Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -12202,12 +12202,81 @@
                      DAG.getNode(ISD::BUILD_VECTOR, DL, VecVT, Ops));
 }
 
-SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
-  // TODO: Check to see if this is a CONCAT_VECTORS of a bunch of
-  // EXTRACT_SUBVECTOR operations.  If so, and if the EXTRACT_SUBVECTOR vector
-  // inputs come from at most two distinct vectors, turn this into a shuffle
-  // node.
+// Check to see if this is a CONCAT_VECTORS of a bunch of EXTRACT_SUBVECTOR
+// operations. If so, and if the EXTRACT_SUBVECTOR vector inputs come from at
+// most two distinct vectors the same size as the result, attempt to turn this
+// into a legal shuffle.
+static SDValue combineConcatVectorOfExtracts(SDNode *N, SelectionDAG &DAG) {
+  EVT VT = N->getValueType(0);
+  EVT OpVT = N->getOperand(0).getValueType();
+  int NumElts = VT.getVectorNumElements();
+  int NumOpElts = OpVT.getVectorNumElements();
+
+  SDValue SV0 = DAG.getUNDEF(VT), SV1 = DAG.getUNDEF(VT);
+  SmallVector<int, 8> Mask;
+
+  for (SDValue Op : N->ops()) {
+    // Peek through any bitcast.
+    while (Op.getOpcode() == ISD::BITCAST)
+      Op = Op.getOperand(0);
+
+    // UNDEF nodes convert to UNDEF shuffle mask values.
+    if (Op.getOpcode() == ISD::UNDEF) {
+      Mask.append((unsigned)NumOpElts, -1);
+      continue;
+    }
+
+    if (Op.getOpcode() != ISD::EXTRACT_SUBVECTOR)
+      return SDValue();
+
+    // What vector are we extracting the subvector from and at what index?
+    SDValue ExtVec = Op.getOperand(0);
+    if (ExtVec.getOpcode() == ISD::UNDEF) {
+      Mask.append((unsigned)NumOpElts, -1);
+      continue;;
+    }
+
+    EVT ExtVT = ExtVec.getValueType();
+    if (!isa<ConstantSDNode>(Op.getOperand(1)))
+      return SDValue();
+    int ExtIdx = dyn_cast<ConstantSDNode>(Op.getOperand(1))->getZExtValue();
 
+    // Ensure that we are extracting a subvector from a vector the same
+    // size as the result.
+    if (ExtVT.getSizeInBits() != VT.getSizeInBits())
+      return SDValue();
+
+    // Scale the subvector index to account for any bitcast.
+    int NumExtElts = ExtVT.getVectorNumElements();
+    if (0 == (NumExtElts % NumElts))
+      ExtIdx /= (NumExtElts / NumElts);
+    else if (0 == (NumElts % NumExtElts))
+      ExtIdx *= (NumElts / NumExtElts);
+    else
+      return SDValue();
+
+    // At most we can reference 2 inputs in the final shuffle.
+    if (SV0.getOpcode() == ISD::UNDEF || SV0 == ExtVec) {
+      SV0 = ExtVec;
+      for (int i = 0; i != NumOpElts; ++i)
+        Mask.push_back(i + ExtIdx);
+    } else if (SV1.getOpcode() == ISD::UNDEF || SV1 == ExtVec) {
+      SV1 = ExtVec;
+      for (int i = 0; i != NumOpElts; ++i)
+        Mask.push_back(i + ExtIdx + NumElts);
+    } else {
+      return SDValue();
+    }
+  }
+
+  if (!DAG.getTargetLoweringInfo().isShuffleMaskLegal(Mask, VT))
+    return SDValue();
+
+  return DAG.getVectorShuffle(VT, SDLoc(N), DAG.getBitcast(VT, SV0),
+                              DAG.getBitcast(VT, SV1), Mask);
+}
+
+SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
   // If we only have one input vector, we don't need to do any concatenation.
   if (N->getNumOperands() == 1)
     return N->getOperand(0);
@@ -12308,6 +12377,11 @@
   if (SDValue V = combineConcatVectorOfScalars(N, DAG))
     return V;
 
