[libc] Non-temporal memory function support

[gchatelet]

Summary

Enhanced version of the framework to support non-temporal loads and stores.

[gchatelet]

• Fix documentation for address.h

[tschuett]

libc/src/string/memory_utils/address.h

33 ↗

(On Diff #430011)

Is enum class or prefix cuter?

[gchatelet]

• Use enum class for Temporal and Aligned attributes

[gchatelet]

libc/src/string/memory_utils/address.h

33 ↗

(On Diff #430011)

Done, thx for the suggestion.

[gchatelet]

• rebase

[gchatelet]

• rebase and squash

[gchatelet]

• fix type mismatch for inline_memset

[gchatelet]

• Add more alignement tests

[gchatelet]

• Factor some code in address

[gchatelet]

• Use a more principled approach to common alignment

[gchatelet]

• Simplify gcd in address

[gchatelet]

• Update patch after submission of D125966

[gchatelet]

• Rename ScalarBackend

[gchatelet]

rebase and address comments

[gchatelet]

rebase

[gchatelet]

rebase

[gchatelet]

rebase

[gchatelet]

remove unrelated change

[gchatelet]

rebase

[gchatelet]

rebase

[gchatelet]

This work was based on llvm libc framework v2 that was too complicated.

libc/src/__support/common.h

 #endif
 #ifndef unlikely
 #define unlikely(x) __builtin_expect(x, 0)
 #endif
 #ifndef UNUSED
 #define UNUSED __attribute__((unused))
 #endif
 
+#ifdef __has_attribute
+#define LIBC_HAVE_ATTRIBUTE(x) __has_attribute(x)
+#else
+#define LIBC_HAVE_ATTRIBUTE(x) 0
+#endif
+
+#if LIBC_HAVE_ATTRIBUTE(aligned) || (defined(__GNUC__) && !defined(__clang__))
+#define LIBC_ATTRIBUTE_FUNC_ALIGN(bytes) __attribute__((aligned(bytes)))
+#else
+#define LIBC_ATTRIBUTE_FUNC_ALIGN(bytes)
+#endif
+
 #ifndef LLVM_LIBC_FUNCTION_ATTR
 #define LLVM_LIBC_FUNCTION_ATTR
 #endif
 
 // MacOS needs to be excluded because it does not support aliasing.
 #if defined(LLVM_LIBC_PUBLIC_PACKAGING) && (!defined(__APPLE__))
 #define LLVM_LIBC_FUNCTION(type, name, arglist)                                \
   LLVM_LIBC_FUNCTION_ATTR decltype(__llvm_libc::name)                          \

libc/src/stdio/printf_core/parser.h

#ifndef LLVM_LIBC_PRINTF_DISABLE_INDEX_MODE
   // TODO: Look into object stores for optimization.
 
 #endif // LLVM_LIBC_PRINTF_DISABLE_INDEX_MODE
 
 public:
 #ifndef LLVM_LIBC_PRINTF_DISABLE_INDEX_MODE
   Parser(const char *__restrict new_str, internal::ArgList &args)
       : str(new_str), args_cur(args), args_start(args) {
-    inline_memset(reinterpret_cast<char *>(desc_arr), 0,
-                  DESC_ARR_LEN * sizeof(TypeDesc));
+    inline_memset(desc_arr, ubyte::ZERO, sizeof(desc_arr));
   }
 #else
   Parser(const char *__restrict new_str, internal::ArgList &args)
       : str(new_str), args_cur(args) {}
 #endif // LLVM_LIBC_PRINTF_DISABLE_INDEX_MODE
 
   // get_next_section will parse the format string until it has a fully
   // specified format section. This can either be a raw format section with no

libc/src/stdio/printf_core/writer.cpp

int Writer::write(const char *new_string, size_t length) {
   chars_written += length;
   return raw_write(output, new_string, length);
 }
 
 int Writer::write_chars(char new_char, size_t length) {
   constexpr size_t BUFF_SIZE = 8;
   char buff[BUFF_SIZE];
   int result;
-  inline_memset(buff, new_char, BUFF_SIZE);
+  inline_memset(buff, static_cast<ubyte>(new_char), BUFF_SIZE);
   while (length > BUFF_SIZE) {
     result = write(buff, BUFF_SIZE);
     if (result < 0)
       return result;
     length -= BUFF_SIZE;
   }
   return write(buff, length);
 }
 
 } // namespace printf_core
 } // namespace __llvm_libc

libc/src/string/bcmp.cpp

 //===-- Implementation of bcmp --------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/bcmp.h"
+
 #include "src/__support/common.h"
 #include "src/string/memory_utils/bcmp_implementations.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, bcmp,
                    (const void *lhs, const void *rhs, size_t count)) {
-  return inline_bcmp(static_cast<const char *>(lhs),
-                     static_cast<const char *>(rhs), count);
+  return inline_bcmp(lhs, rhs, count);
 }
 
 } // namespace __llvm_libc

libc/src/string/bzero.cpp

 //===-- Implementation of bzero -------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/bzero.h"
+
 #include "src/__support/common.h"
 #include "src/string/memory_utils/memset_implementations.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(void, bzero, (void *ptr, size_t count)) {
-  inline_memset(reinterpret_cast<char *>(ptr), 0, count);
+  inline_memset(ptr, ubyte::ZERO, count);
 }
 
 } // namespace __llvm_libc

libc/src/string/memcmp.cpp

 //===-- Implementation of memcmp ------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/memcmp.h"
+
+#include "src/__support/common.h"
 #include "src/string/memory_utils/memcmp_implementations.h"
 
 #include <stddef.h> // size_t
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, memcmp,
                    (const void *lhs, const void *rhs, size_t count)) {
-  return inline_memcmp(static_cast<const char *>(lhs),
-                       static_cast<const char *>(rhs), count);
+  return inline_memcmp(lhs, rhs, count);
 }
 
 } // namespace __llvm_libc

libc/src/string/memcpy.cpp

 //===-- Implementation of memcpy ------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/memcpy.h"
+
 #include "src/__support/common.h"
 #include "src/string/memory_utils/memcpy_implementations.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(void *, memcpy,
                    (void *__restrict dst, const void *__restrict src,
                     size_t size)) {
-  inline_memcpy(reinterpret_cast<char *>(dst),
-                reinterpret_cast<const char *>(src), size);
+  inline_memcpy(dst, src, size);
   return dst;
 }
 
 } // namespace __llvm_libc

libc/src/string/memmove.cpp

 //===-- Implementation of memmove -----------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/memmove.h"
 
 #include "src/__support/common.h"
-#include "src/__support/integer_operations.h"
-#include "src/string/memory_utils/elements.h"
+#include "src/string/memory_utils/algorithm.h"
+#include "src/string/memory_utils/backends.h"
 #include <stddef.h> // size_t, ptrdiff_t
 
 namespace __llvm_libc {
 
-static inline void inline_memmove(char *dst, const char *src, size_t count) {
-  using namespace __llvm_libc::scalar;
+static inline void inline_memmove(DstAddr<1> dst, SrcAddr<1> src,
+                                  size_t count) {
+  using namespace scalar;
   if (count == 0)
     return;
   if (count == 1)
-    return move<_1>(dst, src);
+    return _1::move(dst, src);
   if (count <= 4)
-    return move<HeadTail<_2>>(dst, src, count);
+    return HeadTail<_2>::move(dst, src, count);
   if (count <= 8)
-    return move<HeadTail<_4>>(dst, src, count);
+    return HeadTail<_4>::move(dst, src, count);
   if (count <= 16)
-    return move<HeadTail<_8>>(dst, src, count);
+    return HeadTail<_8>::move(dst, src, count);
   if (count <= 32)
-    return move<HeadTail<_16>>(dst, src, count);
+    return HeadTail<_16>::move(dst, src, count);
   if (count <= 64)
-    return move<HeadTail<_32>>(dst, src, count);
+    return HeadTail<_32>::move(dst, src, count);
   if (count <= 128)
-    return move<HeadTail<_64>>(dst, src, count);
+    return HeadTail<_64>::move(dst, src, count);
 
   using AlignedMoveLoop = Align<_16, Arg::Src>::Then<Loop<_64>>;
-  if (dst < src)
-    return move<AlignedMoveLoop>(dst, src, count);
-  else if (dst > src)
-    return move_backward<AlignedMoveLoop>(dst, src, count);
+  if (dst.ptr() < src.ptr())
+    return AlignedMoveLoop::move(dst, src, count);
+  else if (dst.ptr() > src.ptr())
+    return AlignedMoveLoop::move_backward(dst, src, count);
 }
 
 LLVM_LIBC_FUNCTION(void *, memmove,
                    (void *dst, const void *src, size_t count)) {
-  inline_memmove(reinterpret_cast<char *>(dst),
-                 reinterpret_cast<const char *>(src), count);
+  inline_memmove(dst, src, count);
   return dst;
 }
 
