diff --git a/libc/src/stdfix/countlshk.h b/libc/src/stdfix/countlshk.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSHK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSHK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlshk(short accum x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSHK_H
diff --git a/libc/src/stdfix/countlshr.cpp b/libc/src/stdfix/countlshr.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlshr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlshr, (short fract x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlshr.h b/libc/src/stdfix/countlshr.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSHR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSHR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlshr(short fract x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSHR_H
diff --git a/libc/src/stdfix/countlsk.cpp b/libc/src/stdfix/countlsk.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsk, (accum x)) { return fixed_point::countls(x); }
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsk.h b/libc/src/stdfix/countlsk.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsk(accum x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSK_H
diff --git a/libc/src/stdfix/countlslk.cpp b/libc/src/stdfix/countlslk.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlslk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlslk, (long accum x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlslk.h b/libc/src/stdfix/countlslk.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSLK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSLK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlslk(long accum x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSLK_H
diff --git a/libc/src/stdfix/countlslr.cpp b/libc/src/stdfix/countlslr.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlslr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlslr, (long fract x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlslr.h b/libc/src/stdfix/countlslr.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSLR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSLR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlslr(long fract x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSLR_H
diff --git a/libc/src/stdfix/countlsr.cpp b/libc/src/stdfix/countlsr.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsr, (fract x)) { return fixed_point::countls(x); }
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsr.h b/libc/src/stdfix/countlsr.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsr(fract x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSR_H
diff --git a/libc/src/stdfix/countlsuhk.cpp b/libc/src/stdfix/countlsuhk.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsuhk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsuhk, (unsigned short accum x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsuhk.h b/libc/src/stdfix/countlsuhk.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSUHK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSUHK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsuhk(unsigned short accum x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSUHK_H
diff --git a/libc/src/stdfix/countlsuhr.cpp b/libc/src/stdfix/countlsuhr.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsuhr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsuhr, (unsigned short fract x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsuhr.h b/libc/src/stdfix/countlsuhr.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSUHR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSUHR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsuhr(unsigned short fract x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSUHR_H
diff --git a/libc/src/stdfix/countlsuk.cpp b/libc/src/stdfix/countlsuk.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsuk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsuk, (unsigned accum x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsuk.h b/libc/src/stdfix/countlsuk.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSUK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSUK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsuk(unsigned accum x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSUK_H
diff --git a/libc/src/stdfix/countlsulk.cpp b/libc/src/stdfix/countlsulk.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsulk.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsulk, (unsigned long accum x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsulk.h b/libc/src/stdfix/countlsulk.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSULK_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSULK_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsulk(unsigned long accum x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSULK_H
diff --git a/libc/src/stdfix/countlsulr.cpp b/libc/src/stdfix/countlsulr.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsulr.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsulr, (unsigned long fract x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsulr.h b/libc/src/stdfix/countlsulr.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSULR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSULR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsulr(unsigned long fract x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSULR_H
diff --git a/libc/src/stdfix/countlsur.cpp b/libc/src/stdfix/countlsur.cpp
@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "countlsur.h"
+#include "src/__support/common.h"
+#include "src/__support/fixed_point/fx_bits.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, countlsur, (unsigned fract x)) {
+  return fixed_point::countls(x);
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/stdfix/countlsur.h b/libc/src/stdfix/countlsur.h
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_STDFIX_COUNTLSUR_H
+#define LLVM_LIBC_SRC_STDFIX_COUNTLSUR_H
+
+#include "include/llvm-libc-macros/stdfix-macros.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int countlsur(unsigned fract x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_STDFIX_COUNTLSUR_H
diff --git a/libc/test/src/stdfix/CMakeLists.txt b/libc/test/src/stdfix/CMakeLists.txt
@@ -57,6 +57,39 @@ foreach(suffix IN ITEMS hr r lr hk k lk uhr ur ulr uhk uk ulk)
       libc.src.stdfix.round${suffix}
       libc.src.__support.fixed_point.fx_bits
   )
+
+  add_libc_test(
+    countls${suffix}_test
+    SUITE
+      libc-stdfix-tests
+    HDRS
+      CountlsTest.h
+    SRCS
+      countls${suffix}_test.cpp
+    COMPILE_OPTIONS
+      -O3
+    DEPENDS
+      libc.src.stdfix.countls${suffix}
+      libc.src.__support.fixed_point.fx_rep
+  )
+
+  if(LIBC_COMPILER_HAS_PADDING_ON_UNSIGNED_FIXED_POINT)
+    add_libc_test(
+      countls${suffix}_padding_on_unsigned_fixed_point_test
+      SUITE
+        libc-stdfix-tests
+      HDRS
+        CountlsTest.h
+      SRCS
+        countls${suffix}_test.cpp
+      COMPILE_OPTIONS
+        -O3
+        -Xclang=-fpadding-on-unsigned-fixed-point
+      DEPENDS
+        libc.src.stdfix.countls${suffix}_padding_on_unsigned_fixed_point
+        libc.src.__support.fixed_point.fx_rep
+    )
+  endif()
 endforeach()
 
 add_libc_test(

diff --git a/libc/test/src/stdfix/CountlsTest.h b/libc/test/src/stdfix/CountlsTest.h
@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "test/UnitTest/Test.h"
+
+#include "src/__support/fixed_point/fx_rep.h"
+
+template <typename T> class CountlsTest : public LIBC_NAMESPACE::testing::Test {
+
+  using FXRep = LIBC_NAMESPACE::fixed_point::FXRep<T>;
+  static constexpr T zero = FXRep::ZERO();
+  static constexpr T max = FXRep::MAX();
+  static constexpr T min = FXRep::MIN();
+  static constexpr T one_half = FXRep::ONE_HALF();
+  static constexpr T one_fourth = FXRep::ONE_FOURTH();
+  static constexpr T eps = FXRep::EPS();
+
+  static constexpr auto value_len =
+      LIBC_NAMESPACE::fixed_point::get_value_len<FXRep>();
+
+public:
+  typedef int (*CountlsFunc)(T);
+
+  void testSpecialNumbers(CountlsFunc func) {
+    constexpr bool is_signed = (FXRep::SIGN_LEN > 0);
+
+    EXPECT_EQ(FXRep::INTEGRAL_LEN, func(one_half));
+    EXPECT_EQ(FXRep::INTEGRAL_LEN + 1, func(one_fourth));
+    EXPECT_EQ(value_len, func(zero));
+    EXPECT_EQ(value_len - 1, func(eps));
+    EXPECT_EQ(0, func(max));
+    // If signed, left shifting the minimum value will overflow, so countls = 0.
