[llvm] [LoongArch] Enable tail calls for sret functions and relax argument matching (PR #168506)

[Folkert de Vries via llvm-commits]

folkertdev wrote:

I believe I understand your question better now. The answer is yes, rust would need e.g. the following to work correctly:

```llvm
%struct.5xi32 = type { [5 x i32] }

declare dso_local i32 @FuncFlip(ptr byval(%struct.5xi32) %0, ptr byval(%struct.5xi32) %1)

define dso_local i32 @testFlip(ptr byval(%struct.5xi32) %0, ptr byval(%struct.5xi32) %1) {
  %r = musttail call i32 @FuncFlip(ptr byval(%struct.5xi32) %1, ptr byval(%struct.5xi32) %0)
  ret i32 %r
}
```


https://github.com/llvm/llvm-project/pull/168506