 } // namespace __llvm_libc

libc/src/string/memory_utils/algorithm.h

+//===-- Algorithms to compose sized memory operations ---------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Higher order primitives that build upon the SizedOpT facility.
+// They constitute the basic blocks for composing memory functions.
+// This file defines the following operations:
+// - Skip
+// - Tail
+// - HeadTail
+// - Loop
+// - Align
+//
+// See each class for documentation.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ALGORITHM_H
+#define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ALGORITHM_H
+
+#include "src/string/memory_utils/address.h" // Address
+#include "src/string/memory_utils/utils.h"   // offset_to_next_aligned
+
+#include <stddef.h> // ptrdiff_t
+
+namespace __llvm_libc {
+
+// We are not yet allowed to use asserts in low level memory operations as
+// assert itself could depend on them.
+// We define this empty macro so we can enable them as soon as possible and keep
+// track of invariants.
+#define LIBC_ASSERT(COND)
+
+// An operation that allows to skip the specified amount of bytes.
+template <ptrdiff_t Bytes> struct Skip {
+  template <typename NextT> struct Then {
+    template <typename DstAddrT>
+    static inline void set(DstAddrT dst, ubyte value) {
+      static_assert(NextT::IS_FIXED_SIZE);
+      NextT::set(offsetAddr<Bytes>(dst), value);
+    }
+
+    template <typename SrcAddrT1, typename SrcAddrT2>
+    static inline uint64_t isDifferent(SrcAddrT1 src1, SrcAddrT2 src2) {
+      static_assert(NextT::IS_FIXED_SIZE);
+      return NextT::isDifferent(offsetAddr<Bytes>(src1),
+                                offsetAddr<Bytes>(src2));
+    }
+
+    template <typename SrcAddrT1, typename SrcAddrT2>
+    static inline int32_t threeWayCmp(SrcAddrT1 src1, SrcAddrT2 src2) {
+      static_assert(NextT::IS_FIXED_SIZE);
+      return NextT::threeWayCmp(offsetAddr<Bytes>(src1),
+                                offsetAddr<Bytes>(src2));
+    }
+
+    template <typename SrcAddrT1, typename SrcAddrT2>
+    static inline int32_t threeWayCmp(SrcAddrT1 src1, SrcAddrT2 src2,
+                                      size_t runtime_size) {
+      static_assert(NextT::IS_RUNTIME_SIZE);
+      return NextT::threeWayCmp(offsetAddr<Bytes>(src1),
+                                offsetAddr<Bytes>(src2), runtime_size - Bytes);
+    }
+  };
+};
+
+// Compute the address of a tail operation.
+// Because of the runtime size, we loose the alignment information.
+template <size_t Size, typename AddrT>
+static auto tailAddr(AddrT addr, size_t runtime_size) {
+  static_assert(IsAddressType<AddrT>::Value);
+  return offsetAddrAssumeAligned<1>(addr, runtime_size - Size);
+}
+
+// Perform the operation on the last 'Size' bytes of the buffer.
+//
+// e.g. with
+// [1234567812345678123]
+// [__XXXXXXXXXXXXXX___]
+// [________XXXXXXXX___]
+//
+// Precondition: `runtime_size >= Size`.
+template <typename SizedOpT> struct Tail {
+  static_assert(SizedOpT::IS_FIXED_SIZE);
+  static constexpr bool IS_RUNTIME_SIZE = true;
+  static constexpr size_t SIZE = SizedOpT::SIZE;
+
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void copy(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+    SizedOpT::copy(tailAddr<SIZE>(dst, runtime_size),
+                   tailAddr<SIZE>(src, runtime_size));
+  }
+
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void move(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+    SizedOpT::move(tailAddr<SIZE>(dst, runtime_size),
+                   tailAddr<SIZE>(src, runtime_size));
+  }
+
+  template <typename DstAddrT>
+  static inline void set(DstAddrT dst, ubyte value, size_t runtime_size) {
+    SizedOpT::set(tailAddr<SIZE>(dst, runtime_size), value);
+  }
+
+  template <typename SrcAddrT1, typename SrcAddrT2>
+  static inline uint64_t isDifferent(SrcAddrT1 src1, SrcAddrT2 src2,
+                                     size_t runtime_size) {
+    return SizedOpT::isDifferent(tailAddr<SIZE>(src1, runtime_size),
+                                 tailAddr<SIZE>(src2, runtime_size));
+  }
+
+  template <typename SrcAddrT1, typename SrcAddrT2>
+  static inline int32_t threeWayCmp(SrcAddrT1 src1, SrcAddrT2 src2,
+                                    size_t runtime_size) {
+    return SizedOpT::threeWayCmp(tailAddr<SIZE>(src1, runtime_size),
+                                 tailAddr<SIZE>(src2, runtime_size));
+  }
+};
+
+// Perform the operation on the first and the last `SizedOpT::Size` bytes of the
+// buffer. This is useful for overlapping operations.
+//
+// e.g. with
+// [1234567812345678123]
+// [__XXXXXXXXXXXXXX___]
+// [__XXXXXXXX_________]
+// [________XXXXXXXX___]
+//
+// Precondition: `runtime_size >= Size && runtime_size <= 2 x Size`.
+template <typename SizedOpT> struct HeadTail {
+  static_assert(SizedOpT::IS_FIXED_SIZE);
+  static constexpr bool IS_RUNTIME_SIZE = true;
+
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void copy(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+    LIBC_ASSERT(runtime_size >= SizedOpT::SIZE);
+    SizedOpT::copy(dst, src);
+    Tail<SizedOpT>::copy(dst, src, runtime_size);
+  }
+
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void move(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+    LIBC_ASSERT(runtime_size >= SizedOpT::SIZE);
+    static constexpr size_t BLOCK_SIZE = SizedOpT::SIZE;
+    // The load and store operations can be performed in any order as long as
+    // they are not interleaved. More investigations are needed to determine the
+    // best order.
+    auto head = SizedOpT::load(src);
+    auto tail = SizedOpT::load(tailAddr<BLOCK_SIZE>(src, runtime_size));
+    SizedOpT::store(tailAddr<BLOCK_SIZE>(dst, runtime_size), tail);
+    SizedOpT::store(dst, head);
+  }
+
+  template <typename DstAddrT>
+  static inline void set(DstAddrT dst, ubyte value, size_t runtime_size) {
+    LIBC_ASSERT(runtime_size >= SizedOpT::SIZE);
+    SizedOpT::set(dst, value);
+    Tail<SizedOpT>::set(dst, value, runtime_size);
+  }
+
+  template <typename SrcAddrT1, typename SrcAddrT2>
+  static inline uint64_t isDifferent(SrcAddrT1 src1, SrcAddrT2 src2,
+                                     size_t runtime_size) {
+    LIBC_ASSERT(runtime_size >= SizedOpT::SIZE);
+    // Two strategies can be applied here:
+    // 1. Compute head and tail and compose them with a bitwise or operation.
+    // 2. Stop early if head is different.
+    // We chose the later because HeadTail operations are typically performed
+    // with sizes ranging from 4 to 256 bytes. The cost of the loads is then
+    // significantly larger than the cost of the branch.
+    if (const uint64_t res = SizedOpT::isDifferent(src1, src2))
+      return res;
+    return Tail<SizedOpT>::isDifferent(src1, src2, runtime_size);
+  }
+
+  template <typename SrcAddrT1, typename SrcAddrT2>
+  static inline int32_t threeWayCmp(SrcAddrT1 src1, SrcAddrT2 src2,
+                                    size_t runtime_size) {
+    LIBC_ASSERT(runtime_size >= SizedOpT::SIZE &&
+                runtime_size <= 2 * SizedOpT::SIZE);
+    if (const int32_t res = SizedOpT::threeWayCmp(src1, src2))
+      return res;
+    return Tail<SizedOpT>::threeWayCmp(src1, src2, runtime_size);
+  }
+};
+
+// Simple loop ending with a Tail operation.
+//
+// e.g. with
+// [12345678123456781234567812345678]
+// [__XXXXXXXXXXXXXXXXXXXXXXXXXXXX___]
+// [__XXXXXXXX_______________________]
+// [__________XXXXXXXX_______________]
+// [__________________XXXXXXXX_______]
+// [______________________XXXXXXXX___]
+//
+// Precondition:
+// - runtime_size >= Size
+template <typename SizedOpT> struct Loop {
+  static_assert(SizedOpT::IS_FIXED_SIZE);
+  static constexpr bool IS_RUNTIME_SIZE = true;
+  static constexpr size_t BLOCK_SIZE = SizedOpT::SIZE;
+
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void copy(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+    size_t offset = 0;
+    do {
+      SizedOpT::copy(offsetAddrMultiplesOf<BLOCK_SIZE>(dst, offset),
+                     offsetAddrMultiplesOf<BLOCK_SIZE>(src, offset));
+      offset += BLOCK_SIZE;
+    } while (offset < runtime_size - BLOCK_SIZE);
+    Tail<SizedOpT>::copy(dst, src, runtime_size);
+  }
+
+  // Move forward suitable when dst < src. We load the tail bytes before
+  // handling the loop.
+  //
+  // e.g. Moving two bytes
+  // [   |       |       |       |       |]
+  // [___XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX___]
+  // [_________________________LLLLLLLL___]
+  // [___LLLLLLLL_________________________]
+  // [_SSSSSSSS___________________________]
+  // [___________LLLLLLLL_________________]
+  // [_________SSSSSSSS___________________]
+  // [___________________LLLLLLLL_________]
+  // [_________________SSSSSSSS___________]
+  // [_______________________SSSSSSSS_____]
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void move(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+    const auto tail_value =
+        SizedOpT::load(tailAddr<BLOCK_SIZE>(src, runtime_size));
+    size_t offset = 0;
+    do {
+      SizedOpT::move(offsetAddrMultiplesOf<BLOCK_SIZE>(dst, offset),
+                     offsetAddrMultiplesOf<BLOCK_SIZE>(src, offset));
+      offset += BLOCK_SIZE;
+    } while (offset < runtime_size - BLOCK_SIZE);
+    SizedOpT::store(tailAddr<BLOCK_SIZE>(dst, runtime_size), tail_value);
