§ Bug in the LLVM code generator: Lowering of MO_Add2 and MO_AddWordC

Both of these are lowered the same way , but they should be different. In particular, GHC.Prim explains:

• AddWordC# returns (result, carry)
• PlusWordC# returns (carry, result)

Honestly, this is confusing, but I guess there's some story to having two separate primops for this?