simd.h

#ifndef SIMDJSON_ARM64_SIMD_H
#define SIMDJSON_ARM64_SIMD_H
 
#ifndef SIMDJSON_CONDITIONAL_INCLUDE
#include "simdjson/arm64/base.h"
#include "simdjson/arm64/bitmanipulation.h"
#include "simdjson/internal/simdprune_tables.h"
#endif // SIMDJSON_CONDITIONAL_INCLUDE
 
namespace simdjson {
namespace arm64 {
namespace {
namespace simd {
 
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
namespace {
// Start of private section with Visual Studio workaround
 
 
simdjson_inline uint8x16_t make_uint8x16_t(uint8_t x1,  uint8_t x2,  uint8_t x3,  uint8_t x4,
                                         uint8_t x5,  uint8_t x6,  uint8_t x7,  uint8_t x8,
                                         uint8_t x9,  uint8_t x10, uint8_t x11, uint8_t x12,
                                         uint8_t x13, uint8_t x14, uint8_t x15, uint8_t x16) {
  // Doing a load like so end ups generating worse code.
  // uint8_t array[16] = {x1, x2, x3, x4, x5, x6, x7, x8,
  //                     x9, x10,x11,x12,x13,x14,x15,x16};
  // return vld1q_u8(array);
  uint8x16_t x{};
  // incredibly, Visual Studio does not allow x[0] = x1
  x = vsetq_lane_u8(x1, x, 0);
  x = vsetq_lane_u8(x2, x, 1);
  x = vsetq_lane_u8(x3, x, 2);
  x = vsetq_lane_u8(x4, x, 3);
  x = vsetq_lane_u8(x5, x, 4);
  x = vsetq_lane_u8(x6, x, 5);
  x = vsetq_lane_u8(x7, x, 6);
  x = vsetq_lane_u8(x8, x, 7);
  x = vsetq_lane_u8(x9, x, 8);
  x = vsetq_lane_u8(x10, x, 9);
  x = vsetq_lane_u8(x11, x, 10);
  x = vsetq_lane_u8(x12, x, 11);
  x = vsetq_lane_u8(x13, x, 12);
  x = vsetq_lane_u8(x14, x, 13);
  x = vsetq_lane_u8(x15, x, 14);
  x = vsetq_lane_u8(x16, x, 15);
  return x;
}
 
simdjson_inline uint8x8_t make_uint8x8_t(uint8_t x1,  uint8_t x2,  uint8_t x3,  uint8_t x4,
                                         uint8_t x5,  uint8_t x6,  uint8_t x7,  uint8_t x8) {
  uint8x8_t x{};
  x = vset_lane_u8(x1, x, 0);
  x = vset_lane_u8(x2, x, 1);
  x = vset_lane_u8(x3, x, 2);
  x = vset_lane_u8(x4, x, 3);
  x = vset_lane_u8(x5, x, 4);
  x = vset_lane_u8(x6, x, 5);
  x = vset_lane_u8(x7, x, 6);
  x = vset_lane_u8(x8, x, 7);
  return x;
}
 
// We have to do the same work for make_int8x16_t
simdjson_inline int8x16_t make_int8x16_t(int8_t x1,  int8_t x2,  int8_t x3,  int8_t x4,
                                       int8_t x5,  int8_t x6,  int8_t x7,  int8_t x8,
                                       int8_t x9,  int8_t x10, int8_t x11, int8_t x12,
                                       int8_t x13, int8_t x14, int8_t x15, int8_t x16) {
  // Doing a load like so end ups generating worse code.
  // int8_t array[16] = {x1, x2, x3, x4, x5, x6, x7, x8,
  //                     x9, x10,x11,x12,x13,x14,x15,x16};
  // return vld1q_s8(array);
  int8x16_t x{};
  // incredibly, Visual Studio does not allow x[0] = x1
  x = vsetq_lane_s8(x1, x, 0);
  x = vsetq_lane_s8(x2, x, 1);
  x = vsetq_lane_s8(x3, x, 2);
  x = vsetq_lane_s8(x4, x, 3);
  x = vsetq_lane_s8(x5, x, 4);
  x = vsetq_lane_s8(x6, x, 5);
  x = vsetq_lane_s8(x7, x, 6);
  x = vsetq_lane_s8(x8, x, 7);
  x = vsetq_lane_s8(x9, x, 8);
  x = vsetq_lane_s8(x10, x, 9);
  x = vsetq_lane_s8(x11, x, 10);
  x = vsetq_lane_s8(x12, x, 11);
  x = vsetq_lane_s8(x13, x, 12);
  x = vsetq_lane_s8(x14, x, 13);
  x = vsetq_lane_s8(x15, x, 14);
  x = vsetq_lane_s8(x16, x, 15);
  return x;
}
 
