wasm-external-refs.cc

// Copyright 2016 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 <math.h>
#include <stdint.h>
#include <stdlib.h>
#include <limits>

#include "include/v8config.h"

#include "src/base/bits.h"
#include "src/base/ieee754.h"
#include "src/memcopy.h"
#include "src/utils.h"
#include "src/v8memory.h"
#include "src/wasm/wasm-external-refs.h"

namespace v8 {
namespace internal {
namespace wasm {

void f32_trunc_wrapper(Address data) {
  WriteUnalignedValue<float>(data, truncf(ReadUnalignedValue<float>(data)));
}

void f32_floor_wrapper(Address data) {
  WriteUnalignedValue<float>(data, floorf(ReadUnalignedValue<float>(data)));
}

void f32_ceil_wrapper(Address data) {
  WriteUnalignedValue<float>(data, ceilf(ReadUnalignedValue<float>(data)));
}

void f32_nearest_int_wrapper(Address data) {
  WriteUnalignedValue<float>(data, nearbyintf(ReadUnalignedValue<float>(data)));
}

void f64_trunc_wrapper(Address data) {
  WriteUnalignedValue<double>(data, trunc(ReadUnalignedValue<double>(data)));
}

void f64_floor_wrapper(Address data) {
  WriteUnalignedValue<double>(data, floor(ReadUnalignedValue<double>(data)));
}

void f64_ceil_wrapper(Address data) {
  WriteUnalignedValue<double>(data, ceil(ReadUnalignedValue<double>(data)));
}

void f64_nearest_int_wrapper(Address data) {
  WriteUnalignedValue<double>(data,
                              nearbyint(ReadUnalignedValue<double>(data)));
}

void int64_to_float32_wrapper(Address data) {
  int64_t input = ReadUnalignedValue<int64_t>(data);
  WriteUnalignedValue<float>(data, static_cast<float>(input));
}

void uint64_to_float32_wrapper(Address data) {
  uint64_t input = ReadUnalignedValue<uint64_t>(data);
  float result = static_cast<float>(input);

#if V8_CC_MSVC
  // With MSVC we use static_cast<float>(uint32_t) instead of
  // static_cast<float>(uint64_t) to achieve round-to-nearest-ties-even
  // semantics. The idea is to calculate
  // static_cast<float>(high_word) * 2^32 + static_cast<float>(low_word). To
  // achieve proper rounding in all cases we have to adjust the high_word
  // with a "rounding bit" sometimes. The rounding bit is stored in the LSB of
  // the high_word if the low_word may affect the rounding of the high_word.
  uint32_t low_word = static_cast<uint32_t>(input & 0xFFFFFFFF);
  uint32_t high_word = static_cast<uint32_t>(input >> 32);

  float shift = static_cast<float>(1ull << 32);
  // If the MSB of the high_word is set, then we make space for a rounding bit.
  if (high_word < 0x80000000) {
    high_word <<= 1;
    shift = static_cast<float>(1ull << 31);
  }

  if ((high_word & 0xFE000000) && low_word) {
    // Set the rounding bit.
    high_word |= 1;
  }

  result = static_cast<float>(high_word);
  result *= shift;
  result += static_cast<float>(low_word);
#endif

  WriteUnalignedValue<float>(data, result);
}

void int64_to_float64_wrapper(Address data) {
  int64_t input = ReadUnalignedValue<int64_t>(data);
  WriteUnalignedValue<double>(data, static_cast<double>(input));
}

void uint64_to_float64_wrapper(Address data) {
  uint64_t input = ReadUnalignedValue<uint64_t>(data);
  double result = static_cast<double>(input);

#if V8_CC_MSVC
  // With MSVC we use static_cast<double>(uint32_t) instead of
  // static_cast<double>(uint64_t) to achieve round-to-nearest-ties-even
  // semantics. The idea is to calculate
  // static_cast<double>(high_word) * 2^32 + static_cast<double>(low_word).
  uint32_t low_word = static_cast<uint32_t>(input & 0xFFFFFFFF);
  uint32_t high_word = static_cast<uint32_t>(input >> 32);

  double shift = static_cast<double>(1ull << 32);

  result = static_cast<double>(high_word);
  result *= shift;
  result += static_cast<double>(low_word);
#endif

