diff options
Diffstat (limited to 'llvm/lib/Target/X86/X86ISelLowering.cpp')
| -rw-r--r-- | llvm/lib/Target/X86/X86ISelLowering.cpp | 1029 |
1 files changed, 1029 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp index d7e63e39ec7..3ceeac3b34e 100644 --- a/llvm/lib/Target/X86/X86ISelLowering.cpp +++ b/llvm/lib/Target/X86/X86ISelLowering.cpp @@ -44,11 +44,13 @@ #include "llvm/MC/MCContext.h" #include "llvm/MC/MCExpr.h" #include "llvm/MC/MCSymbol.h" +#include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/MathExtras.h" #include "llvm/Target/TargetOptions.h" #include <bitset> +#include <numeric> #include <cctype> using namespace llvm; @@ -56,6 +58,11 @@ using namespace llvm; STATISTIC(NumTailCalls, "Number of tail calls"); +static cl::opt<bool> ExperimentalVectorShuffleLowering( + "x86-experimental-vector-shuffle-lowering", cl::init(false), + cl::desc("Enable an experimental vector shuffle lowering code path."), + cl::Hidden); + // Forward declarations. static SDValue getMOVL(SelectionDAG &DAG, SDLoc dl, EVT VT, SDValue V1, SDValue V2); @@ -6875,6 +6882,1023 @@ static SDValue LowerCONCAT_VECTORS(SDValue Op, SelectionDAG &DAG) { return LowerAVXCONCAT_VECTORS(Op, DAG); } + +//===----------------------------------------------------------------------===// +// Vector shuffle lowering +// +// This is an experimental code path for lowering vector shuffles on x86. It is +// designed to handle arbitrary vector shuffles and blends, gracefully +// degrading performance as necessary. It works hard to recognize idiomatic +// shuffles and lower them to optimal instruction patterns without leaving +// a framework that allows reasonably efficient handling of all vector shuffle +// patterns. +//===----------------------------------------------------------------------===// + +/// \brief Tiny helper function to identify a no-op mask. +/// +/// This is a somewhat boring predicate function. It checks whether the mask +/// array input, which is assumed to be a single-input shuffle mask of the kind +/// used by the X86 shuffle instructions (not a fully general +/// ShuffleVectorSDNode mask) requires any shuffles to occur. Both undef and an +/// in-place shuffle are 'no-op's. +static bool isNoopShuffleMask(ArrayRef<int> Mask) { + for (int i = 0, Size = Mask.size(); i < Size; ++i) + if (Mask[i] != -1 && Mask[i] != i) + return false; + return true; +} + +/// \brief Helper function to classify a mask as a single-input mask. +/// +/// This isn't a generic single-input test because in the vector shuffle +/// lowering we canonicalize single inputs to be the first input operand. This +/// means we can more quickly test for a single input by only checking whether +/// an input from the second operand exists. We also assume that the size of +/// mask corresponds to the size of the input vectors which isn't true in the +/// fully general case. +static bool isSingleInputShuffleMask(ArrayRef<int> Mask) { + for (int M : Mask) + if (M >= (int)Mask.size()) + return false; + return true; +} + +/// \brief Get a 4-lane 8-bit shuffle immediate for a mask. +/// +/// This helper function produces an 8-bit shuffle immediate corresponding to +/// the ubiquitous shuffle encoding scheme used in x86 instructions for +/// shuffling 4 lanes. It can be used with most of the PSHUF instructions for +/// example. +/// +/// NB: We rely heavily on "undef" masks preserving the input lane. +static SDValue getV4X86ShuffleImm8ForMask(ArrayRef<int> Mask, + SelectionDAG &DAG) { + assert(Mask.size() == 4 && "Only 4-lane shuffle masks"); + assert(Mask[0] >= -1 && Mask[0] < 4 && "Out of bound mask element!"); + assert(Mask[1] >= -1 && Mask[1] < 4 && "Out of bound mask element!"); + assert(Mask[2] >= -1 && Mask[2] < 4 && "Out of bound mask element!"); + assert(Mask[3] >= -1 && Mask[3] < 4 && "Out of bound mask element!"); + + unsigned Imm = 0; + Imm |= (Mask[0] == -1 ? 0 : Mask[0]) << 0; + Imm |= (Mask[1] == -1 ? 1 : Mask[1]) << 2; + Imm |= (Mask[2] == -1 ? 2 : Mask[2]) << 4; + Imm |= (Mask[3] == -1 ? 3 : Mask[3]) << 6; + return DAG.getConstant(Imm, MVT::i8); +} + +/// \brief Handle lowering of 2-lane 64-bit floating point shuffles. +/// +/// This is the basis function for the 2-lane 64-bit shuffles as we have full +/// support for floating point shuffles but not integer shuffles. These +/// instructions will incur a domain crossing penalty on some chips though so +/// it is better to avoid lowering through this for integer vectors where +/// possible. +static SDValue lowerV2F64VectorShuffle(SDValue Op, SDValue V1, SDValue V2, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + SDLoc DL(Op); + assert(Op.getSimpleValueType() == MVT::v2f64 && "Bad shuffle type!"); + assert(V1.getSimpleValueType() == MVT::v2f64 && "Bad operand type!"); + assert(V2.getSimpleValueType() == MVT::v2f64 && "Bad operand type!"); + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> Mask = SVOp->getMask(); + assert(Mask.size() == 2 && "Unexpected mask size for v2 shuffle!"); + + if (isSingleInputShuffleMask(Mask)) { + // Straight shuffle of a single input vector. Simulate this by using the + // single input as both of the "inputs" to this instruction.. + unsigned SHUFPDMask = (Mask[0] == 1) | ((Mask[1] == 1) << 1); + return DAG.getNode(X86ISD::SHUFP, SDLoc(Op), MVT::v2f64, V1, V1, + DAG.getConstant(SHUFPDMask, MVT::i8)); + } + assert(Mask[0] >= 0 && Mask[0] < 2 && "Non-canonicalized blend!"); + assert(Mask[1] >= 2 && "Non-canonicalized