text: //===-- X86ShuffleDecode.cpp - X86 shuffle decode logic -------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // Define several functions to decode x86 specific shuffle semantics into a
  // generic vector mask.
  //
  //===----------------------------------------------------------------------===//
  
  #include "X86ShuffleDecode.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/ArrayRef.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/Support/MathExtras.h"
  
  //===----------------------------------------------------------------------===//
  //  Vector Mask Decoding
  //===----------------------------------------------------------------------===//
  
  namespace llvm {
  
  void DecodeINSERTPSMask(unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
    // Defaults the copying the dest value.
    ShuffleMask.push_back(0);
    ShuffleMask.push_back(1);
    ShuffleMask.push_back(2);
    ShuffleMask.push_back(3);
  
    // Decode the immediate.
    unsigned ZMask = Imm & 15;
    unsigned CountD = (Imm >> 4) & 3;
    unsigned CountS = (Imm >> 6) & 3;
  
    // CountS selects which input element to use.
    unsigned InVal = 4 + CountS;
    // CountD specifies which element of destination to update.
    ShuffleMask[CountD] = InVal;
    // ZMask zaps values, potentially overriding the CountD elt.
    if (ZMask & 1) ShuffleMask[0] = SM_SentinelZero;
    if (ZMask & 2) ShuffleMask[1] = SM_SentinelZero;
    if (ZMask & 4) ShuffleMask[2] = SM_SentinelZero;
    if (ZMask & 8) ShuffleMask[3] = SM_SentinelZero;
  }
  
  void DecodeInsertElementMask(unsigned NumElts, unsigned Idx, unsigned Len,
                               SmallVectorImpl<int> &ShuffleMask) {
    assert((Idx + Len) <= NumElts && "Insertion out of range");
  
    for (unsigned i = 0; i != NumElts; ++i)
      ShuffleMask.push_back(i);
    for (unsigned i = 0; i != Len; ++i)
      ShuffleMask[Idx + i] = NumElts + i;
  }
  
  // <3,1> or <6,7,2,3>
  void DecodeMOVHLPSMask(unsigned NElts, SmallVectorImpl<int> &ShuffleMask) {
    for (unsigned i = NElts / 2; i != NElts; ++i)
      ShuffleMask.push_back(NElts + i);
  
    for (unsigned i = NElts / 2; i != NElts; ++i)
      ShuffleMask.push_back(i);
  }
  
  // <0,2> or <0,1,4,5>
  void DecodeMOVLHPSMask(unsigned NElts, SmallVectorImpl<int> &ShuffleMask) {
    for (unsigned i = 0; i != NElts / 2; ++i)
      ShuffleMask.push_back(i);
  
    for (unsigned i = 0; i != NElts / 2; ++i)
      ShuffleMask.push_back(NElts + i);
  }
  
  void DecodeMOVSLDUPMask(unsigned NumElts, SmallVectorImpl<int> &ShuffleMask) {
    for (int i = 0, e = NumElts / 2; i < e; ++i) {
      ShuffleMask.push_back(2 * i);
      ShuffleMask.push_back(2 * i);
    }
  }
  
  void DecodeMOVSHDUPMask(unsigned NumElts, SmallVectorImpl<int> &ShuffleMask) {
    for (int i = 0, e = NumElts / 2; i < e; ++i) {
      ShuffleMask.push_back(2 * i + 1);
      ShuffleMask.push_back(2 * i + 1);
    }
  }
  
  void DecodeMOVDDUPMask(unsigned NumElts, SmallVectorImpl<int> &ShuffleMask) {
    const unsigned NumLaneElts = 2;
  
    for (unsigned l = 0; l < NumElts; l += NumLaneElts)
      for (unsigned i = 0; i < NumLaneElts; ++i)
        ShuffleMask.push_back(l);
  }
  
  void DecodePSLLDQMask(unsigned NumElts, unsigned Imm,
                        SmallVectorImpl<int> &ShuffleMask) {
    const unsigned NumLaneElts = 16;
  