  WriteUnalignedValue<double>(data, result);
}

int32_t float32_to_int64_wrapper(Address data) {
  // We use "<" here to check the upper bound because of rounding problems: With
  // "<=" some inputs would be considered within int64 range which are actually
  // not within int64 range.
  float input = ReadUnalignedValue<float>(data);
  if (input >= static_cast<float>(std::numeric_limits<int64_t>::min()) &&
      input < static_cast<float>(std::numeric_limits<int64_t>::max())) {
    WriteUnalignedValue<int64_t>(data, static_cast<int64_t>(input));
    return 1;
  }
  return 0;
}

int32_t float32_to_uint64_wrapper(Address data) {
  float input = ReadUnalignedValue<float>(data);
  // We use "<" here to check the upper bound because of rounding problems: With
  // "<=" some inputs would be considered within uint64 range which are actually
  // not within uint64 range.
  if (input > -1.0 &&
      input < static_cast<float>(std::numeric_limits<uint64_t>::max())) {
    WriteUnalignedValue<uint64_t>(data, static_cast<uint64_t>(input));
    return 1;
  }
  return 0;
}

int32_t float64_to_int64_wrapper(Address data) {
  // We use "<" here to check the upper bound because of rounding problems: With
  // "<=" some inputs would be considered within int64 range which are actually
  // not within int64 range.
  double input = ReadUnalignedValue<double>(data);
  if (input >= static_cast<double>(std::numeric_limits<int64_t>::min()) &&
      input < static_cast<double>(std::numeric_limits<int64_t>::max())) {
    WriteUnalignedValue<int64_t>(data, static_cast<int64_t>(input));
    return 1;
  }
  return 0;
}

int32_t float64_to_uint64_wrapper(Address data) {
  // We use "<" here to check the upper bound because of rounding problems: With
  // "<=" some inputs would be considered within uint64 range which are actually
  // not within uint64 range.
  double input = ReadUnalignedValue<double>(data);
  if (input > -1.0 &&
      input < static_cast<double>(std::numeric_limits<uint64_t>::max())) {
    WriteUnalignedValue<uint64_t>(data, static_cast<uint64_t>(input));
    return 1;
  }
  return 0;
}

int32_t int64_div_wrapper(Address data) {
  int64_t dividend = ReadUnalignedValue<int64_t>(data);
  int64_t divisor = ReadUnalignedValue<int64_t>(data + sizeof(dividend));
  if (divisor == 0) {
    return 0;
  }
  if (divisor == -1 && dividend == std::numeric_limits<int64_t>::min()) {
    return -1;
  }
  WriteUnalignedValue<int64_t>(data, dividend / divisor);
  return 1;
}

int32_t int64_mod_wrapper(Address data) {
  int64_t dividend = ReadUnalignedValue<int64_t>(data);
  int64_t divisor = ReadUnalignedValue<int64_t>(data + sizeof(dividend));
  if (divisor == 0) {
    return 0;
  }
  WriteUnalignedValue<int64_t>(data, dividend % divisor);
  return 1;
}

int32_t uint64_div_wrapper(Address data) {
  uint64_t dividend = ReadUnalignedValue<uint64_t>(data);
  uint64_t divisor = ReadUnalignedValue<uint64_t>(data + sizeof(dividend));
  if (divisor == 0) {
    return 0;
  }
  WriteUnalignedValue<uint64_t>(data, dividend / divisor);
  return 1;
}

int32_t uint64_mod_wrapper(Address data) {
  uint64_t dividend = ReadUnalignedValue<uint64_t>(data);
  uint64_t divisor = ReadUnalignedValue<uint64_t>(data + sizeof(dividend));
  if (divisor == 0) {
    return 0;
  }
  WriteUnalignedValue<uint64_t>(data, dividend % divisor);
  return 1;
}

