[libc][stdbit] implement stdc_count_zeros (C23) (llvm#82437)

libc/config/linux/x86_64/entrypoints.txt

@@ -132,6 +132,11 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdbit.stdc_first_trailing_one_ui
     libc.src.stdbit.stdc_first_trailing_one_ul
     libc.src.stdbit.stdc_first_trailing_one_ull
+    libc.src.stdbit.stdc_count_zeros_uc
+    libc.src.stdbit.stdc_count_zeros_us
+    libc.src.stdbit.stdc_count_zeros_ui
+    libc.src.stdbit.stdc_count_zeros_ul
+    libc.src.stdbit.stdc_count_zeros_ull
 
     # stdlib.h entrypoints
     libc.src.stdlib.abs

libc/docs/stdbit.rst

@@ -71,11 +71,11 @@ 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
-stdc_count_zeros_ul
-stdc_count_zeros_ull
+stdc_count_zeros_uc          |check|
+stdc_count_zeros_us          |check|
+stdc_count_zeros_ui          |check|
+stdc_count_zeros_ul          |check|
+stdc_count_zeros_ull         |check|
 stdc_count_ones_uc
 stdc_count_ones_us
 stdc_count_ones_ui
@@ -122,7 +122,7 @@ stdc_first_leading_zero    |check|
 stdc_first_leading_one     |check|
 stdc_first_trailing_zero   |check|
 stdc_first_trailing_one    |check|
-stdc_count_zeros
+stdc_count_zeros           |check|
 stdc_count_ones
 stdc_has_single_bit
 stdc_bit_width

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

@@ -131,6 +131,19 @@ inline unsigned stdc_first_trailing_one(unsigned long x) {
 inline unsigned stdc_first_trailing_one(unsigned long long x) {
   return stdc_first_trailing_one_ull(x);
 }
+inline unsigned stdc_count_zeros(unsigned char x) {
+  return stdc_count_zeros_uc(x);
+}
+inline unsigned stdc_count_zeros(unsigned short x) {
+  return stdc_count_zeros_us(x);
+}
+inline unsigned stdc_count_zeros(unsigned x) { return stdc_count_zeros_ui(x); }
+inline unsigned stdc_count_zeros(unsigned long x) {
+  return stdc_count_zeros_ul(x);
+}
+inline unsigned stdc_count_zeros(unsigned long long x) {
+  return stdc_count_zeros_ull(x);
+}
 #else
 #define stdc_leading_zeros(x)                                                  \
   _Generic((x),                                                                \
@@ -188,6 +201,13 @@ inline unsigned stdc_first_trailing_one(unsigned long long x) {
       unsigned: stdc_first_trailing_one_ui,                                    \
       unsigned long: stdc_first_trailing_one_ul,                               \
       unsigned long long: stdc_first_trailing_one_ull)(x)
+#define stdc_count_zeros(x)                                                    \
+  _Generic((x),                                                                \
+      unsigned char: stdc_count_zeros_uc,                                      \
+      unsigned short: stdc_count_zeros_us,                                     \
+      unsigned: stdc_count_zeros_ui,                                           \
+      unsigned long: stdc_count_zeros_ul,                                      \
+      unsigned long long: stdc_count_zeros_ull)(x)
 #endif // __cplusplus
 
 #endif // __LLVM_LIBC_MACROS_STDBIT_MACROS_H

libc/spec/stdc.td

@@ -790,7 +790,8 @@ def StdC : StandardSpec<"stdc"> {
         Macro<"stdc_first_leading_zero">,
         Macro<"stdc_first_leading_one">,
         Macro<"stdc_first_trailing_zero">,
-        Macro<"stdc_first_trailing_one">
+        Macro<"stdc_first_trailing_one">,
+        Macro<"stdc_count_zeros">
       ], // Macros
       [], // Types
       [], // Enumerations
@@ -829,7 +830,12 @@ def StdC : StandardSpec<"stdc"> {
           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>]>
+          FunctionSpec<"stdc_first_trailing_one_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
+          FunctionSpec<"stdc_count_zeros_uc", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedCharType>]>,
+          FunctionSpec<"stdc_count_zeros_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
+          FunctionSpec<"stdc_count_zeros_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
+          FunctionSpec<"stdc_count_zeros_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
+          FunctionSpec<"stdc_count_zeros_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>
       ] // Functions
   >;
 

libc/src/stdbit/CMakeLists.txt

@@ -7,6 +7,7 @@ set(prefixes
   first_leading_one
   first_trailing_zero
   first_trailing_one
+  count_zeros
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)

