[libc][stdbit] implement stdc_trailing_ones (C23)

libc/config/linux/x86_64/entrypoints.txt

@@ -107,6 +107,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdbit.stdc_trailing_zeros_ui
     libc.src.stdbit.stdc_trailing_zeros_ul
     libc.src.stdbit.stdc_trailing_zeros_ull
+    libc.src.stdbit.stdc_trailing_ones_uc
+    libc.src.stdbit.stdc_trailing_ones_us
+    libc.src.stdbit.stdc_trailing_ones_ui
+    libc.src.stdbit.stdc_trailing_ones_ul
+    libc.src.stdbit.stdc_trailing_ones_ull
 
     # stdlib.h entrypoints
     libc.src.stdlib.abs

libc/include/llvm-libc-macros/stdbit-macros.h

@@ -9,6 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_STDBIT_MACROS_H
 #define __LLVM_LIBC_MACROS_STDBIT_MACROS_H
 
+// TODO(https://github.com/llvm/llvm-project/issues/80509): support _BitInt().
 #ifdef __cplusplus
 inline unsigned stdc_leading_zeros(unsigned char x) {
   return stdc_leading_zeros_uc(x);
@@ -55,6 +56,21 @@ inline unsigned stdc_trailing_zeros(unsigned long x) {
 inline unsigned stdc_trailing_zeros(unsigned long long x) {
   return stdc_trailing_zeros_ull(x);
 }
+inline unsigned stdc_trailing_ones(unsigned char x) {
+  return stdc_trailing_ones_uc(x);
+}
+inline unsigned stdc_trailing_ones(unsigned short x) {
+  return stdc_trailing_ones_us(x);
+}
+inline unsigned stdc_trailing_ones(unsigned x) {
+  return stdc_trailing_ones_ui(x);
+}
+inline unsigned stdc_trailing_ones(unsigned long x) {
+  return stdc_trailing_ones_ul(x);
+}
+inline unsigned stdc_trailing_ones(unsigned long long x) {
+  return stdc_trailing_ones_ull(x);
+}
 #else
 #define stdc_leading_zeros(x)                                                  \
   _Generic((x),                                                                \
@@ -77,6 +93,13 @@ inline unsigned stdc_trailing_zeros(unsigned long long x) {
       unsigned: stdc_trailing_zeros_ui,                                        \
       unsigned long: stdc_trailing_zeros_ul,                                   \
       unsigned long long: stdc_trailing_zeros_ull)(x)
+#define stdc_trailing_ones(x)                                                  \
+  _Generic((x),                                                                \
+      unsigned char: stdc_trailing_ones_uc,                                    \
+      unsigned short: stdc_trailing_ones_us,                                   \
+      unsigned: stdc_trailing_ones_ui,                                         \
+      unsigned long: stdc_trailing_ones_ul,                                    \
+      unsigned long long: stdc_trailing_ones_ull)(x)
 #endif // __cplusplus
 
 #endif // __LLVM_LIBC_MACROS_STDBIT_MACROS_H

libc/spec/stdc.td

@@ -777,7 +777,8 @@ def StdC : StandardSpec<"stdc"> {
       [
         Macro<"stdc_leading_zeros">,
         Macro<"stdc_leading_ones">,
-        Macro<"stdc_trailing_zeros">
+        Macro<"stdc_trailing_zeros">,
+        Macro<"stdc_trailing_ones">
       ], // Macros
       [], // Types
       [], // Enumerations
@@ -796,7 +797,12 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"stdc_trailing_zeros_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
           FunctionSpec<"stdc_trailing_zeros_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
           FunctionSpec<"stdc_trailing_zeros_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
-          FunctionSpec<"stdc_trailing_zeros_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>
+          FunctionSpec<"stdc_trailing_zeros_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
+          FunctionSpec<"stdc_trailing_ones_uc", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedCharType>]>,
+          FunctionSpec<"stdc_trailing_ones_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
+          FunctionSpec<"stdc_trailing_ones_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
+          FunctionSpec<"stdc_trailing_ones_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
+          FunctionSpec<"stdc_trailing_ones_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>
       ] // Functions
   >;
 

libc/src/stdbit/CMakeLists.txt

@@ -2,6 +2,7 @@ set(prefixes
   leading_zeros
   leading_ones
   trailing_zeros
+  trailing_ones
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)

libc/src/stdbit/stdc_trailing_ones_uc.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_trailing_ones_uc ---------------------------===//
+//
+// 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/stdbit/stdc_trailing_ones_uc.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_trailing_ones_uc, (unsigned char value)) {
+  return static_cast<unsigned>(cpp::countr_one(value));
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdbit/stdc_trailing_ones_uc.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_trailing_ones_uc --------*- 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_STDBIT_STDC_TRAILING_ONES_UC_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_UC_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_trailing_ones_uc(unsigned char value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_UC_H

libc/src/stdbit/stdc_trailing_ones_ui.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_trailing_ones_ui ---------------------------===//
+//
+// 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/stdbit/stdc_trailing_ones_ui.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_trailing_ones_ui, (unsigned value)) {
+  return static_cast<unsigned>(cpp::countr_one(value));
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdbit/stdc_trailing_ones_ui.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_trailing_ones_ui --------*- 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_STDBIT_STDC_TRAILING_ONES_UI_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_UI_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_trailing_ones_ui(unsigned value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_UI_H

