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

[Matt Arsenault via llvm-commits]

arsenm wrote:

> 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?

How are the ABIs different? If it's passed as a pair of FP registers or something like that, maybe could override getRegisterTypeForCallingConv+getNumRegistersForCallingConv to split into 2 x f64

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