Return the UINTTOFP_* value for the given types, or UNKNOWN_LIBCALL if there is none.
The UINTTOFP_* libcall for OpVT and RetVT, or UNKNOWN_LIBCALL if none exists.
| Name | Description |
|---|---|
| OpVT | Source unsigned-integer value type. |
| RetVT | Destination floating-point value type. |