// End of private section with Visual Studio workaround
} // namespace
#endif // SIMDJSON_REGULAR_VISUAL_STUDIO
 
 
  template<typename T>
  struct simd8;
 
  //
  // Base class of simd8<uint8_t> and simd8<bool>, both of which use uint8x16_t internally.
  //
  template<typename T, typename Mask=simd8<bool>>
  struct base_u8 {
    uint8x16_t value;
    static const int SIZE = sizeof(value);
 
    // Conversion from/to SIMD register
    simdjson_inline base_u8(const uint8x16_t _value) : value(_value) {}
    simdjson_inline operator const uint8x16_t&() const { return this->value; }
    simdjson_inline operator uint8x16_t&() { return this->value; }
 
    // Bit operations
    simdjson_inline simd8<T> operator|(const simd8<T> other) const { return vorrq_u8(*this, other); }
    simdjson_inline simd8<T> operator&(const simd8<T> other) const { return vandq_u8(*this, other); }
    simdjson_inline simd8<T> operator^(const simd8<T> other) const { return veorq_u8(*this, other); }
    simdjson_inline simd8<T> bit_andnot(const simd8<T> other) const { return vbicq_u8(*this, other); }
    simdjson_inline simd8<T> operator~() const { return *this ^ 0xFFu; }
    simdjson_inline simd8<T>& operator|=(const simd8<T> other) { auto this_cast = static_cast<simd8<T>*>(this); *this_cast = *this_cast | other; return *this_cast; }
    simdjson_inline simd8<T>& operator&=(const simd8<T> other) { auto this_cast = static_cast<simd8<T>*>(this); *this_cast = *this_cast & other; return *this_cast; }
    simdjson_inline simd8<T>& operator^=(const simd8<T> other) { auto this_cast = static_cast<simd8<T>*>(this); *this_cast = *this_cast ^ other; return *this_cast; }
 
    friend simdjson_inline Mask operator==(const simd8<T> lhs, const simd8<T> rhs) { return vceqq_u8(lhs, rhs); }
 
    template<int N=1>
    simdjson_inline simd8<T> prev(const simd8<T> prev_chunk) const {
      return vextq_u8(prev_chunk, *this, 16 - N);
    }
  };
 
  // SIMD byte mask type (returned by things like eq and gt)
  template<>
  struct simd8<bool>: base_u8<bool> {
    typedef uint16_t bitmask_t;
    typedef uint32_t bitmask2_t;
 
    static simdjson_inline simd8<bool> splat(bool _value) { return vmovq_n_u8(uint8_t(-(!!_value))); }
 
    simdjson_inline simd8(const uint8x16_t _value) : base_u8<bool>(_value) {}
    // False constructor
    simdjson_inline simd8() : simd8(vdupq_n_u8(0)) {}
    // Splat constructor
    simdjson_inline simd8(bool _value) : simd8(splat(_value)) {}
 
    // We return uint32_t instead of uint16_t because that seems to be more efficient for most
    // purposes (cutting it down to uint16_t costs performance in some compilers).
    simdjson_inline uint32_t to_bitmask() const {
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
      const uint8x16_t bit_mask =  make_uint8x16_t(0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80,
                                                   0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80);
#else
      const uint8x16_t bit_mask =  {0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80,
                                    0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80};
#endif
      auto minput = *this & bit_mask;
      uint8x16_t tmp = vpaddq_u8(minput, minput);
      tmp = vpaddq_u8(tmp, tmp);
      tmp = vpaddq_u8(tmp, tmp);
      return vgetq_lane_u16(vreinterpretq_u16_u8(tmp), 0);
    }
    simdjson_inline bool any() const { return vmaxvq_u8(*this) != 0; }
  };
 
