LoongArch: Add support for _BitInt [PR117599]

This patch adds support for C23's _BitInt for LoongArch.

From the LoongArch psABI[1]:

> _BitInt(N) objects are stored in little-endian order in memory
> and are signed by default.
>
> For N ≤ 64, a _BitInt(N) object have the same size and alignment
> of the smallest fundamental integral type that can contain it.
> The unused high-order bits within this containing type are filled
> with sign or zero extension of the N-bit value, depending on whether
> the _BitInt(N) object is signed or unsigned. The _BitInt(N) object
> propagates its signedness to the containing type and is laid out
> in a register or memory as an object of this type.
>
> For N > 64, _BitInt(N) objects are implemented as structs of 64-bit
> integer chunks. The number of chunks is the smallest even integer M
> so that M * 64 ≥ N. These objects are of the same size of the struct
> containing the chunks, but always have 16-byte alignment. If there
> are unused bits in the highest-ordered chunk that contains used
> bits, they are defined as the sign- or zero- extension of the used
> bits depending on whether the _BitInt(N) object is signed or
> unsigned. If an entire chunk is unused, its bits are undefined.

[1] https://github.com/loongson/la-abi-specs

	PR target/117599

gcc/ChangeLog:

	* config/loongarch/loongarch.h: Define a PROMOTE_MODE case for
	small _BitInts.
	* config/loongarch/loongarch.cc (loongarch_promote_function_mode):
	Same.
	(loongarch_bitint_type_info): New function.
	(TARGET_C_BITINT_TYPE_INFO): Declare.

libgcc/ChangeLog:

	* config/loongarch/t-softfp-tf: Enable _BitInt helper functions.
	* config/loongarch/t-loongarch: Same.
	* config/loongarch/libgcc-loongarch.ver: New file.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/bitint-alignments.c: New test.
	* gcc.target/loongarch/bitint-args.c: New test.
	* gcc.target/loongarch/bitint-sizes.c: New test.

0 files changed, 0 insertions, 0 deletions