    for (unsigned l = 0; l < NumElts; l += NumLaneElts)
      for (unsigned i = 0; i < NumLaneElts; ++i) {
        int M = SM_SentinelZero;
        if (i >= Imm) M = i - Imm + l;
        ShuffleMask.push_back(M);
      }
  }
  
  void DecodePSRLDQMask(unsigned NumElts, unsigned Imm,
                        SmallVectorImpl<int> &ShuffleMask) {
    const unsigned NumLaneElts = 16;
  
    for (unsigned l = 0; l < NumElts; l += NumLaneElts)
      for (unsigned i = 0; i < NumLaneElts; ++i) {
        unsigned Base = i + Imm;
        int M = Base + l;
        if (Base >= NumLaneElts) M = SM_SentinelZero;
        ShuffleMask.push_back(M);
      }
  }
  
  void DecodePALIGNRMask(unsigned NumElts, unsigned Imm,
                         SmallVectorImpl<int> &ShuffleMask) {
    const unsigned NumLaneElts = 16;
  
    for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
      for (unsigned i = 0; i != NumLaneElts; ++i) {
        unsigned Base = i + Imm;
        // if i+imm is out of this lane then we actually need the other source
        if (Base >= NumLaneElts) Base += NumElts - NumLaneElts;
        ShuffleMask.push_back(Base + l);
      }
    }
  }
  
  void DecodeVALIGNMask(unsigned NumElts, unsigned Imm,
                        SmallVectorImpl<int> &ShuffleMask) {
    // Not all bits of the immediate are used so mask it.
    assert(isPowerOf2_32(NumElts) && "NumElts should be power of 2");
    Imm = Imm & (NumElts - 1);
    for (unsigned i = 0; i != NumElts; ++i)
      ShuffleMask.push_back(i + Imm);
  }
  
  void DecodePSHUFMask(unsigned NumElts, unsigned ScalarBits, unsigned Imm,
                       SmallVectorImpl<int> &ShuffleMask) {
    unsigned Size = NumElts * ScalarBits;
    unsigned NumLanes = Size / 128;
    if (NumLanes == 0) NumLanes = 1;  // Handle MMX
    unsigned NumLaneElts = NumElts / NumLanes;
  
    uint32_t SplatImm = (Imm & 0xff) * 0x01010101;
    for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
      for (unsigned i = 0; i != NumLaneElts; ++i) {
        ShuffleMask.push_back(SplatImm % NumLaneElts + l);
        SplatImm /= NumLaneElts;
      }
    }
  }
  
  void DecodePSHUFHWMask(unsigned NumElts, unsigned Imm,
                         SmallVectorImpl<int> &ShuffleMask) {
    for (unsigned l = 0; l != NumElts; l += 8) {
      unsigned NewImm = Imm;
      for (unsigned i = 0, e = 4; i != e; ++i) {
        ShuffleMask.push_back(l + i);
      }
      for (unsigned i = 4, e = 8; i != e; ++i) {
        ShuffleMask.push_back(l + 4 + (NewImm & 3));
        NewImm >>= 2;
      }
    }
  }
  
  void DecodePSHUFLWMask(unsigned NumElts, unsigned Imm,
                         SmallVectorImpl<int> &ShuffleMask) {
    for (unsigned l = 0; l != NumElts; l += 8) {
      unsigned NewImm = Imm;
      for (unsigned i = 0, e = 4; i != e; ++i) {
        ShuffleMask.push_back(l + (NewImm & 3));
        NewImm >>= 2;
      }
      for (unsigned i = 4, e = 8; i != e; ++i) {
        ShuffleMask.push_back(l + i);
      }
    }
  }
  
  void DecodePSWAPMask(unsigned NumElts, SmallVectorImpl<int> &ShuffleMask) {
    unsigned NumHalfElts = NumElts / 2;
  
    for (unsigned l = 0; l != NumHalfElts; ++l)
      ShuffleMask.push_back(l + NumHalfElts);
    for (unsigned h = 0; h != NumHalfElts; ++h)
      ShuffleMask.push_back(h);
  }
  