  // Unsigned bytes
  template<>
  struct simd8<uint8_t>: base_u8<uint8_t> {
    static simdjson_inline uint8x16_t splat(uint8_t _value) { return vmovq_n_u8(_value); }
    static simdjson_inline uint8x16_t zero() { return vdupq_n_u8(0); }
    static simdjson_inline uint8x16_t load(const uint8_t* values) { return vld1q_u8(values); }
 
    simdjson_inline simd8(const uint8x16_t _value) : base_u8<uint8_t>(_value) {}
    // Zero constructor
    simdjson_inline simd8() : simd8(zero()) {}
    // Array constructor
    simdjson_inline simd8(const uint8_t values[16]) : simd8(load(values)) {}
    // Splat constructor
    simdjson_inline simd8(uint8_t _value) : simd8(splat(_value)) {}
    // Member-by-member initialization
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
    simdjson_inline simd8(
      uint8_t v0,  uint8_t v1,  uint8_t v2,  uint8_t v3,  uint8_t v4,  uint8_t v5,  uint8_t v6,  uint8_t v7,
      uint8_t v8,  uint8_t v9,  uint8_t v10, uint8_t v11, uint8_t v12, uint8_t v13, uint8_t v14, uint8_t v15
    ) : simd8(make_uint8x16_t(
      v0, v1, v2, v3, v4, v5, v6, v7,
      v8, v9, v10,v11,v12,v13,v14,v15
    )) {}
#else
    simdjson_inline simd8(
      uint8_t v0,  uint8_t v1,  uint8_t v2,  uint8_t v3,  uint8_t v4,  uint8_t v5,  uint8_t v6,  uint8_t v7,
      uint8_t v8,  uint8_t v9,  uint8_t v10, uint8_t v11, uint8_t v12, uint8_t v13, uint8_t v14, uint8_t v15
    ) : simd8(uint8x16_t{
      v0, v1, v2, v3, v4, v5, v6, v7,
      v8, v9, v10,v11,v12,v13,v14,v15
    }) {}
#endif
 
    // Repeat 16 values as many times as necessary (usually for lookup tables)
    simdjson_inline static simd8<uint8_t> repeat_16(
      uint8_t v0,  uint8_t v1,  uint8_t v2,  uint8_t v3,  uint8_t v4,  uint8_t v5,  uint8_t v6,  uint8_t v7,
      uint8_t v8,  uint8_t v9,  uint8_t v10, uint8_t v11, uint8_t v12, uint8_t v13, uint8_t v14, uint8_t v15
    ) {
      return simd8<uint8_t>(
        v0, v1, v2, v3, v4, v5, v6, v7,
        v8, v9, v10,v11,v12,v13,v14,v15
      );
    }
 
    // Store to array
    simdjson_inline void store(uint8_t dst[16]) const { return vst1q_u8(dst, *this); }
 
    // Saturated math
    simdjson_inline simd8<uint8_t> saturating_add(const simd8<uint8_t> other) const { return vqaddq_u8(*this, other); }
    simdjson_inline simd8<uint8_t> saturating_sub(const simd8<uint8_t> other) const { return vqsubq_u8(*this, other); }
 
    // Addition/subtraction are the same for signed and unsigned
    simdjson_inline simd8<uint8_t> operator+(const simd8<uint8_t> other) const { return vaddq_u8(*this, other); }
    simdjson_inline simd8<uint8_t> operator-(const simd8<uint8_t> other) const { return vsubq_u8(*this, other); }
    simdjson_inline simd8<uint8_t>& operator+=(const simd8<uint8_t> other) { *this = *this + other; return *this; }
    simdjson_inline simd8<uint8_t>& operator-=(const simd8<uint8_t> other) { *this = *this - other; return *this; }
 
