[X86][SSE] Combine shuffle nodes with multiple uses if all the users are being combined.

[RKSimon]

Summary

Currently we only combine shuffle nodes if they have a single user to prevent us from causing code bloat by splitting the shuffles into several different combines.

We don't take into account that in some cases we will already have combined all the users during recursively calling up the shuffle tree.

This patch keeps a list of all the shuffle nodes that have been combined so far and permits combining of further shuffle nodes if all its users are in that list.

[andreadb]

Hi Simon,

Do you have other code examples (other than function @_clearupper2xi64b) which may benefit from your change?

I am asking this because function @_clearupper2xi64b would be easily optimized before we even reach the code generator.
InstCombine knows how to combine a sequence of constant insertelement into a single shuffle (See function 'foldConstantInsEltIntoShuffle' in InstCombineVectorOps.cpp). If you pass function @_clearupper2xi64b to opt -instcombine you would get this:

define <2 x i64> @_clearupper2xi64b(<2 x i64>) #0 {
  %x32 = bitcast <2 x i64> %0 to <4 x i32>
  %r1 = shufflevector <4 x i32> %x32, <4 x i32> <i32 undef, i32 0, i32 undef, i32 0>, <4 x i32> <i32 0, i32 5, i32 2, i32 7>
  %r = bitcast <4 x i32> %r1 to <2 x i64>
  ret <2 x i64> %r
}

Later on, that shuffle would be lowered into a ANDPS (on pre-SSE4.1 targets):
andps .LCPI0_0(%rip), %xmm0

[RKSimon]

Updated with additional tests - both are stripped down examples of a partially combined build_vector and shuffles all from a single vector source.

[andreadb]

Hi Simon,
thanks for the extra tests.

The patch looks good to me.

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

7129–7141

Correct me if I am wrong.
We can only return false from line 7140 if N has no users.

Assuming that the use_empty() is a valid scenario, you can slightly simplify the code by adding an early check to N->use_empty() at the beginning of the function.

[RKSimon]

Thanks Andrea

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

7129–7141

We can also return false if N has any users that are not contained in Nodes.

I was going for consistency with SDNode::isOnlyUserOf - AFAICT checking for use_empty() is not going to be much quicker than calling use_begin()/use_end(), matching them and not entering the for loop.

Shout if you disagree.

include/llvm/CodeGen/SelectionDAGNodes.h

while (!Worklist.empty()) {
           Found = true;
       }
       if (Found)
         return true;
     }
     return false;
   }
 
+  /// Return true if all the users of N are contained in Nodes.
+  /// NOTE: Requires at least one match, but doesn't require them all.
+  static bool areOnlyUsersOf(ArrayRef<const SDNode *> Nodes, const SDNode *N);
+
   /// Return the number of values used by this operation.
   unsigned getNumOperands() const { return NumOperands; }
 
   /// Helper method returns the integer value of a ConstantSDNode operand.
   inline uint64_t getConstantOperandVal(unsigned Num) const;
 
   const SDValue &getOperand(unsigned Num) const {
     assert(Num < NumOperands && "Invalid child # of SDNode!");

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

if (User == this)
       Seen = true;
     else
       return false;
   }
 
   return Seen;
 }
 
+/// Return true if the only users of N are contained in Nodes.
+bool SDNode::areOnlyUsersOf(ArrayRef<const SDNode *> Nodes, const SDNode *N) {
+  bool Seen = false;
+  for (SDNode::use_iterator I = N->use_begin(), E = N->use_end(); I != E; ++I) {
+    SDNode *User = *I;
+    if (llvm::any_of(Nodes,
+                     [&User](const SDNode *Node) { return User == Node; }))
+      Seen = true;
+    else
+      return false;
+  }
+
+  return Seen;
+}
+
 /// isOperand - Return true if this node is an operand of N.
 ///
 bool SDValue::isOperandOf(const SDNode *N) const {
   for (const SDValue &Op : N->op_values())
     if (*this == Op)
       return true;
   return false;
 }

