This was failing on out of bounds access to the extra operands
on the s_swappc_b64 beyond those in the instruction definition.
This was working, but somehow regressed within the past few weeks,
although I don't see any obvious commit.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309782 91177308-0d34-0410-b5e6-96231b3b80d8
Matt Arsenault