src/string/memory_utils/memmove_implementations.h

//===-- Memmove implementation ----------------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMMOVE_IMPLEMENTATIONS_H
#define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMMOVE_IMPLEMENTATIONS_H

#include "src/__support/common.h"
#include "src/string/memory_utils/op_aarch64.h"
#include "src/string/memory_utils/op_builtin.h"
#include "src/string/memory_utils/op_generic.h"
#include "src/string/memory_utils/op_x86.h"
#include <stddef.h> // size_t, ptrdiff_t

namespace __llvm_libc {

[[maybe_unused]] LIBC_INLINE void
inline_memmove_embedded_tiny(Ptr dst, CPtr src, size_t count) {
  if ((count == 0) || (dst == src))
    return;
  if (dst < src) {
    LLVM_LIBC_LOOP_NOUNROLL
    for (size_t offset = 0; offset < count; ++offset)
      builtin::Memcpy<1>::block(dst + offset, src + offset);
  } else {
    LLVM_LIBC_LOOP_NOUNROLL
    for (ptrdiff_t offset = count - 1; offset >= 0; --offset)
      builtin::Memcpy<1>::block(dst + offset, src + offset);
  }
}

template <size_t MaxSize>
[[maybe_unused]] LIBC_INLINE void inline_memmove_generic(Ptr dst, CPtr src,
                                                         size_t count) {
  if (count == 0)
    return;
  if (count == 1)
    return generic::Memmove<1, MaxSize>::block(dst, src);
  if (count <= 4)
    return generic::Memmove<2, MaxSize>::head_tail(dst, src, count);
  if (count <= 8)
    return generic::Memmove<4, MaxSize>::head_tail(dst, src, count);
  if (count <= 16)
    return generic::Memmove<8, MaxSize>::head_tail(dst, src, count);
  if (count <= 32)
    return generic::Memmove<16, MaxSize>::head_tail(dst, src, count);
  if (count <= 64)
    return generic::Memmove<32, MaxSize>::head_tail(dst, src, count);
  if (count <= 128)
    return generic::Memmove<64, MaxSize>::head_tail(dst, src, count);
  if (dst < src) {
    generic::Memmove<32, MaxSize>::template align_forward<Arg::Src>(dst, src,
                                                                    count);
    return generic::Memmove<64, MaxSize>::loop_and_tail_forward(dst, src,
                                                                count);
  } else {
    generic::Memmove<32, MaxSize>::template align_backward<Arg::Src>(dst, src,
                                                                     count);
    return generic::Memmove<64, MaxSize>::loop_and_tail_backward(dst, src,
                                                                 count);
  }
}

LIBC_INLINE void inline_memmove(Ptr dst, CPtr src, size_t count) {
#if defined(LLVM_LIBC_ARCH_X86) || defined(LLVM_LIBC_ARCH_AARCH64)
#if defined(LLVM_LIBC_ARCH_X86)
  static constexpr size_t kMaxSize = x86::kAvx512F ? 64
                                     : x86::kAvx   ? 32
                                     : x86::kSse2  ? 16
                                                   : 8;
#elif defined(LLVM_LIBC_ARCH_AARCH64)
  static constexpr size_t kMaxSize = aarch64::kNeon ? 16 : 8;
#endif
  // return inline_memmove_generic<kMaxSize>(dst, src, count);
  if (count == 0)
    return;
  if (count == 1)
    return generic::Memmove<1, kMaxSize>::block(dst, src);
  if (count <= 4)
    return generic::Memmove<2, kMaxSize>::head_tail(dst, src, count);
  if (count <= 8)
    return generic::Memmove<4, kMaxSize>::head_tail(dst, src, count);
  if (count <= 16)
    return generic::Memmove<8, kMaxSize>::head_tail(dst, src, count);
  if (count <= 32)
    return generic::Memmove<16, kMaxSize>::head_tail(dst, src, count);
  if (count <= 64)
    return generic::Memmove<32, kMaxSize>::head_tail(dst, src, count);
  if (count <= 128)
    return generic::Memmove<64, kMaxSize>::head_tail(dst, src, count);
  if (dst < src) {
    generic::Memmove<32, kMaxSize>::align_forward<Arg::Src>(dst, src, count);
    return generic::Memmove<64, kMaxSize>::loop_and_tail_forward(dst, src,
                                                                 count);
  } else {
    generic::Memmove<32, kMaxSize>::align_backward<Arg::Src>(dst, src, count);
    return generic::Memmove<64, kMaxSize>::loop_and_tail_backward(dst, src,
                                                                  count);
  }
#elif defined(LLVM_LIBC_ARCH_ARM)
  return inline_memmove_embedded_tiny(dst, src, count);
#elif defined(LLVM_LIBC_ARCH_GPU)
  return inline_memmove_embedded_tiny(dst, src, count);
#else
#error "Unsupported platform"
#endif
}

LIBC_INLINE void inline_memmove(void *dst, const void *src, size_t count) {
  inline_memmove(reinterpret_cast<Ptr>(dst), reinterpret_cast<CPtr>(src),
                 count);
}

} // namespace __llvm_libc

#endif /* LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMMOVE_IMPLEMENTATIONS_H */