LoongArch: Use bstrins instruction for (a & ~mask) and (a & mask) | (b & ~mask) ...

LoongArch: Use bstrins instruction for (a & ~mask) and (a & mask) | (b & ~mask) [PR111252]

If mask is a constant with value ((1 << N) - 1) << M we can perform this
optimization.

gcc/ChangeLog:

	PR target/111252
	* config/loongarch/loongarch-protos.h
	(loongarch_pre_reload_split): Declare new function.
	(loongarch_use_bstrins_for_ior_with_mask): Likewise.
	* config/loongarch/loongarch.cc
	(loongarch_pre_reload_split): Implement.
	(loongarch_use_bstrins_for_ior_with_mask): Likewise.
	* config/loongarch/predicates.md (ins_zero_bitmask_operand):
	New predicate.
	* config/loongarch/loongarch.md (bstrins_<mode>_for_mask):
	New define_insn_and_split.
	(bstrins_<mode>_for_ior_mask): Likewise.
	(define_peephole2): Further optimize code sequence produced by
	bstrins_<mode>_for_ior_mask if possible.

gcc/testsuite/ChangeLog:

	* g++.target/loongarch/bstrins-compile.C: New test.
	* g++.target/loongarch/bstrins-run.C: New test.