  void DecodeSHUFPMask(unsigned NumElts, unsigned ScalarBits,
                       unsigned Imm, SmallVectorImpl<int> &ShuffleMask) {
    unsigned NumLaneElts = 128 / ScalarBits;
  
    unsigned NewImm = Imm;
    for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
      // each half of a lane comes from different source
      for (unsigned s = 0; s != NumElts * 2; s += NumElts) {
        for (unsigned i = 0; i != NumLaneElts / 2; ++i) {
          ShuffleMask.push_back(NewImm % NumLaneElts + s + l);
          NewImm /= NumLaneElts;
        }
      }
      if (NumLaneElts == 4) NewImm = Imm; // reload imm
    }
  }
  
  void DecodeUNPCKHMask(unsigned NumElts, unsigned ScalarBits,
                        SmallVectorImpl<int> &ShuffleMask) {
    // Handle 128 and 256-bit vector lengths. AVX defines UNPCK* to operate
    // independently on 128-bit lanes.
    unsigned NumLanes = (NumElts * ScalarBits) / 128;
    if (NumLanes == 0) NumLanes = 1;  // Handle MMX
    unsigned NumLaneElts = NumElts / NumLanes;
  
    for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
      for (unsigned i = l + NumLaneElts / 2, e = l + NumLaneElts; i != e; ++i) {
        ShuffleMask.push_back(i);           // Reads from dest/src1
        ShuffleMask.push_back(i + NumElts); // Reads from src/src2
      }
    }
  }
  
  void DecodeUNPCKLMask(unsigned NumElts, unsigned ScalarBits,
                        SmallVectorImpl<int> &ShuffleMask) {
    // Handle 128 and 256-bit vector lengths. AVX defines UNPCK* to operate
    // independently on 128-bit lanes.
    unsigned NumLanes = (NumElts * ScalarBits) / 128;
    if (NumLanes == 0 ) NumLanes = 1;  // Handle MMX
    unsigned NumLaneElts = NumElts / NumLanes;
  
    for (unsigned l = 0; l != NumElts; l += NumLaneElts) {
      for (unsigned i = l, e = l + NumLaneElts / 2; i != e; ++i) {
        ShuffleMask.push_back(i);           // Reads from dest/src1
        ShuffleMask.push_back(i + NumElts); // Reads from src/src2
      }
    }
  }
  
  void DecodeVectorBroadcast(unsigned NumElts,
                             SmallVectorImpl<int> &ShuffleMask) {
    ShuffleMask.append(NumElts, 0);
  }
  
  void DecodeSubVectorBroadcast(unsigned DstNumElts, unsigned SrcNumElts,
                                SmallVectorImpl<int> &ShuffleMask) {
    unsigned Scale = DstNumElts / SrcNumElts;
  
    for (unsigned i = 0; i != Scale; ++i)
      for (unsigned j = 0; j != SrcNumElts; ++j)
        ShuffleMask.push_back(j);
  }
  
  void decodeVSHUF64x2FamilyMask(unsigned NumElts, unsigned ScalarSize,
                                 unsigned Imm,
                                 SmallVectorImpl<int> &ShuffleMask) {
    unsigned NumElementsInLane = 128 / ScalarSize;
    unsigned NumLanes = NumElts / NumElementsInLane;
  
    for (unsigned l = 0; l != NumElts; l += NumElementsInLane) {
      unsigned Index = (Imm % NumLanes) * NumElementsInLane;
      Imm /= NumLanes; // Discard the bits we just used.
      // We actually need the other source.
      if (l >= (NumElts / 2))
        Index += NumElts;
      for (unsigned i = 0; i != NumElementsInLane; ++i)
        ShuffleMask.push_back(Index + i);
    }
  }
  
  void DecodeVPERM2X128Mask(unsigned NumElts, unsigned Imm,
                            SmallVectorImpl<int> &ShuffleMask) {
    unsigned HalfSize = NumElts / 2;
  