blend!"); + + unsigned SHUFPDMask = (Mask[0] == 1) | (((Mask[1] - 2) == 1) << 1); + return DAG.getNode(X86ISD::SHUFP, SDLoc(Op), MVT::v2f64, V1, V2, + DAG.getConstant(SHUFPDMask, MVT::i8)); +} + +/// \brief Handle lowering of 2-lane 64-bit integer shuffles. +/// +/// Tries to lower a 2-lane 64-bit shuffle using shuffle operations provided by +/// the integer unit to minimize domain crossing penalties. However, for blends +/// it falls back to the floating point shuffle operation with appropriate bit +/// casting. +static SDValue lowerV2I64VectorShuffle(SDValue Op, SDValue V1, SDValue V2, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + SDLoc DL(Op); + assert(Op.getSimpleValueType() == MVT::v2i64 && "Bad shuffle type!"); + assert(V1.getSimpleValueType() == MVT::v2i64 && "Bad operand type!"); + assert(V2.getSimpleValueType() == MVT::v2i64 && "Bad operand type!"); + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> Mask = SVOp->getMask(); + assert(Mask.size() == 2 && "Unexpected mask size for v2 shuffle!"); + + if (isSingleInputShuffleMask(Mask)) { + // Straight shuffle of a single input vector. For everything from SSE2 + // onward this has a single fast instruction with no scary immediates. + // We have to map the mask as it is actually a v4i32 shuffle instruction. + V1 = DAG.getNode(ISD::BITCAST, DL, MVT::v4i32, V1); + int WidenedMask[4] = { + std::max(Mask[0], 0) * 2, std::max(Mask[0], 0) * 2 + 1, + std::max(Mask[1], 0) * 2, std::max(Mask[1], 0) * 2 + 1}; + return DAG.getNode( + ISD::BITCAST, DL, MVT::v2i64, + DAG.getNode(X86ISD::PSHUFD, SDLoc(Op), MVT::v4i32, V1, + getV4X86ShuffleImm8ForMask(WidenedMask, DAG))); + } + + // We implement this with SHUFPD which is pretty lame because it will likely + // incur 2 cycles of stall for integer vectors on Nehalem and older chips. + // However, all the alternatives are still more cycles and newer chips don't + // have this problem. It would be really nice if x86 had better shuffles here. + V1 = DAG.getNode(ISD::BITCAST, DL, MVT::v2f64, V1); + V2 = DAG.getNode(ISD::BITCAST, DL, MVT::v2f64, V2); + return DAG.getNode(ISD::BITCAST, DL, MVT::v2i64, + DAG.getVectorShuffle(MVT::v2f64, DL, V1, V2, Mask)); +} + +/// \brief Lower 4-lane 32-bit floating point shuffles. +/// +/// Uses instructions exclusively from the floating point unit to minimize +/// domain crossing penalties, as these are sufficient to implement all v4f32 +/// shuffles. +static SDValue lowerV4F32VectorShuffle(SDValue Op, SDValue V1, SDValue V2, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + SDLoc DL(Op); + assert(Op.getSimpleValueType() == MVT::v4f32 && "Bad shuffle type!"); + assert(V1.getSimpleValueType() == MVT::v4f32 && "Bad operand type!"); + assert(V2.getSimpleValueType() == MVT::v4f32 && "Bad operand type!"); + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> Mask = SVOp->getMask(); + assert(Mask.size() == 4 && "Unexpected mask size for v4 shuffle!"); + + SDValue LowV = V1, HighV = V2; + int NewMask[4] = {Mask[0], Mask[1], Mask[2], Mask[3]}; + + int NumV2Elements = + std::count_if(Mask.begin(), Mask.end(), [](int M) { return M >= 4; }); + + if (NumV2Elements == 0) + // Straight shuffle of a single input vector. We pass the input vector to + // both operands to simulate this with a SHUFPS. + return DAG.getNode(X86ISD::SHUFP, DL, MVT::v4f32, V1, V1, + getV4X86ShuffleImm8ForMask(Mask, DAG)); + + if (NumV2Elements == 1) { + int V2Index = + std::find_if(Mask.begin(), Mask.end(), [](int M) { return M >= 4; }) - + Mask.begin(); + // Compute the index adjacent to V2Index and in the same half by toggling + // the low bit. + int V2AdjIndex = V2Index ^ 1; + + if (Mask[V2AdjIndex] == -1) { + // Handles all the cases where we have a single V2 element and an undef. + // This will only ever happen in the high lanes because we commute the + // vector otherwise. + if (V2Index < 2) + std::swap(LowV, HighV); + NewMask[V2Index] -= 4; + } else { + // Handle the case where the V2 element ends up adjacent to a V1 element. + // To make this work, blend them together as the first step. + int V1Index = V2AdjIndex; + int BlendMask[4] = {Mask[V2Index] - 4, 0, Mask[V1Index], 0}; + V2 = DAG.getNode(X86ISD::SHUFP, DL, MVT::v4f32, V2, V1, + getV4X86ShuffleImm8ForMask(BlendMask, DAG)); + + // Now proceed to reconstruct the final blend as we have the necessary + // high or low half formed. + if (V2Index < 2) { + LowV = V2; + HighV = V1; + } else { + HighV = V2; + } + NewMask[V1Index] = 2; // We put the V1 element in V2[2]. + NewMask[V2Index] = 0; // We shifted the V2 element into V2[0]. + } + } else if (NumV2Elements == 2) { + if (Mask[0] < 4 && Mask[1] < 4) { + // Handle the easy case where we have V1 in the low lanes and V2 in the + // high lanes. We never see this reversed because we sort the shuffle. + NewMask[2] -= 4; + NewMask[3] -= 4; + } else { + // We have a mixture of V1 and V2 in both low and high lanes. Rather than + // trying to place elements directly, just blend them and set up the final + // shuffle to place them. + + // The first two blend mask elements are for V1, the second two are for + // V2. + int BlendMask[4] = {Mask[0] < 4 ? Mask[0] : Mask[1], + Mask[2] < 4 ? Mask[2] : Mask[3], + (Mask[0] >= 4 ? Mask[0] : Mask[1]) - 4, + (Mask[2] >= 4 ? Mask[2] : Mask[3]) - 4}; + V1 = DAG.getNode(X86ISD::SHUFP, DL, MVT::v4f32, V1, V2, + getV4X86ShuffleImm8ForMask(BlendMask, DAG)); + + // Now we do a normal shuffle of V1 by giving V1 as both operands to + // a blend. + HighV = V1; + NewMask[0] = Mask[0] < 4 ? 