+    // If unsigned, the minimum value is zero, so countls is the number of value
+    // bits according to ISO/IEC TR 18037.
+    EXPECT_EQ(is_signed ? 0 : value_len, func(min));
+
+    if (10 <= static_cast<int>(max)) {
+      EXPECT_EQ(FXRep::INTEGRAL_LEN - 4, func(10));
+    }
+
+    if (static_cast<int>(min) <= -10) {
+      EXPECT_EQ(FXRep::INTEGRAL_LEN - 4, func(-10));
+    }
+
+    if constexpr (is_signed) {
+      EXPECT_EQ(value_len, func(-eps));
+      EXPECT_EQ(FXRep::INTEGRAL_LEN + 1, func(-one_half));
+      if (FXRep::FRACTION_LEN >= 2) {
+        EXPECT_EQ(FXRep::INTEGRAL_LEN + 2, func(-one_fourth));
+      }
+    }
+  }
+};
+
+#define LIST_COUNTLS_TESTS(T, func)                                            \
+  using LlvmLibcCountlsTest = CountlsTest<T>;                                  \
+  TEST_F(LlvmLibcCountlsTest, SpecialNumbers) { testSpecialNumbers(&func); }   \
+  static_assert(true, "Require semicolon.")
diff --git a/libc/test/src/stdfix/countlshk_test.cpp b/libc/test/src/stdfix/countlshk_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlshk.h"
+
+LIST_COUNTLS_TESTS(short accum, LIBC_NAMESPACE::countlshk);
diff --git a/libc/test/src/stdfix/countlshr_test.cpp b/libc/test/src/stdfix/countlshr_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlshr.h"
+
+LIST_COUNTLS_TESTS(short fract, LIBC_NAMESPACE::countlshr);
diff --git a/libc/test/src/stdfix/countlsk_test.cpp b/libc/test/src/stdfix/countlsk_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsk.h"
+
+LIST_COUNTLS_TESTS(accum, LIBC_NAMESPACE::countlsk);
diff --git a/libc/test/src/stdfix/countlslk_test.cpp b/libc/test/src/stdfix/countlslk_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlslk.h"
+
+LIST_COUNTLS_TESTS(long accum, LIBC_NAMESPACE::countlslk);
diff --git a/libc/test/src/stdfix/countlslr_test.cpp b/libc/test/src/stdfix/countlslr_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlslr.h"
+
+LIST_COUNTLS_TESTS(long fract, LIBC_NAMESPACE::countlslr);
diff --git a/libc/test/src/stdfix/countlsr_test.cpp b/libc/test/src/stdfix/countlsr_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsr.h"
+
+LIST_COUNTLS_TESTS(fract, LIBC_NAMESPACE::countlsr);
diff --git a/libc/test/src/stdfix/countlsuhk_test.cpp b/libc/test/src/stdfix/countlsuhk_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsuhk.h"
+
+LIST_COUNTLS_TESTS(unsigned short accum, LIBC_NAMESPACE::countlsuhk);
diff --git a/libc/test/src/stdfix/countlsuhr_test.cpp b/libc/test/src/stdfix/countlsuhr_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsuhr.h"
+
+LIST_COUNTLS_TESTS(unsigned short fract, LIBC_NAMESPACE::countlsuhr);
diff --git a/libc/test/src/stdfix/countlsuk_test.cpp b/libc/test/src/stdfix/countlsuk_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsuk.h"
+
+LIST_COUNTLS_TESTS(unsigned accum, LIBC_NAMESPACE::countlsuk);
diff --git a/libc/test/src/stdfix/countlsulk_test.cpp b/libc/test/src/stdfix/countlsulk_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsulk.h"
+
+LIST_COUNTLS_TESTS(unsigned long accum, LIBC_NAMESPACE::countlsulk);
diff --git a/libc/test/src/stdfix/countlsulr_test.cpp b/libc/test/src/stdfix/countlsulr_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsulr.h"
+
+LIST_COUNTLS_TESTS(unsigned long fract, LIBC_NAMESPACE::countlsulr);
diff --git a/libc/test/src/stdfix/countlsur_test.cpp b/libc/test/src/stdfix/countlsur_test.cpp
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "CountlsTest.h"
+
+#include "src/stdfix/countlsur.h"
+
+LIST_COUNTLS_TESTS(unsigned fract, LIBC_NAMESPACE::countlsur);