Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -9428,13 +9428,13 @@
 }
 
 // Fold sext/zext of index into index type.
-bool refineIndexType(MaskedScatterSDNode *MSC, SDValue &Index, bool Scaled,
-                     SelectionDAG &DAG) {
+bool refineIndexType(MaskedGatherScatterSDNode *MGS, SDValue &Index,
+                     bool Scaled, SelectionDAG &DAG) {
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   SDValue Op = Index.getOperand(0);
 
   if (Index.getOpcode() == ISD::ZERO_EXTEND) {
-    MSC->setIndexType(Scaled ? ISD::UNSIGNED_SCALED : ISD::UNSIGNED_UNSCALED);
+    MGS->setIndexType(Scaled ? ISD::UNSIGNED_SCALED : ISD::UNSIGNED_UNSCALED);
     if (TLI.shouldRemoveExtendFromGSIndex(Op.getValueType())) {
       Index = Op;
       return true;
@@ -9442,7 +9442,7 @@
   }
 
   if (Index.getOpcode() == ISD::SIGN_EXTEND) {
-    MSC->setIndexType(Scaled ? ISD::SIGNED_SCALED : ISD::SIGNED_UNSCALED);
+    MGS->setIndexType(Scaled ? ISD::SIGNED_SCALED : ISD::SIGNED_UNSCALED);
     if (TLI.shouldRemoveExtendFromGSIndex(Op.getValueType())) {
       Index = Op;
       return true;
@@ -9511,11 +9511,30 @@
 SDValue DAGCombiner::visitMGATHER(SDNode *N) {
   MaskedGatherSDNode *MGT = cast<MaskedGatherSDNode>(N);
   SDValue Mask = MGT->getMask();
+  SDValue Chain = MGT->getChain();
+  SDValue Index = MGT->getIndex();
+  SDValue Scale = MGT->getScale();
+  SDValue PassThru = MGT->getPassThru();
+  SDValue BasePtr = MGT->getBasePtr();
   SDLoc DL(N);
 
   // Zap gathers with a zero mask.
   if (ISD::isBuildVectorAllZeros(Mask.getNode()))
-    return CombineTo(N, MGT->getPassThru(), MGT->getChain());
+    return CombineTo(N, PassThru, MGT->getChain());
+
+  if (refineUniformBase(BasePtr, Index, DAG)) {
+    SDValue Ops[] = {Chain, PassThru, Mask, BasePtr, Index, Scale};
+    return DAG.getMaskedGather(DAG.getVTList(N->getValueType(0), MVT::Other),
+                               PassThru.getValueType(), DL, Ops,
+                               MGT->getMemOperand(), MGT->getIndexType());
+  }
+
+  if (refineIndexType(MGT, Index, MGT->isIndexScaled(), DAG)) {
+    SDValue Ops[] = {Chain, PassThru, Mask, BasePtr, Index, Scale};
+    return DAG.getMaskedGather(DAG.getVTList(N->getValueType(0), MVT::Other),
+                               PassThru.getValueType(), DL, Ops,
+                               MGT->getMemOperand(), MGT->getIndexType());
+  }
 
   return SDValue();
 }
Index: llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -1746,6 +1746,7 @@
   SDValue PassThru = MGT->getPassThru();
   SDValue Index = MGT->getIndex();
   SDValue Scale = MGT->getScale();
+  EVT MemoryVT = MGT->getMemoryVT();
   Align Alignment = MGT->getOriginalAlign();
 
   // Split Mask operand
@@ -1759,6 +1760,10 @@
       std::tie(MaskLo, MaskHi) = DAG.SplitVector(Mask, dl);
   }
 
+  EVT LoMemVT, HiMemVT;
+  // Split MemoryVT
+  std::tie(LoMemVT, HiMemVT) = DAG.GetSplitDestVTs(MemoryVT);
+
   SDValue PassThruLo, PassThruHi;
   if (getTypeAction(PassThru.getValueType()) == TargetLowering::TypeSplitVector)
     GetSplitVector(PassThru, PassThruLo, PassThruHi);
@@ -1777,11 +1782,11 @@
       MGT->getRanges());
 
   SDValue OpsLo[] = {Ch, PassThruLo, MaskLo, Ptr, IndexLo, Scale};
-  Lo = DAG.getMaskedGather(DAG.getVTList(LoVT, MVT::Other), LoVT, dl, OpsLo,
+  Lo = DAG.getMaskedGather(DAG.getVTList(LoVT, MVT::Other), LoMemVT, dl, OpsLo,
                            MMO, MGT->getIndexType());
 
   SDValue OpsHi[] = {Ch, PassThruHi, MaskHi, Ptr, IndexHi, Scale};
-  Hi = DAG.getMaskedGather(DAG.getVTList(HiVT, MVT::Other), HiVT, dl, OpsHi,
+  Hi = DAG.getMaskedGather(DAG.getVTList(HiVT, MVT::Other), HiMemVT, dl, OpsHi,
                            MMO, MGT->getIndexType());
 
   // Build a factor node to remember that this load is independent of the
@@ -2421,11 +2426,11 @@
       MGT->getRanges());
 
   SDValue OpsLo[] = {Ch, PassThruLo, MaskLo, Ptr, IndexLo, Scale};
-  SDValue Lo = DAG.getMaskedGather(DAG.getVTList(LoVT, MVT::Other), LoVT, dl,
+  SDValue Lo = DAG.getMaskedGather(DAG.getVTList(LoVT, MVT::Other), LoMemVT, dl,
                                    OpsLo, MMO, MGT->getIndexType());
 