0 : 2; + NewMask[1] = Mask[0] < 4 ? 2 : 0; + NewMask[2] = Mask[2] < 4 ? 1 : 3; + NewMask[3] = Mask[2] < 4 ? 3 : 1; + } + } + return DAG.getNode(X86ISD::SHUFP, DL, MVT::v4f32, LowV, HighV, + getV4X86ShuffleImm8ForMask(NewMask, DAG)); +} + +/// \brief Lower 4-lane i32 vector shuffles. +/// +/// We try to handle these with integer-domain shuffles where we can, but for +/// blends we use the floating point domain blend instructions. +static SDValue lowerV4I32VectorShuffle(SDValue Op, SDValue V1, SDValue V2, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + SDLoc DL(Op); + assert(Op.getSimpleValueType() == MVT::v4i32 && "Bad shuffle type!"); + assert(V1.getSimpleValueType() == MVT::v4i32 && "Bad operand type!"); + assert(V2.getSimpleValueType() == MVT::v4i32 && "Bad operand type!"); + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> Mask = SVOp->getMask(); + assert(Mask.size() == 4 && "Unexpected mask size for v4 shuffle!"); + + if (isSingleInputShuffleMask(Mask)) + // Straight shuffle of a single input vector. For everything from SSE2 + // onward this has a single fast instruction with no scary immediates. + return DAG.getNode(X86ISD::PSHUFD, DL, MVT::v4i32, V1, + getV4X86ShuffleImm8ForMask(Mask, DAG)); + + // We implement this with SHUFPS because it can blend from two vectors. + // Because we're going to eventually use SHUFPS, we use SHUFPS even to build + // up the inputs, bypassing domain shift penalties that we would encur if we + // directly used PSHUFD on Nehalem and older. For newer chips, this isn't + // relevant. + return DAG.getNode(ISD::BITCAST, DL, MVT::v4i32, + DAG.getVectorShuffle( + MVT::v4f32, DL, + DAG.getNode(ISD::BITCAST, DL, MVT::v4f32, V1), + DAG.getNode(ISD::BITCAST, DL, MVT::v4f32, V2), Mask)); +} + +/// \brief Lowering of single-input v8i16 shuffles is the cornerstone of SSE2 +/// shuffle lowering, and the most complex part. +/// +/// The lowering strategy is to try to form pairs of input lanes which are +/// targeted at the same half of the final vector, and then use a dword shuffle +/// to place them onto the right half, and finally unpack the paired lanes into +/// their final position. +/// +/// The exact breakdown of how to form these dword pairs and align them on the +/// correct sides is really tricky. See the comments within the function for +/// more of the details. +static SDValue lowerV8I16SingleInputVectorShuffle( + SDLoc DL, SDValue V, MutableArrayRef<int> Mask, + const X86Subtarget *Subtarget, SelectionDAG &DAG) { + assert(V.getSimpleValueType() == MVT::v8i16 && "Bad input type!"); + MutableArrayRef<int> LoMask = Mask.slice(0, 4); + MutableArrayRef<int> HiMask = Mask.slice(4, 4); + + auto isLo = [](int M) { return M >= 0 && M < 4; }; + auto isHi = [](int M) { return M >= 4; }; + + SmallVector<int, 4> LoInputs; + std::copy_if(LoMask.begin(), LoMask.end(), std::back_inserter(LoInputs), + [](int M) { return M >= 0; }); + std::sort(LoInputs.begin(), LoInputs.end()); + LoInputs.erase(std::unique(LoInputs.begin(), LoInputs.end()), LoInputs.end()); + SmallVector<int, 4> HiInputs; + std::copy_if(HiMask.begin(), HiMask.end(), std::back_inserter(HiInputs), + [](int M) { return M >= 0; }); + std::sort(HiInputs.begin(), HiInputs.end()); + HiInputs.erase(std::unique(HiInputs.begin(), HiInputs.end()), HiInputs.end()); + int NumLToL = + std::lower_bound(LoInputs.begin(), LoInputs.end(), 4) - LoInputs.begin(); + int NumHToL = LoInputs.size() - NumLToL; + int NumLToH = + std::lower_bound(HiInputs.begin(), HiInputs.end(), 4) - HiInputs.begin(); + int NumHToH = HiInputs.size() - NumLToH; + MutableArrayRef<int> LToLInputs(LoInputs.data(), NumLToL); + MutableArrayRef<int> LToHInputs(HiInputs.data(), NumLToH); + MutableArrayRef<int> HToLInputs(LoInputs.data() + NumLToL, NumHToL); + MutableArrayRef<int> HToHInputs(HiInputs.data() + NumLToH, NumHToH); + + // Simplify the 1-into-3 and 3-into-1 cases with a single pshufd. For all + // such inputs we can swap two of the dwords across the half mark and end up + // with <=2 inputs to each half in each half. Once there, we can fall through + // to the generic code below. For example: + // + // Input: [a, b, c, d, e, f, g, h] -PSHUFD[0,2,1,3]-> [a, b, e, f, c, d, g, h] + // Mask: [0, 1, 2, 7, 4, 5, 6, 3] -----------------> [0, 1, 4, 7, 2, 3, 6, 5] + // + // Before we had 3-1 in the low half and 3-1 in the high half. Afterward, 2-2 + // and 2-2. + auto balanceSides = [&](ArrayRef<int> ThreeInputs, int OneInput, + int ThreeInputHalfSum, int OneInputHalfOffset) { + // Compute the index of dword with only one word among the three inputs in + // a half by taking the sum of the half with three inputs and subtracting + // the sum of the actual three inputs. The difference is the remaining + // slot. + int DWordA = (ThreeInputHalfSum - + std::accumulate(ThreeInputs.begin(), ThreeInputs.end(), 0)) / + 2; + int DWordB = OneInputHalfOffset / 2 + (OneInput / 2 + 1) % 2; + + int PSHUFDMask[] = {0, 1, 2, 3}; + PSHUFDMask[DWordA] = DWordB; + PSHUFDMask[DWordB] = DWordA; + V = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::PSHUFD, DL, MVT::v4i32, + DAG.getNode(ISD::BITCAST, DL, MVT::v4i32, V), + getV4X86ShuffleImm8ForMask(PSHUFDMask, DAG))); + + // Adjust the mask to match the new locations of A and B. + for (int &M : Mask) + if (M != -1 && M/2 == DWordA) + M = 2 * DWordB + M % 2; + else if (M != -1 && M/2 == DWordB) + M = 2 * DWordA + M % 2; + + // Recurse back into this