diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -4944,12 +4944,74 @@
   }
 }
 
+/// Expand source vectors to the size of destination vector.
+static LegalizerHelper::LegalizeResult
+equalizeVectorShuffleLengths(MachineInstr &MI, MachineIRBuilder &MIRBuilder) {
+  MachineRegisterInfo &MRI = *MIRBuilder.getMRI();
+
+  LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
+  LLT SrcTy = MRI.getType(MI.getOperand(1).getReg());
+  ArrayRef<int> Mask = MI.getOperand(3).getShuffleMask();
+  unsigned MaskNumElts = Mask.size();
+  unsigned SrcNumElts = SrcTy.getNumElements();
+  Register DstReg = MI.getOperand(0).getReg();
+  LLT DestEltTy = DstTy.getElementType();
+
+  // TODO: Normalize the shuffle vector since mask and vector length don't
+  // match.
+  if (MaskNumElts <= SrcNumElts) {
+    return LegalizerHelper::LegalizeResult::UnableToLegalize;
+  }
+
+  unsigned PaddedMaskNumElts = alignTo(MaskNumElts, SrcNumElts);
+  unsigned NumConcat = PaddedMaskNumElts / SrcNumElts;
+  LLT PaddedTy = LLT::fixed_vector(PaddedMaskNumElts, DestEltTy);
+
+  // Create new source vectors by concatenating the initial
+  // source vectors with undefined vectors of the same size.
+  auto Undef = MIRBuilder.buildUndef(SrcTy);
+  SmallVector<Register, 8> MOps1(NumConcat, Undef.getReg(0));
+  SmallVector<Register, 8> MOps2(NumConcat, Undef.getReg(0));
+  MOps1[0] = MI.getOperand(1).getReg();
+  MOps2[0] = MI.getOperand(2).getReg();
+
+  auto Src1 = MIRBuilder.buildConcatVectors(PaddedTy, MOps1);
+  auto Src2 = MIRBuilder.buildConcatVectors(PaddedTy, MOps2);
+
+  // Readjust mask for new input vector length.
+  SmallVector<int, 8> MappedOps(PaddedMaskNumElts, -1);
+  for (unsigned I = 0; I != MaskNumElts; ++I) {
+    int Idx = Mask[I];
+    if (Idx >= static_cast<int>(SrcNumElts))
+      Idx += PaddedMaskNumElts - SrcNumElts;
+    MappedOps[I] = Idx;
+  }
+
+  // If we got more elements than required, extract subvector.
+  if (MaskNumElts != PaddedMaskNumElts) {
+    auto Shuffle =
+        MIRBuilder.buildShuffleVector(PaddedTy, Src1, Src2, MappedOps);
+
+    SmallVector<Register, 8> Elts(MaskNumElts);
+    for (unsigned I = 0; I < MaskNumElts; ++I) {
+      Elts[I] = MIRBuilder
+                    .buildExtractVectorElement(
+                        DestEltTy, Shuffle,
+                        MIRBuilder.buildConstant(LLT::scalar(64), I))
+                    .getReg(0);
+    }
+    MIRBuilder.buildBuildVector(DstReg, Elts);
+  } else {
+    MIRBuilder.buildShuffleVector(DstReg, Src1, Src2, MappedOps);
+  }
+
+  MI.eraseFromParent();
+  return LegalizerHelper::LegalizeResult::Legalized;
+}
+
 LegalizerHelper::LegalizeResult
 LegalizerHelper::moreElementsVectorShuffle(MachineInstr &MI,
                                            unsigned int TypeIdx, LLT MoreTy) {
-  if (TypeIdx != 0)
-    return UnableToLegalize;
-
   Register DstReg = MI.getOperand(0).getReg();
   Register Src1Reg = MI.getOperand(1).getReg();
   Register Src2Reg = MI.getOperand(2).getReg();
@@ -4960,6 +5022,14 @@
   unsigned NumElts = DstTy.getNumElements();
   unsigned WidenNumElts = MoreTy.getNumElements();
 
+  if (DstTy.isVector() && Src1Ty.isVector() &&
+      DstTy.getNumElements() > Src1Ty.getNumElements()) {
+    return equalizeVectorShuffleLengths(MI, MIRBuilder);
+  }
+
+  if (TypeIdx != 0)
+    return UnableToLegalize;
+
   // Expect a canonicalized shuffle.