+  // Fold CONCAT_VECTORS of EXTRACT_SUBVECTOR (or undef) to VECTOR_SHUFFLE.
+  if (Level < AfterLegalizeVectorOps)
+    if (SDValue V = combineConcatVectorOfExtracts(N, DAG))
+      return V;
+
   // Type legalization of vectors and DAG canonicalization of SHUFFLE_VECTOR
   // nodes often generate nop CONCAT_VECTOR nodes.
   // Scan the CONCAT_VECTOR operands and look for a CONCAT operations that
Index: test/CodeGen/X86/pr15267.ll
===================================================================
--- test/CodeGen/X86/pr15267.ll
+++ test/CodeGen/X86/pr15267.ll
@@ -65,11 +65,10 @@
 ; CHECK-NEXT:    shlq $60, %rax
 ; CHECK-NEXT:    sarq $63, %rax
 ; CHECK-NEXT:    vpinsrd $3, %eax, %xmm0, %xmm0
+; CHECK-NEXT:    vpmovsxdq %xmm0, %xmm1
+; CHECK-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[2,3,0,1]
 ; CHECK-NEXT:    vpmovsxdq %xmm0, %xmm0
-; CHECK-NEXT:    vmovd %ecx, %xmm1
-; CHECK-NEXT:    vpinsrd $1, %eax, %xmm1, %xmm1
-; CHECK-NEXT:    vpmovsxdq %xmm1, %xmm1
-; CHECK-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm1, %ymm0
 ; CHECK-NEXT:    retq
   %wide.load35 = load <4 x i1>, <4 x i1>* %in, align 1
   %sext = sext <4 x i1> %wide.load35 to <4 x i64>
Index: test/CodeGen/X86/vector-shuffle-256-v16.ll
===================================================================
--- test/CodeGen/X86/vector-shuffle-256-v16.ll
+++ test/CodeGen/X86/vector-shuffle-256-v16.ll
@@ -3262,11 +3262,15 @@
 }
 
 define <16 x i16> @concat_v16i16_0_1_2_3_4_5_6_7_24_25_26_27_28_29_30_31(<16 x i16> %a, <16 x i16> %b) {
-; ALL-LABEL: concat_v16i16_0_1_2_3_4_5_6_7_24_25_26_27_28_29_30_31:
-; ALL:       # BB#0:
-; ALL-NEXT:    vextractf128 $1, %ymm1, %xmm1
-; ALL-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
-; ALL-NEXT:    retq
+; AVX1-LABEL: concat_v16i16_0_1_2_3_4_5_6_7_24_25_26_27_28_29_30_31:
+; AVX1:       # BB#0:
+; AVX1-NEXT:    vblendpd {{.*#+}} ymm0 = ymm0[0,1],ymm1[2,3]
+; AVX1-NEXT:    retq
+;
+; AVX2-LABEL: concat_v16i16_0_1_2_3_4_5_6_7_24_25_26_27_28_29_30_31:
+; AVX2:       # BB#0:
+; AVX2-NEXT:    vpblendd {{.*#+}} ymm0 = ymm0[0,1,2,3],ymm1[4,5,6,7]
+; AVX2-NEXT:    retq
   %alo = shufflevector <16 x i16> %a, <16 x i16> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
   %bhi = shufflevector <16 x i16> %b, <16 x i16> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
   %shuf = shufflevector <8 x i16> %alo, <8 x i16> %bhi, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
@@ -3276,9 +3280,7 @@
 define <16 x i16> @concat_v16i16_8_9_10_11_12_13_14_15_24_25_26_27_28_29_30_31_bc(<16 x i16> %a, <16 x i16> %b) {
 ; ALL-LABEL: concat_v16i16_8_9_10_11_12_13_14_15_24_25_26_27_28_29_30_31_bc:
 ; ALL:       # BB#0:
-; ALL-NEXT:    vextractf128 $1, %ymm0, %xmm0
-; ALL-NEXT:    vextractf128 $1, %ymm1, %xmm1
-; ALL-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; ALL-NEXT:    vperm2f128 {{.*#+}} ymm0 = ymm0[2,3],ymm1[2,3]
 ; ALL-NEXT:    retq
   %ahi = shufflevector <16 x i16> %a, <16 x i16> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
   %bhi = shufflevector <16 x i16> %b, <16 x i16> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
Index: test/CodeGen/X86/vector-shuffle-256-v4.ll
===================================================================
--- test/CodeGen/X86/vector-shuffle-256-v4.ll
+++ test/CodeGen/X86/vector-shuffle-256-v4.ll
@@ -974,11 +974,15 @@
 }
 
