Revert "[libc] Some clean work with memmove."

This reverts commit b659b789c0.

libc/src/string/CMakeLists.txt

@@ -18,6 +18,17 @@ add_entrypoint_object(
     .string_utils
 )
 
+add_entrypoint_object(
+  memmove
+  SRCS
+    memmove.cpp
+  HDRS
+    memmove.h
+  DEPENDS
+    libc.src.__support.integer_operations
+    libc.src.string.memcpy
+)
+
 add_entrypoint_object(
   memrchr
   SRCS
@@ -324,27 +335,6 @@ else()
   add_memcpy(memcpy)
 endif()
 
-# ------------------------------------------------------------------------------
-# memmove
-# ------------------------------------------------------------------------------
-
-function(add_memmove memmove_name)
-  add_implementation(memmove ${memmove_name}
-          SRCS ${MEMMOVE_SRC}
-          HDRS ${LIBC_SOURCE_DIR}/src/string/memmove.h
-          DEPENDS
-          .memory_utils.memory_utils
-          libc.src.__support.integer_operations
-          libc.src.string.memcpy
-          COMPILE_OPTIONS
-          -fno-builtin-memmove
-          ${ARGN}
-          )
-endfunction()
-
-set(MEMMOVE_SRC ${LIBC_SOURCE_DIR}/src/string/memmove.cpp)
-add_memmove(memmove)
-
 # ------------------------------------------------------------------------------
 # memset
 # ------------------------------------------------------------------------------

libc/src/string/memmove.cpp

@@ -15,50 +15,52 @@
 
 namespace __llvm_libc {
 
-static inline void move_byte_backward(char *dst, const char *src,
-                                      size_t count) {
-  for (size_t offset = count - 1; count; --count, --offset)
-    dst[offset] = src[offset];
+static inline void move_byte_forward(char *dest_m, const char *src_m,
+                                     size_t count) {
+  for (size_t offset = 0; count; --count, ++offset)
+    dest_m[offset] = src_m[offset];
 }
 
-static void memmove_impl(char *dst, const char *src, size_t count) {
-
-  // If the distance between `src` and `dst` is equal to or greater
-  // than count (integerAbs(src - dst) >= count), they would not overlap.
-  // e.g. greater     equal       overlapping
-  //      [12345678]  [12345678]  [12345678]
-  // src: [_ab_____]  [_ab_____]  [_ab_____]
-  // dst: [_____yz_]  [___yz___]  [__yz____]
-
-  // Call `memcpy` when `src` and `dst` do not overlap.
-  if (__llvm_libc::integerAbs(src - dst) >= static_cast<ptrdiff_t>(count))
-    __llvm_libc::memcpy(dst, src, count);
-
-  // Overlap cases.
-  // If `dst` starts before `src` (dst < src), copy forward from beginning to
-  // end. If `dst` starts after `src` (dst > src), copy backward from end to
-  // beginning. If `dst` and `src` start at the same address (dst == src), do
-  // nothing.
-  // e.g. forward      backward
-  //             *->    <-*
-  // src: [___abcde_]  [_abcde___]
-  // dst: [_abc--___]  [___--cde_]
-
-  // In `memcpy` implementation, it copies bytes forward from beginning to
-  // end. Otherwise, `memmove` unit tests will break.
-  if (dst < src)
-    __llvm_libc::memcpy(dst, src, count);
-
-  // TODO: Optimize `move_byte_xxx(...)` functions.
-  if (dst > src)
-    move_byte_backward(dst, src, count);
+static inline void move_byte_backward(char *dest_m, const char *src_m,
+                                      size_t count) {
+  for (size_t offset = count - 1; count; --count, --offset)
+    dest_m[offset] = src_m[offset];
 }
 
 LLVM_LIBC_FUNCTION(void *, memmove,
-                   (void *dst, const void *src, size_t count)) {
-  memmove_impl(reinterpret_cast<char *>(dst),
-               reinterpret_cast<const char *>(src), count);
-  return dst;
+                   (void *dest, const void *src, size_t count)) {
+  char *dest_c = reinterpret_cast<char *>(dest);
+  const char *src_c = reinterpret_cast<const char *>(src);
+
+  // If the distance between src_c and dest_c is equal to or greater
+  // than count (integerAbs(src_c - dest_c) >= count), they would not overlap.
+  // e.g.   greater     equal       overlapping
+  //        [12345678]  [12345678]  [12345678]
+  // src_c: [_ab_____]  [_ab_____]  [_ab_____]
+  // dest_c:[_____yz_]  [___yz___]  [__yz____]
+
+  // Use memcpy if src_c and dest_c do not overlap.
+  if (__llvm_libc::integerAbs(src_c - dest_c) >= static_cast<ptrdiff_t>(count))
+    return __llvm_libc::memcpy(dest_c, src_c, count);
+
+  // Overlap cases.
+  // If dest_c starts before src_c (dest_c < src_c), copy forward(pointer add 1)
+  // from beginning to end.
+  // If dest_c starts after src_c (dest_c > src_c), copy backward(pointer add
+  // -1) from end to beginning.
+  // If dest_c and src_c start at the same address (dest_c == src_c),
+  // just return dest.
+  // e.g.    forward      backward
+  //             *-->        <--*
+  // src_c : [___abcde_]  [_abcde___]
+  // dest_c: [_abc--___]  [___--cde_]
+
+  // TODO: Optimize `move_byte_xxx(...)` functions.
+  if (dest_c < src_c)
+    move_byte_forward(dest_c, src_c, count);
+  if (dest_c > src_c)
+    move_byte_backward(dest_c, src_c, count);
+  return dest;
 }
 