+  }
+
+  // Move backward suitable when dst > src. We load the head bytes before
+  // handling the loop.
+  //
+  // e.g. Moving two bytes
+  // [   |       |       |       |       |]
+  // [___XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX___]
+  // [___LLLLLLLL_________________________]
+  // [_________________________LLLLLLLL___]
+  // [___________________________SSSSSSSS_]
+  // [_________________LLLLLLLL___________]
+  // [___________________SSSSSSSS_________]
+  // [_________LLLLLLLL___________________]
+  // [___________SSSSSSSS_________________]
+  // [_____SSSSSSSS_______________________]
+  template <typename DstAddrT, typename SrcAddrT>
+  static inline void move_backward(DstAddrT dst, SrcAddrT src,
+                                   size_t runtime_size) {
+    const auto head_value = SizedOpT::load(src);
+    ptrdiff_t offset = runtime_size - BLOCK_SIZE;
+    do {
+      SizedOpT::move(offsetAddrMultiplesOf<BLOCK_SIZE>(dst, offset),
+                     offsetAddrMultiplesOf<BLOCK_SIZE>(src, offset));
+      offset -= BLOCK_SIZE;
+    } while (offset >= 0);
+    SizedOpT::store(dst, head_value);
+  }
+
+  template <typename DstAddrT>
+  static inline void set(DstAddrT dst, ubyte value, size_t runtime_size) {
+    size_t offset = 0;
+    do {
+      SizedOpT::set(offsetAddrMultiplesOf<BLOCK_SIZE>(dst, offset), value);
+      offset += BLOCK_SIZE;
+    } while (offset < runtime_size - BLOCK_SIZE);
+    Tail<SizedOpT>::set(dst, value, runtime_size);
+  }
+
+  template <typename SrcAddrT1, typename SrcAddrT2>
+  static inline uint64_t isDifferent(SrcAddrT1 src1, SrcAddrT2 src2,
+                                     size_t runtime_size) {
+    size_t offset = 0;
+    do {
+      if (uint64_t res = SizedOpT::isDifferent(
+              offsetAddrMultiplesOf<BLOCK_SIZE>(src1, offset),
+              offsetAddrMultiplesOf<BLOCK_SIZE>(src2, offset)))
+        return res;
+      offset += BLOCK_SIZE;
+    } while (offset < runtime_size - BLOCK_SIZE);
+    return Tail<SizedOpT>::isDifferent(src1, src2, runtime_size);
+  }
+
+  template <typename SrcAddrT1, typename SrcAddrT2>
+  static inline int32_t threeWayCmp(SrcAddrT1 src1, SrcAddrT2 src2,
+                                    size_t runtime_size) {
+    size_t offset = 0;
+    do {
+      if (int32_t res = SizedOpT::threeWayCmp(
+              offsetAddrMultiplesOf<BLOCK_SIZE>(src1, offset),
+              offsetAddrMultiplesOf<BLOCK_SIZE>(src2, offset)))
+        return res;
+      offset += BLOCK_SIZE;
+    } while (offset < runtime_size - BLOCK_SIZE);
+    return Tail<SizedOpT>::threeWayCmp(src1, src2, runtime_size);
+  }
+};
+
+// Aligns using a statically-sized operation, then calls the subsequent NextT
+// operation.
+//
+// e.g. A 16-byte Destination Aligned 32-byte Loop Copy can be written as:
+// Align<_16, Arg::Dst>::Then<Loop<_32>>::copy(dst, src, runtime_size);
+enum class Arg { _1, _2, Dst = _1, Src = _2, Lhs = _1, Rhs = _2 };
+template <typename SizedOpT, Arg AlignOn = Arg::_1> struct Align {
+  static_assert(SizedOpT::IS_FIXED_SIZE);
+
+  template <typename NextT> struct Then {
+    static_assert(NextT::IS_RUNTIME_SIZE);
+
+    template <typename DstAddrT, typename SrcAddrT>
+    static inline void copy(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+      SizedOpT::copy(dst, src);
+      auto aligned = align(dst, src, runtime_size);
+      NextT::copy(aligned.arg1, aligned.arg2, aligned.size);
+    }
+
+    // Move forward suitable when dst < src. The alignment is performed with
+    // an HeadTail operation of size ∈ [Alignment, 2 x Alignment].
+    //
+    // e.g. Moving two bytes and making sure src is then aligned.
+    // [  |       |       |       |      ]
+    // [____XXXXXXXXXXXXXXXXXXXXXXXXXXXX_]
+    // [____LLLLLLLL_____________________]
+    // [___________LLLLLLLL______________]
+    // [_SSSSSSSS________________________]
+    // [________SSSSSSSS_________________]
+    //
+    // e.g. Moving two bytes and making sure dst is then aligned.
+    // [  |       |       |       |      ]
+    // [____XXXXXXXXXXXXXXXXXXXXXXXXXXXX_]
+    // [____LLLLLLLL_____________________]
+    // [______LLLLLLLL___________________]
+    // [_SSSSSSSS________________________]
+    // [___SSSSSSSS______________________]
+    template <typename DstAddrT, typename SrcAddrT>
+    static inline void move(DstAddrT dst, SrcAddrT src, size_t runtime_size) {
+      auto aligned_after_begin = align(dst, src, runtime_size);
+      // We move pointers forward by Size so we can perform HeadTail.
+      auto aligned = aligned_after_begin.stepForward();
+      HeadTail<SizedOpT>::move(dst, src, runtime_size - aligned.size);
+      NextT::move(aligned.arg1, aligned.arg2, aligned.size);
+    }
+
+    // Move backward suitable when dst > src. The alignment is performed with
+    // an HeadTail operation of size ∈ [Alignment, 2 x Alignment].
+    //
+    // e.g. Moving two bytes backward and making sure src is then aligned.
+    // [  |       |       |       |      ]
+    // [____XXXXXXXXXXXXXXXXXXXXXXXX_____]
+    // [ _________________LLLLLLLL_______]
+    // [ ___________________LLLLLLLL_____]
+    // [____________________SSSSSSSS_____]
+    // [______________________SSSSSSSS___]
+    //
+    // e.g. Moving two bytes and making sure dst is then aligned.
+    // [  |       |       |       |      ]
+    // [____XXXXXXXXXXXXXXXXXXXXXXXX_____]
+    // [ _______________LLLLLLLL_________]
+    // [ ___________________LLLLLLLL_____]
+    // [__________________SSSSSSSS_______]
+    // [______________________SSSSSSSS___]
+    template <typename DstAddrT, typename SrcAddrT>
+    static inline void move_backward(DstAddrT dst, SrcAddrT src,
+                                     size_t runtime_size) {
+      const auto dst_end = offsetAddrAssumeAligned<1>(dst, runtime_size);
+      const auto src_end = offsetAddrAssumeAligned<1>(src, runtime_size);
+      auto aligned_after_end = align(dst_end, src_end, 0);
+      // We move pointers back by 2 x Size so we can perform HeadTail.
+      auto aligned = aligned_after_end.stepBack().stepBack();
+      HeadTail<SizedOpT>::move(aligned.arg1, aligned.arg2, aligned.size);
+      NextT::move_backward(dst, src, runtime_size - aligned.size);
+    }
+
+    template <typename DstAddrT>
+    static inline void set(DstAddrT dst, ubyte value, size_t runtime_size) {
+      SizedOpT::set(dst, value);
+      DstAddrT _(nullptr);
+      auto aligned = align(dst, _, runtime_size);
+      NextT::set(aligned.arg1, value, aligned.size);
+    }
+
+    template <typename SrcAddrT1, typename SrcAddrT2>
+    static inline uint64_t isDifferent(SrcAddrT1 src1, SrcAddrT2 src2,
+                                       size_t runtime_size) {
+      if (const uint64_t res = SizedOpT::isDifferent(src1, src2))
+        return res;
+      auto aligned = align(src1, src2, runtime_size);
+      return NextT::isDifferent(aligned.arg1, aligned.arg2, aligned.size);
+    }
+
+    template <typename SrcAddrT1, typename SrcAddrT2>
+    static inline int32_t threeWayCmp(SrcAddrT1 src1, SrcAddrT2 src2,
+                                      size_t runtime_size) {
+      if (const int32_t res = SizedOpT::threeWayCmp(src1, src2))
+        return res;
+      auto aligned = align(src1, src2, runtime_size);
+      return NextT::threeWayCmp(aligned.arg1, aligned.arg2, aligned.size);
+    }
+  };
+
+private:
+  static constexpr size_t ALIGN_OP_SIZE = SizedOpT::SIZE;
+  static_assert(ALIGN_OP_SIZE > 1);
+
+  template <typename Arg1AddrT, typename Arg2AddrT> struct Aligned {
+    Arg1AddrT arg1;
+    Arg2AddrT arg2;
+    size_t size;
+
+    Aligned stepForward() const {
+      return Aligned{offsetAddrMultiplesOf<ALIGN_OP_SIZE>(arg1, ALIGN_OP_SIZE),
+                     offsetAddrMultiplesOf<ALIGN_OP_SIZE>(arg2, ALIGN_OP_SIZE),
+                     size - ALIGN_OP_SIZE};
+    }
+
+    Aligned stepBack() const {
+      return Aligned{offsetAddrMultiplesOf<ALIGN_OP_SIZE>(arg1, -ALIGN_OP_SIZE),
+                     offsetAddrMultiplesOf<ALIGN_OP_SIZE>(arg2, -ALIGN_OP_SIZE),
+                     size + ALIGN_OP_SIZE};
+    }
+  };
+
+  template <typename Arg1AddrT, typename Arg2AddrT>
+  static auto makeAligned(Arg1AddrT arg1, Arg2AddrT arg2, size_t size) {
+    return Aligned<Arg1AddrT, Arg2AddrT>{arg1, arg2, size};
+  }
+
+  template <typename Arg1AddrT, typename Arg2AddrT>
+  static auto align(Arg1AddrT arg1, Arg2AddrT arg2, size_t runtime_size) {
+    static_assert(IsAddressType<Arg1AddrT>::Value);
+    static_assert(IsAddressType<Arg2AddrT>::Value);
+    if constexpr (AlignOn == Arg::_1) {
+      auto offset = offset_to_next_aligned<ALIGN_OP_SIZE>(arg1.ptr_);
+      return makeAligned(offsetAddrAssumeAligned<ALIGN_OP_SIZE>(arg1, offset),
+                         offsetAddrAssumeAligned<1>(arg2, offset),
+                         runtime_size - offset);
+    } else if constexpr (AlignOn == Arg::_2) {
+      auto offset = offset_to_next_aligned<ALIGN_OP_SIZE>(arg2.ptr_);
+      return makeAligned(offsetAddrAssumeAligned<1>(arg1, offset),
+                         offsetAddrAssumeAligned<ALIGN_OP_SIZE>(arg2, offset),
+                         runtime_size - offset);
+    } else {
+      DeferredStaticAssert("AlignOn must be either Arg::_1 or Arg::_2");
+    }
+  }
+};
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ALGORITHM_H

