src/third_party/v8/src/wasm/simd-shuffle.cc

// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/wasm/simd-shuffle.h"

#include "src/common/globals.h"

namespace v8 {
namespace internal {
namespace wasm {

void SimdShuffle::CanonicalizeShuffle(bool inputs_equal, uint8_t* shuffle,
                                      bool* needs_swap, bool* is_swizzle) {
  *needs_swap = false;
  // Inputs equal, then it's a swizzle.
  if (inputs_equal) {
    *is_swizzle = true;
  } else {
    // Inputs are distinct; check that both are required.
    bool src0_is_used = false;
    bool src1_is_used = false;
    for (int i = 0; i < kSimd128Size; ++i) {
      if (shuffle[i] < kSimd128Size) {
        src0_is_used = true;
      } else {
        src1_is_used = true;
      }
    }
    if (src0_is_used && !src1_is_used) {
      *is_swizzle = true;
    } else if (src1_is_used && !src0_is_used) {
      *needs_swap = true;
      *is_swizzle = true;
    } else {
      *is_swizzle = false;
      // Canonicalize general 2 input shuffles so that the first input lanes are
      // encountered first. This makes architectural shuffle pattern matching
      // easier, since we only need to consider 1 input ordering instead of 2.
      if (shuffle[0] >= kSimd128Size) {
        // The second operand is used first. Swap inputs and adjust the shuffle.
        *needs_swap = true;
        for (int i = 0; i < kSimd128Size; ++i) {
          shuffle[i] ^= kSimd128Size;
        }
      }
    }
  }
  if (*is_swizzle) {
    for (int i = 0; i < kSimd128Size; ++i) shuffle[i] &= kSimd128Size - 1;
  }
}

bool SimdShuffle::TryMatchIdentity(const uint8_t* shuffle) {
  for (int i = 0; i < kSimd128Size; ++i) {
    if (shuffle[i] != i) return false;
  }
  return true;
}

bool SimdShuffle::TryMatch32x4Shuffle(const uint8_t* shuffle,
                                      uint8_t* shuffle32x4) {
  for (int i = 0; i < 4; ++i) {
    if (shuffle[i * 4] % 4 != 0) return false;
    for (int j = 1; j < 4; ++j) {
      if (shuffle[i * 4 + j] - shuffle[i * 4 + j - 1] != 1) return false;
    }
    shuffle32x4[i] = shuffle[i * 4] / 4;
  }
  return true;
}

bool SimdShuffle::TryMatch16x8Shuffle(const uint8_t* shuffle,
                                      uint8_t* shuffle16x8) {
  for (int i = 0; i < 8; ++i) {
    if (shuffle[i * 2] % 2 != 0) return false;
    for (int j = 1; j < 2; ++j) {
      if (shuffle[i * 2 + j] - shuffle[i * 2 + j - 1] != 1) return false;
    }
    shuffle16x8[i] = shuffle[i * 2] / 2;
  }
  return true;
}

bool SimdShuffle::TryMatchConcat(const uint8_t* shuffle, uint8_t* offset) {
  // Don't match the identity shuffle (e.g. [0 1 2 ... 15]).
  uint8_t start = shuffle[0];
  if (start == 0) return false;
  DCHECK_GT(kSimd128Size, start);  // The shuffle should be canonicalized.
  // A concatenation is a series of consecutive indices, with at most one jump
  // in the middle from the last lane to the first.
  for (int i = 1; i < kSimd128Size; ++i) {
    if ((shuffle[i]) != ((shuffle[i - 1] + 1))) {
      if (shuffle[i - 1] != 15) return false;
      if (shuffle[i] % kSimd128Size != 0) return false;
    }
  }
  *offset = start;
  return true;
}

bool SimdShuffle::TryMatchBlend(const uint8_t* shuffle) {
  for (int i = 0; i < 16; ++i) {
    if ((shuffle[i] & 0xF) != i) return false;
  }
  return true;
}

uint8_t SimdShuffle::PackShuffle4(uint8_t* shuffle) {
  return (shuffle[0] & 3) | ((shuffle[1] & 3) << 2) | ((shuffle[2] & 3) << 4) |
         ((shuffle[3] & 3) << 6);
}

uint8_t SimdShuffle::PackBlend8(const uint8_t* shuffle16x8) {
  int8_t result = 0;
  for (int i = 0; i < 8; ++i) {
    result |= (shuffle16x8[i] >= 8 ? 1 : 0) << i;
  }
  return result;
}

uint8_t SimdShuffle::PackBlend4(const uint8_t* shuffle32x4) {
  int8_t result = 0;
  for (int i = 0; i < 4; ++i) {
    result |= (shuffle32x4[i] >= 4 ? 0x3 : 0) << (i * 2);
  }
  return result;
}

int32_t SimdShuffle::Pack4Lanes(const uint8_t* shuffle) {
  int32_t result = 0;
  for (int i = 3; i >= 0; --i) {
    result <<= 8;
    result |= shuffle[i];
  }
  return result;
}

void SimdShuffle::Pack16Lanes(uint32_t* dst, const uint8_t* shuffle) {
  for (int i = 0; i < 4; i++) {
    dst[i] = wasm::SimdShuffle::Pack4Lanes(shuffle + (i * 4));
  }
}

}  // namespace wasm
}  // namespace internal
}  // namespace v8