[libc-commits] [libc] [libc][stdfix] Implement fixed point `countlsfx` functions in llvm-libc (PR #125356)

[Krishna Pandey via libc-commits]

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@@ -0,0 +1,63 @@
+//===-- Utility class to test countls -------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#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 =
+      FXRep::INTEGRAL_LEN + FXRep::FRACTION_LEN;
+
+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.")
----------------
krishna2803 wrote:

Resolved in [b146648a](https://github.com/llvm/llvm-project/pull/125356/commits/b146648ae201743d470d5a600acb2f47c50c45a4)

https://github.com/llvm/llvm-project/pull/125356