libc/src/string/memory_utils/bcmp_implementations.h

 //===-- Implementation of bcmp --------------------------------------------===//
 //
 // 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_BCMP_IMPLEMENTATIONS_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_BCMP_IMPLEMENTATIONS_H
 
 #include "src/__support/architectures.h"
-#include "src/__support/common.h"
-#include "src/string/memory_utils/elements.h"
+#include "src/string/memory_utils/algorithm.h"
+#include "src/string/memory_utils/backends.h"
 
 #include <stddef.h> // size_t
 
 namespace __llvm_libc {
 
-// Fixed-size difference between 'lhs' and 'rhs'.
-template <typename Element> bool differs(const char *lhs, const char *rhs) {
-  return !Element::equals(lhs, rhs);
-}
-// Runtime-size difference between 'lhs' and 'rhs'.
-template <typename Element>
-bool differs(const char *lhs, const char *rhs, size_t size) {
-  return !Element::equals(lhs, rhs, size);
-}
-
-static inline int inline_bcmp(const char *lhs, const char *rhs, size_t count) {
+static inline uint64_t inline_bcmp_uint64_t(SrcAddr<1> lhs, SrcAddr<1> rhs,
+                                            size_t count) {
 #if defined(LLVM_LIBC_ARCH_X86)
-  using namespace ::__llvm_libc::x86;
+  using namespace x86;
 #elif defined(LLVM_LIBC_ARCH_AARCH64)
-  using namespace ::__llvm_libc::aarch64;
+  using namespace aarch64;
 #else
-  using namespace ::__llvm_libc::scalar;
+  using namespace scalar;
 #endif
   if (count == 0)
     return 0;
   if (count == 1)
-    return differs<_1>(lhs, rhs);
+    return _1::isDifferent(lhs, rhs);
   if (count == 2)
-    return differs<_2>(lhs, rhs);
+    return _2::isDifferent(lhs, rhs);
   if (count == 3)
-    return differs<_3>(lhs, rhs);
+    return _3::isDifferent(lhs, rhs);
   if (count <= 8)
-    return differs<HeadTail<_4>>(lhs, rhs, count);
+    return HeadTail<_4>::isDifferent(lhs, rhs, count);
   if (count <= 16)
-    return differs<HeadTail<_8>>(lhs, rhs, count);
+    return HeadTail<_8>::isDifferent(lhs, rhs, count);
   if (count <= 32)
-    return differs<HeadTail<_16>>(lhs, rhs, count);
+    return HeadTail<_16>::isDifferent(lhs, rhs, count);
   if (count <= 64)
-    return differs<HeadTail<_32>>(lhs, rhs, count);
+    return HeadTail<_32>::isDifferent(lhs, rhs, count);
   if (count <= 128)
-    return differs<HeadTail<_64>>(lhs, rhs, count);
-  return differs<Align<_32>::Then<Loop<_32>>>(lhs, rhs, count);
+    return HeadTail<_64>::isDifferent(lhs, rhs, count);
+  return Align<_32>::Then<Loop<_32>>::isDifferent(lhs, rhs, count);
+}
+
+static inline int inline_bcmp(SrcAddr<1> lhs, SrcAddr<1> rhs, size_t count) {
+  return !!inline_bcmp_uint64_t(lhs, rhs, count);
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_BCMP_IMPLEMENTATIONS_H

libc/src/string/memory_utils/memcmp_implementations.h

 //===-- Implementation of memcmp ------------------------------------------===//
 //
 // 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_MEMCMP_IMPLEMENTATIONS_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCMP_IMPLEMENTATIONS_H
 
 #include "src/__support/architectures.h"
-#include "src/__support/common.h"
-#include "src/string/memory_utils/elements.h"
+#include "src/string/memory_utils/algorithm.h"
+#include "src/string/memory_utils/backends.h"
 
 #include <stddef.h> // size_t
 
 namespace __llvm_libc {
 
-static inline int inline_memcmp(const char *lhs, const char *rhs,
-                                size_t count) {
+static inline int inline_memcmp(SrcAddr<1> lhs, SrcAddr<1> rhs, size_t count) {
 #if defined(LLVM_LIBC_ARCH_X86)
   /////////////////////////////////////////////////////////////////////////////
   // LLVM_LIBC_ARCH_X86
   /////////////////////////////////////////////////////////////////////////////
-  using namespace __llvm_libc::x86;
+  using namespace x86;
   if (count == 0)
     return 0;
   if (count == 1)
-    return three_way_compare<_1>(lhs, rhs);
+    return _1::threeWayCmp(lhs, rhs);
   if (count == 2)
-    return three_way_compare<_2>(lhs, rhs);
+    return _2::threeWayCmp(lhs, rhs);
   if (count == 3)
-    return three_way_compare<_3>(lhs, rhs);
+    return _3::threeWayCmp(lhs, rhs);
   if (count <= 8)
-    return three_way_compare<HeadTail<_4>>(lhs, rhs, count);
+    return HeadTail<_4>::threeWayCmp(lhs, rhs, count);
   if (count <= 16)
-    return three_way_compare<HeadTail<_8>>(lhs, rhs, count);
+    return HeadTail<_8>::threeWayCmp(lhs, rhs, count);
   if (count <= 32)
-    return three_way_compare<HeadTail<_16>>(lhs, rhs, count);
+    return HeadTail<_16>::threeWayCmp(lhs, rhs, count);
   if (count <= 64)
-    return three_way_compare<HeadTail<_32>>(lhs, rhs, count);
+    return HeadTail<_32>::threeWayCmp(lhs, rhs, count);
   if (count <= 128)
-    return three_way_compare<HeadTail<_64>>(lhs, rhs, count);
-  return three_way_compare<Align<_32>::Then<Loop<_32>>>(lhs, rhs, count);
+    return HeadTail<_64>::threeWayCmp(lhs, rhs, count);
+  return Align<_32>::Then<Loop<_32>>::threeWayCmp(lhs, rhs, count);
 #elif defined(LLVM_LIBC_ARCH_AARCH64)
   /////////////////////////////////////////////////////////////////////////////
   // LLVM_LIBC_ARCH_AARCH64
   /////////////////////////////////////////////////////////////////////////////
-  using namespace ::__llvm_libc::aarch64;
+  using namespace aarch64;
   if (count == 0) // [0, 0]
     return 0;
   if (count == 1) // [1, 1]
-    return three_way_compare<_1>(lhs, rhs);
+    return _1::threeWayCmp(lhs, rhs);
   if (count == 2) // [2, 2]
-    return three_way_compare<_2>(lhs, rhs);
+    return _2::threeWayCmp(lhs, rhs);
   if (count == 3) // [3, 3]
-    return three_way_compare<_3>(lhs, rhs);
+    return _3::threeWayCmp(lhs, rhs);
   if (count < 8) // [4, 7]
-    return three_way_compare<HeadTail<_4>>(lhs, rhs, count);
+    return HeadTail<_4>::threeWayCmp(lhs, rhs, count);
   if (count < 16) // [8, 15]
-    return three_way_compare<HeadTail<_8>>(lhs, rhs, count);
+    return HeadTail<_8>::threeWayCmp(lhs, rhs, count);
   if (unlikely(count >= 128)) // [128, ∞]
-    return three_way_compare<Align<_16>::Then<Loop<_32>>>(lhs, rhs, count);
-  if (!equals<_16>(lhs, rhs)) // [16, 16]
-    return three_way_compare<_16>(lhs, rhs);
+    return Align<_16>::Then<Loop<_32>>::threeWayCmp(lhs, rhs, count);
+  if (_16::isDifferent(lhs, rhs)) // [16, 16]
+    return _16::threeWayCmp(lhs, rhs);
   if (count < 32) // [17, 31]
-    return three_way_compare<Tail<_16>>(lhs, rhs, count);
-  if (!equals<Skip<16>::Then<_16>>(lhs, rhs)) // [32, 32]
-    return three_way_compare<Skip<16>::Then<_16>>(lhs, rhs);
+    return Tail<_16>::threeWayCmp(lhs, rhs, count);
+  if (Skip<16>::Then<_16>::isDifferent(lhs, rhs)) // [32, 32]
+    return Skip<16>::Then<_16>::threeWayCmp(lhs, rhs);
   if (count < 64) // [33, 63]
-    return three_way_compare<Tail<_32>>(lhs, rhs, count);
+    return Tail<_32>::threeWayCmp(lhs, rhs, count);
   // [64, 127]
-  return three_way_compare<Skip<32>::Then<Loop<_16>>>(lhs, rhs, count);
+  return Skip<32>::Then<Loop<_16>>::threeWayCmp(lhs, rhs, count);
 #else
   /////////////////////////////////////////////////////////////////////////////
   // Default
   /////////////////////////////////////////////////////////////////////////////
-  using namespace ::__llvm_libc::scalar;
-
+  using namespace scalar;
   if (count == 0)
     return 0;
   if (count == 1)
-    return three_way_compare<_1>(lhs, rhs);
+    return _1::threeWayCmp(lhs, rhs);
   if (count == 2)
-    return three_way_compare<_2>(lhs, rhs);
+    return _2::threeWayCmp(lhs, rhs);
   if (count == 3)
-    return three_way_compare<_3>(lhs, rhs);
+    return _3::threeWayCmp(lhs, rhs);
   if (count <= 8)
-    return three_way_compare<HeadTail<_4>>(lhs, rhs, count);
+    return HeadTail<_4>::threeWayCmp(lhs, rhs, count);
   if (count <= 16)
-    return three_way_compare<HeadTail<_8>>(lhs, rhs, count);
+    return HeadTail<_8>::threeWayCmp(lhs, rhs, count);
   if (count <= 32)
-    return three_way_compare<HeadTail<_16>>(lhs, rhs, count);
+    return HeadTail<_16>::threeWayCmp(lhs, rhs, count);
   if (count <= 64)
-    return three_way_compare<HeadTail<_32>>(lhs, rhs, count);
+    return HeadTail<_32>::threeWayCmp(lhs, rhs, count);
   if (count <= 128)
-    return three_way_compare<HeadTail<_64>>(lhs, rhs, count);
-  return three_way_compare<Align<_32>::Then<Loop<_32>>>(lhs, rhs, count);
+    return HeadTail<_64>::threeWayCmp(lhs, rhs, count);
+  return Align<_32>::Then<Loop<_32>>::threeWayCmp(lhs, rhs, count);
 #endif
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCMP_IMPLEMENTATIONS_H