lib/Target/X86/X86ISelLowering.cpp

 ///
 /// FIXME: We will currently miss some cases where the redundant shuffling
 /// would simplify under the threshold for PSHUFB formation because of
 /// combine-ordering. To fix this, we should do the redundant instruction
 /// combining in this recursive walk.
 static bool combineX86ShufflesRecursively(ArrayRef<SDValue> SrcOps,
                                           int SrcOpIndex, SDValue Root,
                                           ArrayRef<int> RootMask,
+                                          ArrayRef<const SDNode*> SrcNodes,
                                           int Depth, bool HasVariableMask,
                                           SelectionDAG &DAG,
                                           TargetLowering::DAGCombinerInfo &DCI,
                                           const X86Subtarget &Subtarget) {
   // Bound the depth of our recursive combine because this is ultimately
   // quadratic in nature.
   if (Depth > 8)
     return false;
static bool combineX86ShufflesRecursively(ArrayRef<SDValue> SrcOps,
   }
 
   // Remove unused shuffle source ops.
   resolveTargetShuffleInputsAndMask(Ops, Mask);
   assert(!Ops.empty() && "Shuffle with no inputs detected");
 
   HasVariableMask |= isTargetShuffleVariableMask(Op.getOpcode());
 
-  // See if we can recurse into each shuffle source op (if it's a target shuffle).
+  // Update the list of shuffle nodes that have been combined so far.
+  SmallVector<const SDNode *, 8> CombinedNodes(SrcNodes.begin(),
+                                               SrcNodes.end());
+  CombinedNodes.push_back(Op.getNode());
+
+  // See if we can recurse into each shuffle source op (if it's a target
+  // shuffle). The source op should only be combined if it either has a
+  // single use (i.e. current Op) or all its users have already been combined.
   for (int i = 0, e = Ops.size(); i < e; ++i)
-    if (Ops[i].getNode()->hasOneUse() || Op->isOnlyUserOf(Ops[i].getNode()))
-      if (combineX86ShufflesRecursively(Ops, i, Root, Mask, Depth + 1,
-                                        HasVariableMask, DAG, DCI, Subtarget))
+    if (Ops[i].getNode()->hasOneUse() ||
+        SDNode::areOnlyUsersOf(CombinedNodes, Ops[i].getNode()))
+      if (combineX86ShufflesRecursively(Ops, i, Root, Mask, CombinedNodes,
+                                        Depth + 1, HasVariableMask, DAG, DCI,
+                                        Subtarget))
         return true;
 
   // Attempt to constant fold all of the constant source ops.
   if (combineX86ShufflesConstants(Ops, Mask, Root, HasVariableMask, DAG, DCI,
                                   Subtarget))
     return true;
 
   // We can only combine unary and binary shuffle mask cases.
if (isTargetShuffle(N->getOpcode())) {
 
     // Try recursively combining arbitrary sequences of x86 shuffle
     // instructions into higher-order shuffles. We do this after combining
     // specific PSHUF instruction sequences into their minimal form so that we
     // can evaluate how many specialized shuffle instructions are involved in
     // a particular chain.
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
   }
 
   return SDValue();
 }
 
static SDValue combineVectorShift(SDNode *N, SelectionDAG &DAG,
   if (ISD::isBuildVectorAllZeros(N0.getNode()))
     return getZeroVector(VT.getSimpleVT(), Subtarget, DAG, SDLoc(N));
 
   // We can decode 'whole byte' logical bit shifts as shuffles.
   if (LogicalShift && (ShiftVal.getZExtValue() % 8) == 0) {
     SDValue Op(N, 0);
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
   }
 
   // Constant Folding.
   SmallBitVector UndefElts;
   SmallVector<APInt, 32> EltBits;
assert(
        (N->getOpcode() == X86ISD::PINSRW &&
         N->getValueType(0) == MVT::v8i16)) &&
       "Unexpected vector insertion");
 
   // Attempt to combine PINSRB/PINSRW patterns to a shuffle.
   SDValue Op(N, 0);
   SmallVector<int, 1> NonceMask; // Just a placeholder.
   NonceMask.push_back(0);
-  combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+  combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                 /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                 DCI, Subtarget);
   return SDValue();
 }
 
