[libc] Add bcopy

[sivachandra]

libc/spec/stdc.td

218

This should go in to https://github.com/llvm/llvm-project/blob/main/libc/spec/llvm_libc_ext.td.

[gchatelet]

• move definition in libc extensions

libc/config/darwin/arm/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.isupper
     libc.src.ctype.isxdigit
     libc.src.ctype.toascii
     libc.src.ctype.tolower
     libc.src.ctype.toupper
     
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr
     libc.src.string.memcmp
     libc.src.string.memcpy
     libc.src.string.memmove
     libc.src.string.mempcpy
     libc.src.string.memrchr

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.fcntl.openat
 
     # sched.h entrypoints
     libc.src.sched.sched_getaffinity
     libc.src.sched.sched_setaffinity
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr
     libc.src.string.memcmp
     libc.src.string.memcpy
     libc.src.string.memmove
     libc.src.string.mempcpy
     libc.src.string.memrchr

libc/config/linux/arm/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.isupper
     libc.src.ctype.isxdigit
     libc.src.ctype.toascii
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr
     libc.src.string.memcmp
     libc.src.string.memcpy
     libc.src.string.memmove
     libc.src.string.mempcpy
     libc.src.string.memrchr

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.fcntl.openat
 
     # sched.h entrypoints
     libc.src.sched.sched_getaffinity
     libc.src.sched.sched_setaffinity
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr
     libc.src.string.memcmp
     libc.src.string.memcpy
     libc.src.string.memmove
     libc.src.string.mempcpy
     libc.src.string.memrchr

libc/config/windows/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.isupper
     libc.src.ctype.isxdigit
     libc.src.ctype.toascii
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr
     libc.src.string.memcmp
     libc.src.string.memcpy
     libc.src.string.memmove
     libc.src.string.mempcpy
     libc.src.string.memrchr

libc/docs/strings.rst

 .. TODO(gchatelet): add details about the memory functions.
 
 
 =============  =========
 Function Name  Available
 =============  =========
 bzero          |check|
 bcmp           |check|
+bcopy          |check|       
 memcpy         |check|
 memset         |check|
 memcmp         |check|
 memmove        |check|
 =============  =========
 
 
 Other Raw Memory Functions

libc/spec/stdc.td

HeaderSpec String = HeaderSpec<
                ArgSpec<SizeTType>]
           >,
           FunctionSpec<
               "memmove",
               RetValSpec<VoidPtr>,
               [ArgSpec<VoidPtr>, ArgSpec<ConstVoidPtr>, ArgSpec<SizeTType>]
           >,
           FunctionSpec<
+              "bcopy",
+              RetValSpec<Void>,
+              [ArgSpec<ConstVoidPtr>, ArgSpec<VoidPtr>, ArgSpec<SizeTType>]
+          >,
+          FunctionSpec<
               "memcmp",
               RetValSpec<IntType>,
               [ArgSpec<ConstVoidPtr>, ArgSpec<ConstVoidPtr>, ArgSpec<SizeTType>]
           >,
           FunctionSpec<
               "memchr",
               RetValSpec<VoidPtr>,
               [ArgSpec<ConstVoidPtr>, ArgSpec<IntType>, ArgSpec<SizeTType>]

libc/src/string/CMakeLists.txt

 add_subdirectory(memory_utils)
 
 add_header_library(
   string_utils
   HDRS
     string_utils.h
   DEPENDS
     libc.include.stdlib
     libc.src.__support.CPP.bitset
     .memory_utils.memcpy_implementation
     .memory_utils.bzero_implementation
 )
 
 add_entrypoint_object(
+  bcopy
+  SRCS
+    bcopy.cpp
+  HDRS
+    bcopy.h
+)
+
+add_entrypoint_object(
   memccpy
   SRCS
     memccpy.cpp
   HDRS
     memccpy.h
 )
 
-
 add_entrypoint_object(
   mempcpy
   SRCS
     mempcpy.cpp
   HDRS
     mempcpy.h
   DEPENDS
     .memory_utils.memcpy_implementation

libc/src/string/bcopy.h

+//===-- Implementation header for bcopy -------------------------*- 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_BCOPY_H
+#define LLVM_LIBC_SRC_STRING_BCOPY_H
+
+#include <stddef.h> // size_t
+
+namespace __llvm_libc {
+
+void bcopy(const void *src, void *dest, size_t count);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_BCOPY_H

libc/src/string/bcopy.cpp

+//===-- Implementation of bcopy -------------------------------------------===//
+//
+// 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/bcopy.h"
+#include "src/__support/common.h"
+#include "src/string/memory_utils/memmove_implementations.h"
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(void, bcopy, (const void *src, void *dst, size_t count)) {
+  return inline_memmove(dst, src, count);
+}
+
+} // namespace __llvm_libc

libc/test/src/string/CMakeLists.txt

 add_libc_testsuite(libc_string_unittests)
 
 add_subdirectory(memory_utils)
 
 add_libc_unittest(
+  bcopy_test
+  SUITE
+    libc_string_unittests
+  SRCS
+    bcopy_test.cpp
+  DEPENDS
+    libc.src.string.bcopy
+  LINK_LIBRARIES
+    LibcMemoryHelpers
+)
+
+add_libc_unittest(
   memccpy_test
   SUITE
     libc_string_unittests
   SRCS
     memccpy_test.cpp
   DEPENDS
     libc.src.string.memccpy
 )