libc/src/string/memory_utils/memcpy_implementations.h

 //===-- Memcpy 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_MEMCPY_IMPLEMENTATIONS_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY_IMPLEMENTATIONS_H
 
+#include "src/__support/CPP/TypeTraits.h" // cpp::ConditionalType
 #include "src/__support/architectures.h"
-#include "src/__support/common.h"
-#include "src/string/memory_utils/elements.h"
-#include "src/string/memory_utils/utils.h"
+#include "src/__support/common.h" // LLVM_LIBC_IS_DEFINED
+#include "src/string/memory_utils/algorithm.h"
+#include "src/string/memory_utils/backends.h"
 
 #include <stddef.h> // size_t
 
 // Design rationale
 // ================
 //
 // Using a profiler to observe size distributions for calls into libc
 // functions, it was found most operations act on a small number of bytes.
 // This makes it important to favor small sizes.
 //
 // The tests for `count` are in ascending order so the cost of branching is
 // proportional to the cost of copying.
 //
 // The function is written in C++ for several reasons:
 // - The compiler can __see__ the code, this is useful when performing Profile
 //   Guided Optimization as the optimized code can take advantage of branching
 //   probabilities.
 // - It also allows for easier customization and favors testing multiple
 //   implementation parameters.
 // - As compilers and processors get better, the generated code is improved
 //   with little change on the code side.
 
 namespace __llvm_libc {
 
-static inline void inline_memcpy(char *__restrict dst,
-                                 const char *__restrict src, size_t count) {
-  using namespace __llvm_libc::builtin;
+static inline void inline_memcpy(DstAddr<1> dst, SrcAddr<1> src, size_t count) {
 #if defined(LLVM_LIBC_ARCH_X86)
   /////////////////////////////////////////////////////////////////////////////
   // LLVM_LIBC_ARCH_X86
   /////////////////////////////////////////////////////////////////////////////
-
   // Whether to use only rep;movsb.
   constexpr bool USE_ONLY_REP_MOVSB =
       LLVM_LIBC_IS_DEFINED(LLVM_LIBC_MEMCPY_X86_USE_ONLY_REPMOVSB);
 
   // kRepMovsBSize == -1 : Only CopyAligned is used.
   // kRepMovsBSize ==  0 : Only RepMovsb is used.
   // else CopyAligned is used up to kRepMovsBSize and then RepMovsb.
   constexpr size_t REP_MOVS_B_SIZE =
 #if defined(LLVM_LIBC_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE)
       LLVM_LIBC_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE;
 #else
       -1;
 #endif // LLVM_LIBC_MEMCPY_X86_USE_REPMOVSB_FROM_SIZE
 
+  using namespace x86;
+
   // Whether target supports AVX instructions.
   constexpr bool HAS_AVX = LLVM_LIBC_IS_DEFINED(__AVX__);
-
-#if defined(__AVX__)
-  using LoopBlockSize = _64;
-#else
-  using LoopBlockSize = _32;
-#endif
-
   if (USE_ONLY_REP_MOVSB)
-    return copy<x86::Accelerator>(dst, src, count);
-
+    return repmovsb(as<void>(dst), as<const void>(src), count);
   if (count == 0)
     return;
   if (count == 1)
-    return copy<_1>(dst, src);
+    return _1::copy(dst, src);
   if (count == 2)
-    return copy<_2>(dst, src);
+    return _2::copy(dst, src);
   if (count == 3)
-    return copy<_3>(dst, src);
+    return _3::copy(dst, src);
   if (count == 4)
-    return copy<_4>(dst, src);
+    return _4::copy(dst, src);
   if (count < 8)
-    return copy<HeadTail<_4>>(dst, src, count);
+    return HeadTail<_4>::copy(dst, src, count);
   if (count < 16)
-    return copy<HeadTail<_8>>(dst, src, count);
+    return HeadTail<_8>::copy(dst, src, count);
   if (count < 32)
-    return copy<HeadTail<_16>>(dst, src, count);
+    return HeadTail<_16>::copy(dst, src, count);
   if (count < 64)
-    return copy<HeadTail<_32>>(dst, src, count);
+    return HeadTail<_32>::copy(dst, src, count);
   if (count < 128)
-    return copy<HeadTail<_64>>(dst, src, count);
+    return HeadTail<_64>::copy(dst, src, count);
   if (HAS_AVX && count < 256)
-    return copy<HeadTail<_128>>(dst, src, count);
+    return HeadTail<_128>::copy(dst, src, count);
+  using LoopBlock = cpp::ConditionalType<HAS_AVX, _64, _32>;
   if (count <= REP_MOVS_B_SIZE)
-    return copy<Align<_32, Arg::Dst>::Then<Loop<LoopBlockSize>>>(dst, src,
-                                                                 count);
-  return copy<x86::Accelerator>(dst, src, count);
+    return Align<_32, Arg::Dst>::Then<Loop<LoopBlock>>::copy(dst, src, count);
+  return repmovsb(as<void>(dst), as<const void>(src), count);
+
 #elif defined(LLVM_LIBC_ARCH_AARCH64)
   /////////////////////////////////////////////////////////////////////////////
   // LLVM_LIBC_ARCH_AARCH64
   /////////////////////////////////////////////////////////////////////////////
+  using namespace scalar;
   if (count == 0)
     return;
   if (count == 1)
-    return copy<_1>(dst, src);
+    return _1::copy(dst, src);
   if (count == 2)
-    return copy<_2>(dst, src);
+    return _2::copy(dst, src);
   if (count == 3)
-    return copy<_3>(dst, src);
+    return _3::copy(dst, src);
   if (count == 4)
-    return copy<_4>(dst, src);
+    return _4::copy(dst, src);
   if (count < 8)
-    return copy<HeadTail<_4>>(dst, src, count);
+    return HeadTail<_4>::copy(dst, src, count);
   if (count < 16)
-    return copy<HeadTail<_8>>(dst, src, count);
+    return HeadTail<_8>::copy(dst, src, count);
   if (count < 32)
-    return copy<HeadTail<_16>>(dst, src, count);
+    return HeadTail<_16>::copy(dst, src, count);
   if (count < 64)
-    return copy<HeadTail<_32>>(dst, src, count);
+    return HeadTail<_32>::copy(dst, src, count);
   if (count < 128)
-    return copy<HeadTail<_64>>(dst, src, count);
-  return copy<Align<_16, Arg::Src>::Then<Loop<_64>>>(dst, src, count);
+    return HeadTail<_64>::copy(dst, src, count);
+  return Align<_16, Arg::Src>::Then<Loop<_64>>::copy(dst, src, count);
 #else
   /////////////////////////////////////////////////////////////////////////////
   // Default
   /////////////////////////////////////////////////////////////////////////////
+  using namespace scalar;
   if (count == 0)
     return;
   if (count == 1)
-    return copy<_1>(dst, src);
+    return _1::copy(dst, src);
   if (count == 2)
-    return copy<_2>(dst, src);
+    return _2::copy(dst, src);
   if (count == 3)
-    return copy<_3>(dst, src);
+    return _3::copy(dst, src);
   if (count == 4)
-    return copy<_4>(dst, src);
+    return _4::copy(dst, src);
   if (count < 8)
-    return copy<HeadTail<_4>>(dst, src, count);
+    return HeadTail<_4>::copy(dst, src, count);
   if (count < 16)
-    return copy<HeadTail<_8>>(dst, src, count);
+    return HeadTail<_8>::copy(dst, src, count);
   if (count < 32)
-    return copy<HeadTail<_16>>(dst, src, count);
+    return HeadTail<_16>::copy(dst, src, count);
   if (count < 64)
-    return copy<HeadTail<_32>>(dst, src, count);
+    return HeadTail<_32>::copy(dst, src, count);
   if (count < 128)
-    return copy<HeadTail<_64>>(dst, src, count);
-  return copy<Align<_32, Arg::Src>::Then<Loop<_32>>>(dst, src, count);
+    return HeadTail<_64>::copy(dst, src, count);
+  return Align<_32, Arg::Src>::Then<Loop<_32>>::copy(dst, src, count);
 #endif
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMCPY_IMPLEMENTATIONS_H

libc/src/string/memory_utils/memset_implementations.h

 //===-- Implementation of memset and bzero --------------------------------===//
 //
 // 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_MEMSET_IMPLEMENTATIONS_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMSET_IMPLEMENTATIONS_H
 
 #include "src/__support/architectures.h"
-#include "src/string/memory_utils/elements.h"
-#include "src/string/memory_utils/utils.h"
+#include "src/string/memory_utils/algorithm.h"
+#include "src/string/memory_utils/backends.h"
 
 #include <stddef.h> // size_t
 
 namespace __llvm_libc {
 
 // A general purpose implementation assuming cheap unaligned writes for sizes:
 // 1, 2, 4, 8, 16, 32 and 64 Bytes. Note that some architecture can't store 32
 // or 64 Bytes at a time, the compiler will expand them as needed.

