LiveIntervalAnalysis: Fix handleMoveDown() problem

If we move a last-use register read to a later position we may skip
intermediate segments. This may require us to not only extend the
segment before the NewIdx, but also extend the segment live-in to
OldIdx.

This switches LiveIntervalTest to use AMDGPU so we can test subregister
liveness.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276724 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed