[MCJIT][SystemZ] Use a simpler expression for indirect relocation offsets.

The expressions 'Reloc.Addend - Addend' and 'Reloc.Offset' should always be
equal in this context. The latter is prefered - we want to remove the
RelocationValueRef::Addend field in the future.





git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216418 91177308-0d34-0410-b5e6-96231b3b80d8
ArgPromotion: Don't touch variadic functions

Adding, removing, or changing non-pack parameters can change the ABI
classification of pack parameters. Clang and other frontends encode the
classification in the IR of the call site, but the callee side
determines it dynamically based on the number of registers consumed so
far. Changing the prototype affects the number of registers consumed
would break such code.

Dead argument elimination performs a similar task and already has a
similar check to avoid this problem.

Patch by Thomas Jablin!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216421 91177308-0d34-0410-b5e6-96231b3b80d8