    for (unsigned l = 0; l != 2; ++l) {
      unsigned HalfMask = Imm >> (l * 4);
      unsigned HalfBegin = (HalfMask & 0x3) * HalfSize;
      for (unsigned i = HalfBegin, e = HalfBegin + HalfSize; i != e; ++i)
        ShuffleMask.push_back((HalfMask & 8) ? SM_SentinelZero : (int)i);
    }
  }
  
  void DecodePSHUFBMask(ArrayRef<uint64_t> RawMask, const APInt &UndefElts,
                        SmallVectorImpl<int> &ShuffleMask) {
    for (int i = 0, e = RawMask.size(); i < e; ++i) {
      uint64_t M = RawMask[i];
      if (UndefElts[i]) {
        ShuffleMask.push_back(SM_SentinelUndef);
        continue;
      }
      // For 256/512-bit vectors the base of the shuffle is the 128-bit
      // subvector we're inside.
      int Base = (i / 16) * 16;
      // If the high bit (7) of the byte is set, the element is zeroed.
      if (M & (1 << 7))
        ShuffleMask.push_back(SM_SentinelZero);
      else {
        // Only the least significant 4 bits of the byte are used.
        int Index = Base + (M & 0xf);
        ShuffleMask.push_back(Index);
      }
    }
  }
  
  void DecodeBLENDMask(unsigned NumElts, unsigned Imm,
                       SmallVectorImpl<int> &ShuffleMask) {
    for (unsigned i = 0; i < NumElts; ++i) {
      // If there are more than 8 elements in the vector, then any immediate blend
      // mask wraps around.
      unsigned Bit = i % 8;
      ShuffleMask.push_back(((Imm >> Bit) & 1) ? NumElts + i : i);
    }
  }
  
  void DecodeVPPERMMask(ArrayRef<uint64_t> RawMask, const APInt &UndefElts,
                        SmallVectorImpl<int> &ShuffleMask) {
    assert(RawMask.size() == 16 && "Illegal VPPERM shuffle mask size");
  
    // VPPERM Operation
    // Bits[4:0] - Byte Index (0 - 31)
    // Bits[7:5] - Permute Operation
    //
    // Permute Operation:
    // 0 - Source byte (no logical operation).
    // 1 - Invert source byte.
    // 2 - Bit reverse of source byte.
    // 3 - Bit reverse of inverted source byte.
    // 4 - 00h (zero - fill).
    // 5 - FFh (ones - fill).
    // 6 - Most significant bit of source byte replicated in all bit positions.
    // 7 - Invert most significant bit of source byte and replicate in all bit positions.
    for (int i = 0, e = RawMask.size(); i < e; ++i) {
      if (UndefElts[i]) {
        ShuffleMask.push_back(SM_SentinelUndef);
        continue;
      }
  
      uint64_t M = RawMask[i];
      uint64_t PermuteOp = (M >> 5) & 0x7;
      if (PermuteOp == 4) {
        ShuffleMask.push_back(SM_SentinelZero);
        continue;
      }
      if (PermuteOp != 0) {
        ShuffleMask.clear();
        return;
      }
  
      uint64_t Index = M & 0x1F;
      ShuffleMask.push_back((int)Index);
    }
  }
  
  void DecodeVPERMMask(unsigned NumElts, unsigned Imm,
                       SmallVectorImpl<int> &ShuffleMask) {
    for (unsigned l = 0; l != NumElts; l += 4)
      for (unsigned i = 0; i != 4; ++i)
        ShuffleMask.push_back(l + ((Imm >> (2 * i)) & 3));
  }
  
  void DecodeZeroExtendMask(unsigned SrcScalarBits, unsigned DstScalarBits,
                            unsigned NumDstElts, bool IsAnyExtend,
                            SmallVectorImpl<int> &ShuffleMask) {
    unsigned Scale = DstScalarBits / SrcScalarBits;
    assert(SrcScalarBits < DstScalarBits &&
           "Expected zero extension mask to increase scalar size");
  
    int Sentinel = IsAnyExtend ? SM_SentinelUndef : SM_SentinelZero;
    for (unsigned i = 0; i != NumDstElts; i++) {
      ShuffleMask.push_back(i);
      ShuffleMask.append(Scale - 1, Sentinel);
    }
  }
  