 /// Recognize the distinctive (AND (setcc ...) (setcc ..)) where both setccs
 /// reference the same FP CMP, and rewrite for CMPEQSS and friends. Likewise for
 /// OR -> CMPNEQSS.
static SDValue combineAnd(SDNode *N, SelectionDAG &DAG,
   SDValue N1 = N->getOperand(1);
   SDLoc DL(N);
 
   // Attempt to recursively combine a bitmask AND with shuffles.
   if (VT.isVector() && (VT.getScalarSizeInBits() % 8) == 0) {
     SDValue Op(N, 0);
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
   }
 
   // Create BEXTR instructions
   // BEXTR is ((X >> imm) & (2**size-1))
   if (VT != MVT::i32 && VT != MVT::i64)
static SDValue combineAndnp(SDNode *N, SelectionDAG &DAG,
 
   EVT VT = N->getValueType(0);
 
   // Attempt to recursively combine a bitmask ANDNP with shuffles.
   if (VT.isVector() && (VT.getScalarSizeInBits() % 8) == 0) {
     SDValue Op(N, 0);
     SmallVector<int, 1> NonceMask; // Just a placeholder.
     NonceMask.push_back(0);
-    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask,
+    if (combineX86ShufflesRecursively({Op}, 0, Op, NonceMask, {},
                                       /*Depth*/ 1, /*HasVarMask*/ false, DAG,
                                       DCI, Subtarget))
       return SDValue(); // This routine will use CombineTo to replace N.
   }
 
   return SDValue();
 }
 

test/CodeGen/X86/clear_upper_vector_element_bits.ll

; AVX-NEXT:    retq
   %v14 = insertelement <16 x i8> %v13,  i8 %ext14, i32 14
   %v15 = insertelement <16 x i8> %v14,  i8 %ext15, i32 15
   ret <16 x i8> %v15
 }
 
 define <2 x i64> @_clearupper2xi64b(<2 x i64>) nounwind {
 ; SSE-LABEL: _clearupper2xi64b:
 ; SSE:       # BB#0:
-; SSE-NEXT:    xorps %xmm2, %xmm2
-; SSE-NEXT:    xorps %xmm1, %xmm1
-; SSE-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,0],xmm0[0,0]
-; SSE-NEXT:    shufps {{.*#+}} xmm1 = xmm1[2,0],xmm0[2,3]
-; SSE-NEXT:    shufps {{.*#+}} xmm2 = xmm2[0,0],xmm1[2,0]
-; SSE-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,1],xmm2[2,0]
-; SSE-NEXT:    movaps %xmm1, %xmm0
+; SSE-NEXT:    andps {{.*}}(%rip), %xmm0
 ; SSE-NEXT:    retq
 ;
 ; AVX1-LABEL: _clearupper2xi64b:
 ; AVX1:       # BB#0:
 ; AVX1-NEXT:    vpxor %xmm1, %xmm1, %xmm1
 ; AVX1-NEXT:    vpblendw {{.*#+}} xmm0 = xmm0[0,1],xmm1[2,3],xmm0[4,5],xmm1[6,7]
 ; AVX1-NEXT:    retq
 ;

test/CodeGen/X86/vector-shuffle-combining-avx2.ll

; X64-NEXT:    retq
   %2 = bitcast <4 x i64> %1 to <32 x i8>
   %3 = tail call <32 x i8> @llvm.x86.avx2.pshuf.b(<32 x i8> %2, <32 x i8> <i8 7, i8 6, i8 5, i8 4, i8 3, i8 2, i8 1, i8 0, i8 15, i8 14, i8 13, i8 12, i8 11, i8 10, i8 9, i8 8, i8 23, i8 22, i8 21, i8 20, i8 19, i8 18, i8 17, i8 31, i8 30, i8 29, i8 28, i8 27, i8 26, i8 25, i8 24, i8 23>)
   ret <32 x i8> %3
 }
 
