Based on this RFC:
https://discourse.llvm.org/t/rfc-allow-the-scalarizer-pass-to-scalarize-vectors-returned-in-structs/82306
LLVM intrinsics do not support out params. To get around this limitation
implementers will make intrinsics return structs to capture a return
type and an out param. This implementation detail should not impact
scalarization since these cases should be elementwise operations.
## Three changes are needed.
- The CallInst visitor needs to be updated to handle Structs
- A new visitor is needed for `ExtractValue` instructions
- finsh needs to be update to handle structs so that insert elements are
properly propogated.
## Testing changes
- Add support for `llvm.frexp`
- Add support for `llvm.dx.splitdouble`
fixes https://github.com/llvm/llvm-project/issues/111437
dcbf2c2ca0