IBM Z: Store long doubles in vector registers when possible

On z14+, there are instructions for working with 128-bit floats (long
doubles) in vector registers.  It's beneficial to use them instead of
instructions that operate on floating point register pairs, because it
allows to store 4 times more data in registers at a time, relieving
register pressure.  The raw performance of the new instructions is
almost the same as that of the new ones.

Implement by storing TFmode values in vector registers on z14+.  Since
not all operations are available with the new instructions, keep the
old ones available using the new FPRX2 mode, and convert between it and
TFmode when necessary (this is called "forwarder" expanders below).
Change the existing TFmode expanders to call either new- or old-style
ones depending on whether we are on z14+ or older machines
("dispatcher" expanders).

gcc/ChangeLog:

2020-11-03  Ilya Leoshkevich  <iii@linux.ibm.com>

	* config/s390/s390-modes.def (FPRX2): New mode.
	* config/s390/s390-protos.h (s390_fma_allowed_p): New function.
	* config/s390/s390.c (s390_fma_allowed_p): Likewise.
	(s390_build_signbit_mask): Support 128-bit masks.
	(print_operand): Support printing the second word of a TFmode
	operand as vector register.
	(constant_modes): Add FPRX2mode.
	(s390_class_max_nregs): Return 1 for TFmode on z14+.
	(s390_is_fpr128): New function.
	(s390_is_vr128): Likewise.
	(s390_can_change_mode_class): Use s390_is_fpr128 and
	s390_is_vr128 in order to determine whether mode refers to a FPR
	pair or to a VR.
	(s390_emit_compare): Force TFmode operands into registers on
	z14+.
	* config/s390/s390.h (HAVE_TF): New macro.
	(EXPAND_MOVTF): New macro.
	(EXPAND_TF): Likewise.
	* config/s390/s390.md (PFPO_OP_TYPE_FPRX2): PFPO_OP_TYPE_TF
	alias.
	(ALL): Add FPRX2.
	(FP_ALL): Add FPRX2 for z14+, restrict TFmode to z13-.
	(FP): Likewise.
	(FP_ANYTF): New mode iterator.
	(BFP): Add FPRX2 for z14+, restrict TFmode to z13-.
	(TD_TF): Likewise.
	(xde): Add FPRX2.
	(nBFP): Likewise.
	(nDFP): Likewise.
	(DSF): Likewise.
	(DFDI): Likewise.
	(SFSI): Likewise.
	(DF): Likewise.
	(SF): Likewise.
	(fT0): Likewise.
	(bt): Likewise.
	(_d): Likewise.
	(HALF_TMODE): Likewise.
	(tf_fpr): New mode_attr.
	(type): New mode_attr.
	(*cmp<mode>_ccz_0): Use type instead of mode with fsimp.
	(*cmp<mode>_ccs_0_fastmath): Likewise.
	(*cmptf_ccs): New pattern for wfcxb.
	(*cmptf_ccsfps): New pattern for wfkxb.
	(mov<mode>): Rename to mov<mode><tf_fpr>.
	(signbit<mode>2): Rename to signbit<mode>2<tf_fpr>.
	(isinf<mode>2): Renamed to isinf<mode>2<tf_fpr>.
	(*TDC_insn_<mode>): Use type instead of mode with fsimp.
	(fixuns_trunc<FP:mode><GPR:mode>2): Rename to
	fixuns_trunc<FP:mode><GPR:mode>2<FP:tf_fpr>.
	(fix_trunctf<mode>2): Rename to fix_trunctf<mode>2_fpr.
	(floatdi<mode>2): Rename to floatdi<mode>2<tf_fpr>, use type
	instead of mode with itof.
	(floatsi<mode>2): Rename to floatsi<mode>2<tf_fpr>, use type
	instead of mode with itof.
	(*floatuns<GPR:mode><FP:mode>2): Use type instead of mode for
	itof.
	(floatuns<GPR:mode><FP:mode>2): Rename to
	floatuns<GPR:mode><FP:mode>2<tf_fpr>.
	(trunctf<mode>2): Rename to trunctf<mode>2_fpr, use type instead
	of mode with fsimp.
	(extend<DSF:mode><BFP:mode>2): Rename to
	extend<DSF:mode><BFP:mode>2<BFP:tf_fpr>.
	(<FPINT:fpint_name><BFP:mode>2): Rename to
	<FPINT:fpint_name><BFP:mode>2<BFP:tf_fpr>, use type instead of
	mode with fsimp.
	(rint<BFP:mode>2): Rename to rint<BFP:mode>2<BFP:tf_fpr>, use
	type instead of mode with fsimp.
	(<FPINT:fpint_name><DFP:mode>2): Use type instead of mode for
	fsimp.
	(rint<DFP:mode>2): Likewise.
	(trunc<BFP:mode><DFP_ALL:mode>2): Rename to
	trunc<BFP:mode><DFP_ALL:mode>2<BFP:tf_fpr>.
	(trunc<DFP_ALL:mode><BFP:mode>2): Rename to
	trunc<DFP_ALL:mode><BFP:mode>2<BFP:tf_fpr>.
	(extend<BFP:mode><DFP_ALL:mode>2): Rename to
	extend<BFP:mode><DFP_ALL:mode>2<BFP:tf_fpr>.
