LiveIntervals: Fix handleMoveUp with subreg def moving across a def

If a subregister def was moved across another subregister def and
another use, the main range was not correctly updated. The end point
of the moved interval ended too early and missed the use from theh
other lanes in the subreg def.

llvm-svn: 375300

1 files changed, 16 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervals.cpp b/llvm/lib/CodeGen/LiveIntervals.cpp
index 9d85fc3e08d..2989930ad09 100644
--- a/llvm/lib/CodeGen/LiveIntervals.cpp
+++ b/llvm/lib/CodeGen/LiveIntervals.cpp
@@ -1288,6 +1288,20 @@ private:
           const SlotIndex SplitPos = NewIdxDef;
           OldIdxVNI = OldIdxIn->valno;
 
+          SlotIndex NewDefEndPoint = std::next(NewIdxIn)->end;
+          LiveRange::iterator Prev = std::prev(OldIdxIn);
+          if (OldIdxIn != LR.begin() &&
+              SlotIndex::isEarlierInstr(NewIdx, Prev->end)) {
+            // If the segment before OldIdx read a value defined earlier than
+            // NewIdx, the moved instruction also reads and forwards that
+            // value. Extend the lifetime of the new def point.
+
+            // Extend to where the previous range started, unless there is
+            // another redef first.
+            NewDefEndPoint = std::min(OldIdxIn->start,
+                                      std::next(NewIdxOut)->start);
+          }
+
           // Merge the OldIdxIn and OldIdxOut segments into OldIdxOut.
           OldIdxOut->valno->def = OldIdxIn->start;
           *OldIdxOut = LiveRange::Segment(OldIdxIn->start, OldIdxOut->end,
@@ -1305,7 +1319,8 @@ private:
             // There is no gap between NewSegment and its predecessor.
             *NewSegment = LiveRange::Segment(Next->start, SplitPos,
                                              Next->valno);
-            *Next = LiveRange::Segment(SplitPos, Next->end, OldIdxVNI);
+
+            *Next = LiveRange::Segment(SplitPos, NewDefEndPoint, OldIdxVNI);
             Next->valno->def = SplitPos;
           } else {
             // There is a gap between NewSegment and its predecessor