libc/src/stdbit/stdc_trailing_ones_ul.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_trailing_ones_ul ---------------------------===//
+//
+// 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/stdbit/stdc_trailing_ones_ul.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_trailing_ones_ul, (unsigned long value)) {
+  return static_cast<unsigned>(cpp::countr_one(value));
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdbit/stdc_trailing_ones_ul.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_trailing_ones_ul --------*- 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_STDBIT_STDC_TRAILING_ONES_UL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_UL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_trailing_ones_ul(unsigned long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_UL_H

libc/src/stdbit/stdc_trailing_ones_ull.cpp

@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_trailing_ones_ull --------------------------===//
+//
+// 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/stdbit/stdc_trailing_ones_ull.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_trailing_ones_ull,
+                   (unsigned long long value)) {
+  return static_cast<unsigned>(cpp::countr_one(value));
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdbit/stdc_trailing_ones_ull.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_trailing_ones_ull --------*- 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_STDBIT_STDC_TRAILING_ONES_ULL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_ULL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_trailing_ones_ull(unsigned long long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_ULL_H

libc/src/stdbit/stdc_trailing_ones_us.cpp

@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_trailing_ones_us ---------------------------===//
+//
+// 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/stdbit/stdc_trailing_ones_us.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_trailing_ones_us, (unsigned short value)) {
+  return static_cast<unsigned>(cpp::countr_one(value));
+}
+
+} // namespace LIBC_NAMESPACE

libc/src/stdbit/stdc_trailing_ones_us.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_trailing_ones_us --------*- 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_STDBIT_STDC_TRAILING_ONES_US_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_US_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_trailing_ones_us(unsigned short value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_TRAILING_ONES_US_H

libc/test/include/stdbit_test.cpp

@@ -38,6 +38,11 @@ unsigned stdc_trailing_zeros_us(unsigned short) noexcept { return 0xCBU; }
 unsigned stdc_trailing_zeros_ui(unsigned) noexcept { return 0xCCU; }
 unsigned stdc_trailing_zeros_ul(unsigned long) noexcept { return 0xCDU; }
 unsigned stdc_trailing_zeros_ull(unsigned long long) noexcept { return 0xCFU; }
+unsigned stdc_trailing_ones_uc(unsigned char) noexcept { return 0xDAU; }
+unsigned stdc_trailing_ones_us(unsigned short) noexcept { return 0xDBU; }
+unsigned stdc_trailing_ones_ui(unsigned) noexcept { return 0xDCU; }
+unsigned stdc_trailing_ones_ul(unsigned long) noexcept { return 0xDDU; }
+unsigned stdc_trailing_ones_ull(unsigned long long) noexcept { return 0xDFU; }
 }
 
 #include "include/llvm-libc-macros/stdbit-macros.h"
@@ -65,3 +70,11 @@ TEST(LlvmLibcStdbitTest, TypeGenericMacroTrailingZeros) {
   EXPECT_EQ(stdc_trailing_zeros(0UL), 0xCDU);
   EXPECT_EQ(stdc_trailing_zeros(0ULL), 0xCFU);
 }
+
+TEST(LlvmLibcStdbitTest, TypeGenericMacroTrailingOnes) {
+  EXPECT_EQ(stdc_trailing_ones(static_cast<unsigned char>(0U)), 0xDAU);
+  EXPECT_EQ(stdc_trailing_ones(static_cast<unsigned short>(0U)), 0xDBU);
+  EXPECT_EQ(stdc_trailing_ones(0U), 0xDCU);
+  EXPECT_EQ(stdc_trailing_ones(0UL), 0xDDU);
+  EXPECT_EQ(stdc_trailing_ones(0ULL), 0xDFU);
+}

libc/test/src/stdbit/CMakeLists.txt

@@ -4,6 +4,7 @@ set(prefixes
   leading_zeros
   leading_ones
   trailing_zeros
+  trailing_ones
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)

libc/test/src/stdbit/stdc_trailing_ones_uc_test.cpp

@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_trailing_ones_uc -------------------------------===//
+//
+// 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/limits.h"
+#include "src/stdbit/stdc_trailing_ones_uc.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcTrailingOnesUcTest, ALL) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_trailing_ones_uc(UCHAR_MAX),
+            static_cast<unsigned>(UCHAR_WIDTH));
+}
+
+TEST(LlvmLibcStdcTrailingOnesUcTest, ZeroHot) {
+  for (unsigned i = 0U; i != UCHAR_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_trailing_ones_uc(~(1U << i)), i);
+}

libc/test/src/stdbit/stdc_trailing_ones_ui_test.cpp

@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_trailing_ones_ui -------------------------------===//
+//
+// 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/limits.h"
+#include "src/stdbit/stdc_trailing_ones_ui.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcTrailingOnesUiTest, ALL) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_trailing_ones_ui(UINT_MAX),
+            static_cast<unsigned>(UINT_WIDTH));
+}
+
+TEST(LlvmLibcStdcTrailingOnesUiTest, ZeroHot) {
+  for (unsigned i = 0U; i != UINT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_trailing_ones_ui(~(1U << i)), i);
+}

libc/test/src/stdbit/stdc_trailing_ones_ul_test.cpp

@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_trailing_ones_ul -------------------------------===//
+//
+// 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/limits.h"
+#include "src/stdbit/stdc_trailing_ones_ul.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcTrailingOnesUlTest, ALL) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_trailing_ones_ul(ULONG_MAX),
+            static_cast<unsigned>(ULONG_WIDTH));
+}
+
+TEST(LlvmLibcStdcTrailingOnesUlTest, ZeroHot) {
+  for (unsigned i = 0U; i != ULONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_trailing_ones_ul(~(1UL << i)), i);
+}