[libc] Some clean work with memmove.
- Replace `move_byte_forward()` with `memcpy`. In `memcpy` implementation,
it copies bytes forward from beginning to end. Otherwise, `memmove` unit
tests will break.
- Make `memmove` unit tests work.
Reviewed By: gchatelet
Differential Revision: https://reviews.llvm.org/D109316
GitOrigin-RevId: b659b789c03ac339e28d7b91406b67bb887a426d
diff --git a/src/string/CMakeLists.txt b/src/string/CMakeLists.txt
index b652bef..cfd8bf8 100644
--- a/src/string/CMakeLists.txt
+++ b/src/string/CMakeLists.txt
@@ -19,17 +19,6 @@
)
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
memrchr.cpp
@@ -336,6 +325,27 @@
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
# ------------------------------------------------------------------------------
diff --git a/src/string/memmove.cpp b/src/string/memmove.cpp
index ebbe464..86aa6d4 100644
--- a/src/string/memmove.cpp
+++ b/src/string/memmove.cpp
@@ -15,52 +15,50 @@
namespace __llvm_libc {
-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 inline void move_byte_backward(char *dest_m, const char *src_m,
+static inline void move_byte_backward(char *dst, const char *src,
size_t count) {
for (size_t offset = count - 1; count; --count, --offset)
- dest_m[offset] = src_m[offset];
+ dst[offset] = src[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);
}
LLVM_LIBC_FUNCTION(void *, memmove,
- (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;
+ (void *dst, const void *src, size_t count)) {
+ memmove_impl(reinterpret_cast<char *>(dst),
+ reinterpret_cast<const char *>(src), count);
+ return dst;
}
} // namespace __llvm_libc
diff --git a/test/src/string/memmove_test.cpp b/test/src/string/memmove_test.cpp
index e13722d..22e0b3b 100644
--- a/test/src/string/memmove_test.cpp
+++ b/test/src/string/memmove_test.cpp
@@ -6,64 +6,65 @@
//
//===----------------------------------------------------------------------===//
-#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 *dest, const void *src, size_t count, const void *str,
+ void check_memmove(void *dst, const void *src, size_t count,
+ const unsigned char *str,
const __llvm_libc::cpp::ArrayRef<unsigned char> expected) {
- 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);
+ 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]);
}
};
TEST_F(LlvmLibcMemmoveTest, MoveZeroByte) {
- unsigned char dest[] = {'a', 'b'};
+ unsigned char dst[] = {'a', 'b'};
const unsigned char src[] = {'y', 'z'};
const unsigned char expected[] = {'a', 'b'};
- check_memmove(dest, src, 0, dest, expected);
+ check_memmove(dst, src, 0, dst, expected);
}
-TEST_F(LlvmLibcMemmoveTest, OverlapThatDestAndSrcPointToSameAddress) {
+TEST_F(LlvmLibcMemmoveTest, OverlapThatDstAndSrcPointToSameAddress) {
unsigned char str[] = {'a', 'b'};
const unsigned char expected[] = {'a', 'b'};
check_memmove(str, str, 1, str, expected);
}
-TEST_F(LlvmLibcMemmoveTest, OverlapThatDestStartsBeforeSrc) {
+TEST_F(LlvmLibcMemmoveTest, OverlapThatDstStartsBeforeSrc) {
// 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'};
- // dest is &str[1].
+ // `dst` is `&str[1]`.
check_memmove(&str[1], &str[2], 2, str, expected);
}
-TEST_F(LlvmLibcMemmoveTest, OverlapThatDestStartsAfterSrc) {
+TEST_F(LlvmLibcMemmoveTest, OverlapThatDstStartsAfterSrc) {
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. dest follow src.
+// e.g. `dst` follow `src`.
// str: [abcdefghij]
// [__src_____]
-// [_____dest_]
-TEST_F(LlvmLibcMemmoveTest, SrcFollowDest) {
+// [_____dst__]
+TEST_F(LlvmLibcMemmoveTest, SrcFollowDst) {
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, DestFollowSrc) {
+TEST_F(LlvmLibcMemmoveTest, DstFollowSrc) {
unsigned char str[] = {'z', 'a', 'b', 'z'};
const unsigned char expected[] = {'z', 'a', 'a', 'z'};
check_memmove(&str[2], &str[1], 1, str, expected);
