[libc-commits] [libc] [libc][stdbit] implement stdc_bit_floor (C23) (PR #84233)

Nick Desaulniers via libc-commits libc-commits at lists.llvm.org
Wed Mar 6 12:52:14 PST 2024 

https://github.com/nickdesaulniers created https://github.com/llvm/llvm-project/pull/84233

None

>From 2ebd87cd7ad150001993ab1e2e034cf501377da5 Mon Sep 17 00:00:00 2001
From: Nick Desaulniers <ndesaulniers at google.com>
Date: Wed, 6 Mar 2024 12:23:31 -0800
Subject: [PATCH] [libc][stdbit] implement stdc_bit_floor (C23)

---
 libc/config/linux/x86_64/entrypoints.txt      |  5 +++++
 libc/docs/stdbit.rst                          | 12 +++++-----
 libc/include/llvm-libc-macros/stdbit-macros.h | 20 +++++++++++++++++
 libc/spec/stdc.td                             | 10 +++++++--
 libc/src/__support/CPP/bit.h                  |  2 +-
 libc/src/stdbit/CMakeLists.txt                |  1 +
 libc/src/stdbit/stdc_bit_floor_uc.cpp         | 20 +++++++++++++++++
 libc/src/stdbit/stdc_bit_floor_ui.cpp         | 20 +++++++++++++++++
 libc/src/stdbit/stdc_bit_floor_ui.h           | 18 +++++++++++++++
 libc/src/stdbit/stdc_bit_floor_ul.cpp         | 20 +++++++++++++++++
 libc/src/stdbit/stdc_bit_floor_ul.h           | 18 +++++++++++++++
 libc/src/stdbit/stdc_bit_floor_ull.cpp        | 21 ++++++++++++++++++
 libc/src/stdbit/stdc_bit_floor_ull.h          | 18 +++++++++++++++
 libc/src/stdbit/stdc_bit_floor_us.cpp         | 20 +++++++++++++++++
 libc/src/stdbit/stdc_bit_floor_us.h           | 18 +++++++++++++++
 libc/test/include/stdbit_test.cpp             | 17 ++++++++++++++
 libc/test/src/stdbit/CMakeLists.txt           |  1 +
 .../src/stdbit/stdc_bit_floor_uc_test.cpp     | 22 +++++++++++++++++++
 .../src/stdbit/stdc_bit_floor_ui_test.cpp     | 21 ++++++++++++++++++
 .../src/stdbit/stdc_bit_floor_ul_test.cpp     | 21 ++++++++++++++++++
 .../src/stdbit/stdc_bit_floor_ull_test.cpp    | 21 ++++++++++++++++++
 .../src/stdbit/stdc_bit_floor_us_test.cpp     | 22 +++++++++++++++++++
 22 files changed, 339 insertions(+), 9 deletions(-)
 create mode 100644 libc/src/stdbit/stdc_bit_floor_uc.cpp
 create mode 100644 libc/src/stdbit/stdc_bit_floor_ui.cpp
 create mode 100644 libc/src/stdbit/stdc_bit_floor_ui.h
 create mode 100644 libc/src/stdbit/stdc_bit_floor_ul.cpp
 create mode 100644 libc/src/stdbit/stdc_bit_floor_ul.h
 create mode 100644 libc/src/stdbit/stdc_bit_floor_ull.cpp
 create mode 100644 libc/src/stdbit/stdc_bit_floor_ull.h
 create mode 100644 libc/src/stdbit/stdc_bit_floor_us.cpp
 create mode 100644 libc/src/stdbit/stdc_bit_floor_us.h
 create mode 100644 libc/test/src/stdbit/stdc_bit_floor_uc_test.cpp
 create mode 100644 libc/test/src/stdbit/stdc_bit_floor_ui_test.cpp
 create mode 100644 libc/test/src/stdbit/stdc_bit_floor_ul_test.cpp
 create mode 100644 libc/test/src/stdbit/stdc_bit_floor_ull_test.cpp
 create mode 100644 libc/test/src/stdbit/stdc_bit_floor_us_test.cpp

