re PR target/80376 (Some vec_xxpermdi usage lead to ICE)

re PR target/80376 (Some vec_xxpermdi usage lead to ICE)

2017-04-11  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	PR target/80376
	PR target/80315
	* config/rs6000/rs6000.c (rs6000_expand_unop_builtin): Return
	CONST0_RTX (mode) rather than const0_rtx where appropriate.
	(rs6000_expand_binop_builtin): Likewise.
	(rs6000_expand_ternop_builtin): Likewise; also add missing
	vsx_xxpermdi_* variants; also fix typo (arg1 => arg2) for
	vshasigma built-ins.
	* doc/extend.texi: Document that vec_xxpermdi's third argument
	must be a constant.

From-SVN: r246859