  void DecodeZeroMoveLowMask(unsigned NumElts,
                             SmallVectorImpl<int> &ShuffleMask) {
    ShuffleMask.push_back(0);
    ShuffleMask.append(NumElts - 1, SM_SentinelZero);
  }
  
  void DecodeScalarMoveMask(unsigned NumElts, bool IsLoad,
                            SmallVectorImpl<int> &ShuffleMask) {
    // First element comes from the first element of second source.
    // Remaining elements: Load zero extends / Move copies from first source.
    ShuffleMask.push_back(NumElts);
    for (unsigned i = 1; i < NumElts; i++)
      ShuffleMask.push_back(IsLoad ? static_cast<int>(SM_SentinelZero) : i);
  }
  
  void DecodeEXTRQIMask(unsigned NumElts, unsigned EltSize, int Len, int Idx,
                        SmallVectorImpl<int> &ShuffleMask) {
    unsigned HalfElts = NumElts / 2;
  
    // Only the bottom 6 bits are valid for each immediate.
    Len &= 0x3F;
    Idx &= 0x3F;
  
    // We can only decode this bit extraction instruction as a shuffle if both the
    // length and index work with whole elements.
    if (0 != (Len % EltSize) || 0 != (Idx % EltSize))
      return;
  
    // A length of zero is equivalent to a bit length of 64.
    if (Len == 0)
      Len = 64;
  
    // If the length + index exceeds the bottom 64 bits the result is undefined.
    if ((Len + Idx) > 64) {
      ShuffleMask.append(NumElts, SM_SentinelUndef);
      return;
    }
  
    // Convert index and index to work with elements.
    Len /= EltSize;
    Idx /= EltSize;
  
    // EXTRQ: Extract Len elements starting from Idx. Zero pad the remaining
    // elements of the lower 64-bits. The upper 64-bits are undefined.
    for (int i = 0; i != Len; ++i)
      ShuffleMask.push_back(i + Idx);
    for (int i = Len; i != (int)HalfElts; ++i)
      ShuffleMask.push_back(SM_SentinelZero);
    for (int i = HalfElts; i != (int)NumElts; ++i)
      ShuffleMask.push_back(SM_SentinelUndef);
  }
  
  void DecodeINSERTQIMask(unsigned NumElts, unsigned EltSize, int Len, int Idx,
                          SmallVectorImpl<int> &ShuffleMask) {
    unsigned HalfElts = NumElts / 2;
  
    // Only the bottom 6 bits are valid for each immediate.
    Len &= 0x3F;
    Idx &= 0x3F;
  
    // We can only decode this bit insertion instruction as a shuffle if both the
    // length and index work with whole elements.
    if (0 != (Len % EltSize) || 0 != (Idx % EltSize))
      return;
  
    // A length of zero is equivalent to a bit length of 64.
    if (Len == 0)
      Len = 64;
  
    // If the length + index exceeds the bottom 64 bits the result is undefined.
    if ((Len + Idx) > 64) {
      ShuffleMask.append(NumElts, SM_SentinelUndef);
      return;
    }
  
    // Convert index and index to work with elements.
    Len /= EltSize;
    Idx /= EltSize;
  
    // INSERTQ: Extract lowest Len elements from lower half of second source and
    // insert over first source starting at Idx element. The upper 64-bits are
    // undefined.
    for (int i = 0; i != Idx; ++i)
      ShuffleMask.push_back(i);
    for (int i = 0; i != Len; ++i)
      ShuffleMask.push_back(i + NumElts);
    for (int i = Idx + Len; i != (int)HalfElts; ++i)
      ShuffleMask.push_back(i);
    for (int i = HalfElts; i != (int)NumElts; ++i)
      ShuffleMask.push_back(SM_SentinelUndef);
  }
  