    // Order-specific operations
    simdjson_inline uint8_t max_val() const { return vmaxvq_u8(*this); }
    simdjson_inline uint8_t min_val() const { return vminvq_u8(*this); }
    simdjson_inline simd8<uint8_t> max_val(const simd8<uint8_t> other) const { return vmaxq_u8(*this, other); }
    simdjson_inline simd8<uint8_t> min_val(const simd8<uint8_t> other) const { return vminq_u8(*this, other); }
    simdjson_inline simd8<bool> operator<=(const simd8<uint8_t> other) const { return vcleq_u8(*this, other); }
    simdjson_inline simd8<bool> operator>=(const simd8<uint8_t> other) const { return vcgeq_u8(*this, other); }
    simdjson_inline simd8<bool> operator<(const simd8<uint8_t> other) const { return vcltq_u8(*this, other); }
    simdjson_inline simd8<bool> operator>(const simd8<uint8_t> other) const { return vcgtq_u8(*this, other); }
    // Same as >, but instead of guaranteeing all 1's == true, false = 0 and true = nonzero. For ARM, returns all 1's.
    simdjson_inline simd8<uint8_t> gt_bits(const simd8<uint8_t> other) const { return simd8<uint8_t>(*this > other); }
    // Same as <, but instead of guaranteeing all 1's == true, false = 0 and true = nonzero. For ARM, returns all 1's.
    simdjson_inline simd8<uint8_t> lt_bits(const simd8<uint8_t> other) const { return simd8<uint8_t>(*this < other); }
 
    // Bit-specific operations
    simdjson_inline simd8<bool> any_bits_set(simd8<uint8_t> bits) const { return vtstq_u8(*this, bits); }
    simdjson_inline bool any_bits_set_anywhere() const { return this->max_val() != 0; }
    simdjson_inline bool any_bits_set_anywhere(simd8<uint8_t> bits) const { return (*this & bits).any_bits_set_anywhere(); }
    template<int N>
    simdjson_inline simd8<uint8_t> shr() const { return vshrq_n_u8(*this, N); }
    template<int N>
    simdjson_inline simd8<uint8_t> shl() const { return vshlq_n_u8(*this, N); }
 
    // Perform a lookup assuming the value is between 0 and 16 (undefined behavior for out of range values)
    template<typename L>
    simdjson_inline simd8<L> lookup_16(simd8<L> lookup_table) const {
      return lookup_table.apply_lookup_16_to(*this);
    }
 
 
    // Copies to 'output" all bytes corresponding to a 0 in the mask (interpreted as a bitset).
    // Passing a 0 value for mask would be equivalent to writing out every byte to output.
    // Only the first 16 - count_ones(mask) bytes of the result are significant but 16 bytes
    // get written.
    // Design consideration: it seems like a function with the
    // signature simd8<L> compress(uint16_t mask) would be
    // sensible, but the AVX ISA makes this kind of approach difficult.
    template<typename L>
    simdjson_inline void compress(uint16_t mask, L * output) const {
      using internal::thintable_epi8;
      using internal::BitsSetTable256mul2;
      using internal::pshufb_combine_table;
      // this particular implementation was inspired by work done by @animetosho
      // we do it in two steps, first 8 bytes and then second 8 bytes
      uint8_t mask1 = uint8_t(mask); // least significant 8 bits
      uint8_t mask2 = uint8_t(mask >> 8); // most significant 8 bits
      // next line just loads the 64-bit values thintable_epi8[mask1] and
      // thintable_epi8[mask2] into a 128-bit register, using only
      // two instructions on most compilers.
      uint64x2_t shufmask64 = {thintable_epi8[mask1], thintable_epi8[mask2]};
      uint8x16_t shufmask = vreinterpretq_u8_u64(shufmask64);
      // we increment by 0x08 the second half of the mask
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
      uint8x16_t inc = make_uint8x16_t(0, 0, 0, 0, 0, 0, 0, 0, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08);
#else
      uint8x16_t inc = {0, 0, 0, 0, 0, 0, 0, 0, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08};
#endif
      shufmask = vaddq_u8(shufmask, inc);
      // this is the version "nearly pruned"
      uint8x16_t pruned = vqtbl1q_u8(*this, shufmask);
      // we still need to put the two halves together.
      // we compute the popcount of the first half:
      int pop1 = BitsSetTable256mul2[mask1];
      // then load the corresponding mask, what it does is to write
      // only the first pop1 bytes from the first 8 bytes, and then
      // it fills in with the bytes from the second 8 bytes + some filling
      // at the end.
      uint8x16_t compactmask = vld1q_u8(reinterpret_cast<const uint8_t *>(pshufb_combine_table + pop1 * 8));
      uint8x16_t answer = vqtbl1q_u8(pruned, compactmask);
      vst1q_u8(reinterpret_cast<uint8_t*>(output), answer);
    }
 
