[clang] [clang][LoongArch] Match GCC ABI handling of integer complex types (PR #215222)

[via cfe-commits]

wangleiat wrote:

> > LGTM, thanks. Should we also update the ABI documentation to explicitly describe the calling convention for GNU integer complex types? @SixWeining
> 
> Thanks! I followed this rule:
> 
> https://github.com/loongson/la-abi-specs/blob/44ef5f63e1755e1a165915ea3b2d98d35f68eed0/lapcs.adoc?plain=1#L565-L569
> 
> ```
> *Structures without floating-point members*
> 
> * 0 < w~arg~ ≤ GRLEN
> 
> ** The argument is passed in a GAR if there is one available with the members
> laid out as if they were stored in memory. Otherwise, it is passed on the
> stack.
> ```

Sorry, I missed this detail. The ABI documentation already covers this case, so no update is needed.

https://github.com/llvm/llvm-project/pull/215222