/rs6000-builtin.def (VREPLACE_ELT_V4SI,
	VREPLACE_ELT_UV4SI, VREPLACE_ELT_V4SF, VREPLACE_ELT_UV2DI,
	VREPLACE_ELT_V2DF, VREPLACE_UN_V4SI, VREPLACE_UN_UV4SI,
	VREPLACE_UN_V4SF, VREPLACE_UN_V2DI, VREPLACE_UN_UV2DI,
	VREPLACE_UN_V2DF, (REPLACE_ELT, REPLACE_UN, VREPLACE_ELT_V2DI): New builtin
	entries.
	* config/rs6000/rs6000-call.c (P10_BUILTIN_VEC_REPLACE_ELT,
	P10_BUILTIN_VEC_REPLACE_UN): New builtin argument definitions.
	(rs6000_expand_quaternop_builtin): Add 3rd argument checks for
	CODE_FOR_vreplace_elt_v4si, CODE_FOR_vreplace_elt_v4sf,
	CODE_FOR_vreplace_un_v4si, CODE_FOR_vreplace_un_v4sf.
	(builtin_function_type) [P10_BUILTIN_VREPLACE_ELT_UV4SI,
	P10_BUILTIN_VREPLACE_ELT_UV2DI, P10_BUILTIN_VREPLACE_UN_UV4SI,
	P10_BUILTIN_VREPLACE_UN_UV2DI]: New cases.
	* doc/extend.texi: Add description for vec_replace_elt and
	vec_replace_unaligned builtins.

gcc/testsuite/ChangeLog

	    2020-08-04 Carl Love  <cel@us.ibm.com>

	* gcc.target/powerpc/vec-replace-word-runnable.c: New test.