R600/SI: Implement add i64, but do not yet enable.

Test doesn't actually check the output. I need
to fix add i64 being matched for the addressing
calculations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195040 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed