[llvm] [Mips] Fix compiler crash when returning fp128 after calling a functi… (PR #117525)

[Nikita Popov via llvm-commits]

nikic wrote:

> I'm still confused by this change, but it seems to be just following prior art in Mips that's been there since at least 2014. Whatever pre-processing it's doing should be consistently applied in all the calling convention contexts.
> 
> I don't understand why originalTypeIsF128 special cases a single element struct, and doesn't need to try to figure out the original element type from the EVT, or why this is how it implements that. But that's all pre-existing

For MIPS the ABI for f128 and i128 is different, but the calling convention code sees this as just two i64s in both cases. Is there some cleaner way to distinguish these cases, short of making f128 a legal type?

https://github.com/llvm/llvm-project/pull/117525