[reland][libc] Add bcopy

Differential Revision: https://reviews.llvm.org/D138994

libc/config/darwin/arm/entrypoints.txt

@@ -19,6 +19,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr

libc/config/linux/aarch64/entrypoints.txt

@@ -28,6 +28,7 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr

libc/config/linux/arm/entrypoints.txt

@@ -19,6 +19,7 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr

libc/config/linux/x86_64/entrypoints.txt

@@ -28,6 +28,7 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr

libc/config/windows/entrypoints.txt

@@ -19,6 +19,7 @@ set(TARGET_LIBC_ENTRYPOINTS
 
     # string.h entrypoints
     libc.src.string.bcmp
+    libc.src.string.bcopy
     libc.src.string.bzero
     libc.src.string.memccpy
     libc.src.string.memchr

libc/docs/strings.rst

@@ -36,6 +36,7 @@ Function Name  Available
 =============  =========
 bzero          |check|
 bcmp           |check|
+bcopy          |check|       
 memcpy         |check|
 memset         |check|
 memcmp         |check|

libc/spec/llvm_libc_ext.td

@@ -5,6 +5,11 @@ def LLVMLibcExt : StandardSpec<"llvm_libc_ext"> {
       [], // Types
       [], // Enumerations
       [
+          FunctionSpec<
+              "bcopy",
+              RetValSpec<VoidType>,
+              [ArgSpec<ConstVoidPtr>, ArgSpec<VoidPtr>, ArgSpec<SizeTType>]
+          >,
           FunctionSpec<
               "bzero",
               RetValSpec<VoidType>,

libc/src/string/CMakeLists.txt

@@ -20,6 +20,14 @@ add_header_library(
     .memory_utils.memcpy_implementation
 )
 
+add_entrypoint_object(
+  bcopy
+  SRCS
+    bcopy.cpp
+  HDRS
+    bcopy.h
+)
+
 add_entrypoint_object(
   memccpy
   SRCS
@@ -28,7 +36,6 @@ add_entrypoint_object(
     memccpy.h
 )
 
-
 add_entrypoint_object(
   mempcpy
   SRCS

libc/src/string/bcopy.cpp

@@ -0,0 +1,19 @@
+//===-- 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/src/string/bcopy.h

@@ -0,0 +1,20 @@
+//===-- 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/test/src/string/CMakeLists.txt

@@ -2,6 +2,18 @@ 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/test/src/string/bcopy_test.cpp

@@ -0,0 +1,104 @@
+//===-- 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

@@ -1124,6 +1124,17 @@ libc_function(
     ],
 )
 
+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"],

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

@@ -146,6 +146,18 @@ libc_test(
     ],
 )
 
+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"],