[libc-commits] [libc] 6297479 - [libc][stdbit] implement stdc_first_trailing_one (C23) (#81768)
via libc-commits
libc-commits at lists.llvm.org
Wed Feb 14 11:10:52 PST 2024
Author: Nick Desaulniers
Date: 2024-02-14T11:10:48-08:00
New Revision: 6297479ff0808e7c5335ec9ec837513e1cff610f
URL: https://github.com/llvm/llvm-project/commit/6297479ff0808e7c5335ec9ec837513e1cff610f
DIFF: https://github.com/llvm/llvm-project/commit/6297479ff0808e7c5335ec9ec837513e1cff610f.diff
LOG: [libc][stdbit] implement stdc_first_trailing_one (C23) (#81768)
Added:
libc/src/stdbit/stdc_first_trailing_one_uc.cpp
libc/src/stdbit/stdc_first_trailing_one_uc.h
libc/src/stdbit/stdc_first_trailing_one_ui.cpp
libc/src/stdbit/stdc_first_trailing_one_ui.h
libc/src/stdbit/stdc_first_trailing_one_ul.cpp
libc/src/stdbit/stdc_first_trailing_one_ul.h
libc/src/stdbit/stdc_first_trailing_one_ull.cpp
libc/src/stdbit/stdc_first_trailing_one_ull.h
libc/src/stdbit/stdc_first_trailing_one_us.cpp
libc/src/stdbit/stdc_first_trailing_one_us.h
libc/test/src/stdbit/stdc_first_trailing_one_uc_test.cpp
libc/test/src/stdbit/stdc_first_trailing_one_ui_test.cpp
libc/test/src/stdbit/stdc_first_trailing_one_ul_test.cpp
libc/test/src/stdbit/stdc_first_trailing_one_ull_test.cpp
libc/test/src/stdbit/stdc_first_trailing_one_us_test.cpp
Modified:
libc/config/linux/x86_64/entrypoints.txt
libc/docs/stdbit.rst
libc/include/llvm-libc-macros/stdbit-macros.h
libc/spec/stdc.td
libc/src/__support/CPP/bit.h
libc/src/stdbit/CMakeLists.txt
libc/test/include/stdbit_test.cpp
libc/test/src/__support/CPP/bit_test.cpp
libc/test/src/stdbit/CMakeLists.txt
Removed:
################################################################################
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index d53b225e4d87e2..57b4a1e0f93d4f 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -127,6 +127,11 @@ set(TARGET_LIBC_ENTRYPOINTS
libc.src.stdbit.stdc_first_trailing_zero_ui
libc.src.stdbit.stdc_first_trailing_zero_ul
libc.src.stdbit.stdc_first_trailing_zero_ull
+ libc.src.stdbit.stdc_first_trailing_one_uc
+ libc.src.stdbit.stdc_first_trailing_one_us
+ libc.src.stdbit.stdc_first_trailing_one_ui
+ libc.src.stdbit.stdc_first_trailing_one_ul
+ libc.src.stdbit.stdc_first_trailing_one_ull
# stdlib.h entrypoints
libc.src.stdlib.abs
diff --git a/libc/docs/stdbit.rst b/libc/docs/stdbit.rst
index 790a747baaa2da..3bd83ff70c8924 100644
--- a/libc/docs/stdbit.rst
+++ b/libc/docs/stdbit.rst
@@ -66,11 +66,11 @@ stdc_first_trailing_zero_us |check|
stdc_first_trailing_zero_ui |check|
stdc_first_trailing_zero_ul |check|
stdc_first_trailing_zero_ull |check|
-stdc_first_trailing_one_uc
-stdc_first_trailing_one_us
-stdc_first_trailing_one_ui
-stdc_first_trailing_one_ul
-stdc_first_trailing_one_ull
+stdc_first_trailing_one_uc |check|
+stdc_first_trailing_one_us |check|
+stdc_first_trailing_one_ui |check|
+stdc_first_trailing_one_ul |check|
+stdc_first_trailing_one_ull |check|
stdc_count_zeros_uc
stdc_count_zeros_us
stdc_count_zeros_ui
@@ -121,7 +121,7 @@ stdc_trailing_ones |check|
stdc_first_leading_zero |check|
stdc_first_leading_one |check|
stdc_first_trailing_zero |check|
-stdc_first_trailing_one
+stdc_first_trailing_one |check|
stdc_count_zeros
stdc_count_ones
stdc_has_single_bit
diff --git a/libc/include/llvm-libc-macros/stdbit-macros.h b/libc/include/llvm-libc-macros/stdbit-macros.h
index 0ec8aef10d3e0a..0c97da96ebba29 100644
--- a/libc/include/llvm-libc-macros/stdbit-macros.h
+++ b/libc/include/llvm-libc-macros/stdbit-macros.h
@@ -116,6 +116,21 @@ inline unsigned stdc_first_trailing_zero(unsigned long x) {
inline unsigned stdc_first_trailing_zero(unsigned long long x) {
return stdc_first_trailing_zero_ull(x);
}
+inline unsigned stdc_first_trailing_one(unsigned char x) {
+ return stdc_first_trailing_one_uc(x);
+}
+inline unsigned stdc_first_trailing_one(unsigned short x) {
+ return stdc_first_trailing_one_us(x);
+}