	(extend<DFP_ALL:mode><BFP:mode>2): Rename to
	extend<DFP_ALL:mode><BFP:mode>2<BFP:tf_fpr>.
	(add<mode>3): Rename to add<mode>3<tf_fpr>, use type instead of
	mode with fsimp.
	(*add<mode>3_cc): Use type instead of mode with fsimp.
	(*add<mode>3_cconly): Likewise.
	(sub<mode>3): Rename to sub<mode>3<tf_fpr>, use type instead of
	mode with fsimp.
	(*sub<mode>3_cc): Use type instead of mode with fsimp.
	(*sub<mode>3_cconly): Likewise.
	(mul<mode>3): Rename to mul<mode>3<tf_fpr>, use type instead of
	mode with fsimp.
	(fma<mode>4): Restrict using s390_fma_allowed_p.
	(fms<mode>4): Restrict using s390_fma_allowed_p.
	(div<mode>3): Rename to div<mode>3<tf_fpr>, use type instead of
	mode with fdiv.
	(neg<mode>2): Rename to neg<mode>2<tf_fpr>.
	(*neg<mode>2_cc): Use type instead of mode with fsimp.
	(*neg<mode>2_cconly): Likewise.
	(*neg<mode>2_nocc): Likewise.
	(*neg<mode>2): Likeiwse.
	(abs<mode>2): Rename to abs<mode>2<tf_fpr>, use type instead of
	mode with fdiv.
	(*abs<mode>2_cc): Use type instead of mode with fsimp.
	(*abs<mode>2_cconly): Likewise.
	(*abs<mode>2_nocc): Likewise.
	(*abs<mode>2): Likewise.
	(*negabs<mode>2_cc): Likewise.
	(*negabs<mode>2_cconly): Likewise.
	(*negabs<mode>2_nocc): Likewise.
	(*negabs<mode>2): Likewise.
	(sqrt<mode>2): Rename to sqrt<mode>2<tf_fpr>, use type instead
	of mode with fsqrt.
	(cbranch<mode>4): Use FP_ANYTF instead of FP.
	(copysign<mode>3): Rename to copysign<mode>3<tf_fpr>, use type
	instead of mode with fsimp.
	* config/s390/s390.opt (flag_vx_long_double_fma): New
	undocumented option.
	* config/s390/vector.md (V_HW): Add TF for z14+.
	(V_HW2): Likewise.
	(VFT): Likewise.
	(VF_HW): Likewise.
	(V_128): Likewise.
	(tf_vr): New mode_attr.
	(tointvec): Add TF.
	(mov<mode>): Rename to mov<mode><tf_vr>.
	(movetf): New dispatcher.
	(*vec_tf_to_v1tf): Rename to *vec_tf_to_v1tf_fpr, restrict to
	z13-.
	(*vec_tf_to_v1tf_vr): New pattern for z14+.
	(*fprx2_to_tf): Likewise.
	(*mov_tf_to_fprx2_0): Likewise.
	(*mov_tf_to_fprx2_1): Likewise.
	(add<mode>3): Rename to add<mode>3<tf_vr>.
	(addtf3): New dispatcher.
	(sub<mode>3): Rename to sub<mode>3<tf_vr>.
	(subtf3): New dispatcher.
	(mul<mode>3): Rename to mul<mode>3<tf_vr>.
	(multf3): New dispatcher.
	(div<mode>3): Rename to div<mode>3<tf_vr>.
	(divtf3): New dispatcher.
	(sqrt<mode>2): Rename to sqrt<mode>2<tf_vr>.
	(sqrttf2): New dispatcher.
	(fma<mode>4): Restrict using s390_fma_allowed_p.
	(fms<mode>4): Likewise.
	(neg_fma<mode>4): Likewise.
	(neg_fms<mode>4): Likewise.
	(neg<mode>2): Rename to neg<mode>2<tf_vr>.
	(negtf2): New dispatcher.
	(abs<mode>2): Rename to abs<mode>2<tf_vr>.
	(abstf2): New dispatcher.
	(float<mode>tf2_vr): New forwarder.
	(float<mode>tf2): New dispatcher.
	(floatuns<mode>tf2_vr): New forwarder.
	(floatuns<mode>tf2): New dispatcher.
	(fix_trunctf<mode>2_vr): New forwarder.
	(fix_trunctf<mode>2): New dispatcher.
	(fixuns_trunctf<mode>2_vr): New forwarder.
	(fixuns_trunctf<mode>2): New dispatcher.
	(<FPINT:fpint_name><VF_HW:mode>2<VF_HW:tf_vr>): New pattern.
	(<FPINT:fpint_name>tf2): New forwarder.
	(rint<mode>2<tf_vr>): New pattern.
	(rinttf2): New forwarder.
	(*trunctfdf2_vr): New pattern.
	(trunctfdf2_vr): New forwarder.
	(trunctfdf2): New dispatcher.
	(trunctfsf2_vr): New forwarder.
	(trunctfsf2): New dispatcher.
	(extenddftf2_vr): New pattern.
	(extenddftf2): New dispatcher.
	(extendsftf2_vr): New forwarder.
	(extendsftf2): New dispatcher.
	(signbittf2_vr): New forwarder.
	(signbittf2): New dispatchers.
	(isinftf2_vr): New forwarder.
	(isinftf2): New dispatcher.
	* config/s390/vx-builtins.md (*vftci<mode>_cconly): Use VF_HW
	instead of VECF_HW, add missing constraint, add vw support.
	(vftci<mode>_intcconly): Use VF_HW instead of VECF_HW.
	(*vftci<mode>): Rename to vftci<mode>, use VF_HW instead of
	VECF_HW, and vw support.
	(vftci<mode>_intcc): Use VF_HW instead of VECF_HW.