routine to re-compute state now that this isn't + // a 3 and 1 problem. + return DAG.getVectorShuffle(MVT::v8i16, DL, V, DAG.getUNDEF(MVT::v8i16), + Mask); + }; + if (NumLToL == 3 && NumHToL == 1) + return balanceSides(LToLInputs, HToLInputs[0], 0 + 1 + 2 + 3, 4); + else if (NumLToL == 1 && NumHToL == 3) + return balanceSides(HToLInputs, LToLInputs[0], 4 + 5 + 6 + 7, 0); + else if (NumLToH == 1 && NumHToH == 3) + return balanceSides(HToHInputs, LToHInputs[0], 4 + 5 + 6 + 7, 0); + else if (NumLToH == 3 && NumHToH == 1) + return balanceSides(LToHInputs, HToHInputs[0], 0 + 1 + 2 + 3, 4); + + // At this point there are at most two inputs to the low and high halves from + // each half. That means the inputs can always be grouped into dwords and + // those dwords can then be moved to the correct half with a dword shuffle. + // We use at most one low and one high word shuffle to collect these paired + // inputs into dwords, and finally a dword shuffle to place them. + int PSHUFLMask[4] = {-1, -1, -1, -1}; + int PSHUFHMask[4] = {-1, -1, -1, -1}; + int PSHUFDMask[4] = {-1, -1, -1, -1}; + + // First fix the masks for all the inputs that are staying in their + // original halves. This will then dictate the targets of the cross-half + // shuffles. + auto fixInPlaceInputs = [&PSHUFDMask]( + ArrayRef<int> InPlaceInputs, MutableArrayRef<int> SourceHalfMask, + MutableArrayRef<int> HalfMask, int HalfOffset) { + if (InPlaceInputs.empty()) + return; + if (InPlaceInputs.size() == 1) { + SourceHalfMask[InPlaceInputs[0] - HalfOffset] = + InPlaceInputs[0] - HalfOffset; + PSHUFDMask[InPlaceInputs[0] / 2] = InPlaceInputs[0] / 2; + return; + } + + assert(InPlaceInputs.size() == 2 && "Cannot handle 3 or 4 inputs!"); + SourceHalfMask[InPlaceInputs[0] - HalfOffset] = + InPlaceInputs[0] - HalfOffset; + // Put the second input next to the first so that they are packed into + // a dword. We find the adjacent index by toggling the low bit. + int AdjIndex = InPlaceInputs[0] ^ 1; + SourceHalfMask[AdjIndex - HalfOffset] = InPlaceInputs[1] - HalfOffset; + std::replace(HalfMask.begin(), HalfMask.end(), InPlaceInputs[1], AdjIndex); + PSHUFDMask[AdjIndex / 2] = AdjIndex / 2; + }; + if (!HToLInputs.empty()) + fixInPlaceInputs(LToLInputs, PSHUFLMask, LoMask, 0); + if (!LToHInputs.empty()) + fixInPlaceInputs(HToHInputs, PSHUFHMask, HiMask, 4); + + // Now gather the cross-half inputs and place them into a free dword of + // their target half. + // FIXME: This operation could almost certainly be simplified dramatically to + // look more like the 3-1 fixing operation. + auto moveInputsToRightHalf = [&PSHUFDMask]( + MutableArrayRef<int> IncomingInputs, ArrayRef<int> ExistingInputs, + MutableArrayRef<int> SourceHalfMask, MutableArrayRef<int> HalfMask, + int SourceOffset, int DestOffset) { + auto isWordClobbered = [](ArrayRef<int> SourceHalfMask, int Word) { + return SourceHalfMask[Word] != -1 && SourceHalfMask[Word] != Word; + }; + auto isDWordClobbered = [&isWordClobbered](ArrayRef<int> SourceHalfMask, + int Word) { + int LowWord = Word & ~1; + int HighWord = Word | 1; + return isWordClobbered(SourceHalfMask, LowWord) || + isWordClobbered(SourceHalfMask, HighWord); + }; + + if (IncomingInputs.empty()) + return; + + if (ExistingInputs.empty()) { + // Map any dwords with inputs from them into the right half. + for (int Input : IncomingInputs) { + // If the source half mask maps over the inputs, turn those into + // swaps and use the swapped lane. + if (isWordClobbered(SourceHalfMask, Input - SourceOffset)) { + if (SourceHalfMask[SourceHalfMask[Input - SourceOffset]] == -1) { + SourceHalfMask[SourceHalfMask[Input - SourceOffset]] = + Input - SourceOffset; + // We have to swap the uses in our half mask in one sweep. + for (int &M : HalfMask) + if (M == SourceHalfMask[Input - SourceOffset]) + M = Input; + else if (M == Input) + M = SourceHalfMask[Input - SourceOffset] + SourceOffset; + } else { + assert(SourceHalfMask[SourceHalfMask[Input - SourceOffset]] == + Input - SourceOffset && + "Previous placement doesn't match!"); + } + // Note that this correctly re-maps both when we do a swap and when + // we observe the other side of the swap above. We rely on that to + // avoid swapping the members of the input list directly. + Input = SourceHalfMask[Input - SourceOffset] + SourceOffset; + } + + // Map the input's dword into the correct half. + if (PSHUFDMask[(Input - SourceOffset + DestOffset) / 2] == -1) + PSHUFDMask[(Input - SourceOffset + DestOffset) / 2] = Input / 2; + else + assert(PSHUFDMask[(Input - SourceOffset + DestOffset) / 2] == + Input / 2 && + "Previous placement doesn't match!"); + } + + // And just directly shift any other-half mask elements to be same-half + // as we will have mirrored the dword containing the element into the + // same position within that half. + for (int &M : HalfMask) + if (M >= SourceOffset && M < SourceOffset + 4) { + M = M - SourceOffset + DestOffset; + assert(M >= 0 && "This should never wrap below zero!"); + } + return; + } + + // Ensure we have the input in a viable dword of its current half. This + // is particularly tricky because the original position may be clobbered + // by inputs being moved and *staying* in that half. + if (IncomingInputs.size() == 1) { + if (isWordClobbered(SourceHalfMask, IncomingInputs[0] - SourceOffset)) { + int InputFixed = std::find(std::begin(SourceHalfMask), + std::end(SourceHalfMask), -1) - + std::begin(SourceHalfMask) + SourceOffset; + SourceHalfMask[InputFixed - SourceOffset] = + IncomingInputs[0] - SourceOffset; + std::replace(HalfMask.begin(), HalfMask.end(), IncomingInputs[0], + InputFixed); + IncomingInputs[0] = InputFixed; + } + } else if (IncomingInputs.size() == 2) { + if (IncomingInputs[0] / 2 != IncomingInputs[1] / 2 || + isDWordClobbered(SourceHalfMask, IncomingInputs[0] - SourceOffset)) { + int SourceDWordBase = !isDWordClobbered(SourceHalfMask, 0) ? 