1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 06802aac81e..843d2875832 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33691,6 +33691,15 @@ static SDValue combineExtractWithShuffle(SDNode *N, SelectionDAG &DAG,
       scaleShuffleMask<int>(Scale, Mask, ScaledMask);
       Mask = std::move(ScaledMask);
     } else if ((Mask.size() % NumSrcElts) == 0) {
+      // Simplify Mask based on demanded element.
+      int ExtractIdx = (int)N->getConstantOperandVal(1);
+      int Scale = Mask.size() / NumSrcElts;
+      int Lo = Scale * ExtractIdx;
+      int Hi = Scale * (ExtractIdx + 1);
+      for (int i = 0, e = (int)Mask.size(); i != e; ++i)
+        if (i < Lo || Hi <= i)
+          Mask[i] = SM_SentinelUndef;
+
       SmallVector<int, 16> WidenedMask;
       while (Mask.size() > NumSrcElts &&
              canWidenShuffleElements(Mask, WidenedMask))