libc/test/src/string/bcopy_test.cpp

+//===-- Unittests for bcopy -----------------------------------------------===//
+//
+// 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/__support/CPP/span.h"
+#include "src/string/bcopy.h"
+#include "utils/UnitTest/MemoryMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+using __llvm_libc::cpp::array;
+using __llvm_libc::cpp::span;
+
+TEST(LlvmLibcBcopyTest, MoveZeroByte) {
+  char Buffer[] = {'a', 'b', 'y', 'z'};
+  const char Expected[] = {'a', 'b', 'y', 'z'};
+  void *const Dst = Buffer;
+  __llvm_libc::bcopy(Buffer + 2, Dst, 0);
+  ASSERT_MEM_EQ(Buffer, Expected);
+}
+
+TEST(LlvmLibcBcopyTest, DstAndSrcPointToSameAddress) {
+  char Buffer[] = {'a', 'b'};
+  const char Expected[] = {'a', 'b'};
+  void *const Dst = Buffer;
+  __llvm_libc::bcopy(Buffer, Dst, 1);
+  ASSERT_MEM_EQ(Buffer, Expected);
+}
+
+TEST(LlvmLibcBcopyTest, DstStartsBeforeSrc) {
+  // Set boundary at beginning and end for not overstepping when
+  // copy forward or backward.
+  char Buffer[] = {'z', 'a', 'b', 'c', 'z'};
+  const char Expected[] = {'z', 'b', 'c', 'c', 'z'};
+  void *const Dst = Buffer + 1;
+  __llvm_libc::bcopy(Buffer + 2, Dst, 2);
+  ASSERT_MEM_EQ(Buffer, Expected);
+}
+
+TEST(LlvmLibcBcopyTest, DstStartsAfterSrc) {
+  char Buffer[] = {'z', 'a', 'b', 'c', 'z'};
+  const char Expected[] = {'z', 'a', 'a', 'b', 'z'};
+  void *const Dst = Buffer + 2;
+  __llvm_libc::bcopy(Buffer + 1, Dst, 2);
+  ASSERT_MEM_EQ(Buffer, Expected);
+}
+
+// e.g. `Dst` follow `src`.
+// str: [abcdefghij]
+//      [__src_____]
+//      [_____Dst__]
+TEST(LlvmLibcBcopyTest, SrcFollowDst) {
+  char Buffer[] = {'z', 'a', 'b', 'z'};
+  const char Expected[] = {'z', 'b', 'b', 'z'};
+  void *const Dst = Buffer + 1;
+  __llvm_libc::bcopy(Buffer + 2, Dst, 1);
+  ASSERT_MEM_EQ(Buffer, Expected);
+}
+
+TEST(LlvmLibcBcopyTest, DstFollowSrc) {
+  char Buffer[] = {'z', 'a', 'b', 'z'};
+  const char Expected[] = {'z', 'a', 'a', 'z'};
+  void *const Dst = Buffer + 2;
+  __llvm_libc::bcopy(Buffer + 1, Dst, 1);
+  ASSERT_MEM_EQ(Buffer, Expected);
+}
+
+static constexpr int kMaxSize = 512;
+
+char GetRandomChar() {
+  static constexpr const uint64_t A = 1103515245;
+  static constexpr const uint64_t C = 12345;
+  static constexpr const uint64_t M = 1ULL << 31;
+  static uint64_t Seed = 123456789;
+  Seed = (A * Seed + C) % M;
+  return Seed;
+}
+
+void Randomize(span<char> Buffer) {
+  for (auto &current : Buffer)
+    current = GetRandomChar();
+}
+
+TEST(LlvmLibcBcopyTest, SizeSweep) {
+  using LargeBuffer = array<char, 3 * kMaxSize>;
+  LargeBuffer GroundTruth;
+  Randomize(GroundTruth);
+  for (int Size = 0; Size < kMaxSize; ++Size) {
+    for (int Offset = -Size; Offset < Size; ++Offset) {
+      LargeBuffer Buffer = GroundTruth;
+      LargeBuffer Expected = GroundTruth;
+      size_t DstOffset = kMaxSize;
+      size_t SrcOffset = kMaxSize + Offset;
+      for (int I = 0; I < Size; ++I)
+        Expected[DstOffset + I] = GroundTruth[SrcOffset + I];
+      void *const Dst = Buffer.data() + DstOffset;
+      __llvm_libc::bcopy(Buffer.data() + SrcOffset, Dst, Size);
+      ASSERT_MEM_EQ(Buffer, Expected);
+    }
+  }
+}

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

libc_function(
     features = no_sanitize_features,
     deps = [
         ":__support_common",
         ":string_memory_utils",
     ],
 )
 
 libc_function(
+    name = "bcopy",
+    srcs = ["src/string/bcopy.cpp"],
+    hdrs = ["src/string/bcopy.h"],
+    features = no_sanitize_features,
+    deps = [
+        ":__support_common",
+        ":string_memory_utils",
+    ],
+)
+
+libc_function(
     name = "memcmp",
     srcs = ["src/string/memcmp.cpp"],
     hdrs = ["src/string/memcmp.h"],
     features = no_sanitize_features,
     deps = [
         ":__support_common",
         ":__support_integer_operations",
         ":string_memory_utils",

utils/bazel/llvm-project-overlay/libc/test/src/string/BUILD.bazel

libc_test(
     ],
     deps = [
         "//libc:__support_cpp_span",
         "//libc/utils/UnitTest:memory_matcher",
     ],
 )
 
 libc_test(
+    name = "bcopy_test",
+    srcs = ["bcopy_test.cpp"],
+    libc_function_deps = [
+        "//libc:bcopy",
+    ],
+    deps = [
+        "//libc:__support_cpp_span",
+        "//libc/utils/UnitTest:memory_matcher",
+    ],
+)
+
+libc_test(
     name = "memcmp_test",
     srcs = ["memcmp_test.cpp"],
     libc_function_deps = [
         "//libc:memcmp",
     ],
     deps = [":memory_check_utils"],
 )