uint32_t word32_ctz_wrapper(Address data) {
  return base::bits::CountTrailingZeros(ReadUnalignedValue<uint32_t>(data));
}

uint32_t word64_ctz_wrapper(Address data) {
  return base::bits::CountTrailingZeros(ReadUnalignedValue<uint64_t>(data));
}

uint32_t word32_popcnt_wrapper(Address data) {
  return base::bits::CountPopulation(ReadUnalignedValue<uint32_t>(data));
}

uint32_t word64_popcnt_wrapper(Address data) {
  return base::bits::CountPopulation(ReadUnalignedValue<uint64_t>(data));
}

uint32_t word32_rol_wrapper(Address data) {
  uint32_t input = ReadUnalignedValue<uint32_t>(data);
  uint32_t shift = ReadUnalignedValue<uint32_t>(data + sizeof(input)) & 31;
  return (input << shift) | (input >> ((32 - shift) & 31));
}

uint32_t word32_ror_wrapper(Address data) {
  uint32_t input = ReadUnalignedValue<uint32_t>(data);
  uint32_t shift = ReadUnalignedValue<uint32_t>(data + sizeof(input)) & 31;
  return (input >> shift) | (input << ((32 - shift) & 31));
}

void float64_pow_wrapper(Address data) {
  double x = ReadUnalignedValue<double>(data);
  double y = ReadUnalignedValue<double>(data + sizeof(x));
  WriteUnalignedValue<double>(data, base::ieee754::pow(x, y));
}

// Asan on Windows triggers exceptions in this function to allocate
// shadow memory lazily. When this function is called from WebAssembly,
// these exceptions would be handled by the trap handler before they get
// handled by Asan, and thereby confuse the thread-in-wasm flag.
// Therefore we disable ASAN for this function. Alternatively we could
// reset the thread-in-wasm flag before calling this function. However,
// as this is only a problem with Asan on Windows, we did not consider
// it worth the overhead.
DISABLE_ASAN void memory_copy_wrapper(Address dst, Address src, uint32_t size) {
  // Use explicit forward and backward copy to match the required semantics for
  // the memory.copy instruction. It is assumed that the caller of this
  // function has already performed bounds checks, so {src + size} and
  // {dst + size} should not overflow.
  DCHECK(src + size >= src && dst + size >= dst);
  uint8_t* dst8 = reinterpret_cast<uint8_t*>(dst);
  uint8_t* src8 = reinterpret_cast<uint8_t*>(src);
  if (src < dst && src + size > dst && dst + size > src) {
    dst8 += size - 1;
    src8 += size - 1;
    for (; size > 0; size--) {
      *dst8-- = *src8--;
    }
  } else {
    for (; size > 0; size--) {
      *dst8++ = *src8++;
    }
  }
}

// Asan on Windows triggers exceptions in this function that confuse the
// WebAssembly trap handler, so Asan is disabled. See the comment on
// memory_copy_wrapper above for more info.
DISABLE_ASAN void memory_fill_wrapper(Address dst, uint32_t value,
                                      uint32_t size) {
  // Use an explicit forward copy to match the required semantics for the
  // memory.fill instruction. It is assumed that the caller of this function
  // has already performed bounds checks, so {dst + size} should not overflow.
  DCHECK(dst + size >= dst);
  uint8_t* dst8 = reinterpret_cast<uint8_t*>(dst);
  uint8_t value8 = static_cast<uint8_t>(value);
  for (; size > 0; size--) {
    *dst8++ = value8;
  }
}

static WasmTrapCallbackForTesting wasm_trap_callback_for_testing = nullptr;

void set_trap_callback_for_testing(WasmTrapCallbackForTesting callback) {
  wasm_trap_callback_for_testing = callback;
}

void call_trap_callback_for_testing() {
  if (wasm_trap_callback_for_testing) {
    wasm_trap_callback_for_testing();
  }
}

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