    // Copies all bytes corresponding to a 0 in the low half of the mask (interpreted as a
    // bitset) to output1, then those corresponding to a 0 in the high half to output2.
    template<typename L>
    simdjson_inline void compress_halves(uint16_t mask, L *output1, L *output2) const {
      using internal::thintable_epi8;
      uint8_t mask1 = uint8_t(mask); // least significant 8 bits
      uint8_t mask2 = uint8_t(mask >> 8); // most significant 8 bits
      uint8x8_t compactmask1 = vcreate_u8(thintable_epi8[mask1]);
      uint8x8_t compactmask2 = vcreate_u8(thintable_epi8[mask2]);
      // we increment by 0x08 the second half of the mask
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
      uint8x8_t inc = make_uint8x8_t(0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08);
#else
      uint8x8_t inc = {0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08};
#endif
      compactmask2 = vadd_u8(compactmask2, inc);
      // store each result (with the second store possibly overlapping the first)
      vst1_u8((uint8_t*)output1, vqtbl1_u8(*this, compactmask1));
      vst1_u8((uint8_t*)output2, vqtbl1_u8(*this, compactmask2));
    }
 
    template<typename L>
    simdjson_inline simd8<L> lookup_16(
        L replace0,  L replace1,  L replace2,  L replace3,
        L replace4,  L replace5,  L replace6,  L replace7,
        L replace8,  L replace9,  L replace10, L replace11,
        L replace12, L replace13, L replace14, L replace15) const {
      return lookup_16(simd8<L>::repeat_16(
        replace0,  replace1,  replace2,  replace3,
        replace4,  replace5,  replace6,  replace7,
        replace8,  replace9,  replace10, replace11,
        replace12, replace13, replace14, replace15
      ));
    }
 
    template<typename T>
    simdjson_inline simd8<uint8_t> apply_lookup_16_to(const simd8<T> original) {
      return vqtbl1q_u8(*this, simd8<uint8_t>(original));
    }
  };
 
  // Signed bytes
  template<>
  struct simd8<int8_t> {
    int8x16_t value;
 
    static simdjson_inline simd8<int8_t> splat(int8_t _value) { return vmovq_n_s8(_value); }
    static simdjson_inline simd8<int8_t> zero() { return vdupq_n_s8(0); }
    static simdjson_inline simd8<int8_t> load(const int8_t values[16]) { return vld1q_s8(values); }
 
    // Conversion from/to SIMD register
    simdjson_inline simd8(const int8x16_t _value) : value{_value} {}
    simdjson_inline operator const int8x16_t&() const { return this->value; }
    simdjson_inline operator int8x16_t&() { return this->value; }
 
    // Zero constructor
    simdjson_inline simd8() : simd8(zero()) {}
    // Splat constructor
    simdjson_inline simd8(int8_t _value) : simd8(splat(_value)) {}
    // Array constructor
    simdjson_inline simd8(const int8_t* values) : simd8(load(values)) {}
    // Member-by-member initialization
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
    simdjson_inline simd8(
      int8_t v0,  int8_t v1,  int8_t v2,  int8_t v3, int8_t v4,  int8_t v5,  int8_t v6,  int8_t v7,
      int8_t v8,  int8_t v9,  int8_t v10, int8_t v11, int8_t v12, int8_t v13, int8_t v14, int8_t v15
    ) : simd8(make_int8x16_t(
      v0, v1, v2, v3, v4, v5, v6, v7,
      v8, v9, v10,v11,v12,v13,v14,v15
    )) {}
#else
    simdjson_inline simd8(
      int8_t v0,  int8_t v1,  int8_t v2,  int8_t v3, int8_t v4,  int8_t v5,  int8_t v6,  int8_t v7,
      int8_t v8,  int8_t v9,  int8_t v10, int8_t v11, int8_t v12, int8_t v13, int8_t v14, int8_t v15
    ) : simd8(int8x16_t{
      v0, v1, v2, v3, v4, v5, v6, v7,
      v8, v9, v10,v11,v12,v13,v14,v15
    }) {}
#endif
    // Repeat 16 values as many times as necessary (usually for lookup tables)
    simdjson_inline static simd8<int8_t> repeat_16(
      int8_t v0,  int8_t v1,  int8_t v2,  int8_t v3,  int8_t v4,  int8_t v5,  int8_t v6,  int8_t v7,
      int8_t v8,  int8_t v9,  int8_t v10, int8_t v11, int8_t v12, int8_t v13, int8_t v14, int8_t v15
    ) {
      return simd8<int8_t>(
        v0, v1, v2, v3, v4, v5, v6, v7,
        v8, v9, v10,v11,v12,v13,v14,v15
      );
    }
 