+inline unsigned stdc_first_trailing_one(unsigned x) {
+ return stdc_first_trailing_one_ui(x);
+}
+inline unsigned stdc_first_trailing_one(unsigned long x) {
+ return stdc_first_trailing_one_ul(x);
+}
+inline unsigned stdc_first_trailing_one(unsigned long long x) {
+ return stdc_first_trailing_one_ull(x);
+}
#else
#define stdc_leading_zeros(x) \
_Generic((x), \
@@ -166,6 +181,13 @@ inline unsigned stdc_first_trailing_zero(unsigned long long x) {
unsigned: stdc_first_trailing_zero_ui, \
unsigned long: stdc_first_trailing_zero_ul, \
unsigned long long: stdc_first_trailing_zero_ull)(x)
+#define stdc_first_trailing_one(x) \
+ _Generic((x), \
+ unsigned char: stdc_first_trailing_one_uc, \
+ unsigned short: stdc_first_trailing_one_us, \
+ unsigned: stdc_first_trailing_one_ui, \
+ unsigned long: stdc_first_trailing_one_ul, \
+ unsigned long long: stdc_first_trailing_one_ull)(x)
#endif // __cplusplus
#endif // __LLVM_LIBC_MACROS_STDBIT_MACROS_H
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
index b97e90d1a8ae34..9ed94638f522ca 100644
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -783,7 +783,8 @@ def StdC : StandardSpec<"stdc"> {
Macro<"stdc_trailing_ones">,
Macro<"stdc_first_leading_zero">,
Macro<"stdc_first_leading_one">,
- Macro<"stdc_first_trailing_zero">
+ Macro<"stdc_first_trailing_zero">,
+ Macro<"stdc_first_trailing_one">
], // Macros
[], // Types
[], // Enumerations
@@ -818,11 +819,11 @@ def StdC : StandardSpec<"stdc"> {
FunctionSpec<"stdc_first_leading_one_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
FunctionSpec<"stdc_first_leading_one_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
FunctionSpec<"stdc_first_leading_one_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
- FunctionSpec<"stdc_first_trailing_zero_uc", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedCharType>]>,
- FunctionSpec<"stdc_first_trailing_zero_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
- FunctionSpec<"stdc_first_trailing_zero_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
- FunctionSpec<"stdc_first_trailing_zero_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
- FunctionSpec<"stdc_first_trailing_zero_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
+ FunctionSpec<"stdc_first_trailing_one_uc", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedCharType>]>,
+ FunctionSpec<"stdc_first_trailing_one_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
+ FunctionSpec<"stdc_first_trailing_one_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
+ FunctionSpec<"stdc_first_trailing_one_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
+ FunctionSpec<"stdc_first_trailing_one_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>
] // Functions
>;
diff --git a/libc/src/__support/CPP/bit.h b/libc/src/__support/CPP/bit.h
index 5afcc875752cff..f5e50262371f26 100644
--- a/libc/src/__support/CPP/bit.h
+++ b/libc/src/__support/CPP/bit.h
@@ -243,6 +243,11 @@ template <typename T, typename = cpp::enable_if_t<cpp::is_unsigned_v<T>>>
: countr_zero(static_cast<T>(~value)) + 1;
}
+template <typename T, typename = cpp::enable_if_t<cpp::is_unsigned_v<T>>>
+[[nodiscard]] LIBC_INLINE constexpr int first_trailing_one(T value) {
+ return value == cpp::numeric_limits<T>::max() ? 0 : countr_zero(value) + 1;
+}
+
} // namespace LIBC_NAMESPACE::cpp
#endif // LLVM_LIBC_SRC___SUPPORT_CPP_BIT_H
diff --git a/libc/src/stdbit/CMakeLists.txt b/libc/src/stdbit/CMakeLists.txt
index fa68d4a90dbb7e..14cc26e206e0d3 100644
--- a/libc/src/stdbit/CMakeLists.txt
+++ b/libc/src/stdbit/CMakeLists.txt
@@ -6,6 +6,7 @@ set(prefixes
first_leading_zero
first_leading_one
first_trailing_zero
+ first_trailing_one
)
set(suffixes c s i l ll)
foreach(prefix IN LISTS prefixes)
diff --git a/libc/src/stdbit/stdc_first_trailing_one_uc.cpp b/libc/src/stdbit/stdc_first_trailing_one_uc.cpp
new file mode 100644
index 00000000000000..6ed35966be61a0