0 : 2; + assert(!isDWordClobbered(SourceHalfMask, SourceDWordBase) && + "Not all dwords can be clobbered!"); + SourceHalfMask[SourceDWordBase] = IncomingInputs[0] - SourceOffset; + SourceHalfMask[SourceDWordBase + 1] = IncomingInputs[1] - SourceOffset; + for (int &M : HalfMask) + if (M == IncomingInputs[0]) + M = SourceDWordBase + SourceOffset; + else if (M == IncomingInputs[1]) + M = SourceDWordBase + 1 + SourceOffset; + IncomingInputs[0] = SourceDWordBase + SourceOffset; + IncomingInputs[1] = SourceDWordBase + 1 + SourceOffset; + } + } else { + llvm_unreachable("Unhandled input size!"); + } + + // Now hoist the DWord down to the right half. + int FreeDWord = (PSHUFDMask[DestOffset / 2] == -1 ? 0 : 1) + DestOffset / 2; + assert(PSHUFDMask[FreeDWord] == -1 && "DWord not free"); + PSHUFDMask[FreeDWord] = IncomingInputs[0] / 2; + for (int Input : IncomingInputs) + std::replace(HalfMask.begin(), HalfMask.end(), Input, + FreeDWord * 2 + Input % 2); + }; + moveInputsToRightHalf(HToLInputs, LToLInputs, PSHUFHMask, LoMask, + /*SourceOffset*/ 4, /*DestOffset*/ 0); + moveInputsToRightHalf(LToHInputs, HToHInputs, PSHUFLMask, HiMask, + /*SourceOffset*/ 0, /*DestOffset*/ 4); + + // Now enact all the shuffles we've computed to move the inputs into their + // target half. + if (!isNoopShuffleMask(PSHUFLMask)) + V = DAG.getNode(X86ISD::PSHUFLW, DL, MVT::v8i16, V, + getV4X86ShuffleImm8ForMask(PSHUFLMask, DAG)); + if (!isNoopShuffleMask(PSHUFHMask)) + V = DAG.getNode(X86ISD::PSHUFHW, DL, MVT::v8i16, V, + getV4X86ShuffleImm8ForMask(PSHUFHMask, DAG)); + if (!isNoopShuffleMask(PSHUFDMask)) + V = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::PSHUFD, DL, MVT::v4i32, + DAG.getNode(ISD::BITCAST, DL, MVT::v4i32, V), + getV4X86ShuffleImm8ForMask(PSHUFDMask, DAG))); + + // At this point, each half should contain all its inputs, and we can then + // just shuffle them into their final position. + assert(std::count_if(LoMask.begin(), LoMask.end(), isHi) == 0 && + "Failed to lift all the high half inputs to the low mask!"); + assert(std::count_if(HiMask.begin(), HiMask.end(), isLo) == 0 && + "Failed to lift all the low half inputs to the high mask!"); + + // Do a half shuffle for the low mask. + if (!isNoopShuffleMask(LoMask)) + V = DAG.getNode(X86ISD::PSHUFLW, DL, MVT::v8i16, V, + getV4X86ShuffleImm8ForMask(LoMask, DAG)); + + // Do a half shuffle with the high mask after shifting its values down. + for (int &M : HiMask) + if (M >= 0) + M -= 4; + if (!isNoopShuffleMask(HiMask)) + V = DAG.getNode(X86ISD::PSHUFHW, DL, MVT::v8i16, V, + getV4X86ShuffleImm8ForMask(HiMask, DAG)); + + return V; +} + +/// \brief Detect whether the mask pattern should be lowered through +/// interleaving. +/// +/// This essentially tests whether viewing the mask as an interleaving of two +/// sub-sequences reduces the cross-input traffic of a blend operation. If so, +/// lowering it through interleaving is a significantly better strategy. +static bool shouldLowerAsInterleaving(ArrayRef<int> Mask) { + int NumEvenInputs[2] = {0, 0}; + int NumOddInputs[2] = {0, 0}; + int NumLoInputs[2] = {0, 0}; + int NumHiInputs[2] = {0, 0}; + for (int i = 0, Size = Mask.size(); i < Size; ++i) { + if (Mask[i] < 0) + continue; + + int InputIdx = Mask[i] >= Size; + + if (i < Size / 2) + ++NumLoInputs[InputIdx]; + else + ++NumHiInputs[InputIdx]; + + if ((i % 2) == 0) + ++NumEvenInputs[InputIdx]; + else + ++NumOddInputs[InputIdx]; + } + + // The minimum number of cross-input results for both the interleaved and + // split cases. If interleaving results in fewer cross-input results, return + // true. + int InterleavedCrosses = std::min(NumEvenInputs[1] + NumOddInputs[0], + NumEvenInputs[0] + NumOddInputs[1]); + int SplitCrosses = std::min(NumLoInputs[1] + NumHiInputs[0], + NumLoInputs[0] + NumHiInputs[1]); + return InterleavedCrosses < SplitCrosses; +} + +/// \brief Blend two v8i16 vectors using a naive unpack strategy. +/// +/// This strategy only works when the inputs from each vector fit into a single +/// half of that vector, and generally there are not so many inputs as to leave +/// the in-place shuffles required highly constrained (and thus expensive). It +/// shifts all the inputs into a single side of both input vectors and then +/// uses an unpack to interleave these inputs in a single vector. At that +/// point, we will fall back on the generic single input shuffle lowering. +static SDValue lowerV8I16BasicBlendVectorShuffle(SDLoc DL, SDValue V1, + SDValue V2, + MutableArrayRef<int> Mask, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + assert(V1.getSimpleValueType() == MVT::v8i16 && "Bad input type!"); + assert(V2.getSimpleValueType() == MVT::v8i16 && "Bad input type!"); + SmallVector<int, 3> LoV1Inputs, HiV1Inputs, LoV2Inputs, HiV2Inputs; + for (int i = 0; i < 8; ++i) + if (Mask[i] >= 0 && Mask[i] < 4) + LoV1Inputs.push_back(i); + else if (Mask[i] >= 4 && Mask[i] < 8) + HiV1Inputs.push_back(i); + else if (Mask[i] >= 8 && Mask[i] < 12) + LoV2Inputs.push_back(i); + else if (Mask[i] >= 