 define <4 x i64> @concat_v4i64_0167(<4 x i64> %a0, <4 x i64> %a1) {
-; ALL-LABEL: concat_v4i64_0167:
-; ALL:       # BB#0:
-; ALL-NEXT:    vextractf128 $1, %ymm1, %xmm1
-; ALL-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
-; ALL-NEXT:    retq
+; AVX1-LABEL: concat_v4i64_0167:
+; AVX1:       # BB#0:
+; AVX1-NEXT:    vblendpd {{.*#+}} ymm0 = ymm0[0,1],ymm1[2,3]
+; AVX1-NEXT:    retq
+;
+; AVX2-LABEL: concat_v4i64_0167:
+; AVX2:       # BB#0:
+; AVX2-NEXT:    vpblendd {{.*#+}} ymm0 = ymm0[0,1,2,3],ymm1[4,5,6,7]
+; AVX2-NEXT:    retq
   %a0lo = shufflevector <4 x i64> %a0, <4 x i64> %a1, <2 x i32> <i32 0, i32 1>
   %a1hi = shufflevector <4 x i64> %a0, <4 x i64> %a1, <2 x i32> <i32 6, i32 7>
   %shuffle64 = shufflevector <2 x i64> %a0lo, <2 x i64> %a1hi, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
Index: test/CodeGen/X86/vector-shuffle-256-v8.ll
===================================================================
--- test/CodeGen/X86/vector-shuffle-256-v8.ll
+++ test/CodeGen/X86/vector-shuffle-256-v8.ll
@@ -2099,11 +2099,15 @@
 }
 
 define <8 x i32> @concat_v8i32_0123CDEF(<8 x i32> %a, <8 x i32> %b) {
-; ALL-LABEL: concat_v8i32_0123CDEF:
-; ALL:       # BB#0:
-; ALL-NEXT:    vextractf128 $1, %ymm1, %xmm1
-; ALL-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
-; ALL-NEXT:    retq
+; AVX1-LABEL: concat_v8i32_0123CDEF:
+; AVX1:       # BB#0:
+; AVX1-NEXT:    vblendpd {{.*#+}} ymm0 = ymm0[0,1],ymm1[2,3]
+; AVX1-NEXT:    retq
+;
+; AVX2-LABEL: concat_v8i32_0123CDEF:
+; AVX2:       # BB#0:
+; AVX2-NEXT:    vpblendd {{.*#+}} ymm0 = ymm0[0,1,2,3],ymm1[4,5,6,7]
+; AVX2-NEXT:    retq
   %alo = shufflevector <8 x i32> %a, <8 x i32> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 3>
   %bhi = shufflevector <8 x i32> %b, <8 x i32> undef, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
   %shuf = shufflevector <4 x i32> %alo, <4 x i32> %bhi, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
@@ -2113,9 +2117,7 @@
 define <8 x i32> @concat_v8i32_4567CDEF_bc(<8 x i32> %a0, <8 x i32> %a1) {
 ; ALL-LABEL: concat_v8i32_4567CDEF_bc:
 ; ALL:       # BB#0:
-; ALL-NEXT:    vextractf128 $1, %ymm0, %xmm0
-; ALL-NEXT:    vextractf128 $1, %ymm1, %xmm1
-; ALL-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
+; ALL-NEXT:    vperm2f128 {{.*#+}} ymm0 = ymm0[2,3],ymm1[2,3]
 ; ALL-NEXT:    retq
   %a0hi = shufflevector <8 x i32> %a0, <8 x i32> %a1, <4 x i32> <i32 4, i32 5, i32 6, i32 7>
   %a1hi = shufflevector <8 x i32> %a0, <8 x i32> %a1, <4 x i32> <i32 12, i32 13, i32 14, i32 15>