1 files changed, 6 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index e64652dedfd..c2426a69c8c 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -241,9 +241,13 @@ void LiveIntervals::computeRegMasks() {
       }
     }
 
-    // Some block ends, such as funclet returns, create masks.
+    // Some block ends, such as funclet returns, create masks. Put the mask on
+    // the last instruction of the block, because MBB slot index intervals are
+    // half-open.
     if (const uint32_t *Mask = MBB.getEndClobberMask(TRI)) {
-      RegMaskSlots.push_back(Indexes->getMBBEndIdx(&MBB));
+      assert(!MBB.empty() && "empty return block?");
+      RegMaskSlots.push_back(
+          Indexes->getInstructionIndex(&MBB.back()).getRegSlot());
       RegMaskBits.push_back(Mask);
     }