  void DecodeVPERMILPMask(unsigned NumElts, unsigned ScalarBits,
                          ArrayRef<uint64_t> RawMask, const APInt &UndefElts,
                          SmallVectorImpl<int> &ShuffleMask) {
    unsigned VecSize = NumElts * ScalarBits;
    unsigned NumLanes = VecSize / 128;
    unsigned NumEltsPerLane = NumElts / NumLanes;
    assert((VecSize == 128 || VecSize == 256 || VecSize == 512) &&
           "Unexpected vector size");
    assert((ScalarBits == 32 || ScalarBits == 64) && "Unexpected element size");
  
    for (unsigned i = 0, e = RawMask.size(); i < e; ++i) {
      if (UndefElts[i]) {
        ShuffleMask.push_back(SM_SentinelUndef);
        continue;
      }
      uint64_t M = RawMask[i];
      M = (ScalarBits == 64 ? ((M >> 1) & 0x1) : (M & 0x3));
      unsigned LaneOffset = i & ~(NumEltsPerLane - 1);
      ShuffleMask.push_back((int)(LaneOffset + M));
    }
  }
  
  void DecodeVPERMIL2PMask(unsigned NumElts, unsigned ScalarBits, unsigned M2Z,
                           ArrayRef<uint64_t> RawMask, const APInt &UndefElts,
                           SmallVectorImpl<int> &ShuffleMask) {
    unsigned VecSize = NumElts * ScalarBits;
    unsigned NumLanes = VecSize / 128;
    unsigned NumEltsPerLane = NumElts / NumLanes;
    assert((VecSize == 128 || VecSize == 256) && "Unexpected vector size");
    assert((ScalarBits == 32 || ScalarBits == 64) && "Unexpected element size");
    assert((NumElts == RawMask.size()) && "Unexpected mask size");
  
    for (unsigned i = 0, e = RawMask.size(); i < e; ++i) {
      if (UndefElts[i]) {
        ShuffleMask.push_back(SM_SentinelUndef);
        continue;
      }
  
      // VPERMIL2 Operation.
      // Bits[3] - Match Bit.
      // Bits[2:1] - (Per Lane) PD Shuffle Mask.
      // Bits[2:0] - (Per Lane) PS Shuffle Mask.
      uint64_t Selector = RawMask[i];
      unsigned MatchBit = (Selector >> 3) & 0x1;
  
      // M2Z[0:1]     MatchBit
      //   0Xb           X        Source selected by Selector index.
      //   10b           0        Source selected by Selector index.
      //   10b           1        Zero.
      //   11b           0        Zero.
      //   11b           1        Source selected by Selector index.
      if ((M2Z & 0x2) != 0 && MatchBit != (M2Z & 0x1)) {
        ShuffleMask.push_back(SM_SentinelZero);
        continue;
      }
  
      int Index = i & ~(NumEltsPerLane - 1);
      if (ScalarBits == 64)
        Index += (Selector >> 1) & 0x1;
      else
        Index += Selector & 0x3;
  
      int Src = (Selector >> 2) & 0x1;
      Index += Src * NumElts;
      ShuffleMask.push_back(Index);
    }
  }
  
  void DecodeVPERMVMask(ArrayRef<uint64_t> RawMask, const APInt &UndefElts,
                        SmallVectorImpl<int> &ShuffleMask) {
    uint64_t EltMaskSize = RawMask.size() - 1;
    for (int i = 0, e = RawMask.size(); i != e; ++i) {
      if (UndefElts[i]) {
        ShuffleMask.push_back(SM_SentinelUndef);
        continue;
      }
      uint64_t M = RawMask[i];
      M &= EltMaskSize;
      ShuffleMask.push_back((int)M);
    }
  }
  
  void DecodeVPERMV3Mask(ArrayRef<uint64_t> RawMask, const APInt &UndefElts,
                        SmallVectorImpl<int> &ShuffleMask) {
    uint64_t EltMaskSize = (RawMask.size() * 2) - 1;
    for (int i = 0, e = RawMask.size(); i != e; ++i) {
      if (UndefElts[i]) {
        ShuffleMask.push_back(SM_SentinelUndef);
        continue;
      }
      uint64_t M = RawMask[i];
      M &= EltMaskSize;
      ShuffleMask.push_back((int)M);
    }
  }
  
  } // namespace llvm
  