Index: lib/Transforms/InstCombine/InstCombineVectorOps.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -1135,6 +1135,29 @@
   return true;
 }
 
+/// If a shuffle operand is an insert element to a lane that is not accessed
+/// by the shuffle, then bypass the insert element and use the insert's source
+/// operand vector directly. This is a specialization of a demanded elements
+/// fold that does not require hasOneUse().
+static Value *replaceInsertEltShuffleOperand(Value *ShufOp, bool IsRHS,
+                                             const SmallVectorImpl<int> &Mask) {
+  if (auto *InsElt = dyn_cast<InsertElementInst>(ShufOp)) {
+    if (auto *InsertIndexOp = dyn_cast<ConstantInt>(InsElt->getOperand(2))) {
+      // Translate the insert index to the shuffle's mask element values.
+      int InsertIndex = InsertIndexOp->getZExtValue();
+      if (IsRHS)
+        InsertIndex += ShufOp->getType()->getVectorNumElements();
+
+      // If the inserted value is not in the shuffle mask, then the
+      // insertelement does not affect the result of the shuffle.
+      if (none_of(Mask, [&](int Elt) { return Elt == InsertIndex; }))
+        return InsElt->getOperand(0);
+    }
+  }
+
+  return nullptr;
+}
+
 Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
   Value *LHS = SVI.getOperand(0);
   Value *RHS = SVI.getOperand(1);
@@ -1158,6 +1181,17 @@
     MadeChange = true;
   }
 
+  // shuffle (insertelement V1, S, C), V2, M --> shuffle V1, V2, M
+  if (Value *NewOp = replaceInsertEltShuffleOperand(LHS, false, Mask)) {
+    SVI.setOperand(0, NewOp);
+    return &SVI;
+  }
+  // shuffle V1, (insertelement V2, S, C), M --> shuffle V1, V2, M
+  if (Value *NewOp = replaceInsertEltShuffleOperand(RHS, true, Mask)) {
+    SVI.setOperand(1, NewOp);
+    return &SVI;
+  }
+
   unsigned LHSWidth = LHS->getType()->getVectorNumElements();
 
   // Canonicalize shuffle(x    ,x,mask) -> shuffle(x, undef,mask')
Index: test/Transforms/InstCombine/vec_demanded_elts.ll
===================================================================
--- test/Transforms/InstCombine/vec_demanded_elts.ll
+++ test/Transforms/InstCombine/vec_demanded_elts.ll
@@ -146,9 +146,7 @@
 
 define <4 x float> @inselt_shuf_no_demand(float %a1, float %a2, float %a3) {
 ; CHECK-LABEL: @inselt_shuf_no_demand(
-; CHECK-NEXT:    [[OUT1:%.*]] = insertelement <4 x float> undef, float %a1, i32 1
-; CHECK-NEXT:    [[OUT12:%.*]] = insertelement <4 x float> [[OUT1]], float %a2, i32 2
-; CHECK-NEXT:    ret <4 x float> [[OUT12]]
+; CHECK-NEXT:    ret <4 x float> undef
 ;
   %out1 = insertelement <4 x float> undef, float %a1, i32 1
   %out12 = insertelement <4 x float> %out1, float %a2, i32 2
@@ -161,9 +159,7 @@
 
 define <4 x float> @inselt_shuf_no_demand_commute(float %a1, float %a2, float %a3) {
 ; CHECK-LABEL: @inselt_shuf_no_demand_commute(
-; CHECK-NEXT:    [[OUT1:%.*]] = insertelement <4 x float> undef, float %a1, i32 1
-; CHECK-NEXT:    [[OUT12:%.*]] = insertelement <4 x float> [[OUT1]], float %a2, i32 2
-; CHECK-NEXT:    ret <4 x float> [[OUT12]]
+; CHECK-NEXT:    ret <4 x float> undef
 ;
   %out1 = insertelement <4 x float> undef, float %a1, i32 1
   %out12 = insertelement <4 x float> %out1, float %a2, i32 2