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_uc.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_first_trailing_one_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_first_trailing_one_uc.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_trailing_one_uc,
+ (unsigned char value)) {
+ return static_cast<unsigned>(cpp::first_trailing_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_trailing_one_uc.h b/libc/src/stdbit/stdc_first_trailing_one_uc.h
new file mode 100644
index 00000000000000..d733ce850de0fb
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_uc.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_trailing_one_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_FIRST_TRAILING_ONE_UC_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_UC_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_trailing_one_uc(unsigned char value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_UC_H
diff --git a/libc/src/stdbit/stdc_first_trailing_one_ui.cpp b/libc/src/stdbit/stdc_first_trailing_one_ui.cpp
new file mode 100644
index 00000000000000..a89083bd49507a
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_ui.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_first_trailing_one_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_first_trailing_one_ui.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_trailing_one_ui, (unsigned value)) {
+ return static_cast<unsigned>(cpp::first_trailing_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_trailing_one_ui.h b/libc/src/stdbit/stdc_first_trailing_one_ui.h
new file mode 100644
index 00000000000000..6a6a5046709aec
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_ui.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_trailing_one_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_FIRST_TRAILING_ONE_UI_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_UI_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_trailing_one_ui(unsigned value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_UI_H
diff --git a/libc/src/stdbit/stdc_first_trailing_one_ul.cpp b/libc/src/stdbit/stdc_first_trailing_one_ul.cpp
new file mode 100644
index 00000000000000..f30078d0f5ffaa
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_ul.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_first_trailing_one_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_first_trailing_one_ul.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_trailing_one_ul,
+ (unsigned long value)) {
+ return static_cast<unsigned>(cpp::first_trailing_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_trailing_one_ul.h b/libc/src/stdbit/stdc_first_trailing_one_ul.h
new file mode 100644
index 00000000000000..09b6a9bbbe34a1
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_ul.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_trailing_one_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_FIRST_TRAILING_ONE_UL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_UL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_trailing_one_ul(unsigned long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_UL_H
diff --git a/libc/src/stdbit/stdc_first_trailing_one_ull.cpp b/libc/src/stdbit/stdc_first_trailing_one_ull.cpp
new file mode 100644
index 00000000000000..2e526a890cda9c
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_ull.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_first_trailing_one_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_first_trailing_one_ull.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_trailing_one_ull,
+ (unsigned long long value)) {
+ return static_cast<unsigned>(cpp::first_trailing_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_trailing_one_ull.h b/libc/src/stdbit/stdc_first_trailing_one_ull.h
new file mode 100644
index 00000000000000..3e12a1d7456691
