[libc][math][c23] Add MPFR unit tests for {ceil,floor,round,roundeven,trunc}f16 (#94383)

12 files changed, 264 insertions, 53 deletions

diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 102188c..e4a3087 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -141,6 +141,7 @@ add_fp_unittest(
     TruncTest.h
   DEPENDS
     libc.src.math.trunc
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -155,6 +156,7 @@ add_fp_unittest(
     TruncTest.h
   DEPENDS
     libc.src.math.truncf
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -169,6 +171,22 @@ add_fp_unittest(
     TruncTest.h
   DEPENDS
     libc.src.math.truncl
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_fp_unittest(
+  truncf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    truncf16_test.cpp
+  HDRS
+    TruncTest.h
+  DEPENDS
+    libc.src.math.truncf16
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -183,6 +201,7 @@ add_fp_unittest(
     CeilTest.h
   DEPENDS
     libc.src.math.ceil
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -197,6 +216,7 @@ add_fp_unittest(
     CeilTest.h
   DEPENDS
     libc.src.math.ceilf
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -211,6 +231,22 @@ add_fp_unittest(
     CeilTest.h
   DEPENDS
     libc.src.math.ceill
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_fp_unittest(
+  ceilf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    ceilf16_test.cpp
+  HDRS
+    CeilTest.h
+  DEPENDS
+    libc.src.math.ceilf16
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -225,6 +261,7 @@ add_fp_unittest(
     FloorTest.h
   DEPENDS
     libc.src.math.floor
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -239,6 +276,7 @@ add_fp_unittest(
     FloorTest.h
   DEPENDS
     libc.src.math.floorf
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -253,6 +291,22 @@ add_fp_unittest(
     FloorTest.h
   DEPENDS
     libc.src.math.floorl
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_fp_unittest(
+  floorf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    floorf16_test.cpp
+  HDRS
+    FloorTest.h
+  DEPENDS
+    libc.src.math.floorf16
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -267,6 +321,7 @@ add_fp_unittest(
     RoundTest.h
   DEPENDS
     libc.src.math.round
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -281,6 +336,7 @@ add_fp_unittest(
     RoundTest.h
   DEPENDS
     libc.src.math.roundf
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -295,6 +351,22 @@ add_fp_unittest(
     RoundTest.h
   DEPENDS
     libc.src.math.roundl
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_fp_unittest(
+  roundf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    roundf16_test.cpp
+  HDRS
+    RoundTest.h
+  DEPENDS
+    libc.src.math.roundf16
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -309,6 +381,7 @@ add_fp_unittest(
   RoundEvenTest.h
   DEPENDS
     libc.src.math.roundeven
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -323,6 +396,7 @@ add_fp_unittest(
   RoundEvenTest.h
   DEPENDS
     libc.src.math.roundevenf
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
@@ -337,6 +411,22 @@ add_fp_unittest(
   RoundEvenTest.h
   DEPENDS
     libc.src.math.roundevenl
+    libc.src.__support.CPP.algorithm
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_fp_unittest(
+  roundevenf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    roundevenf16_test.cpp
+  HDRS
+  RoundEvenTest.h
+  DEPENDS
+    libc.src.math.roundevenf16
+    libc.src.__support.CPP.algorithm
     libc.src.__support.FPUtil.fp_bits
 )
 
diff --git a/libc/test/src/math/CeilTest.h b/libc/test/src/math/CeilTest.h
index b4c3752..3af8742 100644
--- a/libc/test/src/math/CeilTest.h
+++ b/libc/test/src/math/CeilTest.h
@@ -6,6 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifndef LLVM_LIBC_TEST_SRC_MATH_CEILTEST_H
+#define LLVM_LIBC_TEST_SRC_MATH_CEILTEST_H
+
+#include "src/__support/CPP/algorithm.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -59,18 +63,21 @@ public:
     EXPECT_FP_EQ(T(-10.0), func(T(-10.32)));
     EXPECT_FP_EQ(T(11.0), func(T(10.65)));
     EXPECT_FP_EQ(T(-10.0), func(T(-10.65)));
-    EXPECT_FP_EQ(T(1235.0), func(T(1234.38)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1234.38)));
-    EXPECT_FP_EQ(T(1235.0), func(T(1234.96)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1234.96)));
+    EXPECT_FP_EQ(T(124.0), func(T(123.38)));
+    EXPECT_FP_EQ(T(-123.0), func(T(-123.38)));
+    EXPECT_FP_EQ(T(124.0), func(T(123.96)));
+    EXPECT_FP_EQ(T(-123.0), func(T(-123.96)));
   }
 
   void testRange(CeilFunc func) {
-    constexpr StorageType COUNT = 100'000;
-    constexpr StorageType STEP = STORAGE_MAX / COUNT;
-    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
-      T x = FPBits(v).get_val();
-      if (isnan(x) || isinf(x))
+    constexpr int COUNT = 100'000;
+    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
+        static_cast<StorageType>(STORAGE_MAX / COUNT), StorageType(1));
+    StorageType v = 0;
+    for (int i = 0; i <= COUNT; ++i, v += STEP) {
+      FPBits xbits(v);
+      T x = xbits.get_val();
+      if (xbits.is_inf_or_nan())
         continue;
 