12) + HiV2Inputs.push_back(i); + + int NumV1Inputs = LoV1Inputs.size() + HiV1Inputs.size(); + int NumV2Inputs = LoV2Inputs.size() + HiV2Inputs.size(); + + assert(NumV1Inputs > 0 && NumV1Inputs <= 3 && "At most 3 inputs supported"); + assert(NumV2Inputs > 0 && NumV2Inputs <= 3 && "At most 3 inputs supported"); + assert(NumV1Inputs + NumV2Inputs <= 4 && "At most 4 combined inputs"); + + bool MergeFromLo = LoV1Inputs.size() + LoV2Inputs.size() >= + HiV1Inputs.size() + HiV2Inputs.size(); + + auto moveInputsToHalf = [&](SDValue V, ArrayRef<int> LoInputs, + ArrayRef<int> HiInputs, bool MoveToLo, + int MaskOffset) { + ArrayRef<int> GoodInputs = MoveToLo ? LoInputs : HiInputs; + ArrayRef<int> BadInputs = MoveToLo ? HiInputs : LoInputs; + if (BadInputs.empty()) + return V; + + int MoveMask[] = {-1, -1, -1, -1, -1, -1, -1, -1}; + int MoveOffset = MoveToLo ? 0 : 4; + + if (GoodInputs.empty()) { + for (int BadInput : BadInputs) { + MoveMask[Mask[BadInput] % 4 + MoveOffset] = Mask[BadInput] - MaskOffset; + Mask[BadInput] = Mask[BadInput] % 4 + MoveOffset + MaskOffset; + } + } else { + if (GoodInputs.size() == 2) { + // If the low inputs are spread across two dwords, pack them into + // a single dword. + MoveMask[Mask[GoodInputs[0]] % 2 + MoveOffset] = + Mask[GoodInputs[0]] - MaskOffset; + MoveMask[Mask[GoodInputs[1]] % 2 + MoveOffset] = + Mask[GoodInputs[1]] - MaskOffset; + Mask[GoodInputs[0]] = Mask[GoodInputs[0]] % 2 + MoveOffset + MaskOffset; + Mask[GoodInputs[1]] = Mask[GoodInputs[0]] % 2 + MoveOffset + MaskOffset; + } else { + // Otherwise pin the low inputs. + for (int GoodInput : GoodInputs) + MoveMask[Mask[GoodInput]] = Mask[GoodInput] - MaskOffset; + } + + int MoveMaskIdx = + std::find(std::begin(MoveMask) + MoveOffset, std::end(MoveMask), -1) - + std::begin(MoveMask); + assert(MoveMaskIdx >= MoveOffset && "Established above"); + + if (BadInputs.size() == 2) { + assert(MoveMask[MoveMaskIdx] == -1 && "Expected empty slot"); + assert(MoveMask[MoveMaskIdx + 1] == -1 && "Expected empty slot"); + MoveMask[MoveMaskIdx + Mask[BadInputs[0]] % 2] = + Mask[BadInputs[0]] - MaskOffset; + MoveMask[MoveMaskIdx + Mask[BadInputs[1]] % 2] = + Mask[BadInputs[1]] - MaskOffset; + Mask[BadInputs[0]] = MoveMaskIdx + Mask[BadInputs[0]] % 2 + MaskOffset; + Mask[BadInputs[1]] = MoveMaskIdx + Mask[BadInputs[1]] % 2 + MaskOffset; + } else { + assert(BadInputs.size() == 1 && "All sizes handled"); + MoveMask[MoveMaskIdx] = Mask[BadInputs[0]] - MaskOffset; + Mask[BadInputs[0]] = MoveMaskIdx + MaskOffset; + } + } + + return DAG.getVectorShuffle(MVT::v8i16, DL, V, DAG.getUNDEF(MVT::v8i16), + MoveMask); + }; + V1 = moveInputsToHalf(V1, LoV1Inputs, HiV1Inputs, MergeFromLo, + /*MaskOffset*/ 0); + V2 = moveInputsToHalf(V2, LoV2Inputs, HiV2Inputs, MergeFromLo, + /*MaskOffset*/ 8); + + // FIXME: Select an interleaving of the merge of V1 and V2 that minimizes + // cross-half traffic in the final shuffle. + + // Munge the mask to be a single-input mask after the unpack merges the + // results. + for (int &M : Mask) + if (M != -1) + M = 2 * (M % 4) + (M / 8); + + return DAG.getVectorShuffle( + MVT::v8i16, DL, DAG.getNode(MergeFromLo ? X86ISD::UNPCKL : X86ISD::UNPCKH, + DL, MVT::v8i16, V1, V2), + DAG.getUNDEF(MVT::v8i16), Mask); +} + +/// \brief Generic lowering of 8-lane i16 shuffles. +/// +/// This handles both single-input shuffles and combined shuffle/blends with +/// two inputs. The single input shuffles are immediately delegated to +/// a dedicated lowering routine. +/// +/// The blends are lowered in one of three fundamental ways. If there are few +/// enough inputs, it delegates to a basic UNPCK-based strategy. If the shuffle +/// of the input is significantly cheaper when lowered as an interleaving of +/// the two inputs, try to interleave them. Otherwise, blend the low and high +/// halves of the inputs separately (making them have relatively few inputs) +/// and then concatenate them. +static SDValue lowerV8I16VectorShuffle(SDValue Op, SDValue V1, SDValue V2, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + SDLoc DL(Op); + assert(Op.getSimpleValueType() == MVT::v8i16 && "Bad shuffle type!"); + assert(V1.getSimpleValueType() == MVT::v8i16 && "Bad operand type!"); + assert(V2.getSimpleValueType() == MVT::v8i16 && "Bad operand type!"); + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> OrigMask = SVOp->getMask(); + int MaskStorage[8] = {OrigMask[0], OrigMask[1], OrigMask[2], OrigMask[3], + OrigMask[4], OrigMask[5], OrigMask[6], OrigMask[7]}; + MutableArrayRef<int> Mask(MaskStorage); + + assert(Mask.size() == 8 && "Unexpected mask size for v8 shuffle!"); + + int Size = Mask.size(); + assert(Size == 8 && "Unexpected mask size for v8 shuffle!"); + + auto isV1 = [](int M) { return M >= 0 && M < 8; }; + auto isV2 = [](int M) { return M >= 8; }; + + int NumV1Inputs = std::count_if(Mask.begin(), Mask.end(), isV1); + int NumV2Inputs = std::count_if(Mask.begin(), Mask.end(), isV2); + + if (NumV2Inputs == 0) + return lowerV8I16SingleInputVectorShuffle(DL, V1, Mask, Subtarget, DAG); + + assert(NumV1Inputs > 0 && "All single-input shuffles should be canonicalized " + "to be V1-input shuffles."); + + if (NumV1Inputs + NumV2Inputs <= 4) + return lowerV8I16BasicBlendVectorShuffle(DL, V1, V2, Mask, Subtarget, DAG); + + // Check whether an interleaving lowering is likely to be more efficient. + // This isn't perfect but it is a strong heuristic that tends to work well on + // the kinds of shuffles that show up in