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index a6c3041773dfcc..3ca3b45fe274c6 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -152,6 +152,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdbit.stdc_bit_width_ui
     libc.src.stdbit.stdc_bit_width_ul
     libc.src.stdbit.stdc_bit_width_ull
+    libc.src.stdbit.stdc_bit_floor_uc
+    libc.src.stdbit.stdc_bit_floor_us
+    libc.src.stdbit.stdc_bit_floor_ui
+    libc.src.stdbit.stdc_bit_floor_ul
+    libc.src.stdbit.stdc_bit_floor_ull
 
     # stdlib.h entrypoints
     libc.src.stdlib.abs
diff --git a/libc/docs/stdbit.rst b/libc/docs/stdbit.rst
index ccd1393ef5d926..3ec46cf8d8ffa4 100644
--- a/libc/docs/stdbit.rst
+++ b/libc/docs/stdbit.rst
@@ -91,11 +91,11 @@ stdc_bit_width_us            |check|
 stdc_bit_width_ui            |check|
 stdc_bit_width_ul            |check|
 stdc_bit_width_ull           |check|
-stdc_bit_floor_uc
-stdc_bit_floor_us
-stdc_bit_floor_ui
-stdc_bit_floor_ul
-stdc_bit_floor_ull
+stdc_bit_floor_uc            |check|
+stdc_bit_floor_us            |check|
+stdc_bit_floor_ui            |check|
+stdc_bit_floor_ul            |check|
+stdc_bit_floor_ull           |check|
 stdc_bit_ceil_uc
 stdc_bit_ceil_us
 stdc_bit_ceil_ui
@@ -126,7 +126,7 @@ stdc_count_zeros           |check|
 stdc_count_ones            |check|
 stdc_has_single_bit        |check|
 stdc_bit_width             |check|
-stdc_bit_floor
+stdc_bit_floor             |check|
 stdc_bit_ceil
 =========================  =========
 
diff --git a/libc/include/llvm-libc-macros/stdbit-macros.h b/libc/include/llvm-libc-macros/stdbit-macros.h
index 104418ca4856ba..5b51068f866b71 100644
--- a/libc/include/llvm-libc-macros/stdbit-macros.h
+++ b/libc/include/llvm-libc-macros/stdbit-macros.h
@@ -181,6 +181,19 @@ inline unsigned stdc_bit_width(unsigned long x) { return stdc_bit_width_ul(x); }
 inline unsigned stdc_bit_width(unsigned long long x) {
   return stdc_bit_width_ull(x);
 }
+inline unsigned char stdc_bit_floor(unsigned char x) {
+  return stdc_bit_floor_uc(x);
+}
+inline unsigned short stdc_bit_floor(unsigned short x) {
+  return stdc_bit_floor_us(x);
+}
+inline unsigned stdc_bit_floor(unsigned x) { return stdc_bit_floor_ui(x); }
+inline unsigned long stdc_bit_floor(unsigned long x) {
+  return stdc_bit_floor_ul(x);
+}
+inline unsigned long long stdc_bit_floor(unsigned long long x) {
+  return stdc_bit_floor_ull(x);
+}
 #else
 #define stdc_leading_zeros(x)                                                  \
   _Generic((x),                                                                \
@@ -266,6 +279,13 @@ inline unsigned stdc_bit_width(unsigned long long x) {
       unsigned: stdc_bit_width_ui,                                             \
       unsigned long: stdc_bit_width_ul,                                        \
       unsigned long long: stdc_bit_width_ull)(x)
+#define stdc_bit_floor(x)                                                      \
+  _Generic((x),                                                                \
+      unsigned char: stdc_bit_floor_ui,                                        \
+      unsigned short: stdc_bit_floor_us,                                       \
+      unsigned: stdc_bit_floor_ui,                                             \
+      unsigned long: stdc_bit_floor_ul,                                        \
+      unsigned long long: stdc_bit_floor_ull)(x)
 #endif // __cplusplus
 
