Builtins.h

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/*
 * Copyright 2016-present Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#if defined(_WIN32) && !defined(__clang__)
#include <assert.h>
#include <folly/Portability.h>
#include <intrin.h>
#include <stdint.h>

namespace folly {
namespace portability {
namespace detail {
void call_flush_instruction_cache_self_pid(void* begin, size_t size);
}
} // namespace portability
} // namespace folly

FOLLY_ALWAYS_INLINE void __builtin___clear_cache(char* begin, char* end) {
  if (folly::kIsArchAmd64) {
    // x86_64 doesn't require the instruction cache to be flushed after
    // modification.
  } else {
    // Default to flushing it for everything else, such as ARM.
    folly::portability::detail::call_flush_instruction_cache_self_pid(
        static_cast<void*>(begin), static_cast<size_t>(end - begin));
  }
}

FOLLY_ALWAYS_INLINE int __builtin_clz(unsigned int x) {
  unsigned long index;
  return int(_BitScanReverse(&index, (unsigned long)x) ? 31 - index : 32);
}

FOLLY_ALWAYS_INLINE int __builtin_clzl(unsigned long x) {
  return __builtin_clz((unsigned int)x);
}

FOLLY_ALWAYS_INLINE int __builtin_clzll(unsigned long long x) {
  unsigned long index;
  return int(_BitScanReverse64(&index, x) ? 63 - index : 64);
}

FOLLY_ALWAYS_INLINE int __builtin_ctz(unsigned int x) {
  unsigned long index;
  return int(_BitScanForward(&index, (unsigned long)x) ? index : 32);
}

FOLLY_ALWAYS_INLINE int __builtin_ctzl(unsigned long x) {
  return __builtin_ctz((unsigned int)x);
}

FOLLY_ALWAYS_INLINE int __builtin_ctzll(unsigned long long x) {
  unsigned long index;
  return int(_BitScanForward64(&index, x) ? index : 64);
}

FOLLY_ALWAYS_INLINE int __builtin_ffs(int x) {
  unsigned long index;
  return int(_BitScanForward(&index, (unsigned long)x) ? index + 1 : 0);
}

FOLLY_ALWAYS_INLINE int __builtin_ffsl(long x) {
  return __builtin_ffs(int(x));
}

FOLLY_ALWAYS_INLINE int __builtin_ffsll(long long x) {
  unsigned long index;
  return int(_BitScanForward64(&index, (unsigned long long)x) ? index + 1 : 0);
}

FOLLY_ALWAYS_INLINE int __builtin_popcount(unsigned int x) {
  return int(__popcnt(x));
}

FOLLY_ALWAYS_INLINE int __builtin_popcountl(unsigned long x) {
  static_assert(sizeof(x) == 4, "");
  return int(__popcnt(x));
}

FOLLY_ALWAYS_INLINE int __builtin_popcountll(unsigned long long x) {
  return int(__popcnt64(x));
}

FOLLY_ALWAYS_INLINE void* __builtin_return_address(unsigned int frame) {
  // I really hope frame is zero...
  (void)frame;
  assert(frame == 0);
  return _ReturnAddress();
}
#endif