practice. + // + // FIXME: Handle 1x, 2x, and 4x interleaving. + if (shouldLowerAsInterleaving(Mask)) { + // FIXME: Figure out whether we should pack these into the low or high + // halves. + + int EMask[8], OMask[8]; + for (int i = 0; i < 4; ++i) { + EMask[i] = Mask[2*i]; + OMask[i] = Mask[2*i + 1]; + EMask[i + 4] = -1; + OMask[i + 4] = -1; + } + + SDValue Evens = DAG.getVectorShuffle(MVT::v8i16, DL, V1, V2, EMask); + SDValue Odds = DAG.getVectorShuffle(MVT::v8i16, DL, V1, V2, OMask); + + return DAG.getNode(X86ISD::UNPCKL, DL, MVT::v8i16, Evens, Odds); + } + + int LoBlendMask[8] = {-1, -1, -1, -1, -1, -1, -1, -1}; + int HiBlendMask[8] = {-1, -1, -1, -1, -1, -1, -1, -1}; + + for (int i = 0; i < 4; ++i) { + LoBlendMask[i] = Mask[i]; + HiBlendMask[i] = Mask[i + 4]; + } + + SDValue LoV = DAG.getVectorShuffle(MVT::v8i16, DL, V1, V2, LoBlendMask); + SDValue HiV = DAG.getVectorShuffle(MVT::v8i16, DL, V1, V2, HiBlendMask); + LoV = DAG.getNode(ISD::BITCAST, DL, MVT::v2i64, LoV); + HiV = DAG.getNode(ISD::BITCAST, DL, MVT::v2i64, HiV); + + return DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::UNPCKL, DL, MVT::v2i64, LoV, HiV)); +} + +/// \brief Generic lowering of v16i8 shuffles. +/// +/// This is a hybrid strategy to lower v16i8 vectors. It first attempts to +/// detect any complexity reducing interleaving. If that doesn't help, it uses +/// UNPCK to spread the i8 elements across two i16-element vectors, and uses +/// the existing lowering for v8i16 blends on each half, finally PACK-ing them +/// back together. +static SDValue lowerV16I8VectorShuffle(SDValue Op, SDValue V1, SDValue V2, + const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + SDLoc DL(Op); + assert(Op.getSimpleValueType() == MVT::v16i8 && "Bad shuffle type!"); + assert(V1.getSimpleValueType() == MVT::v16i8 && "Bad operand type!"); + assert(V2.getSimpleValueType() == MVT::v16i8 && "Bad operand type!"); + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> OrigMask = SVOp->getMask(); + assert(OrigMask.size() == 16 && "Unexpected mask size for v16 shuffle!"); + int MaskStorage[16] = { + OrigMask[0], OrigMask[1], OrigMask[2], OrigMask[3], + OrigMask[4], OrigMask[5], OrigMask[6], OrigMask[7], + OrigMask[8], OrigMask[9], OrigMask[10], OrigMask[11], + OrigMask[12], OrigMask[13], OrigMask[14], OrigMask[15]}; + MutableArrayRef<int> Mask(MaskStorage); + MutableArrayRef<int> LoMask = Mask.slice(0, 8); + MutableArrayRef<int> HiMask = Mask.slice(8, 8); + + // Check whether an interleaving lowering is likely to be more efficient. + // This isn't perfect but it is a strong heuristic that tends to work well on + // the kinds of shuffles that show up in practice. + // + // FIXME: We need to handle other interleaving widths (i16, i32, ...). + if (shouldLowerAsInterleaving(Mask)) { + // FIXME: Figure out whether we should pack these into the low or high + // halves. + + int EMask[16], OMask[16]; + for (int i = 0; i < 8; ++i) { + EMask[i] = Mask[2*i]; + OMask[i] = Mask[2*i + 1]; + EMask[i + 8] = -1; + OMask[i + 8] = -1; + } + + SDValue Evens = DAG.getVectorShuffle(MVT::v16i8, DL, V1, V2, EMask); + SDValue Odds = DAG.getVectorShuffle(MVT::v16i8, DL, V1, V2, OMask); + + return DAG.getNode(X86ISD::UNPCKL, DL, MVT::v16i8, Evens, Odds); + } + + SDValue LoV1 = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::UNPCKL, DL, MVT::v16i8, V1, + DAG.getUNDEF(MVT::v8i16))); + SDValue HiV1 = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::UNPCKH, DL, MVT::v16i8, V1, + DAG.getUNDEF(MVT::v8i16))); + SDValue LoV2 = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::UNPCKL, DL, MVT::v16i8, V2, + DAG.getUNDEF(MVT::v8i16))); + SDValue HiV2 = DAG.getNode(ISD::BITCAST, DL, MVT::v8i16, + DAG.getNode(X86ISD::UNPCKH, DL, MVT::v16i8, V2, + DAG.getUNDEF(MVT::v8i16))); + + int V1LoBlendMask[8] = {-1, -1, -1, -1, -1, -1, -1, -1}; + int V1HiBlendMask[8] = {-1, -1, -1, -1, -1, -1, -1, -1}; + int V2LoBlendMask[8] = {-1, -1, -1, -1, -1, -1, -1, -1}; + int V2HiBlendMask[8] = {-1, -1, -1, -1, -1, -1, -1, -1}; + + auto buildBlendMasks = [](MutableArrayRef<int> HalfMask, + MutableArrayRef<int> V1HalfBlendMask, + MutableArrayRef<int> V2HalfBlendMask) { + for (int i = 0; i < 8; ++i) + if (HalfMask[i] >= 0 && HalfMask[i] < 16) { + V1HalfBlendMask[i] = HalfMask[i]; + HalfMask[i] = i; + } else if (HalfMask[i] >= 16) { + V2HalfBlendMask[i] = HalfMask[i] - 16; + HalfMask[i] = i + 8; + } + }; + buildBlendMasks(LoMask, V1LoBlendMask, V2LoBlendMask); + buildBlendMasks(HiMask, V1HiBlendMask, V2HiBlendMask); + + SDValue V1Lo = DAG.getVectorShuffle(MVT::v8i16, DL, LoV1, HiV1, V1LoBlendMask); + SDValue V2Lo = DAG.getVectorShuffle(MVT::v8i16, DL, LoV2, HiV2, V2LoBlendMask); + SDValue V1Hi = DAG.getVectorShuffle(MVT::v8i16, DL, LoV1, HiV1, V1HiBlendMask); + SDValue V2Hi = DAG.getVectorShuffle(MVT::v8i16, DL, LoV2, HiV2, V2HiBlendMask); + + SDValue LoV = DAG.getVectorShuffle(MVT::v8i16, DL, V1Lo, V2Lo, LoMask); + SDValue HiV = DAG.getVectorShuffle(MVT::v8i16, DL, V1Hi, V2Hi, HiMask); + + return DAG.getNode(X86ISD::PACKUS, DL, MVT::v16i8, LoV, HiV); +} + +/// \brief Dispatching routine to lower various 128-bit x86 vector shuffles. +/// +/// This routine breaks down the specific type of 128-bit shuffle and +/// dispatches to the lowering routines accordingly. +static SDValue lower128BitVectorShuffle(SDValue Op, SDValue V1, SDValue V2, + MVT VT, const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + switch (VT.SimpleTy) { + case MVT::v2i64: + return