   if (DstTy != Src1Ty || DstTy != Src2Ty)
     return UnableToLegalize;
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
--- a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
+++ b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.h
@@ -47,6 +47,7 @@
                                   MachineIRBuilder &MIRBuilder,
                                   GISelChangeObserver &Observer) const;
   bool legalizeVectorTrunc(MachineInstr &MI, LegalizerHelper &Helper) const;
+  bool legalizeShuffleVector(MachineInstr &MI, LegalizerHelper &Helper) const;
   bool legalizeBitfieldExtract(MachineInstr &MI, MachineRegisterInfo &MRI,
                                LegalizerHelper &Helper) const;
   bool legalizeRotate(MachineInstr &MI, MachineRegisterInfo &MRI,
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
--- a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
@@ -686,6 +686,13 @@
       .lowerIf([=](const LegalityQuery &Query) {
         return !Query.Types[1].isVector();
       })
+      .moreElementsIf(
+          [](const LegalityQuery &Query) {
+            return Query.Types[0].isVector() && Query.Types[1].isVector() &&
+                   Query.Types[0].getNumElements() >
+                       Query.Types[1].getNumElements();
+          },
+          changeTo(1, 0))
       .moreElementsToNextPow2(0)
       .clampNumElements(0, v4s32, v4s32)
       .clampNumElements(0, v2s64, v2s64);
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-shuffle-vector.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-shuffle-vector.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-shuffle-vector.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-shuffle-vector.mir
@@ -298,3 +298,138 @@
     RET_ReallyLR
 
 ...
+---
+name:            shuffle_v4i32_v2i32
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $q0, $d1
+
+    ; CHECK-LABEL: name: shuffle_v4i32_v2i32
+    ; CHECK: liveins: $q0, $d1
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(<2 x s32>) = COPY $d0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(<2 x s32>) = COPY $d1
+    ; CHECK-NEXT: [[DEF:%[0-9]+]]:_(<2 x s32>) = G_IMPLICIT_DEF
+    ; CHECK-NEXT: [[CONCAT_VECTORS:%[0-9]+]]:_(<4 x s32>) = G_CONCAT_VECTORS [[COPY]](<2 x s32>), [[DEF]](<2 x s32>)
+    ; CHECK-NEXT: [[CONCAT_VECTORS1:%[0-9]+]]:_(<4 x s32>) = G_CONCAT_VECTORS [[COPY1]](<2 x s32>), [[DEF]](<2 x s32>)
+    ; CHECK-NEXT: [[SHUF:%[0-9]+]]:_(<4 x s32>) = G_SHUFFLE_VECTOR [[CONCAT_VECTORS]](<4 x s32>), [[CONCAT_VECTORS1]], shufflemask(0, 1, 4, 5)
+    ; CHECK-NEXT: $q0 = COPY [[SHUF]](<4 x s32>)
+    ; CHECK-NEXT: RET_ReallyLR implicit $q0
+    %0:_(<2 x s32>) = COPY $d0
+    %1:_(<2 x s32>) = COPY $d1
+    %2:_(<4 x s32>) = G_SHUFFLE_VECTOR %0(<2 x s32>), %1, shufflemask(0, 1, 2, 3)
+    $q0 = COPY %2(<4 x s32>)
+    RET_ReallyLR implicit $q0
+
+...