    // Store to array
    simdjson_inline void store(int8_t dst[16]) const { return vst1q_s8(dst, *this); }
 
    // Explicit conversion to/from unsigned
    //
    // Under Visual Studio/ARM64 uint8x16_t and int8x16_t are apparently the same type.
    // In theory, we could check this occurrence with std::same_as and std::enabled_if but it is C++14
    // and relatively ugly and hard to read.
#ifndef SIMDJSON_REGULAR_VISUAL_STUDIO
    simdjson_inline explicit simd8(const uint8x16_t other): simd8(vreinterpretq_s8_u8(other)) {}
#endif
    simdjson_inline explicit operator simd8<uint8_t>() const { return vreinterpretq_u8_s8(this->value); }
 
    // Math
    simdjson_inline simd8<int8_t> operator+(const simd8<int8_t> other) const { return vaddq_s8(*this, other); }
    simdjson_inline simd8<int8_t> operator-(const simd8<int8_t> other) const { return vsubq_s8(*this, other); }
    simdjson_inline simd8<int8_t>& operator+=(const simd8<int8_t> other) { *this = *this + other; return *this; }
    simdjson_inline simd8<int8_t>& operator-=(const simd8<int8_t> other) { *this = *this - other; return *this; }
 
    // Order-sensitive comparisons
    simdjson_inline simd8<int8_t> max_val(const simd8<int8_t> other) const { return vmaxq_s8(*this, other); }
    simdjson_inline simd8<int8_t> min_val(const simd8<int8_t> other) const { return vminq_s8(*this, other); }
    simdjson_inline simd8<bool> operator>(const simd8<int8_t> other) const { return vcgtq_s8(*this, other); }
    simdjson_inline simd8<bool> operator<(const simd8<int8_t> other) const { return vcltq_s8(*this, other); }
    simdjson_inline simd8<bool> operator==(const simd8<int8_t> other) const { return vceqq_s8(*this, other); }
 
    template<int N=1>
    simdjson_inline simd8<int8_t> prev(const simd8<int8_t> prev_chunk) const {
      return vextq_s8(prev_chunk, *this, 16 - N);
    }
 
    // Perform a lookup assuming no value is larger than 16
    template<typename L>
    simdjson_inline simd8<L> lookup_16(simd8<L> lookup_table) const {
      return lookup_table.apply_lookup_16_to(*this);
    }
    template<typename L>
    simdjson_inline simd8<L> lookup_16(
        L replace0,  L replace1,  L replace2,  L replace3,
        L replace4,  L replace5,  L replace6,  L replace7,
        L replace8,  L replace9,  L replace10, L replace11,
        L replace12, L replace13, L replace14, L replace15) const {
      return lookup_16(simd8<L>::repeat_16(
        replace0,  replace1,  replace2,  replace3,
        replace4,  replace5,  replace6,  replace7,
        replace8,  replace9,  replace10, replace11,
        replace12, replace13, replace14, replace15
      ));
    }
 
    template<typename T>
    simdjson_inline simd8<int8_t> apply_lookup_16_to(const simd8<T> original) {
      return vqtbl1q_s8(*this, simd8<uint8_t>(original));
    }
  };
 
  template<typename T>
  struct simd8x64 {
    static constexpr int NUM_CHUNKS = 64 / sizeof(simd8<T>);
    static_assert(NUM_CHUNKS == 4, "ARM kernel should use four registers per 64-byte block.");
    const simd8<T> chunks[NUM_CHUNKS];
 
