rs6000, Add vector splat builtin support

rs6000, Add vector splat builtin support

GCC maintainers:

The following patch adds support for the vec_splati, vec_splatid and
vec_splati_ins builtins.

This patch adds support for instructions that take a 32-bit immediate
value that represents a floating point value.  This support adds new
predicates and a support function to properly handle the immediate value.

The patch has been compiled and tested on

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

with no regression errors.

The test case was compiled on a Power 9 system and then tested on
Mambo.

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 (vec_splati, vec_splatid, vec_splati_ins):
	Add defines.
	* config/rs6000/altivec.md (UNSPEC_XXSPLTIW, UNSPEC_XXSPLTID,
	UNSPEC_XXSPLTI32DX): New.
	(vxxspltiw_v4si, vxxspltiw_v4sf_inst, vxxspltidp_v2df_inst,
	vxxsplti32dx_v4si_inst, vxxsplti32dx_v4sf_inst): New define_insn.
	(vxxspltiw_v4sf, vxxspltidp_v2df, vxxsplti32dx_v4si,
	vxxsplti32dx_v4sf.): New define_expands.
	* config/rs6000/predicates.md (u1bit_cint_operand,
	s32bit_cint_operand, c32bit_cint_operand): New predicates.
	* config/rs6000/rs6000-builtin.def (VXXSPLTIW_V4SI, VXXSPLTIW_V4SF,
	VXXSPLTID): New definitions.
	(VXXSPLTI32DX_V4SI, VXXSPLTI32DX_V4SF): New BU_P10V_3
	definitions.
	(XXSPLTIW, XXSPLTID): New definitions.
	(XXSPLTI32DX): Add definitions.
	* config/rs6000/rs6000-call.c (P10_BUILTIN_VEC_XXSPLTIW,
	P10_BUILTIN_VEC_XXSPLTID, P10_BUILTIN_VEC_XXSPLTI32DX):
	New definitions.
	* config/rs6000/rs6000-protos.h (rs6000_constF32toI32): New extern
	declaration.
	* config/rs6000/rs6000.c (rs6000_constF32toI32): New function.
	* doc/extend.texi: Add documentation for vec_splati,
	vec_splatid, and vec_splati_ins.

gcc/testsuite/ChangeLog

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

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