[libc] Add [l|ll]abs implementation.

[cheng.w]

Summary

Implement abs, labs and llabs with template.

[sivachandra]

Thanks for the patch. Feel free to do labs and llabs as well. You can drive all of them off of a C++ template implementation.

[sivachandra]

Forgot to mention couple of nits.

libc/src/stdlib/abs.cpp

21

Fix.

libc/src/stdlib/abs.h

19

Fix.

[cheng.w]

Thanks for your guidance. memmove needs abs. ; )

[cheng.w]

Implement abs, labs and llabs with template.

[sivachandra]

libc/src/stdlib/abs_utils.h

14 ↗

(On Diff #310442)

Nit: May be give it a name integer_abs and avoid the _ prefix.

[cheng.w]

Fix nit.

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.isupper
     libc.src.ctype.isxdigit
     libc.src.ctype.tolower
     libc.src.ctype.toupper
     
     # errno.h entrypoints
     libc.src.errno.__errno_location
 
+    # stdlib.h entrypoints
+    libc.src.stdlib.abs
+
     # string.h entrypoints
     libc.src.string.bzero
     libc.src.string.memchr
     libc.src.string.memcpy
     libc.src.string.memset
     libc.src.string.memrchr
     libc.src.string.strcat
     libc.src.string.strchr

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.signal.sigemptyset
     libc.src.signal.sigprocmask
     libc.src.signal.sigfillset
     libc.src.signal.signal
 
     # stdlib.h entrypoints
     libc.src.stdlib._Exit
     libc.src.stdlib.abort
+    libc.src.stdlib.abs
 
     # string.h entrypoints
     libc.src.string.bzero
     libc.src.string.memchr
     libc.src.string.memcpy
     libc.src.string.memrchr
     libc.src.string.memset
     libc.src.string.strcat

libc/spec/stdc.td

def StdC : StandardSpec<"stdc"> {
 
   HeaderSpec StdLib = HeaderSpec<
       "stdlib.h",
       [], // Macros
       [], // Types
       [], // Enumerations
       [
           FunctionSpec<"abort", RetValSpec<NoReturn>, [ArgSpec<VoidType>]>,
+          FunctionSpec<"abs", RetValSpec<IntType>, [ArgSpec<IntType>]>,
           FunctionSpec<"_Exit", RetValSpec<NoReturn>, [ArgSpec<IntType>]>,
       ]
   >;
 
   HeaderSpec Errno = HeaderSpec<
       "errno.h",
       [
         Macro<"errno">,

libc/src/stdlib/CMakeLists.txt

SRCS
     abort.cpp
   HDRS
     abort.h
   DEPENDS
     libc.include.stdlib
     libc.src.signal.raise
     ._Exit
 )
+
+add_entrypoint_object(
+  abs
+  SRCS
+    abs.cpp
+  HDRS
+    abs.h
+)

libc/src/stdlib/abs.h

+//===-- Implementation header for abs ---------------------------*- 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_STDLIB_ABS_H
+#define LLVM_LIBC_SRC_STDLIB_ABS_H
+
+namespace __llvm_libc {
+
+int abs(int n);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STDLIB_ABS_H
 No newline at end of file

libc/src/stdlib/abs.cpp

+//===-- Implementation of abs ---------------------------------------------===//
+//
+// 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/stdlib/abs.h"
+#include "src/__support/common.h"
+
+namespace __llvm_libc {
+
+int LLVM_LIBC_ENTRYPOINT(abs)(int n) {
+  if (n < 0)
+    return -n;
+  return n;
+}
+
+} // namespace __llvm_libc
 No newline at end of file

libc/test/src/stdlib/CMakeLists.txt

SRCS
     abort_test.cpp
   DEPENDS
     libc.include.stdlib
     libc.include.signal
     libc.src.stdlib.abort
     libc.src.stdlib._Exit
     libc.src.signal.raise
 )
+
+add_libc_unittest(
+  abs_test
+  SUITE
+    libc_stdlib_unittests
+  SRCS
+    abs_test.cpp
+  DEPENDS
+    libc.src.stdlib.abs
+)

libc/test/src/stdlib/abs_test.cpp

+//===-- Unittests for abs -------------------------------------------------===//
+//
+// 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/stdlib/abs.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(AbsTest, Zero) { EXPECT_EQ(__llvm_libc::abs(0), 0); }
+
+TEST(AbsTest, Positive) { EXPECT_EQ(__llvm_libc::abs(1), 1); }
+
+TEST(AbsTest, Negative) { EXPECT_EQ(__llvm_libc::abs(-1), 1); }