    simd8x64(const simd8x64<T>& o) = delete; // no copy allowed
    simd8x64<T>& operator=(const simd8<T>& other) = delete; // no assignment allowed
    simd8x64() = delete; // no default constructor allowed
 
    simdjson_inline simd8x64(const simd8<T> chunk0, const simd8<T> chunk1, const simd8<T> chunk2, const simd8<T> chunk3) : chunks{chunk0, chunk1, chunk2, chunk3} {}
    simdjson_inline simd8x64(const T ptr[64]) : chunks{simd8<T>::load(ptr), simd8<T>::load(ptr+16), simd8<T>::load(ptr+32), simd8<T>::load(ptr+48)} {}
 
    simdjson_inline void store(T ptr[64]) const {
      this->chunks[0].store(ptr+sizeof(simd8<T>)*0);
      this->chunks[1].store(ptr+sizeof(simd8<T>)*1);
      this->chunks[2].store(ptr+sizeof(simd8<T>)*2);
      this->chunks[3].store(ptr+sizeof(simd8<T>)*3);
    }
 
    simdjson_inline simd8<T> reduce_or() const {
      return (this->chunks[0] | this->chunks[1]) | (this->chunks[2] | this->chunks[3]);
    }
 
 
    simdjson_inline uint64_t compress(uint64_t mask, T * output) const {
      uint64_t popcounts = vget_lane_u64(vreinterpret_u64_u8(vcnt_u8(vcreate_u8(~mask))), 0);
      // compute the prefix sum of the popcounts of each byte
      uint64_t offsets = popcounts * 0x0101010101010101;
      this->chunks[0].compress_halves(uint16_t(mask), output, &output[popcounts & 0xFF]);
      this->chunks[1].compress_halves(uint16_t(mask >> 16), &output[(offsets >> 8) & 0xFF], &output[(offsets >> 16) & 0xFF]);
      this->chunks[2].compress_halves(uint16_t(mask >> 32), &output[(offsets >> 24) & 0xFF], &output[(offsets >> 32) & 0xFF]);
      this->chunks[3].compress_halves(uint16_t(mask >> 48), &output[(offsets >> 40) & 0xFF], &output[(offsets >> 48) & 0xFF]);
      return offsets >> 56;
    }
 
    simdjson_inline uint64_t to_bitmask() const {
#ifdef SIMDJSON_REGULAR_VISUAL_STUDIO
      const uint8x16_t bit_mask = make_uint8x16_t(
        0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80,
        0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80
      );
#else
      const uint8x16_t bit_mask = {
        0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80,
        0x01, 0x02, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80
      };
#endif
      // Add each of the elements next to each other, successively, to stuff each 8 byte mask into one.
      uint8x16_t sum0 = vpaddq_u8(this->chunks[0] & bit_mask, this->chunks[1] & bit_mask);
      uint8x16_t sum1 = vpaddq_u8(this->chunks[2] & bit_mask, this->chunks[3] & bit_mask);
      sum0 = vpaddq_u8(sum0, sum1);
      sum0 = vpaddq_u8(sum0, sum0);
      return vgetq_lane_u64(vreinterpretq_u64_u8(sum0), 0);
    }
 
    simdjson_inline uint64_t eq(const T m) const {
      const simd8<T> mask = simd8<T>::splat(m);
      return  simd8x64<bool>(
        this->chunks[0] == mask,
        this->chunks[1] == mask,
        this->chunks[2] == mask,
        this->chunks[3] == mask
      ).to_bitmask();
    }
 
    simdjson_inline uint64_t lteq(const T m) const {
      const simd8<T> mask = simd8<T>::splat(m);
      return  simd8x64<bool>(
        this->chunks[0] <= mask,
        this->chunks[1] <= mask,
        this->chunks[2] <= mask,
        this->chunks[3] <= mask
      ).to_bitmask();
    }
  }; // struct simd8x64<T>
 
} // namespace simd
} // unnamed namespace
} // namespace arm64
} // namespace simdjson
 
#endif // SIMDJSON_ARM64_SIMD_H