 } // namespace __llvm_libc

libc/test/src/string/memmove_test.cpp

@@ -6,65 +6,64 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/string/memcmp.h"
 #include "src/string/memmove.h"
 #include "utils/CPP/ArrayRef.h"
 #include "utils/UnitTest/Test.h"
 
 class LlvmLibcMemmoveTest : public __llvm_libc::testing::Test {
 public:
-  void check_memmove(void *dst, const void *src, size_t count,
-                     const unsigned char *str,
+  void check_memmove(void *dest, const void *src, size_t count, const void *str,
                      const __llvm_libc::cpp::ArrayRef<unsigned char> expected) {
-    void *result = __llvm_libc::memmove(dst, src, count);
-    // Making sure the pointer returned is same with `dst`.
-    EXPECT_EQ(result, dst);
-    // `expected` is designed according to `str`.
-    // `dst` and `src` might be part of `str`.
-    // Making sure `str` is same with `expected`.
-    for (size_t i = 0; i < expected.size(); ++i)
-      EXPECT_EQ(str[i], expected[i]);
+    void *result = __llvm_libc::memmove(dest, src, count);
+    // Making sure the pointer returned is same with dest.
+    EXPECT_EQ(result, dest);
+    // expected is designed according to str.
+    // dest and src might be part of str.
+    // Making sure the str is same with expected.
+    EXPECT_EQ(__llvm_libc::memcmp(str, expected.data(), expected.size()), 0);
   }
 };
 
 TEST_F(LlvmLibcMemmoveTest, MoveZeroByte) {
-  unsigned char dst[] = {'a', 'b'};
+  unsigned char dest[] = {'a', 'b'};
   const unsigned char src[] = {'y', 'z'};
   const unsigned char expected[] = {'a', 'b'};
-  check_memmove(dst, src, 0, dst, expected);
+  check_memmove(dest, src, 0, dest, expected);
 }
 
-TEST_F(LlvmLibcMemmoveTest, OverlapThatDstAndSrcPointToSameAddress) {
+TEST_F(LlvmLibcMemmoveTest, OverlapThatDestAndSrcPointToSameAddress) {
   unsigned char str[] = {'a', 'b'};
   const unsigned char expected[] = {'a', 'b'};
   check_memmove(str, str, 1, str, expected);
 }
 
-TEST_F(LlvmLibcMemmoveTest, OverlapThatDstStartsBeforeSrc) {
+TEST_F(LlvmLibcMemmoveTest, OverlapThatDestStartsBeforeSrc) {
   // Set boundary at beginning and end for not overstepping when
   // copy forward or backward.
   unsigned char str[] = {'z', 'a', 'b', 'c', 'z'};
   const unsigned char expected[] = {'z', 'b', 'c', 'c', 'z'};
-  // `dst` is `&str[1]`.
+  // dest is &str[1].
   check_memmove(&str[1], &str[2], 2, str, expected);
 }
 
-TEST_F(LlvmLibcMemmoveTest, OverlapThatDstStartsAfterSrc) {
+TEST_F(LlvmLibcMemmoveTest, OverlapThatDestStartsAfterSrc) {
   unsigned char str[] = {'z', 'a', 'b', 'c', 'z'};
   const unsigned char expected[] = {'z', 'a', 'a', 'b', 'z'};
   check_memmove(&str[2], &str[1], 2, str, expected);
 }
 
-// e.g. `dst` follow `src`.
+// e.g. dest follow src.
 // str: [abcdefghij]
 //      [__src_____]
-//      [_____dst__]
-TEST_F(LlvmLibcMemmoveTest, SrcFollowDst) {
+//      [_____dest_]
+TEST_F(LlvmLibcMemmoveTest, SrcFollowDest) {
   unsigned char str[] = {'z', 'a', 'b', 'z'};
   const unsigned char expected[] = {'z', 'b', 'b', 'z'};
   check_memmove(&str[1], &str[2], 1, str, expected);
 }
 
-TEST_F(LlvmLibcMemmoveTest, DstFollowSrc) {
+TEST_F(LlvmLibcMemmoveTest, DestFollowSrc) {
   unsigned char str[] = {'z', 'a', 'b', 'z'};
   const unsigned char expected[] = {'z', 'a', 'a', 'z'};
   check_memmove(&str[2], &str[1], 1, str, expected);