+---
+name:            shuffle_v8i16_v4i16
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $d0, $d1
+
+    ; CHECK-LABEL: name: shuffle_v8i16_v4i16
+    ; CHECK: liveins: $d0, $d1
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(<4 x s16>) = COPY $d0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(<4 x s16>) = COPY $d1
+    ; CHECK-NEXT: [[DEF:%[0-9]+]]:_(<4 x s16>) = G_IMPLICIT_DEF
+    ; CHECK-NEXT: [[CONCAT_VECTORS:%[0-9]+]]:_(<8 x s16>) = G_CONCAT_VECTORS [[COPY]](<4 x s16>), [[DEF]](<4 x s16>)
+    ; CHECK-NEXT: [[CONCAT_VECTORS1:%[0-9]+]]:_(<8 x s16>) = G_CONCAT_VECTORS [[COPY1]](<4 x s16>), [[DEF]](<4 x s16>)
+    ; CHECK-NEXT: [[SHUF:%[0-9]+]]:_(<8 x s16>) = G_SHUFFLE_VECTOR [[CONCAT_VECTORS]](<8 x s16>), [[CONCAT_VECTORS1]], shufflemask(11, 10, 9, 8, 3, 2, 1, 0)
+    ; CHECK-NEXT: $q0 = COPY [[SHUF]](<8 x s16>)
+    ; CHECK-NEXT: RET_ReallyLR implicit $q0
+    %0:_(<4 x s16>) = COPY $d0
+    %1:_(<4 x s16>) = COPY $d1
+    %2:_(<8 x s16>) = G_SHUFFLE_VECTOR %0(<4 x s16>), %1, shufflemask(7, 6, 5, 4, 3, 2, 1, 0)
+    $q0 = COPY %2(<8 x s16>)
+    RET_ReallyLR implicit $q0
+
+...
+---
+name:            shuffle_v16i8_v8i8
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $d0, $d1
+
+    ; CHECK-LABEL: name: shuffle_v16i8_v8i8
+    ; CHECK: liveins: $d0, $d1
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(<8 x s8>) = COPY $d0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(<8 x s8>) = COPY $d1
+    ; CHECK-NEXT: [[DEF:%[0-9]+]]:_(<8 x s8>) = G_IMPLICIT_DEF
+    ; CHECK-NEXT: [[CONCAT_VECTORS:%[0-9]+]]:_(<16 x s8>) = G_CONCAT_VECTORS [[COPY]](<8 x s8>), [[DEF]](<8 x s8>)
+    ; CHECK-NEXT: [[CONCAT_VECTORS1:%[0-9]+]]:_(<16 x s8>) = G_CONCAT_VECTORS [[COPY1]](<8 x s8>), [[DEF]](<8 x s8>)
+    ; CHECK-NEXT: [[SHUF:%[0-9]+]]:_(<16 x s8>) = G_SHUFFLE_VECTOR [[CONCAT_VECTORS]](<16 x s8>), [[CONCAT_VECTORS1]], shufflemask(7, 21, 6, 4, 5, 3, 0, 0, 0, 0, 0, 0, 0, 0, 23, 0)
+    ; CHECK-NEXT: $q0 = COPY [[SHUF]](<16 x s8>)
+    ; CHECK-NEXT: RET_ReallyLR implicit $q0
+    %0:_(<8 x s8>) = COPY $d0
+    %1:_(<8 x s8>) = COPY $d1
+    %2:_(<16 x s8>) = G_SHUFFLE_VECTOR %0(<8 x s8>), %1, shufflemask(7, 13, 6, 4, 5, 3, 0, 0, 0, 0, 0, 0, 0, 0, 15, 0)
+    $q0 = COPY %2(<16 x s8>)
+    RET_ReallyLR implicit $q0
+
+...
