1 files changed, 17 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index cb99c057a1f..8b79d5b2933 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -34750,6 +34750,23 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
       return true;
   }
 
+  // If we don't demand all elements, then attempt to combine to a simpler
+  // shuffle.
+  // TODO: Handle other depths, but first we need to handle the fact that
+  // it might combine to the same shuffle.
+  if (!DemandedElts.isAllOnesValue() && Depth == 0) {
+    SmallVector<int, 64> DemandedMask(NumElts, SM_SentinelUndef);
+    for (int i = 0; i != NumElts; ++i)
+      if (DemandedElts[i])
+        DemandedMask[i] = i;
+
+    SDValue NewShuffle = combineX86ShufflesRecursively(
+        {Op}, 0, Op, DemandedMask, {}, Depth, /*HasVarMask*/ false,
+        /*AllowVarMask*/ true, TLO.DAG, Subtarget);
+    if (NewShuffle)
+      return TLO.CombineTo(Op, NewShuffle);
+  }
+
   return false;
 }