 #endif // __LLVM_LIBC_MACROS_STDBIT_MACROS_H
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
index cfebc60a0a9a8e..a3a856a4ec8507 100644
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -801,7 +801,8 @@ def StdC : StandardSpec<"stdc"> {
         Macro<"stdc_count_zeros">,
         Macro<"stdc_count_ones">,
         Macro<"stdc_has_single_bit">,
-        Macro<"std_bit_width">
+        Macro<"std_bit_width">,
+        Macro<"std_bit_floor">
       ], // Macros
       [], // Types
       [], // Enumerations
@@ -860,7 +861,12 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"stdc_bit_width_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
           FunctionSpec<"stdc_bit_width_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
           FunctionSpec<"stdc_bit_width_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
-          FunctionSpec<"stdc_bit_width_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>
+          FunctionSpec<"stdc_bit_width_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
+          FunctionSpec<"stdc_bit_floor_uc", RetValSpec<UnsignedCharType>, [ArgSpec<UnsignedCharType>]>,
+          FunctionSpec<"stdc_bit_floor_us", RetValSpec<UnsignedShortType>, [ArgSpec<UnsignedShortType>]>,
+          FunctionSpec<"stdc_bit_floor_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
+          FunctionSpec<"stdc_bit_floor_ul", RetValSpec<UnsignedLongType>, [ArgSpec<UnsignedLongType>]>,
+          FunctionSpec<"stdc_bit_floor_ull", RetValSpec<UnsignedLongLongType>, [ArgSpec<UnsignedLongLongType>]>
       ] // Functions
   >;
 
diff --git a/libc/src/__support/CPP/bit.h b/libc/src/__support/CPP/bit.h
index 7d11e7d5c497e0..504974ce2c60af 100644
--- a/libc/src/__support/CPP/bit.h
+++ b/libc/src/__support/CPP/bit.h
@@ -169,7 +169,7 @@ template <typename T, typename = cpp::enable_if_t<cpp::is_unsigned_v<T>>>
 [[nodiscard]] LIBC_INLINE constexpr T bit_floor(T value) {
   if (!value)
     return 0;
-  return T(1) << (cpp::bit_width(value) - 1);
+  return static_cast<T>(T(1) << (cpp::bit_width(value) - 1));
 }
 