 define <32 x i8> @combine_unpack_unpack_pshufb(<32 x i8> %a0) {
 ; X32-LABEL: combine_unpack_unpack_pshufb:
 ; X32:       # BB#0:
-; X32-NEXT:    vpshufd {{.*#+}} ymm1 = ymm0[0,0,0,0,4,4,4,4]
-; X32-NEXT:    vpshufd {{.*#+}} ymm2 = ymm0[1,1,2,3,5,5,6,7]
-; X32-NEXT:    vpshufd {{.*#+}} ymm0 = ymm0[2,3,2,3,6,7,6,7]
-; X32-NEXT:    vpunpcklbw {{.*#+}} ymm2 = ymm1[0],ymm2[0],ymm1[1],ymm2[1],ymm1[2],ymm2[2],ymm1[3],ymm2[3],ymm1[4],ymm2[4],ymm1[5],ymm2[5],ymm1[6],ymm2[6],ymm1[7],ymm2[7],ymm1[16],ymm2[16],ymm1[17],ymm2[17],ymm1[18],ymm2[18],ymm1[19],ymm2[19],ymm1[20],ymm2[20],ymm1[21],ymm2[21],ymm1[22],ymm2[22],ymm1[23],ymm2[23]
-; X32-NEXT:    vpunpcklbw {{.*#+}} ymm0 = ymm1[0],ymm0[0],ymm1[1],ymm0[1],ymm1[2],ymm0[2],ymm1[3],ymm0[3],ymm1[4],ymm0[4],ymm1[5],ymm0[5],ymm1[6],ymm0[6],ymm1[7],ymm0[7],ymm1[16],ymm0[16],ymm1[17],ymm0[17],ymm1[18],ymm0[18],ymm1[19],ymm0[19],ymm1[20],ymm0[20],ymm1[21],ymm0[21],ymm1[22],ymm0[22],ymm1[23],ymm0[23]
-; X32-NEXT:    vpunpcklbw {{.*#+}} ymm0 = ymm2[0],ymm0[0],ymm2[1],ymm0[1],ymm2[2],ymm0[2],ymm2[3],ymm0[3],ymm2[4],ymm0[4],ymm2[5],ymm0[5],ymm2[6],ymm0[6],ymm2[7],ymm0[7],ymm2[16],ymm0[16],ymm2[17],ymm0[17],ymm2[18],ymm0[18],ymm2[19],ymm0[19],ymm2[20],ymm0[20],ymm2[21],ymm0[21],ymm2[22],ymm0[22],ymm2[23],ymm0[23]
+; X32-NEXT:    vpshufb {{.*#+}} ymm0 = ymm0[0,0,4,8,1,1,5,9,2,2,6,10,3,3,7,11,16,16,20,24,17,17,21,25,18,18,22,26,19,19,23,27]
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: combine_unpack_unpack_pshufb:
 ; X64:       # BB#0:
-; X64-NEXT:    vpshufd {{.*#+}} ymm1 = ymm0[0,0,0,0,4,4,4,4]
-; X64-NEXT:    vpshufd {{.*#+}} ymm2 = ymm0[1,1,2,3,5,5,6,7]
-; X64-NEXT:    vpshufd {{.*#+}} ymm0 = ymm0[2,3,2,3,6,7,6,7]
-; X64-NEXT:    vpunpcklbw {{.*#+}} ymm2 = ymm1[0],ymm2[0],ymm1[1],ymm2[1],ymm1[2],ymm2[2],ymm1[3],ymm2[3],ymm1[4],ymm2[4],ymm1[5],ymm2[5],ymm1[6],ymm2[6],ymm1[7],ymm2[7],ymm1[16],ymm2[16],ymm1[17],ymm2[17],ymm1[18],ymm2[18],ymm1[19],ymm2[19],ymm1[20],ymm2[20],ymm1[21],ymm2[21],ymm1[22],ymm2[22],ymm1[23],ymm2[23]
-; X64-NEXT:    vpunpcklbw {{.*#+}} ymm0 = ymm1[0],ymm0[0],ymm1[1],ymm0[1],ymm1[2],ymm0[2],ymm1[3],ymm0[3],ymm1[4],ymm0[4],ymm1[5],ymm0[5],ymm1[6],ymm0[6],ymm1[7],ymm0[7],ymm1[16],ymm0[16],ymm1[17],ymm0[17],ymm1[18],ymm0[18],ymm1[19],ymm0[19],ymm1[20],ymm0[20],ymm1[21],ymm0[21],ymm1[22],ymm0[22],ymm1[23],ymm0[23]