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_ull.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_trailing_one_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_FIRST_TRAILING_ONE_ULL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_ULL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_trailing_one_ull(unsigned long long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_ULL_H
diff --git a/libc/src/stdbit/stdc_first_trailing_one_us.cpp b/libc/src/stdbit/stdc_first_trailing_one_us.cpp
new file mode 100644
index 00000000000000..e4c88e0d7906b9
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_us.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_first_trailing_one_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_first_trailing_one_us.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_trailing_one_us,
+ (unsigned short value)) {
+ return static_cast<unsigned>(cpp::first_trailing_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_trailing_one_us.h b/libc/src/stdbit/stdc_first_trailing_one_us.h
new file mode 100644
index 00000000000000..f380898fc68cde
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_trailing_one_us.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_trailing_one_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_FIRST_TRAILING_ONE_US_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_US_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_trailing_one_us(unsigned short value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_TRAILING_ONE_US_H
diff --git a/libc/test/include/stdbit_test.cpp b/libc/test/include/stdbit_test.cpp
index 238c2d44fac45a..22d5533df1e854 100644
--- a/libc/test/include/stdbit_test.cpp
+++ b/libc/test/include/stdbit_test.cpp
@@ -64,6 +64,13 @@ unsigned stdc_first_trailing_zero_ul(unsigned long) noexcept { return 0x0DU; }
unsigned stdc_first_trailing_zero_ull(unsigned long long) noexcept {
return 0x0FU;
}
+unsigned stdc_first_trailing_one_uc(unsigned char) noexcept { return 0x1AU; }
+unsigned stdc_first_trailing_one_us(unsigned short) noexcept { return 0x1BU; }
+unsigned stdc_first_trailing_one_ui(unsigned) noexcept { return 0x1CU; }
+unsigned stdc_first_trailing_one_ul(unsigned long) noexcept { return 0x1DU; }
+unsigned stdc_first_trailing_one_ull(unsigned long long) noexcept {
+ return 0x1FU;
+}
}
#include "include/llvm-libc-macros/stdbit-macros.h"
@@ -123,3 +130,11 @@ TEST(LlvmLibcStdbitTest, TypeGenericMacroFirstTrailingZero) {
EXPECT_EQ(stdc_first_trailing_zero(0UL), 0x0DU);
EXPECT_EQ(stdc_first_trailing_zero(0ULL), 0x0FU);
}
+
+TEST(LlvmLibcStdbitTest, TypeGenericMacroFirstTrailingOne) {
+ EXPECT_EQ(stdc_first_trailing_one(static_cast<unsigned char>(0U)), 0x1AU);
+ EXPECT_EQ(stdc_first_trailing_one(static_cast<unsigned short>(0U)), 0x1BU);
+ EXPECT_EQ(stdc_first_trailing_one(0U), 0x1CU);
+ EXPECT_EQ(stdc_first_trailing_one(0UL), 0x1DU);
+ EXPECT_EQ(stdc_first_trailing_one(0ULL), 0x1FU);
+}
diff --git a/libc/test/src/__support/CPP/bit_test.cpp b/libc/test/src/__support/CPP/bit_test.cpp
index 914c6ca823c8ef..5d1f451776a5fe 100644
--- a/libc/test/src/__support/CPP/bit_test.cpp
+++ b/libc/test/src/__support/CPP/bit_test.cpp
@@ -226,4 +226,10 @@ TYPED_TEST(LlvmLibcBitTest, FirstTrailingZero, UnsignedTypes) {
EXPECT_EQ(first_trailing_zero<T>(~(T(1) << i)), i + 1);
}
+TYPED_TEST(LlvmLibcBitTest, FirstTrailingOne, UnsignedTypes) {
+ EXPECT_EQ(first_trailing_one<T>(cpp::numeric_limits<T>::max()), 0);
+ for (int i = 0U; i != cpp::numeric_limits<T>::digits; ++i)
+ EXPECT_EQ(first_trailing_one<T>(T(1) << i), i + 1);
+}
+
} // namespace LIBC_NAMESPACE::cpp
diff --git a/libc/test/src/stdbit/CMakeLists.txt b/libc/test/src/stdbit/CMakeLists.txt
index d5896ad83dbfab..203f48bda99a44 100644
--- a/libc/test/src/stdbit/CMakeLists.txt
+++ b/libc/test/src/stdbit/CMakeLists.txt
@@ -8,6 +8,7 @@ set(prefixes
first_leading_zero
first_leading_one
first_trailing_zero
+ first_trailing_one
)
set(suffixes c s i l ll)
foreach(prefix IN LISTS prefixes)
