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.

llvm-svn: 276724

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 5f3281f6771..8fd0585f976 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1039,6 +1039,8 @@ private:
           LiveRange::iterator Prev = std::prev(NewIdxIn);
           Prev->end = NewIdx.getRegSlot();
         }
+        // Extend OldIdxIn.
+        OldIdxIn->end = Next->start;
         return;
       }