-; X64-NEXT:    vpunpcklbw {{.*#+}} ymm0 = ymm2[0],ymm0[0],ymm2[1],ymm0[1],ymm2[2],ymm0[2],ymm2[3],ymm0[3],ymm2[4],ymm0[4],ymm2[5],ymm0[5],ymm2[6],ymm0[6],ymm2[7],ymm0[7],ymm2[16],ymm0[16],ymm2[17],ymm0[17],ymm2[18],ymm0[18],ymm2[19],ymm0[19],ymm2[20],ymm0[20],ymm2[21],ymm0[21],ymm2[22],ymm0[22],ymm2[23],ymm0[23]
+; X64-NEXT:    vpshufb {{.*#+}} ymm0 = ymm0[0,0,4,8,1,1,5,9,2,2,6,10,3,3,7,11,16,16,20,24,17,17,21,25,18,18,22,26,19,19,23,27]
 ; X64-NEXT:    retq
   %1 = shufflevector <32 x i8> %a0, <32 x i8> undef, <32 x i32> <i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3, i32 0, i32 1, i32 2, i32 3, i32 16, i32 17, i32 18, i32 19, i32 16, i32 17, i32 18, i32 19, i32 16, i32 17, i32 18, i32 19, i32 16, i32 17, i32 18, i32 19>
   %2 = shufflevector <32 x i8> %a0, <32 x i8> undef, <32 x i32> <i32 4, i32 5, i32 6, i32 7, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 20, i32 21, i32 22, i32 23, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
   %3 = shufflevector <32 x i8> %a0, <32 x i8> undef, <32 x i32> <i32 8, i32 9, i32 10, i32 11, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 24, i32 25, i32 26, i32 27, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
   %4 = shufflevector <32 x i8> %1, <32 x i8> %2, <32 x i32> <i32 0, i32 32, i32 1, i32 33, i32 2, i32 34, i32 3, i32 35, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 16, i32 48, i32 17, i32 49, i32 18, i32 50, i32 19, i32 51, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
   %5 = shufflevector <32 x i8> %1, <32 x i8> %3, <32 x i32> <i32 0, i32 32, i32 1, i32 33, i32 2, i32 34, i32 3, i32 35, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 16, i32 48, i32 17, i32 49, i32 18, i32 50, i32 19, i32 51, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
   %6 = shufflevector <32 x i8> %4, <32 x i8> %5, <32 x i32> <i32 0, i32 32, i32 1, i32 33, i32 2, i32 34, i32 3, i32 35, i32 4, i32 36, i32 5, i32 37, i32 6, i32 38, i32 7, i32 39, i32 16, i32 48, i32 17, i32 49, i32 18, i32 50, i32 19, i32 51, i32 20, i32 52, i32 21, i32 53, i32 22, i32 54, i32 23, i32 55>
   ret <32 x i8> %6