 // conditional were expensive, even on processor that do not support writing 64B
 // at a time (pre-AVX512F). We also want to favor short functions that allow
 // more hot code to fit in the iL1 cache.
 //
 // Above 128 we have to use conditionals since we don't know the upper bound in
 // advance. SetAlignedBlocks<64> may waste up to 63 Bytes, SetAlignedBlocks<32>
 // may waste up to 31 Bytes. Benchmarks showed that SetAlignedBlocks<64> was not
 // superior for sizes that mattered.
-inline static void inline_memset(char *dst, unsigned char value, size_t count) {
+inline static void inline_memset(DstAddr<1> dst, ubyte value, size_t count) {
 #if defined(LLVM_LIBC_ARCH_X86)
   /////////////////////////////////////////////////////////////////////////////
   // LLVM_LIBC_ARCH_X86
   /////////////////////////////////////////////////////////////////////////////
-  using namespace __llvm_libc::x86;
+  using namespace x86;
   if (count == 0)
     return;
   if (count == 1)
-    return splat_set<_1>(dst, value);
+    return _1::set(dst, value);
   if (count == 2)
-    return splat_set<_2>(dst, value);
+    return _2::set(dst, value);
   if (count == 3)
-    return splat_set<_3>(dst, value);
+    return _3::set(dst, value);
   if (count <= 8)
-    return splat_set<HeadTail<_4>>(dst, value, count);
+    return HeadTail<_4>::set(dst, value, count);
   if (count <= 16)
-    return splat_set<HeadTail<_8>>(dst, value, count);
+    return HeadTail<_8>::set(dst, value, count);
   if (count <= 32)
-    return splat_set<HeadTail<_16>>(dst, value, count);
+    return HeadTail<_16>::set(dst, value, count);
   if (count <= 64)
-    return splat_set<HeadTail<_32>>(dst, value, count);
+    return HeadTail<_32>::set(dst, value, count);
   if (count <= 128)
-    return splat_set<HeadTail<_64>>(dst, value, count);
-  return splat_set<Align<_32, Arg::Dst>::Then<Loop<_32>>>(dst, value, count);
+    return HeadTail<_64>::set(dst, value, count);
+  return Align<_32, Arg::Dst>::Then<Loop<_32>>::set(dst, value, count);
 #elif defined(LLVM_LIBC_ARCH_AARCH64)
   /////////////////////////////////////////////////////////////////////////////
   // LLVM_LIBC_ARCH_AARCH64
   /////////////////////////////////////////////////////////////////////////////
-  using namespace __llvm_libc::aarch64_memset;
+  using namespace aarch64;
   if (count == 0)
     return;
   if (count <= 3) {
-    splat_set<_1>(dst, value);
+    _1::set(dst, value);
     if (count > 1)
-      splat_set<Tail<_2>>(dst, value, count);
+      Tail<_2>::set(dst, value, count);
     return;
   }
   if (count <= 8)
-    return splat_set<HeadTail<_4>>(dst, value, count);
+    return HeadTail<_4>::set(dst, value, count);
   if (count <= 16)
-    return splat_set<HeadTail<_8>>(dst, value, count);
+    return HeadTail<_8>::set(dst, value, count);
   if (count <= 32)
-    return splat_set<HeadTail<_16>>(dst, value, count);
+    return HeadTail<_16>::set(dst, value, count);
   if (count <= 96) {
-    splat_set<_32>(dst, value);
+    _32::set(dst, value);
     if (count <= 64)
-      return splat_set<Tail<_32>>(dst, value, count);
-    splat_set<Skip<32>::Then<_32>>(dst, value);
-    splat_set<Tail<_32>>(dst, value, count);
+      return Tail<_32>::set(dst, value, count);
+    Skip<32>::Then<_32>::set(dst, value);
+    Tail<_32>::set(dst, value, count);
     return;
   }
-  if (count < 448 || value != 0 || !AArch64ZVA(dst, count))
-    return splat_set<Align<_16, Arg::_1>::Then<Loop<_64>>>(dst, value, count);
+  if (count >= 448 && value == ubyte::ZERO && hasZva())
+    return Align<_64, Arg::_1>::Then<Loop<Zva64>>::set(dst, ubyte::ZERO, count);
+  else
+    return Align<_16, Arg::_1>::Then<Loop<_64>>::set(dst, value, count);
 #else
   /////////////////////////////////////////////////////////////////////////////
   // Default
   /////////////////////////////////////////////////////////////////////////////
-  using namespace ::__llvm_libc::scalar;
-
+  using namespace scalar;
   if (count == 0)
     return;
   if (count == 1)
-    return splat_set<_1>(dst, value);
+    return _1::set(dst, value);
   if (count == 2)
-    return splat_set<_2>(dst, value);
+    return _2::set(dst, value);
   if (count == 3)
-    return splat_set<_3>(dst, value);
+    return _3::set(dst, value);
   if (count <= 8)
-    return splat_set<HeadTail<_4>>(dst, value, count);
+    return HeadTail<_4>::set(dst, value, count);
   if (count <= 16)
-    return splat_set<HeadTail<_8>>(dst, value, count);
+    return HeadTail<_8>::set(dst, value, count);
   if (count <= 32)
-    return splat_set<HeadTail<_16>>(dst, value, count);
+    return HeadTail<_16>::set(dst, value, count);
   if (count <= 64)
-    return splat_set<HeadTail<_32>>(dst, value, count);
+    return HeadTail<_32>::set(dst, value, count);
   if (count <= 128)
-    return splat_set<HeadTail<_64>>(dst, value, count);
-  return splat_set<Align<_32, Arg::Dst>::Then<Loop<_32>>>(dst, value, count);
+    return HeadTail<_64>::set(dst, value, count);
+  return Align<_32, Arg::Dst>::Then<Loop<_32>>::set(dst, value, count);
 #endif
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMSET_IMPLEMENTATIONS_H

libc/src/string/memory_utils/sized_op.h

 #define LLVM_LIBC_USE_BUILTIN_MEMSET_INLINE                                    \
   __has_builtin(__builtin_memset_inline)
 #endif // LLVM_LIBC_USE_BUILTIN_MEMSET_INLINE
 
 namespace __llvm_libc {
 
 template <typename Backend, size_t Size> struct SizedOp {
   static constexpr size_t SIZE = Size;
+  // Define instantiations of SizedOp as a fixed size operation.
+  // i.e. an operation that is composable by types in algorithm.h
+  static constexpr bool IS_FIXED_SIZE = true;
 
 private:
   static_assert(Backend::IS_BACKEND_TYPE);
   static_assert(SIZE > 0);
   using type = typename Backend::template getNextType<Size>;
   static constexpr size_t TYPE_SIZE = sizeof(type);
   static_assert(SIZE >= TYPE_SIZE);
   static constexpr size_t NEXT_SIZE = Size - TYPE_SIZE;

libc/src/string/mempcpy.cpp

 #include "src/string/memory_utils/memcpy_implementations.h"
 
 #include "src/__support/common.h"
 #include <stddef.h> // For size_t.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(void *, mempcpy,
-                   (void *__restrict dest, const void *__restrict src,
+                   (void *__restrict dst, const void *__restrict src,
                     size_t count)) {
-  char *result = reinterpret_cast<char *>(dest);
-  inline_memcpy(result, reinterpret_cast<const char *>(src), count);
-  return result + count;
+  inline_memcpy(dst, src, count);
+  return reinterpret_cast<char *>(dst) + count;
 }
 
 } // namespace __llvm_libc

libc/src/string/memset.cpp

 //===-- Implementation of memset ------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/memset.h"
+
 #include "src/__support/common.h"
 #include "src/string/memory_utils/memset_implementations.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(void *, memset, (void *dst, int value, size_t count)) {
-  inline_memset(reinterpret_cast<char *>(dst),
-                static_cast<unsigned char>(value), count);
+  inline_memset(dst, static_cast<ubyte>(value), count);
   return dst;
 }
 
 } // namespace __llvm_libc

libc/src/string/stpncpy.cpp

 //===-- Implementation of stpncpy -----------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "src/string/stpncpy.h"
-#include "src/string/memory_utils/memset_implementations.h"
 