   SDValue OpsHi[] = {Ch, PassThruHi, MaskHi, Ptr, IndexHi, Scale};
-  SDValue Hi = DAG.getMaskedGather(DAG.getVTList(HiVT, MVT::Other), HiVT, dl,
+  SDValue Hi = DAG.getMaskedGather(DAG.getVTList(HiVT, MVT::Other), HiMemVT, dl,
                                    OpsHi, MMO, MGT->getIndexType());
 
   // Build a factor node to remember that this load is independent of the
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4416,7 +4416,7 @@
   if (!UniformBase) {
     Base = DAG.getConstant(0, sdl, TLI.getPointerTy(DAG.getDataLayout()));
     Index = getValue(Ptr);
-    IndexType = ISD::SIGNED_SCALED;
+    IndexType = ISD::SIGNED_UNSCALED;
     Scale = DAG.getTargetConstant(1, sdl, TLI.getPointerTy(DAG.getDataLayout()));
   }
   SDValue Ops[] = { Root, Src0, Mask, Base, Index, Scale };
Index: llvm/test/CodeGen/X86/masked_gather_scatter.ll
===================================================================
--- llvm/test/CodeGen/X86/masked_gather_scatter.ll
+++ llvm/test/CodeGen/X86/masked_gather_scatter.ll
@@ -765,45 +765,41 @@
 define <16 x float> @test14(float* %base, i32 %ind, <16 x float*> %vec) {
 ; KNL_64-LABEL: test14:
 ; KNL_64:       # %bb.0:
-; KNL_64-NEXT:    vpbroadcastq %xmm0, %zmm0
-; KNL_64-NEXT:    vmovd %esi, %xmm1
-; KNL_64-NEXT:    vpbroadcastd %xmm1, %ymm1
-; KNL_64-NEXT:    vpmovsxdq %ymm1, %zmm1
-; KNL_64-NEXT:    vpsllq $2, %zmm1, %zmm1
-; KNL_64-NEXT:    vpaddq %zmm1, %zmm0, %zmm0
+; KNL_64-NEXT:    vmovq %xmm0, %rax
+; KNL_64-NEXT:    vmovd %esi, %xmm0
+; KNL_64-NEXT:    vpbroadcastd %xmm0, %ymm0
+; KNL_64-NEXT:    vpmovsxdq %ymm0, %zmm0
+; KNL_64-NEXT:    vpsllq $2, %zmm0, %zmm0
 ; KNL_64-NEXT:    kxnorw %k0, %k0, %k1
-; KNL_64-NEXT:    vgatherqps (,%zmm0), %ymm1 {%k1}
+; KNL_64-NEXT:    vgatherqps (%rax,%zmm0), %ymm1 {%k1}
 ; KNL_64-NEXT:    vinsertf64x4 $1, %ymm1, %zmm1, %zmm0
 ; KNL_64-NEXT:    retq
 ;
 ; KNL_32-LABEL: test14:
 ; KNL_32:       # %bb.0:
-; KNL_32-NEXT:    vpbroadcastd %xmm0, %zmm0
+; KNL_32-NEXT:    vmovd %xmm0, %eax
 ; KNL_32-NEXT:    vpslld $2, {{[0-9]+}}(%esp){1to16}, %zmm1
-; KNL_32-NEXT:    vpaddd %zmm1, %zmm0, %zmm1
 ; KNL_32-NEXT:    kxnorw %k0, %k0, %k1
-; KNL_32-NEXT:    vgatherdps (,%zmm1), %zmm0 {%k1}
+; KNL_32-NEXT:    vgatherdps (%eax,%zmm1), %zmm0 {%k1}
 ; KNL_32-NEXT:    retl
 ;
 ; SKX-LABEL: test14:
 ; SKX:       # %bb.0:
-; SKX-NEXT:    vpbroadcastq %xmm0, %zmm0
-; SKX-NEXT:    vpbroadcastd %esi, %ymm1
-; SKX-NEXT:    vpmovsxdq %ymm1, %zmm1
-; SKX-NEXT:    vpsllq $2, %zmm1, %zmm1
-; SKX-NEXT:    vpaddq %zmm1, %zmm0, %zmm0
+; SKX-NEXT:    vmovq %xmm0, %rax
+; SKX-NEXT:    vpbroadcastd %esi, %ymm0
+; SKX-NEXT:    vpmovsxdq %ymm0, %zmm0
+; SKX-NEXT:    vpsllq $2, %zmm0, %zmm0
 ; SKX-NEXT:    kxnorw %k0, %k0, %k1
-; SKX-NEXT:    vgatherqps (,%zmm0), %ymm1 {%k1}
+; SKX-NEXT:    vgatherqps (%rax,%zmm0), %ymm1 {%k1}
 ; SKX-NEXT:    vinsertf64x4 $1, %ymm1, %zmm1, %zmm0
 ; SKX-NEXT:    retq
 ;
 ; SKX_32-LABEL: test14:
 ; SKX_32:       # %bb.0:
-; SKX_32-NEXT:    vpbroadcastd %xmm0, %zmm0
+; SKX_32-NEXT:    vmovd %xmm0, %eax
 ; SKX_32-NEXT:    vpslld $2, {{[0-9]+}}(%esp){1to16}, %zmm1
-; SKX_32-NEXT:    vpaddd %zmm1, %zmm0, %zmm1
 ; SKX_32-NEXT:    kxnorw %k0, %k0, %k1
-; SKX_32-NEXT:    vgatherdps (,%zmm1), %zmm0 {%k1}
+; SKX_32-NEXT:    vgatherdps (%eax,%zmm1), %zmm0 {%k1}
 ; SKX_32-NEXT:    retl
 
   %broadcast.splatinsert = insertelement <16 x float*> %vec, float* %base, i32 1