test/CodeGen/X86/vector-shuffle-combining-ssse3.ll

; AVX-NEXT:    retq
   %1 = shufflevector <16 x i8> %a0, <16 x i8> %a1, <16 x i32> <i32 0, i32 16, i32 1, i32 17, i32 2, i32 18, i32 3, i32 19, i32 4, i32 20, i32 5, i32 21, i32 6, i32 22, i32 7, i32 23>
   %2 = tail call <16 x i8> @llvm.x86.ssse3.pshuf.b.128(<16 x i8> %1, <16 x i8> <i8 1, i8 -1, i8 -1, i8 -1, i8 1, i8 -1, i8 -1, i8 -1, i8 1, i8 -1, i8 -1, i8 -1, i8 1, i8 -1, i8 -1, i8 -1>)
   ret <16 x i8> %2
 }
 
 define <8 x i16> @shuffle_combine_unpack_insert(<8 x i16> %a0) {
 ; SSE-LABEL: shuffle_combine_unpack_insert:
 ; SSE:       # BB#0:
-; SSE-NEXT:    pextrw $2, %xmm0, %eax
-; SSE-NEXT:    pextrw $4, %xmm0, %ecx
-; SSE-NEXT:    movdqa %xmm0, %xmm2
-; SSE-NEXT:    pinsrw $4, %eax, %xmm2
-; SSE-NEXT:    movdqa %xmm0, %xmm1
-; SSE-NEXT:    pinsrw $2, %ecx, %xmm1
-; SSE-NEXT:    movdqa %xmm2, %xmm3
-; SSE-NEXT:    punpcklwd {{.*#+}} xmm3 = xmm3[0],xmm1[0],xmm3[1],xmm1[1],xmm3[2],xmm1[2],xmm3[3],xmm1[3]
-; SSE-NEXT:    movdqa %xmm3, %xmm1
-; SSE-NEXT:    punpckhwd {{.*#+}} xmm1 = xmm1[4],xmm2[4],xmm1[5],xmm2[5],xmm1[6],xmm2[6],xmm1[7],xmm2[7]
-; SSE-NEXT:    punpckhwd {{.*#+}} xmm3 = xmm3[4],xmm0[4],xmm3[5],xmm0[5],xmm3[6],xmm0[6],xmm3[7],xmm0[7]
-; SSE-NEXT:    punpcklwd {{.*#+}} xmm1 = xmm1[0],xmm3[0],xmm1[1],xmm3[1],xmm1[2],xmm3[2],xmm1[3],xmm3[3]
-; SSE-NEXT:    movdqa %xmm1, %xmm0
+; SSE-NEXT:    pshufb {{.*#+}} xmm0 = xmm0[4,5,4,5,4,5,8,9,8,9,8,9,10,11,10,11]
 ; SSE-NEXT:    retq
 ;
 ; AVX-LABEL: shuffle_combine_unpack_insert:
 ; AVX:       # BB#0:
-; AVX-NEXT:    vpextrw $2, %xmm0, %eax
-; AVX-NEXT:    vpextrw $4, %xmm0, %ecx
-; AVX-NEXT:    vpinsrw $4, %eax, %xmm0, %xmm1
-; AVX-NEXT:    vpinsrw $2, %ecx, %xmm0, %xmm2
-; AVX-NEXT:    vpunpcklwd {{.*#+}} xmm2 = xmm1[0],xmm2[0],xmm1[1],xmm2[1],xmm1[2],xmm2[2],xmm1[3],xmm2[3]
-; AVX-NEXT:    vpunpckhwd {{.*#+}} xmm1 = xmm2[4],xmm1[4],xmm2[5],xmm1[5],xmm2[6],xmm1[6],xmm2[7],xmm1[7]
-; AVX-NEXT:    vpunpckhwd {{.*#+}} xmm0 = xmm2[4],xmm0[4],xmm2[5],xmm0[5],xmm2[6],xmm0[6],xmm2[7],xmm0[7]
-; AVX-NEXT:    vpunpcklwd {{.*#+}} xmm0 = xmm1[0],xmm0[0],xmm1[1],xmm0[1],xmm1[2],xmm0[2],xmm1[3],xmm0[3]
+; AVX-NEXT:    vpshufb {{.*#+}} xmm0 = xmm0[4,5,4,5,4,5,8,9,8,9,8,9,10,11,10,11]
 ; AVX-NEXT:    retq
   %1 = extractelement <8 x i16> %a0, i32 2
   %2 = extractelement <8 x i16> %a0, i32 4
   %3 = insertelement <8 x i16> %a0, i16 %1, i32 4
   %4 = insertelement <8 x i16> %a0, i16 %2, i32 2
   %5 = shufflevector <8 x i16> %3, <8 x i16> %4, <8 x i32> <i32 0, i32 8, i32 1, i32 9, i32 2, i32 10, i32 3, i32 11>
   %6 = shufflevector <8 x i16> %5, <8 x i16> %3, <8 x i32> <i32 4, i32 12, i32 5, i32 13, i32 undef, i32 undef, i32 undef, i32 undef>
   %7 = shufflevector <8 x i16> %5, <8 x i16> %a0, <8 x i32> <i32 4, i32 12, i32 5, i32 13, i32 undef, i32 undef, i32 undef, i32 undef>