[libc] Add implementation of few floating point manipulation functions.

Implementations of copysign[f], frexp[f], logb[f], and modf[f] are added.

Reviewers: asteinhauser

Differential Revision: https://reviews.llvm.org/D81134

1 files changed, 63 insertions, 0 deletions

diff --git a/libc/test/src/math/copysign_test.cpp b/libc/test/src/math/copysign_test.cpp
new file mode 100644
index 000000000000..e0638467c5b9
--- /dev/null
+++ b/libc/test/src/math/copysign_test.cpp
@@ -0,0 +1,63 @@
+//===-- Unittests for copysign --------------------------------------------===//
+//
+// 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 "include/math.h"
+#include "src/math/copysign.h"
+#include "utils/FPUtil/BitPatterns.h"
+#include "utils/FPUtil/FloatOperations.h"
+#include "utils/FPUtil/FloatProperties.h"
+#include "utils/UnitTest/Test.h"
+
+using __llvm_libc::fputil::valueAsBits;
+using __llvm_libc::fputil::valueFromBits;
+
+using BitPatterns = __llvm_libc::fputil::BitPatterns<double>;
+using Properties = __llvm_libc::fputil::FloatProperties<double>;
+
+TEST(CopySignTest, SpecialNumbers) {
+  EXPECT_EQ(BitPatterns::aNegativeQuietNaN,
+            valueAsBits(__llvm_libc::copysign(
+                valueFromBits(BitPatterns::aQuietNaN), -1.0)));
+  EXPECT_EQ(BitPatterns::aQuietNaN,
+            valueAsBits(__llvm_libc::copysign(
+                valueFromBits(BitPatterns::aNegativeQuietNaN), 1.0)));
+
+  EXPECT_EQ(BitPatterns::aNegativeSignallingNaN,
+            valueAsBits(__llvm_libc::copysign(
+                valueFromBits(BitPatterns::aSignallingNaN), -1.0)));
+  EXPECT_EQ(BitPatterns::aSignallingNaN,
+            valueAsBits(__llvm_libc::copysign(
+                valueFromBits(BitPatterns::aNegativeSignallingNaN), 1.0)));
+
+  EXPECT_EQ(BitPatterns::negInf, valueAsBits(__llvm_libc::copysign(
+                                     valueFromBits(BitPatterns::inf), -1.0)));
+  EXPECT_EQ(BitPatterns::inf, valueAsBits(__llvm_libc::copysign(
+                                  valueFromBits(BitPatterns::negInf), 1.0)));
+
+  EXPECT_EQ(BitPatterns::negZero, valueAsBits(__llvm_libc::copysign(
+                                      valueFromBits(BitPatterns::zero), -1.0)));
+  EXPECT_EQ(BitPatterns::zero, valueAsBits(__llvm_libc::copysign(
+                                   valueFromBits(BitPatterns::negZero), 1.0)));
+}
+
+TEST(CopySignTest, InDoubleRange) {
+  using BitsType = Properties::BitsType;
+  constexpr BitsType count = 1000000;
+  constexpr BitsType step = UINT64_MAX / count;
+  for (BitsType i = 0, v = 0; i <= count; ++i, v += step) {
+    double x = valueFromBits(v);
+    if (isnan(x) || isinf(x) || x == 0)
+      continue;
+
+    double res1 = __llvm_libc::copysign(x, -x);
+    ASSERT_TRUE(res1 == -x);
+
+    double res2 = __llvm_libc::copysign(x, x);
+    ASSERT_TRUE(res2 == x);
+  }
+}