Revert recent internal-fn changes [PR105975]

Revert recent internal-fn changes [PR105975]

The recent internal-fn “clean-ups” triggered problems on nvptx
because some of the omp_simt_* patterns had modeless operands.
I wondered about adapting expand_fn_using_insn to cope with that,
but then the problem becomes: what should the mode of operand 0
be when there is no lhs?  The answer depends on the target insn.
For GOMP_SIMT_ENTER_ALLOC the answer was: use Pmode.
For GOMP_SIMT_ORDERED_PRED and others the answer was: elide the call.
(However, GOMP_SIMT_ORDERED_PRED doesn't seem to have ECF_* flags
that would normally allow it to be dropped at the gimple level.)

So these instructions seem to be special enough that they need
their own code after all.  This patch reverts the second patch
and most of the first.  The only part retained from the first
is splitting expand_fn_using_insn out of expand_direct_optab_fn,
since I think expand_fn_using_insn could still be useful in future.

gcc/
	PR middle-end/105975
	Revert everything apart from the expand_fn_using_insn and
	expand_direct_optab_fn changes from:

	* internal-fn.def (DEF_INTERNAL_INSN_FN): New macro.
	(GOMP_SIMT_ENTER_ALLOC, GOMP_SIMT_EXIT, GOMP_SIMT_LANE)
	(GOMP_SIMT_LAST_LANE, GOMP_SIMT_ORDERED_PRED, GOMP_SIMT_VOTE_ANY)
	(GOMP_SIMT_XCHG_BFLY, GOMP_SIMT_XCHG_IDX): Use it.
	* internal-fn.h (direct_internal_fn_info::directly_mapped): New
	member variable.
	(direct_internal_fn_info::vectorizable): Reduce to 1 bit.
	(direct_internal_fn_p): Also return true for internal functions
	that map directly to instructions defined target-insns.def.
	(direct_internal_fn): Adjust comment accordingly.
	* internal-fn.cc (direct_insn, optab1, optab2, vectorizable_optab1)
	(vectorizable_optab2): New local macros.
	(not_direct): Initialize directly_mapped.
	(mask_load_direct, load_lanes_direct, mask_load_lanes_direct)
	(gather_load_direct, len_load_direct, mask_store_direct)
	(store_lanes_direct, mask_store_lanes_direct, vec_cond_mask_direct)
	(vec_cond_direct, scatter_store_direct, len_store_direct)
	(vec_set_direct, unary_direct, binary_direct, ternary_direct)
	(cond_unary_direct, cond_binary_direct, cond_ternary_direct)
	(while_direct, fold_extract_direct, fold_left_direct)
	(mask_fold_left_direct, check_ptrs_direct): Use the macros above.
	(expand_GOMP_SIMT_ENTER_ALLOC, expand_GOMP_SIMT_EXIT): Delete
	(expand_GOMP_SIMT_LANE, expand_GOMP_SIMT_LAST_LANE): Likewise;
	(expand_GOMP_SIMT_ORDERED_PRED, expand_GOMP_SIMT_VOTE_ANY): Likewise.
	(expand_GOMP_SIMT_XCHG_BFLY, expand_GOMP_SIMT_XCHG_IDX): Likewise.
	(direct_internal_fn_types): Handle functions that map to instructions
	defined in target-insns.def.
	(direct_internal_fn_types): Likewise.
	(direct_internal_fn_supported_p): Likewise.
	(internal_fn_expanders): Likewise.

	(expand_fn_using_insn): New function,
	split out and adapted from...
	(expand_direct_optab_fn): ...here.
	(expand_GOMP_SIMT_ENTER_ALLOC): Use it.
	(expand_GOMP_SIMT_EXIT): Likewise.
	(expand_GOMP_SIMT_LANE): Likewise.
	(expand_GOMP_SIMT_LAST_LANE): Likewise.
	(expand_GOMP_SIMT_ORDERED_PRED): Likewise.
	(expand_GOMP_SIMT_VOTE_ANY): Likewise.
	(expand_GOMP_SIMT_XCHG_BFLY): Likewise.
	(expand_GOMP_SIMT_XCHG_IDX): Likewise.