 #include "src/__support/common.h"
+#include "src/string/memory_utils/memset_implementations.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(char *, stpncpy,
                    (char *__restrict dest, const char *__restrict src,
                     size_t n)) {
   size_t i;
   // Copy up until \0 is found.
   for (i = 0; i < n && src[i] != '\0'; ++i)
     dest[i] = src[i];
   // When n>strlen(src), n-strlen(src) \0 are appended.
   if (n > i)
-    inline_memset(dest + i, 0, n - i);
+    inline_memset(dest + i, ubyte::ZERO, n - i);
   return dest + i;
 }
 
 } // namespace __llvm_libc

libc/src/string/string_utils.h

 
 static inline size_t strlcpy(char *__restrict dst, const char *__restrict src,
                              size_t size) {
   size_t len = internal::string_length(src);
   if (!size)
     return len;
   size_t n = len < size - 1 ? len : size - 1;
   inline_memcpy(dst, src, n);
-  inline_memset(dst + n, 0, size - n);
+  inline_memset(dst + n, ubyte::ZERO, size - n);
   return len;
 }
 
 } // namespace internal
 } // namespace __llvm_libc
 
 #endif //  LIBC_SRC_STRING_STRING_UTILS_H

libc/test/src/string/memcmp_test.cpp

TEST(LlvmLibcMemcmpTest, Sweep) {
   const auto reset = [](char *const ptr) {
     for (size_t i = 0; i < K_MAX_SIZE; ++i)
       ptr[i] = 'a';
   };
 
   reset(lhs);
   reset(rhs);
   for (size_t i = 0; i < K_MAX_SIZE; ++i)
-    EXPECT_EQ(__llvm_libc::memcmp(lhs, rhs, i), 0);
+    ASSERT_EQ(__llvm_libc::memcmp(lhs, rhs, i), 0);
 
   reset(lhs);
   reset(rhs);
   for (size_t i = 0; i < K_MAX_SIZE; ++i) {
     rhs[i] = 'z';
-    EXPECT_LT(__llvm_libc::memcmp(lhs, rhs, K_MAX_SIZE), 0);
+    ASSERT_LT(__llvm_libc::memcmp(lhs, rhs, K_MAX_SIZE), 0);
     rhs[i] = 'a';
   }
 }

libc/test/src/string/memory_utils/CMakeLists.txt

 add_libc_unittest(
   utils_test
   SUITE
     libc_string_unittests
   SRCS
     address_test.cpp
+    algorithm_test.cpp
     backend_test.cpp
     elements_test.cpp
     memory_access_test.cpp
     utils_test.cpp
   COMPILE_OPTIONS
     ${LIBC_COMPILE_OPTIONS_NATIVE}
     -ffreestanding
   DEPENDS
     libc.src.string.memory_utils.memory_utils
     libc.src.__support.CPP.array
     libc.src.__support.CPP.array_ref
 )