diff --git a/libc/test/src/stdbit/stdc_first_trailing_one_uc_test.cpp b/libc/test/src/stdbit/stdc_first_trailing_one_uc_test.cpp
new file mode 100644
index 00000000000000..ed2b4921cdada4
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_first_trailing_one_uc_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_first_trailing_one_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_first_trailing_one_uc.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcFirstTrailingOneUcTest, ALL) {
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_uc(UCHAR_MAX), 0U);
+}
+
+TEST(LlvmLibcStdcFirstTrailingOneUcTest, OneHot) {
+ for (unsigned i = 0U; i != UCHAR_WIDTH; ++i)
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_uc(1U << i), i + 1);
+}
diff --git a/libc/test/src/stdbit/stdc_first_trailing_one_ui_test.cpp b/libc/test/src/stdbit/stdc_first_trailing_one_ui_test.cpp
new file mode 100644
index 00000000000000..137c8a42e407df
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_first_trailing_one_ui_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_first_trailing_one_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_first_trailing_one_ui.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcFirstTrailingOneUiTest, ALL) {
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_ui(UINT_MAX), 0U);
+}
+
+TEST(LlvmLibcStdcFirstTrailingOneUiTest, OneHot) {
+ for (unsigned i = 0U; i != UINT_WIDTH; ++i)
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_ui(1U << i), i + 1);
+}
diff --git a/libc/test/src/stdbit/stdc_first_trailing_one_ul_test.cpp b/libc/test/src/stdbit/stdc_first_trailing_one_ul_test.cpp
new file mode 100644
index 00000000000000..3fc1f3f16c60de
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_first_trailing_one_ul_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_first_trailing_one_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_first_trailing_one_ul.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcFirstTrailingOneUlTest, ALL) {
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_ul(ULONG_MAX), 0U);
+}
+
+TEST(LlvmLibcStdcFirstTrailingOneUlTest, OneHot) {
+ for (unsigned i = 0U; i != ULONG_WIDTH; ++i)
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_ul(1UL << i), i + 1);
+}
diff --git a/libc/test/src/stdbit/stdc_first_trailing_one_ull_test.cpp b/libc/test/src/stdbit/stdc_first_trailing_one_ull_test.cpp
new file mode 100644
index 00000000000000..5719e09a5120a0
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_first_trailing_one_ull_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_first_trailing_one_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/__support/CPP/limits.h"
+#include "src/stdbit/stdc_first_trailing_one_ull.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcFirstTrailingOneUllTest, ALL) {
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_ull(ULLONG_MAX), 0U);
+}
+
+TEST(LlvmLibcStdcFirstTrailingOneUllTest, OneHot) {
+ for (unsigned i = 0U; i != ULLONG_WIDTH; ++i)
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_ull(1ULL << i), i + 1);
+}
diff --git a/libc/test/src/stdbit/stdc_first_trailing_one_us_test.cpp b/libc/test/src/stdbit/stdc_first_trailing_one_us_test.cpp
new file mode 100644
index 00000000000000..60021552310bee
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_first_trailing_one_us_test.cpp
@@ -0,0 +1,20 @@
+//===-- Unittests for stdc_first_trailing_one_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/__support/CPP/limits.h"
+#include "src/stdbit/stdc_first_trailing_one_us.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcFirstTrailingOneUsTest, ALL) {
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_us(USHRT_MAX), 0U);
+}
+
+TEST(LlvmLibcStdcFirstTrailingOneUsTest, OneHot) {
+ for (unsigned i = 0U; i != USHRT_WIDTH; ++i)
+ EXPECT_EQ(LIBC_NAMESPACE::stdc_first_trailing_one_us(1U << i), i + 1);
+}
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