 /// Returns the smallest integral power of two no smaller than value if value is
diff --git a/libc/src/stdbit/CMakeLists.txt b/libc/src/stdbit/CMakeLists.txt
index f077baeee6d275..7ab4fee4454a15 100644
--- a/libc/src/stdbit/CMakeLists.txt
+++ b/libc/src/stdbit/CMakeLists.txt
@@ -11,6 +11,7 @@ set(prefixes
   count_ones
   has_single_bit
   bit_width
+  bit_floor
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)
diff --git a/libc/src/stdbit/stdc_bit_floor_uc.cpp b/libc/src/stdbit/stdc_bit_floor_uc.cpp
new file mode 100644
index 00000000000000..6cb04c9eb43e62
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_uc.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_bit_floor_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_bit_floor_uc.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned char, stdc_bit_floor_uc, (unsigned char value)) {
+  return cpp::bit_floor(value);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_bit_floor_ui.cpp b/libc/src/stdbit/stdc_bit_floor_ui.cpp
new file mode 100644
index 00000000000000..149b63f190cf37
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_ui.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_bit_floor_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_bit_floor_ui.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_bit_floor_ui, (unsigned value)) {
+  return cpp::bit_floor(value);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_bit_floor_ui.h b/libc/src/stdbit/stdc_bit_floor_ui.h
new file mode 100644
index 00000000000000..fcc606386f86d3
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_ui.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_bit_floor_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_BIT_FLOOR_UI_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_UI_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_bit_floor_ui(unsigned value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_UI_H
diff --git a/libc/src/stdbit/stdc_bit_floor_ul.cpp b/libc/src/stdbit/stdc_bit_floor_ul.cpp
new file mode 100644
index 00000000000000..a29a044545684e
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_ul.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_bit_floor_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_bit_floor_ul.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned long, stdc_bit_floor_ul, (unsigned long value)) {
+  return cpp::bit_floor(value);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_bit_floor_ul.h b/libc/src/stdbit/stdc_bit_floor_ul.h
new file mode 100644
index 00000000000000..08327aa60c9069
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_ul.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_bit_floor_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_BIT_FLOOR_UL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_UL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned long stdc_bit_floor_ul(unsigned long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_UL_H
diff --git a/libc/src/stdbit/stdc_bit_floor_ull.cpp b/libc/src/stdbit/stdc_bit_floor_ull.cpp
new file mode 100644
index 00000000000000..d1084b63573227
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_ull.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_bit_floor_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_bit_floor_ull.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned long long, stdc_bit_floor_ull,
+                   (unsigned long long value)) {
+  return cpp::bit_floor(value);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_bit_floor_ull.h b/libc/src/stdbit/stdc_bit_floor_ull.h
new file mode 100644
index 00000000000000..8f360b23855ad6
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_ull.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_bit_floor_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_BIT_FLOOR_ULL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_ULL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned long long stdc_bit_floor_ull(unsigned long long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_ULL_H
diff --git a/libc/src/stdbit/stdc_bit_floor_us.cpp b/libc/src/stdbit/stdc_bit_floor_us.cpp
new file mode 100644
index 00000000000000..d1357a980e3a8a
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_us.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_bit_floor_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_bit_floor_us.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned short, stdc_bit_floor_us, (unsigned short value)) {
+  return cpp::bit_floor(value);
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_bit_floor_us.h b/libc/src/stdbit/stdc_bit_floor_us.h
new file mode 100644
index 00000000000000..fcd0b9e3c549a1
--- /dev/null
+++ b/libc/src/stdbit/stdc_bit_floor_us.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_bit_floor_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_BIT_FLOOR_US_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_US_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned short stdc_bit_floor_us(unsigned short value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_BIT_FLOOR_US_H
diff --git a/libc/test/include/stdbit_test.cpp b/libc/test/include/stdbit_test.cpp
index dfb7c97e3d9ee0..20820d52fbdede 100644
--- a/libc/test/include/stdbit_test.cpp
+++ b/libc/test/include/stdbit_test.cpp
@@ -91,6 +91,13 @@ unsigned stdc_bit_width_us(unsigned short) noexcept { return 0x4BU; }
 unsigned stdc_bit_width_ui(unsigned) noexcept { return 0x4CU; }
 unsigned stdc_bit_width_ul(unsigned long) noexcept { return 0x4DU; }
 unsigned stdc_bit_width_ull(unsigned long long) noexcept { return 0x4EU; }
+unsigned char stdc_bit_floor_uc(unsigned char) noexcept { return 0x5AU; }
+unsigned short stdc_bit_floor_us(unsigned short) noexcept { return 0x5BU; }
+unsigned stdc_bit_floor_ui(unsigned) noexcept { return 0x5CU; }
+unsigned long stdc_bit_floor_ul(unsigned long) noexcept { return 0x5DU; }
+unsigned long long stdc_bit_floor_ull(unsigned long long) noexcept {
+  return 0x5EU;
+}
 }
 
