diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index b505cc77af24..f24a7228a4f1 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -23901,18 +23901,23 @@ static SDValue LowerScalarImmediateShift(SDValue Op, SelectionDAG &DAG,
   return SDValue();
 }
 
-// Determine if V is a splat value, and return the scalar.
+// If V is a splat value, return the source vector and splat index;
 // TODO - can we make this generic and move to SelectionDAG?
-static SDValue IsSplatValue(MVT VT, SDValue V, const SDLoc &dl,
-                            SelectionDAG &DAG) {
+static SDValue IsSplatVector(MVT VT, SDValue V, int &SplatIdx) {
   V = peekThroughEXTRACT_SUBVECTORs(V);
 
   // Check if this is a splat build_vector node.
   if (BuildVectorSDNode *BV = dyn_cast<BuildVectorSDNode>(V)) {
-    SDValue SplatAmt = BV->getSplatValue();
-    if (SplatAmt && SplatAmt.isUndef())
-      return SDValue();
-    return SplatAmt;
+    BitVector BVUndefElts;
+    SDValue SplatAmt = BV->getSplatValue(&BVUndefElts);
+    if (SplatAmt && !SplatAmt.isUndef()) {
+      for (int i = 0, e = BVUndefElts.size(); i != e; ++i)
+        if (!BVUndefElts[i]) {
+          SplatIdx = i;
+          return V;
+        }
+    }
+    return SDValue();
   }
 
   // Check for SUB(SPLAT_BV, SPLAT) cases from rotate patterns.
@@ -23925,11 +23930,12 @@ static SDValue IsSplatValue(MVT VT, SDValue V, const SDLoc &dl,
     BuildVectorSDNode *BV0 = dyn_cast<BuildVectorSDNode>(LHS);
     ShuffleVectorSDNode *SVN1 = dyn_cast<ShuffleVectorSDNode>(RHS);
     if (BV0 && SVN1 && BV0->getSplatValue(&UndefElts) && SVN1->isSplat()) {
-      unsigned SplatIdx = (unsigned)SVN1->getSplatIndex();
-      if (!UndefElts[SplatIdx])
-        return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl,
-                           VT.getVectorElementType(), V,
-                           DAG.getIntPtrConstant(SplatIdx, dl));
+      int Idx = SVN1->getSplatIndex();
+      if (!UndefElts[Idx]) {
+        SplatIdx = Idx;
+        return V;
+      }
+      return SDValue();
     }
   }
 
@@ -23937,23 +23943,19 @@ static SDValue IsSplatValue(MVT VT, SDValue V, const SDLoc &dl,
   ShuffleVectorSDNode *SVN = dyn_cast<ShuffleVectorSDNode>(V);
   if (!SVN || !SVN->isSplat())
     return SDValue();
+  int Idx = SVN->getSplatIndex();
+  int NumElts = V.getValueType().getVectorNumElements();
+  SplatIdx = Idx % NumElts;
+  return V.getOperand(Idx / NumElts);
+}
 
-  unsigned SplatIdx = (unsigned)SVN->getSplatIndex();
-  SDValue InVec = V.getOperand(0);
-  if (InVec.getOpcode() == ISD::BUILD_VECTOR) {
-    assert((SplatIdx < VT.getVectorNumElements()) &&
-           "Unexpected shuffle index found!");
-    return InVec.getOperand(SplatIdx);
-  } else if (InVec.getOpcode() == ISD::INSERT_VECTOR_ELT) {
-    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(InVec.getOperand(2)))
-      if (C->getZExtValue() == SplatIdx)
-        return InVec.getOperand(1);
-  }
-
-  // Avoid introducing an extract element from a shuffle.
-  return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl,
-                     VT.getVectorElementType(), InVec,
-                     DAG.getIntPtrConstant(SplatIdx, dl));
+static SDValue GetSplatValue(MVT VT, SDValue V, const SDLoc &dl,
+                            SelectionDAG &DAG) {
+  int SplatIdx;
+  if (SDValue SrcVector = IsSplatVector(VT, V, SplatIdx))
+    return DAG.getNode(ISD::EXTRACT_VECTOR_ELT, dl, VT.getVectorElementType(),
+                       SrcVector, DAG.getIntPtrConstant(SplatIdx, dl));
+  return SDValue();
 }
 
 static SDValue LowerScalarVariableShift(SDValue Op, SelectionDAG &DAG,
@@ -23968,7 +23970,7 @@ static SDValue LowerScalarVariableShift(SDValue Op, SelectionDAG &DAG,
 
   Amt = peekThroughEXTRACT_SUBVECTORs(Amt);
 
-  if (SDValue BaseShAmt = IsSplatValue(VT, Amt, dl, DAG)) {
+  if (SDValue BaseShAmt = GetSplatValue(VT, Amt, dl, DAG)) {
     if (SupportedVectorShiftWithBaseAmnt(VT, Subtarget, Opcode)) {
       MVT EltVT = VT.getVectorElementType();
       assert(EltVT.bitsLE(MVT::i64) && "Unexpected element type!");
@@ -24670,13 +24672,15 @@ static SDValue LowerRotate(SDValue Op, const X86Subtarget &Subtarget,
 
   // Rotate by splat - expand back to shifts.
   // TODO - legalizers should be able to handle this.
-  if ((EltSizeInBits >= 16 || Subtarget.hasBWI()) &&
-      IsSplatValue(VT, Amt, DL, DAG)) {
-    SDValue AmtR = DAG.getConstant(EltSizeInBits, DL, VT);
-    AmtR = DAG.getNode(ISD::SUB, DL, VT, AmtR, Amt);
-    SDValue SHL = DAG.getNode(ISD::SHL, DL, VT, R, Amt);
-    SDValue SRL = DAG.getNode(ISD::SRL, DL, VT, R, AmtR);
-    return DAG.getNode(ISD::OR, DL, VT, SHL, SRL);
+  if (EltSizeInBits >= 16 || Subtarget.hasBWI()) {
+    int SplatIdx;
+    if (IsSplatVector(VT, Amt, SplatIdx)) {
+      SDValue AmtR = DAG.getConstant(EltSizeInBits, DL, VT);
+      AmtR = DAG.getNode(ISD::SUB, DL, VT, AmtR, Amt);
+      SDValue SHL = DAG.getNode(ISD::SHL, DL, VT, R, Amt);
+      SDValue SRL = DAG.getNode(ISD::SRL, DL, VT, R, AmtR);
+      return DAG.getNode(ISD::OR, DL, VT, SHL, SRL);
+    }
   }
 
   // v16i8/v32i8: Split rotation into rot4/rot2/rot1 stages and select by