lowerV2I64VectorShuffle(Op, V1, V2, Subtarget, DAG); + case MVT::v2f64: + return lowerV2F64VectorShuffle(Op, V1, V2, Subtarget, DAG); + case MVT::v4i32: + return lowerV4I32VectorShuffle(Op, V1, V2, Subtarget, DAG); + case MVT::v4f32: + return lowerV4F32VectorShuffle(Op, V1, V2, Subtarget, DAG); + case MVT::v8i16: + return lowerV8I16VectorShuffle(Op, V1, V2, Subtarget, DAG); + case MVT::v16i8: + return lowerV16I8VectorShuffle(Op, V1, V2, Subtarget, DAG); + + default: + llvm_unreachable("Unimplemented!"); + } +} + +/// \brief Tiny helper function to test whether adjacent masks are sequential. +static bool areAdjacentMasksSequential(ArrayRef<int> Mask) { + for (int i = 0, Size = Mask.size(); i < Size; i += 2) + if (Mask[i] + 1 != Mask[i+1]) + return false; + + return true; +} + +/// \brief Top-level lowering for x86 vector shuffles. +/// +/// This handles decomposition, canonicalization, and lowering of all x86 +/// vector shuffles. Most of the specific lowering strategies are encapsulated +/// above in helper routines. The canonicalization attempts to widen shuffles +/// to involve fewer lanes of wider elements, consolidate symmetric patterns +/// s.t. only one of the two inputs needs to be tested, etc. +static SDValue lowerVectorShuffle(SDValue Op, const X86Subtarget *Subtarget, + SelectionDAG &DAG) { + ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op); + ArrayRef<int> Mask = SVOp->getMask(); + SDValue V1 = Op.getOperand(0); + SDValue V2 = Op.getOperand(1); + MVT VT = Op.getSimpleValueType(); + int NumElements = VT.getVectorNumElements(); + SDLoc dl(Op); + + assert(VT.getSizeInBits() != 64 && "Can't lower MMX shuffles"); + + bool V1IsUndef = V1.getOpcode() == ISD::UNDEF; + bool V2IsUndef = V2.getOpcode() == ISD::UNDEF; + if (V1IsUndef && V2IsUndef) + return DAG.getUNDEF(VT); + + // When we create a shuffle node we put the UNDEF node to second operand, + // but in some cases the first operand may be transformed to UNDEF. + // In this case we should just commute the node. + if (V1IsUndef) + return CommuteVectorShuffle(SVOp, DAG); + + // Check for non-undef masks pointing at an undef vector and make the masks + // undef as well. This makes it easier to match the shuffle based solely on + // the mask. + if (V2IsUndef) + for (int M : Mask) + if (M >= NumElements) { + SmallVector<int, 8> NewMask(Mask.begin(), Mask.end()); + for (int &M : NewMask) + if (M >= NumElements) + M = -1; + return DAG.getVectorShuffle(VT, dl, V1, V2, NewMask); + } + + // For integer vector shuffles, try to collapse them into a shuffle of fewer + // lanes but wider integers. We cap this to not form integers larger than i64 + // but it might be interesting to form i128 integers to handle flipping the + // low and high halves of AVX 256-bit vectors. + if (VT.isInteger() && VT.getScalarSizeInBits() < 64 && + areAdjacentMasksSequential(Mask)) { + SmallVector<int, 8> NewMask; + for (int i = 0, Size = Mask.size(); i < Size; i += 2) + NewMask.push_back(Mask[i] / 2); + MVT NewVT = + MVT::getVectorVT(MVT::getIntegerVT(VT.getScalarSizeInBits() * 2), + VT.getVectorNumElements() / 2); + V1 = DAG.getNode(ISD::BITCAST, dl, NewVT, V1); + V2 = DAG.getNode(ISD::BITCAST, dl, NewVT, V2); + return DAG.getNode(ISD::BITCAST, dl, VT, + DAG.getVectorShuffle(NewVT, dl, V1, V2, NewMask)); + } + + int NumV1Elements = 0, NumUndefElements = 0, NumV2Elements = 0; + for (int M : SVOp->getMask()) + if (M < 0) + ++NumUndefElements; + else if (M < NumElements) + ++NumV1Elements; + else + ++NumV2Elements; + + // Commute the shuffle as needed such that more elements come from V1 than + // V2. This allows us to match the shuffle pattern strictly on how many + // elements come from V1 without handling the symmetric cases. + if (NumV2Elements > NumV1Elements) + return CommuteVectorShuffle(SVOp, DAG); + + // When the number of V1 and V2 elements are the same, try to minimize the + // number of uses of V2 in the low half of the vector. + if (NumV1Elements == NumV2Elements) { + int LowV1Elements = 0, LowV2Elements = 0; + for (int M : SVOp->getMask().slice(0, NumElements / 2)) + if (M >= NumElements) + ++LowV2Elements; + else if (M >= 0) + ++LowV1Elements; + if (LowV2Elements > LowV1Elements) + return CommuteVectorShuffle(SVOp, DAG); + } + + // For each vector width, delegate to a specialized lowering routine. + if (VT.getSizeInBits() == 128) + return lower128BitVectorShuffle(Op, V1, V2, VT, Subtarget, DAG); + + llvm_unreachable("Unimplemented!"); +} + + +//===----------------------------------------------------------------------===// +// Legacy vector shuffle lowering +// +// This code is the legacy code handling vector shuffles until the above +// replaces its functionality and performance. +//===----------------------------------------------------------------------===// + static bool isBlendMask(ArrayRef<int> MaskVals, MVT VT, bool hasSSE41, bool hasInt256, unsigned *MaskOut = nullptr) { MVT EltVT = VT.getVectorElementType(); @@ -8127,6 +9151,11 @@ X86TargetLowering::LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const { bool OptForSize = MF.getFunction()->getAttributes(). hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize); + // Check if we should use the experimental vector shuffle lowering. If so, + // delegate completely to that code path. + if (ExperimentalVectorShuffleLowering) + return lowerVectorShuffle(Op, Subtarget, DAG); + assert(VT.getSizeInBits() != 64 && "Can't lower MMX shuffles"); if (V1IsUndef && V2IsUndef) |