 #include "include/llvm-libc-macros/stdbit-macros.h"
@@ -190,3 +197,13 @@ TEST(LlvmLibcStdbitTest, TypeGenericMacroBitWidth) {
   EXPECT_EQ(stdc_bit_width(1UL), 0x4DU);
   EXPECT_EQ(stdc_bit_width(1ULL), 0x4EU);
 }
+
+TEST(LlvmLibcStdbitTest, TypeGenericMacroBitFloor) {
+  EXPECT_EQ(stdc_bit_floor(static_cast<unsigned char>(0U)),
+            static_cast<unsigned char>(0x5AU));
+  EXPECT_EQ(stdc_bit_floor(static_cast<unsigned short>(0U)),
+            static_cast<unsigned short>(0x5BU));
+  EXPECT_EQ(stdc_bit_floor(0U), 0x5CU);
+  EXPECT_EQ(stdc_bit_floor(0UL), 0x5DUL);
+  EXPECT_EQ(stdc_bit_floor(0ULL), 0x5EULL);
+}
diff --git a/libc/test/src/stdbit/CMakeLists.txt b/libc/test/src/stdbit/CMakeLists.txt
index f7e17d73229935..3aed56c0e92380 100644
--- a/libc/test/src/stdbit/CMakeLists.txt
+++ b/libc/test/src/stdbit/CMakeLists.txt
@@ -13,6 +13,7 @@ set(prefixes
   count_ones
   has_single_bit
   bit_width
+  bit_floor
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)
diff --git a/libc/test/src/stdbit/stdc_bit_floor_uc_test.cpp b/libc/test/src/stdbit/stdc_bit_floor_uc_test.cpp
new file mode 100644
index 00000000000000..254abd043d6e0c
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_bit_floor_uc_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_bit_floor_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_bit_floor_uc.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitfloorUcTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_uc(0U),
+            static_cast<unsigned char>(0));
+}
+
+TEST(LlvmLibcStdcBitfloorUcTest, Ones) {
+  for (unsigned i = 0U; i != UCHAR_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_uc(UCHAR_MAX >> i),
+              static_cast<unsigned char>(1 << (UCHAR_WIDTH - i - 1)));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_floor_ui_test.cpp b/libc/test/src/stdbit/stdc_bit_floor_ui_test.cpp
new file mode 100644
index 00000000000000..53790402a9bda9
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_bit_floor_ui_test.cpp
@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_bit_floor_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_bit_floor_ui.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitfloorUiTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_ui(0U), 0U);
+}
+
+TEST(LlvmLibcStdcBitfloorUiTest, Ones) {
+  for (unsigned i = 0U; i != INT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_ui(UINT_MAX >> i),
+              1U << (UINT_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_floor_ul_test.cpp b/libc/test/src/stdbit/stdc_bit_floor_ul_test.cpp
new file mode 100644
index 00000000000000..1c574437e02b79
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_bit_floor_ul_test.cpp
@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_bit_floor_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_bit_floor_ul.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitfloorUlTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_ul(0UL), 0UL);
+}
+
+TEST(LlvmLibcStdcBitfloorUlTest, Ones) {
+  for (unsigned i = 0U; i != ULONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_ul(ULONG_MAX >> i),
+              1UL << (ULONG_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_floor_ull_test.cpp b/libc/test/src/stdbit/stdc_bit_floor_ull_test.cpp
new file mode 100644
index 00000000000000..4717d427a40a72
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_bit_floor_ull_test.cpp
@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_bit_floor_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_bit_floor_ull.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitfloorUllTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_ull(0ULL), 0ULL);
+}
+
+TEST(LlvmLibcStdcBitfloorUllTest, Ones) {
+  for (unsigned i = 0U; i != ULLONG_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_ull(ULLONG_MAX >> i),
+              1ULL << (ULLONG_WIDTH - i - 1));
+}
diff --git a/libc/test/src/stdbit/stdc_bit_floor_us_test.cpp b/libc/test/src/stdbit/stdc_bit_floor_us_test.cpp
new file mode 100644
index 00000000000000..4df87fb079ba76
--- /dev/null
+++ b/libc/test/src/stdbit/stdc_bit_floor_us_test.cpp
@@ -0,0 +1,22 @@
+//===-- Unittests for stdc_bit_floor_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_bit_floor_us.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcBitfloorUsTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_us(0U),
+            static_cast<unsigned short>(0));
+}
+
+TEST(LlvmLibcStdcBitfloorUsTest, Ones) {
+  for (unsigned i = 0U; i != USHRT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_bit_floor_us(USHRT_MAX >> i),
+              static_cast<unsigned short>(1 << (USHRT_WIDTH - i - 1)));
+}

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