+---
+name:            size_shuffle_v6i32_v4i32
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $s0, $s1, $s2, $s3, $s4, $s5, $s6, $s7, $x0
+
+    ; CHECK-LABEL: name: size_shuffle_v6i32_v4i32
+    ; CHECK: liveins: $s0, $s1, $s2, $s3, $s4, $s5, $s6, $s7, $x0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY $s0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(s32) = COPY $s1
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:_(s32) = COPY $s2
+    ; CHECK-NEXT: [[COPY3:%[0-9]+]]:_(s32) = COPY $s3
+    ; CHECK-NEXT: [[BUILD_VECTOR:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[COPY]](s32), [[COPY1]](s32), [[COPY2]](s32), [[COPY3]](s32)
+    ; CHECK-NEXT: [[COPY4:%[0-9]+]]:_(s32) = COPY $s4
+    ; CHECK-NEXT: [[COPY5:%[0-9]+]]:_(s32) = COPY $s5
+    ; CHECK-NEXT: [[COPY6:%[0-9]+]]:_(s32) = COPY $s6
+    ; CHECK-NEXT: [[COPY7:%[0-9]+]]:_(s32) = COPY $s7
+    ; CHECK-NEXT: [[BUILD_VECTOR1:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[COPY4]](s32), [[COPY5]](s32), [[COPY6]](s32), [[COPY7]](s32)
+    ; CHECK-NEXT: [[COPY8:%[0-9]+]]:_(p0) = COPY $x0
+    ; CHECK-NEXT: [[SHUF:%[0-9]+]]:_(<4 x s32>) = G_SHUFFLE_VECTOR [[BUILD_VECTOR]](<4 x s32>), [[BUILD_VECTOR1]], shufflemask(3, 4, 7, 0)
+    ; CHECK-NEXT: [[SHUF1:%[0-9]+]]:_(<4 x s32>) = G_SHUFFLE_VECTOR [[BUILD_VECTOR]](<4 x s32>), [[BUILD_VECTOR1]], shufflemask(1, 5, undef, undef)
+    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK-NEXT: [[EVEC:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[SHUF]](<4 x s32>), [[C]](s64)
+    ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 1
+    ; CHECK-NEXT: [[EVEC1:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[SHUF]](<4 x s32>), [[C1]](s64)
+    ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 2
+    ; CHECK-NEXT: [[EVEC2:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[SHUF]](<4 x s32>), [[C2]](s64)
+    ; CHECK-NEXT: [[C3:%[0-9]+]]:_(s64) = G_CONSTANT i64 3
+    ; CHECK-NEXT: [[EVEC3:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[SHUF]](<4 x s32>), [[C3]](s64)
+    ; CHECK-NEXT: [[EVEC4:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[SHUF1]](<4 x s32>), [[C]](s64)
+    ; CHECK-NEXT: [[EVEC5:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[SHUF1]](<4 x s32>), [[C1]](s64)
+    ; CHECK-NEXT: [[BUILD_VECTOR2:%[0-9]+]]:_(<4 x s32>) = G_BUILD_VECTOR [[EVEC]](s32), [[EVEC1]](s32), [[EVEC2]](s32), [[EVEC3]](s32)
+    ; CHECK-NEXT: [[BUILD_VECTOR3:%[0-9]+]]:_(<2 x s32>) = G_BUILD_VECTOR [[EVEC4]](s32), [[EVEC5]](s32)
+    ; CHECK-NEXT: G_STORE [[BUILD_VECTOR2]](<4 x s32>), [[COPY8]](p0) :: (store (<4 x s32>), align 32)
+    ; CHECK-NEXT: [[C4:%[0-9]+]]:_(s64) = G_CONSTANT i64 16
+    ; CHECK-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY8]], [[C4]](s64)
+    ; CHECK-NEXT: G_STORE [[BUILD_VECTOR3]](<2 x s32>), [[PTR_ADD]](p0) :: (store (<2 x s32>) into unknown-address + 16, align 16)
+    ; CHECK-NEXT: RET_ReallyLR
+    %3:_(s32) = COPY $s0
+    %4:_(s32) = COPY $s1
+    %5:_(s32) = COPY $s2
+    %6:_(s32) = COPY $s3
+    %0:_(<4 x s32>) = G_BUILD_VECTOR %3(s32), %4(s32), %5(s32), %6(s32)
+    %7:_(s32) = COPY $s4
+    %8:_(s32) = COPY $s5
+    %9:_(s32) = COPY $s6
+    %10:_(s32) = COPY $s7
+    %1:_(<4 x s32>) = G_BUILD_VECTOR %7(s32), %8(s32), %9(s32), %10(s32)
+    %2:_(p0) = COPY $x0
+    %19:_(<6 x s32>) = G_SHUFFLE_VECTOR %0(<4 x s32>), %1, shufflemask(3, 4, 7, 0, 1, 5)
+    G_STORE %19(<6 x s32>), %2(p0) :: (store (<6 x s32>), align 32)
+    RET_ReallyLR
+
+...