Index: lib/CodeGen/SelectionDAG/TargetLowering.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1411,6 +1411,40 @@
     KnownZero.insertBits(SubZero, SubIdx);
     break;
   }
+  case ISD::INSERT_VECTOR_ELT: {
+    SDValue Vec = Op.getOperand(0);
+    SDValue Scl = Op.getOperand(1);
+    auto *CIdx = dyn_cast<ConstantSDNode>(Op.getOperand(2));
+
+    // For a legal, constant insertion index, if we don't need this insertion
+    // then strip it, else remove it from the demanded elts.
+    if (CIdx && CIdx->getAPIntValue().ult(NumElts)) {
+      unsigned Idx = CIdx->getZExtValue();
+      if (!DemandedElts[Idx])
+        return TLO.CombineTo(Op, Vec);
+      DemandedElts.clearBit(Idx);
+
+      if (SimplifyDemandedVectorElts(Vec, DemandedElts, KnownUndef,
+                                     KnownZero, TLO, Depth + 1))
+        return true;
+
+      KnownUndef.clearBit(Idx);
+      if (Scl.isUndef())
+        KnownUndef.setBit(Idx);
+
+      KnownZero.clearBit(Idx);
+      if (isNullConstant(Scl) || isNullFPConstant(Scl))
+        KnownZero.setBit(Idx);
+      break;
+    }
+
+    APInt VecUndef, VecZero;
+    if (SimplifyDemandedVectorElts(Vec, DemandedElts, VecUndef, VecZero, TLO,
+                                   Depth + 1))
+      return true;
+    // Without knowing the insertion index we can't set KnownUndef/KnownZero.
+    break;
+  }
   case ISD::VSELECT: {
     APInt DemandedLHS(DemandedElts);
     APInt DemandedRHS(DemandedElts);
Index: test/CodeGen/X86/known-bits-vector.ll
===================================================================
--- test/CodeGen/X86/known-bits-vector.ll
+++ test/CodeGen/X86/known-bits-vector.ll
@@ -51,7 +51,7 @@
 ; X32:       # %bb.0:
 ; X32-NEXT:    movzwl {{[0-9]+}}(%esp), %eax
 ; X32-NEXT:    movzwl {{[0-9]+}}(%esp), %ecx
-; X32-NEXT:    vpinsrd $0, %eax, %xmm0, %xmm0
+; X32-NEXT:    vmovd %eax, %xmm0
 ; X32-NEXT:    vpinsrd $2, %ecx, %xmm0, %xmm0
 ; X32-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,2,2]
 ; X32-NEXT:    vcvtdq2ps %xmm0, %xmm0
@@ -61,7 +61,7 @@
 ; X64:       # %bb.0:
 ; X64-NEXT:    movzwl %di, %eax
 ; X64-NEXT:    movzwl %si, %ecx
-; X64-NEXT:    vpinsrd $0, %eax, %xmm0, %xmm0
+; X64-NEXT:    vmovd %eax, %xmm0
 ; X64-NEXT:    vpinsrd $2, %ecx, %xmm0, %xmm0
 ; X64-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[0,0,2,2]
 ; X64-NEXT:    vcvtdq2ps %xmm0, %xmm0
Index: test/CodeGen/X86/masked_gather_scatter.ll
===================================================================
--- test/CodeGen/X86/masked_gather_scatter.ll
+++ test/CodeGen/X86/masked_gather_scatter.ll
@@ -757,7 +757,6 @@
 define <16 x float> @test14(float* %base, i32 %ind, <16 x float*> %vec) {
 ; KNL_64-LABEL: test14:
 ; KNL_64:       # %bb.0:
-; KNL_64-NEXT:    vpinsrq $1, %rdi, %xmm0, %xmm0
 ; KNL_64-NEXT:    vpbroadcastq %xmm0, %zmm0
 ; KNL_64-NEXT:    vmovd %esi, %xmm1
 ; KNL_64-NEXT:    vpbroadcastd %xmm1, %ymm1
@@ -771,7 +770,6 @@
 ;
 ; KNL_32-LABEL: test14:
 ; KNL_32:       # %bb.0:
-; KNL_32-NEXT:    vpinsrd $1, {{[0-9]+}}(%esp), %xmm0, %xmm0
 ; KNL_32-NEXT:    vpbroadcastd %xmm0, %zmm0
 ; KNL_32-NEXT:    vpslld $2, {{[0-9]+}}(%esp){1to16}, %zmm1
 ; KNL_32-NEXT:    vpaddd %zmm1, %zmm0, %zmm1
@@ -781,7 +779,6 @@
 ;
 ; SKX-LABEL: test14:
 ; SKX:       # %bb.0:
-; SKX-NEXT:    vpinsrq $1, %rdi, %xmm0, %xmm0
 ; SKX-NEXT:    vpbroadcastq %xmm0, %zmm0
 ; SKX-NEXT:    vpbroadcastd %esi, %ymm1
 ; SKX-NEXT:    vpmovsxdq %ymm1, %zmm1
@@ -794,7 +791,6 @@
 ;
 ; SKX_32-LABEL: test14:
 ; SKX_32:       # %bb.0:
-; SKX_32-NEXT:    vpinsrd $1, {{[0-9]+}}(%esp), %xmm0, %xmm0
 ; SKX_32-NEXT:    vpbroadcastd %xmm0, %zmm0
 ; SKX_32-NEXT:    vpslld $2, {{[0-9]+}}(%esp){1to16}, %zmm1
 ; SKX_32-NEXT:    vpaddd %zmm1, %zmm0, %zmm1
Index: test/CodeGen/X86/vec_insert-7.ll
===================================================================
--- test/CodeGen/X86/vec_insert-7.ll
+++ test/CodeGen/X86/vec_insert-7.ll
@@ -9,13 +9,9 @@
 ; X32-LABEL: mmx_movzl:
 ; X32:       ## %bb.0:
 ; X32-NEXT:    subl $20, %esp
-; X32-NEXT:    movq %mm0, {{[0-9]+}}(%esp)
-; X32-NEXT:    pmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X32-NEXT:    movl $32, %eax
-; X32-NEXT:    pinsrd $0, %eax, %xmm0
-; X32-NEXT:    pxor %xmm1, %xmm1
-; X32-NEXT:    pblendw {{.*#+}} xmm1 = xmm0[0,1],xmm1[2,3,4,5,6,7]
-; X32-NEXT:    movq %xmm1, (%esp)
+; X32-NEXT:    movd %eax, %xmm0
+; X32-NEXT:    movq %xmm0, (%esp)
 ; X32-NEXT:    movq (%esp), %mm0
 ; X32-NEXT:    addl $20, %esp
 ; X32-NEXT:    retl