aarch64: Use VNx16BI for more permutations [PR121294]

aarch64: Use VNx16BI for more permutations [PR121294]

The patterns for the predicate forms of svtrn1/2, svuzp1/2,
and svzip1/2 are shared with aarch64_vectorize_vec_perm_const.
The .H, .S, and .D forms operate on VNx8BI, VNx4BI, and VNx2BI
respectively.  Thus, for all four element widths, there is one
significant bit per element, for both the inputs and the output.

That's appropriate for aarch64_vectorize_vec_perm_const but not
for the ACLE intrinsics, where every bit of the output is
significant, and where every bit of the selected input elements
is therefore also significant.  The current expansion can lead
the optimisers to simplify inputs by changing the upper bits
of the input elements (since the current patterns claim that
those bits don't matter), which in turn leads to wrong code.

The ACLE expansion should operate on VNx16BI instead, for all
element widths.

There was already a pattern for a VNx16BI-only form of TRN1, for
constructing certain predicate constants.  The patch generalises it to
handle the other five permutations as well.  For the reasons given in
the comments, this is done by making the permutation unspec an operand
to a new UNSPEC_PERMUTE_PRED, rather than overloading the existing
unspecs, and rather than adding a new unspec for each permutation.

gcc/
	PR target/121294
	* config/aarch64/iterators.md (UNSPEC_TRN1_CONV): Delete.
	(UNSPEC_PERMUTE_PRED): New unspec.
	* config/aarch64/aarch64-sve.md (@aarch64_sve_trn1_conv<mode>):
	Replace with...
	(@aarch64_sve_<perm_insn><mode>_acle)
	(*aarch64_sve_<perm_insn><mode>_acle): ...these new patterns.
	* config/aarch64/aarch64.cc (aarch64_expand_sve_const_pred_trn):
	Update accordingly.
	* config/aarch64/aarch64-sve-builtins-functions.h
	(binary_permute::expand): Use the new _acle patterns for
	predicate operations.

gcc/testsuite/
	PR target/121294
	* gcc.target/aarch64/sve/acle/general/perm_2.c: New test.
	* gcc.target/aarch64/sve/acle/general/perm_3.c: Likewise.
	* gcc.target/aarch64/sve/acle/general/perm_4.c: Likewise.
	* gcc.target/aarch64/sve/acle/general/perm_5.c: Likewise.
	* gcc.target/aarch64/sve/acle/general/perm_6.c: Likewise.
	* gcc.target/aarch64/sve/acle/general/perm_7.c: Likewise.