libc/test/src/string/memory_utils/algorithm_test.cpp

+
+#define LLVM_LIBC_USE_BUILTIN_MEMCPY_INLINE 0
+
+#include "utils/UnitTest/Test.h"
+#include <src/__support/CPP/Array.h>
+#include <src/string/memory_utils/algorithm.h>
+#include <src/string/memory_utils/backends.h>
+
+#include <sstream>
+
+namespace __llvm_libc {
+
+struct alignas(64) Buffer : cpp::Array<char, 128> {
+  bool contains(const char *ptr) const {
+    return ptr >= data() && ptr < (data() + size());
+  }
+  size_t getOffset(const char *ptr) const { return ptr - data(); }
+  void fill(char c) {
+    for (auto itr = begin(); itr != end(); ++itr)
+      *itr = c;
+  }
+};
+
+static Buffer buffer1;
+static Buffer buffer2;
+static std::ostringstream LOG;
+
+struct TestBackend {
+  static constexpr bool IS_BACKEND_TYPE = true;
+
+  template <typename T> static void log(const char *Action, const char *ptr) {
+    LOG << Action << "<" << sizeof(T) << "> ";
+    if (buffer1.contains(ptr))
+      LOG << "a[" << buffer1.getOffset(ptr) << "]";
+    else if (buffer2.contains(ptr))
+      LOG << "b[" << buffer2.getOffset(ptr) << "]";
+    LOG << "\n";
+  }
+
+  template <typename T, Temporality TS, Aligned AS>
+  static T load(const T *src) {
+    log<T>((AS == Aligned::YES ? "LdA" : "LdU"),
+           reinterpret_cast<const char *>(src));
+    return Scalar64BitBackend::load<T, TS, AS>(src);
+  }
+
+  template <typename T, Temporality TS, Aligned AS>
+  static void store(T *dst, T value) {
+    log<T>((AS == Aligned::YES ? "StA" : "StU"),
+           reinterpret_cast<const char *>(dst));
+    Scalar64BitBackend::store<T, TS, AS>(dst, value);
+  }
+
+  template <typename T> static inline T splat(ubyte value) {
+    LOG << "Splat<" << sizeof(T) << "> " << (unsigned)value << '\n';
+    return Scalar64BitBackend::splat<T>(value);
+  }
+
+  template <typename T> static inline uint64_t notEquals(T v1, T v2) {
+    LOG << "Neq<" << sizeof(T) << ">\n";
+    return Scalar64BitBackend::notEquals<T>(v1, v2);
+  }
+
+  template <typename T> static inline int32_t threeWayCmp(T v1, T v2) {
+    LOG << "Diff<" << sizeof(T) << ">\n";
+    return Scalar64BitBackend::threeWayCmp<T>(v1, v2);
+  }
+
+  template <size_t Size>
+  using getNextType = Scalar64BitBackend::getNextType<Size>;
+};
+
+struct LlvmLibcAlgorithm : public testing::Test {
+  void SetUp() override {
+    LOG = std::ostringstream();
+    LOG << '\n';
+  }
+
+  void fillEqual() {
+    buffer1.fill('a');
+    buffer2.fill('a');
+  }
+
+  void fillDifferent() {
+    buffer1.fill('a');
+    buffer2.fill('b');
+  }
+
+  const char *getTrace() {
+    trace_ = LOG.str();
+    return trace_.c_str();
+  }
+
+  const char *stripComments(const char *expected) {
+    expected_.clear();
+    std::stringstream ss(expected);
+    std::string line;
+    while (std::getline(ss, line, '\n')) {
+      const auto pos = line.find('#');
+      if (pos == std::string::npos) {
+        expected_ += line;
+      } else {
+        auto log = line.substr(0, pos);
+        while (!log.empty() && std::isspace(log.back()))
+          log.pop_back();
+        expected_ += log;
+      }
+      expected_ += '\n';
+    }
+    return expected_.c_str();
+  }
+
+  template <size_t Align = 1> SrcAddr<Align> buf1(size_t offset = 0) const {
+    return buffer1.data() + offset;
+  }
+  template <size_t Align = 1> SrcAddr<Align> buf2(size_t offset = 0) const {
+    return buffer2.data() + offset;
+  }
+  template <size_t Align = 1> DstAddr<Align> dst(size_t offset = 0) const {
+    return buffer1.data() + offset;
+  }
+  template <size_t Align = 1> SrcAddr<Align> src(size_t offset = 0) const {
+    return buffer2.data() + offset;
+  }
+
+private:
+  std::string trace_;
+  std::string expected_;
+};
+
+using _8 = SizedOp<TestBackend, 8>;
+
+///////////////////////////////////////////////////////////////////////////////
+//// Testing fixed fized forward operations
+///////////////////////////////////////////////////////////////////////////////
+
+///////////////////////////////////////////////////////////////////////////////
+// Copy
+
+TEST_F(LlvmLibcAlgorithm, copy_1) {
+  SizedOp<TestBackend, 1>::copy(dst(), src());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<1> b[0]
+StU<1> a[0]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, copy_15) {
+  SizedOp<TestBackend, 15>::copy(dst(), src());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0]
+LdU<4> b[8]
+StU<4> a[8]
+LdU<2> b[12]
+StU<2> a[12]
+LdU<1> b[14]
+StU<1> a[14]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, copy_16) {
+  SizedOp<TestBackend, 16>::copy(dst(), src());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0]
+LdU<8> b[8]
+StU<8> a[8]
+)"));
+}
+///////////////////////////////////////////////////////////////////////////////
+// Move
+
+TEST_F(LlvmLibcAlgorithm, move_1) {
+  SizedOp<TestBackend, 1>::move(dst(), src());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<1> b[0]
+StU<1> a[0]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, move_15) {
+  SizedOp<TestBackend, 15>::move(dst(), src());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+LdU<4> b[8]
+LdU<2> b[12]
+LdU<1> b[14]
+StU<1> a[14]
+StU<2> a[12]
+StU<4> a[8]
+StU<8> a[0]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, move_16) {
+  SizedOp<TestBackend, 16>::move(dst(), src());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+LdU<8> b[8]
+StU<8> a[8]
+StU<8> a[0]
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// set
+
+TEST_F(LlvmLibcAlgorithm, set_1) {
+  SizedOp<TestBackend, 1>::set(dst(), ubyte{42});
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+Splat<1> 42
+StU<1> a[0]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, set_15) {
+  SizedOp<TestBackend, 15>::set(dst(), ubyte{42});
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+Splat<8> 42
+StU<8> a[0]
+Splat<4> 42
+StU<4> a[8]
+Splat<2> 42
+StU<2> a[12]
+Splat<1> 42
+StU<1> a[14]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, set_16) {
+  SizedOp<TestBackend, 16>::set(dst(), ubyte{42});
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+Splat<8> 42
+StU<8> a[0]
+Splat<8> 42
+StU<8> a[8]
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// different
+
+TEST_F(LlvmLibcAlgorithm, different_1) {
+  fillEqual();
+  SizedOp<TestBackend, 1>::isDifferent(buf1(), buf2());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<1> a[0]
+LdU<1> b[0]
+Neq<1>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, different_15) {
+  fillEqual();
+  SizedOp<TestBackend, 15>::isDifferent(buf1(), buf2());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[0]
+LdU<8> b[0]
+Neq<8>
+LdU<4> a[8]
+LdU<4> b[8]
+Neq<4>
+LdU<2> a[12]
+LdU<2> b[12]
+Neq<2>
+LdU<1> a[14]
+LdU<1> b[14]
+Neq<1>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, different_15_no_shortcircuit) {
+  fillDifferent();
+  SizedOp<TestBackend, 15>::isDifferent(buf1(), buf2());
+  // If buffer compare isDifferent we continue to aggregate.
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[0]
+LdU<8> b[0]
+Neq<8>
+LdU<4> a[8]
+LdU<4> b[8]
+Neq<4>
+LdU<2> a[12]
+LdU<2> b[12]
+Neq<2>
+LdU<1> a[14]
+LdU<1> b[14]
+Neq<1>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, different_16) {
+  fillEqual();
+  SizedOp<TestBackend, 16>::isDifferent(buf1(), buf2());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[0]
+LdU<8> b[0]
+Neq<8>
+LdU<8> a[8]
+LdU<8> b[8]
+Neq<8>
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// three_way_cmp
+
+TEST_F(LlvmLibcAlgorithm, three_way_cmp_eq_1) {
+  fillEqual();
+  SizedOp<TestBackend, 1>::threeWayCmp(buf1(), buf2());
+  // Buffer compare equal, returning 0 and no call to Diff.
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<1> a[0]
+LdU<1> b[0]
+Diff<1>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, three_way_cmp_eq_15) {
+  fillEqual();
+  SizedOp<TestBackend, 15>::threeWayCmp(buf1(), buf2());
+  // Buffer compare equal, returning 0 and no call to Diff.
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[0]
+LdU<8> b[0]
+Diff<8>
+LdU<4> a[8]
+LdU<4> b[8]
+Diff<4>
+LdU<2> a[12]
+LdU<2> b[12]
+Diff<2>
+LdU<1> a[14]
+LdU<1> b[14]
+Diff<1>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, three_way_cmp_neq_15_shortcircuit) {
+  fillDifferent();
+  SizedOp<TestBackend, 16>::threeWayCmp(buf1(), buf2());
+  // If buffer compare isDifferent we stop early.
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[0]
+LdU<8> b[0]
+Diff<8>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, three_way_cmp_eq_16) {
+  fillEqual();
+  SizedOp<TestBackend, 16>::threeWayCmp(buf1(), buf2());
+  // Buffer compare equal, returning 0 and no call to Diff.
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[0]
+LdU<8> b[0]
+Diff<8>
+LdU<8> a[8]
+LdU<8> b[8]
+Diff<8>
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//// Testing skip operations
+///////////////////////////////////////////////////////////////////////////////
+
+TEST_F(LlvmLibcAlgorithm, skip_and_set) {
+  Skip<11>::Then<SizedOp<TestBackend, 1>>::set(dst(), ubyte{42});
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+Splat<1> 42
+StU<1> a[11]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, skip_and_different_1) {
+  Skip<11>::Then<SizedOp<TestBackend, 1>>::isDifferent(buf1(), buf2());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<1> a[11]
+LdU<1> b[11]
+Neq<1>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, skip_and_three_way_cmp_8) {
+  Skip<11>::Then<SizedOp<TestBackend, 1>>::threeWayCmp(buf1(), buf2());
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<1> a[11]
+LdU<1> b[11]
+Diff<1>
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//// Testing tail operations
+///////////////////////////////////////////////////////////////////////////////
+
+TEST_F(LlvmLibcAlgorithm, tail_copy_8) {
+  Tail<_8>::copy(dst(), src(), 16);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[8]
+StU<8> a[8]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, tail_move_8) {
+  Tail<_8>::move(dst(), src(), 16);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[8]
+StU<8> a[8]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, tail_set_8) {
+  Tail<_8>::set(dst(), ubyte{42}, 16);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+Splat<8> 42
+StU<8> a[8]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, tail_different_8) {
+  fillEqual();
+  Tail<_8>::isDifferent(buf1(), buf2(), 16);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[8]
+LdU<8> b[8]
+Neq<8>
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, tail_three_way_cmp_8) {
+  fillEqual();
+  Tail<_8>::threeWayCmp(buf1(), buf2(), 16);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> a[8]
+LdU<8> b[8]
+Diff<8>
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//// Testing HeadTail operations
+///////////////////////////////////////////////////////////////////////////////
+
+TEST_F(LlvmLibcAlgorithm, head_tail_copy_8) {
+  HeadTail<_8>::copy(dst(), src(), 16);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0]
+LdU<8> b[8]
+StU<8> a[8]
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//// Testing Loop operations
+///////////////////////////////////////////////////////////////////////////////
+
+TEST_F(LlvmLibcAlgorithm, loop_copy_one_iteration_and_tail) {
+  Loop<_8>::copy(dst(), src(), 10);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0] # covers 0-7
+LdU<8> b[2]
+StU<8> a[2] # covers 2-9
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, loop_copy_two_iteration_and_tail) {
+  Loop<_8>::copy(dst(), src(), 17);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0] # covers 0-7
+LdU<8> b[8]
+StU<8> a[8] # covers 8-15
+LdU<8> b[9]
+StU<8> a[9] # covers 9-16
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, loop_with_one_turn_is_inefficient_but_ok) {
+  Loop<_8>::copy(dst(), src(), 8);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0] # first iteration covers 0-7
+LdU<8> b[0] # tail also covers 0-7 but since Loop is supposed to be used
+StU<8> a[0] # with a sufficient number of iterations the tail cost is amortised
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, loop_with_round_number_of_turn) {
+  Loop<_8>::copy(dst(), src(), 24);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StU<8> a[0] # first iteration covers 0-7
+LdU<8> b[8]
+StU<8> a[8] # second iteration covers 8-15
+LdU<8> b[16]
+StU<8> a[16]
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, dst_aligned_loop) {
+  Loop<_8>::copy(dst<16>(), src(), 23);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[0]
+StA<8> a[0] # store is aligned on 16B
+LdU<8> b[8]
+StA<8> a[8] # subsequent stores are aligned
+LdU<8> b[15]
+StU<8> a[15] # Tail is always unaligned
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, aligned_loop) {
+  Loop<_8>::copy(dst<16>(), src<8>(), 23);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdA<8> b[0] # load is aligned on 8B
+StA<8> a[0] # store is aligned on 16B
+LdA<8> b[8] # subsequent loads are aligned
+StA<8> a[8] # subsequent stores are aligned
+LdU<8> b[15] # Tail is always unaligned
+StU<8> a[15] # Tail is always unaligned
+)"));
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//// Testing Align operations
+///////////////////////////////////////////////////////////////////////////////
+
+TEST_F(LlvmLibcAlgorithm, align_dst_copy_8) {
+  Align<_8, Arg::Dst>::Then<Loop<_8>>::copy(dst(2), src(3), 31);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[3]
+StU<8> a[2] # First store covers unaligned bytes
+LdU<8> b[9]
+StA<8> a[8] # First aligned store
+LdU<8> b[17]
+StA<8> a[16] # Subsequent stores are aligned
+LdU<8> b[25]
+StA<8> a[24] # Subsequent stores are aligned
+LdU<8> b[26]
+StU<8> a[25] # Last store covers remaining bytes
+)"));
+}
+
+TEST_F(LlvmLibcAlgorithm, align_src_copy_8) {
+  Align<_8, Arg::Src>::Then<Loop<_8>>::copy(dst(2), src(3), 31);
+  EXPECT_STREQ(getTrace(), stripComments(R"(
+LdU<8> b[3] # First load covers unaligned bytes
+StU<8> a[2]
+LdA<8> b[8] # First aligned load
+StU<8> a[7]
+LdA<8> b[16] # Subsequent loads are aligned
+StU<8> a[15]
+LdA<8> b[24] # Subsequent loads are aligned
+StU<8> a[23]
+LdU<8> b[26] # Last load covers remaining bytes
+StU<8> a[25]
+)"));
+}
+
+} // namespace __llvm_libc

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

no_sanitize_features = [
     "-msan",
     "-tsan",
     "-ubsan",
 ]
 
 cc_library(
     name = "string_memory_utils",
     hdrs = [
-        "src/string/memory_utils/elements.h",
-        "src/string/memory_utils/elements_aarch64.h",
-        "src/string/memory_utils/elements_x86.h",
+        "src/string/memory_utils/address.h",
+        "src/string/memory_utils/algorithm.h",
+        "src/string/memory_utils/backends.h",
+        "src/string/memory_utils/backend_scalar.h",
+        "src/string/memory_utils/backend_x86.h",
+        "src/string/memory_utils/backend_aarch64.h",
+        "src/string/memory_utils/sized_op.h",
         "src/string/memory_utils/utils.h",
     ],
     textual_hdrs = [
         "src/string/memory_utils/bcmp_implementations.h",
         "src/string/memory_utils/memcmp_implementations.h",
         "src/string/memory_utils/memcpy_implementations.h",
         "src/string/memory_utils/memset_implementations.h",
     ],
     deps = [
         ":__support_common",
         ":__support_cpp_bit",
+        ":__support_cpp_type_traits",
         ":libc_root",
     ],
 )
 
 cc_library(
     name = "string_utils",
     hdrs = ["src/string/string_utils.h"],
     deps = [