LoongArch: Machine description files for LA32

LoongArch: Machine description files for LA32

gcc/ChangeLog:

	* config/loongarch/constraints.md: Disable k on LA32.
	* config/loongarch/loongarch.md (*and<mode>3): Delete.
	(*and<mode>3_extend): New.
	(zero_extend<SHORT:mode><GPR:mode>2_la32r): New.
	(extend<SHORT:mode><GPR:mode>2_la32r): New.
	(extendqihi2_la32r): New.
	(*movdi_32bit): Remove not working split, use existing
	loongarch_split_move instead.
	(move_doubleword_2_<mode>): New.
	(load_low<mode>): New.
	(load_high<mode>): New.
	(store_word<mode>): New.
	(movgr2frh<mode>): New.
	(movfrh2gr<mode>): New.
	* config/loongarch/predicates.md: Disable low_bitmask_operand and
	ins_zero_bitmask_operand on LA32. Enable const_call_insn_operand on LA32.
	* config/loongarch/sync.md (atomic_<amop><mode>): Change to define_expand.
	(la64_atomic_<amop><mode>): New.
	(la32_atomic_<amop>si): New.
	(atomic_fetch_<amop><mode>): Change to define_expand.
	(la64_atomic_fetch_<amop><mode>): New.
	(la32_atomic_fetch_<amop>si): New.
	(atomic_exchange<mode>): Change to define_expand.
	(la64_atomic_exchange<mode>): New.
	(la32_atomic_exchangesi): New.

Co-authored-by: Jiajie Chen <c@jia.je>
Reviewed-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Lulu Cheng <chenglulu@loongson.cn>