LoongArch: Accept ADD, IOR or XOR when combining objects with no bits in common ...

LoongArch: Accept ADD, IOR or XOR when combining objects with no bits in common [PR115478]

Since r15-1120, multi-word shifts/rotates produces PLUS instead of IOR.
It's generally a good thing (allowing to use our alsl instruction or
similar instrunction on other architectures), but it's preventing us
from using bytepick.  For example, if we shift a __int128 by 16 bits,
the higher word can be produced via a single bytepick.d instruction with
immediate 2, but we got:

	srli.d	$r12,$r4,48
	slli.d	$r5,$r5,16
	slli.d	$r4,$r4,16
	add.d	$r5,$r12,$r5
	jr	$r1

This wasn't work with GCC 14, but after r15-6490 it's supposed to work
if IOR was used instead of PLUS.

To fix this, add a code iterator to match IOR, XOR, and PLUS and use it
instead of just IOR if we know the operands have no overlapping bits.

gcc/ChangeLog:

	PR target/115478
	* config/loongarch/loongarch.md (any_or_plus): New
	define_code_iterator.
	(bstrins_<mode>_for_ior_mask): Use any_or_plus instead of ior.
	(bytepick_w_<bytepick_imm>): Likewise.
	(bytepick_d_<bytepick_imm>): Likewise.
	(bytepick_d_<bytepick_imm>_rev): Likewise.

gcc/testsuite/ChangeLog:

	PR target/115478
	* gcc.target/loongarch/bytepick_shift_128.c: New test.