libc/src/stdbit/stdc_count_zeros_uc.cpp

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

libc/src/stdbit/stdc_count_zeros_uc.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_count_zeros_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_COUNT_ZEROS_UC_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_UC_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_count_zeros_uc(unsigned char value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_UC_H

libc/src/stdbit/stdc_count_zeros_ui.cpp

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

libc/src/stdbit/stdc_count_zeros_ui.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_count_zeros_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_COUNT_ZEROS_UI_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_UI_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_count_zeros_ui(unsigned value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_UI_H

libc/src/stdbit/stdc_count_zeros_ul.cpp

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

libc/src/stdbit/stdc_count_zeros_ul.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_count_zeros_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_COUNT_ZEROS_UL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_UL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_count_zeros_ul(unsigned long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_UL_H

libc/src/stdbit/stdc_count_zeros_ull.cpp

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

libc/src/stdbit/stdc_count_zeros_ull.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_count_zeros_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_COUNT_ZEROS_ULL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_ULL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_count_zeros_ull(unsigned long long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_ULL_H

libc/src/stdbit/stdc_count_zeros_us.cpp

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

libc/src/stdbit/stdc_count_zeros_us.h

@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_count_zeros_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_COUNT_ZEROS_US_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_US_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_count_zeros_us(unsigned short value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_COUNT_ZEROS_US_H

libc/test/include/stdbit_test.cpp

@@ -71,6 +71,11 @@ unsigned stdc_first_trailing_one_ul(unsigned long) noexcept { return 0x1DU; }
 unsigned stdc_first_trailing_one_ull(unsigned long long) noexcept {
   return 0x1FU;
 }
+unsigned stdc_count_zeros_uc(unsigned char) noexcept { return 0x2AU; }
+unsigned stdc_count_zeros_us(unsigned short) noexcept { return 0x2BU; }
+unsigned stdc_count_zeros_ui(unsigned) noexcept { return 0x2CU; }
+unsigned stdc_count_zeros_ul(unsigned long) noexcept { return 0x2DU; }
+unsigned stdc_count_zeros_ull(unsigned long long) noexcept { return 0x2FU; }
 }
 
 #include "include/llvm-libc-macros/stdbit-macros.h"
@@ -138,3 +143,11 @@ TEST(LlvmLibcStdbitTest, TypeGenericMacroFirstTrailingOne) {
   EXPECT_EQ(stdc_first_trailing_one(0UL), 0x1DU);
   EXPECT_EQ(stdc_first_trailing_one(0ULL), 0x1FU);
 }
+
+TEST(LlvmLibcStdbitTest, TypeGenericMacroCountZeros) {
+  EXPECT_EQ(stdc_count_zeros(static_cast<unsigned char>(0U)), 0x2AU);
+  EXPECT_EQ(stdc_count_zeros(static_cast<unsigned short>(0U)), 0x2BU);
+  EXPECT_EQ(stdc_count_zeros(0U), 0x2CU);
+  EXPECT_EQ(stdc_count_zeros(0UL), 0x2DU);
+  EXPECT_EQ(stdc_count_zeros(0ULL), 0x2FU);
+}

libc/test/src/stdbit/CMakeLists.txt

@@ -9,6 +9,7 @@ set(prefixes
   first_leading_one
   first_trailing_zero
   first_trailing_one
+  count_zeros
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)

libc/test/src/stdbit/stdc_count_zeros_uc_test.cpp

@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_count_zeros_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_count_zeros_uc.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcCountZerosUcTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_count_zeros_uc(0U),
+            static_cast<unsigned>(UCHAR_WIDTH));
+}
+
+TEST(LlvmLibcStdcCountZerosUcTest, Ones) {
+  for (unsigned i = 0U; i != UCHAR_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_count_zeros_uc(UCHAR_MAX >> i), i);
+}

libc/test/src/stdbit/stdc_count_zeros_ui_test.cpp

@@ -0,0 +1,21 @@
+//===-- Unittests for stdc_count_zeros_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_count_zeros_ui.h"
+#include "test/UnitTest/Test.h"
+
+TEST(LlvmLibcStdcCountZerosUiTest, Zero) {
+  EXPECT_EQ(LIBC_NAMESPACE::stdc_count_zeros_ui(0U),
+            static_cast<unsigned>(UINT_WIDTH));
+}
+
+TEST(LlvmLibcStdcCountZerosUiTest, Ones) {
+  for (unsigned i = 0U; i != UINT_WIDTH; ++i)
+    EXPECT_EQ(LIBC_NAMESPACE::stdc_count_zeros_ui(UINT_MAX >> i), i);
+}