Compute numeric type identifiers for indirect calls using generalized type
identifiers passed from the front-end, and carry them to the back-end with
CallSiteInfo.
The numeric type identifiers will be used at the back-end in the call graph
section.
Original RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-June/151044.html
Updated RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-July/151739.html
Try to extract separate NFC patch for SmallVector<ArgRegPair, 1> -> struct CallSiteInfo