       ASSERT_MPFR_MATCH(mpfr::Operation::Ceil, x, func(x), 0.0);
@@ -84,3 +91,5 @@ public:
   TEST_F(LlvmLibcCeilTest, RoundedNubmers) { testRoundedNumbers(&func); }      \
   TEST_F(LlvmLibcCeilTest, Fractions) { testFractions(&func); }                \
   TEST_F(LlvmLibcCeilTest, Range) { testRange(&func); }
+
+#endif // LLVM_LIBC_TEST_SRC_MATH_CEILTEST_H
diff --git a/libc/test/src/math/FloorTest.h b/libc/test/src/math/FloorTest.h
index 9103a5b..cce0c73 100644
--- a/libc/test/src/math/FloorTest.h
+++ b/libc/test/src/math/FloorTest.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_TEST_SRC_MATH_FLOORTEST_H
 #define LLVM_LIBC_TEST_SRC_MATH_FLOORTEST_H
 
+#include "src/__support/CPP/algorithm.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -62,18 +63,21 @@ public:
     EXPECT_FP_EQ(T(-11.0), func(T(-10.32)));
     EXPECT_FP_EQ(T(10.0), func(T(10.65)));
     EXPECT_FP_EQ(T(-11.0), func(T(-10.65)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1234.38)));
-    EXPECT_FP_EQ(T(-1235.0), func(T(-1234.38)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1234.96)));
-    EXPECT_FP_EQ(T(-1235.0), func(T(-1234.96)));
+    EXPECT_FP_EQ(T(123.0), func(T(123.38)));
+    EXPECT_FP_EQ(T(-124.0), func(T(-123.38)));
+    EXPECT_FP_EQ(T(123.0), func(T(123.96)));
+    EXPECT_FP_EQ(T(-124.0), func(T(-123.96)));
   }
 
   void testRange(FloorFunc func) {
-    constexpr StorageType COUNT = 100'000;
-    constexpr StorageType STEP = STORAGE_MAX / COUNT;
-    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
-      T x = FPBits(v).get_val();
-      if (isnan(x) || isinf(x))
+    constexpr int COUNT = 100'000;
+    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
+        static_cast<StorageType>(STORAGE_MAX / COUNT), StorageType(1));
+    StorageType v = 0;
+    for (int i = 0; i <= COUNT; ++i, v += STEP) {
+      FPBits xbits(v);
+      T x = xbits.get_val();
+      if (xbits.is_inf_or_nan())
         continue;
 
       ASSERT_MPFR_MATCH(mpfr::Operation::Floor, x, func(x), 0.0);
diff --git a/libc/test/src/math/RoundEvenTest.h b/libc/test/src/math/RoundEvenTest.h
index d70555d..5ecda66 100644
--- a/libc/test/src/math/RoundEvenTest.h
+++ b/libc/test/src/math/RoundEvenTest.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_TEST_SRC_MATH_ROUNDEVENTEST_H
 #define LLVM_LIBC_TEST_SRC_MATH_ROUNDEVENTEST_H
 
+#include "src/__support/CPP/algorithm.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -60,22 +61,25 @@ public:
     EXPECT_FP_EQ(T(-2.0), func(T(-1.75)));
     EXPECT_FP_EQ(T(11.0), func(T(10.65)));
     EXPECT_FP_EQ(T(-11.0), func(T(-10.65)));
-    EXPECT_FP_EQ(T(1233.0), func(T(1233.25)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1233.50)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1233.75)));
-    EXPECT_FP_EQ(T(-1233.0), func(T(-1233.25)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1233.50)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1233.75)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1234.50)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1234.50)));
+    EXPECT_FP_EQ(T(123.0), func(T(123.25)));
+    EXPECT_FP_EQ(T(124.0), func(T(123.50)));
+    EXPECT_FP_EQ(T(124.0), func(T(123.75)));
+    EXPECT_FP_EQ(T(-123.0), func(T(-123.25)));
+    EXPECT_FP_EQ(T(-124.0), func(T(-123.50)));
+    EXPECT_FP_EQ(T(-124.0), func(T(-123.75)));
+    EXPECT_FP_EQ(T(124.0), func(T(124.50)));
+    EXPECT_FP_EQ(T(-124.0), func(T(-124.50)));
   }
 
   void testRange(RoundEvenFunc func) {
-    constexpr StorageType COUNT = 100'000;
-    constexpr StorageType STEP = STORAGE_MAX / COUNT;
-    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
-      T x = FPBits(v).get_val();
-      if (isnan(x) || isinf(x))
+    constexpr int COUNT = 100'000;
+    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
+        static_cast<StorageType>(STORAGE_MAX / COUNT), StorageType(1));
+    StorageType v = 0;
+    for (int i = 0; i <= COUNT; ++i, v += STEP) {
+      FPBits xbits(v);
+      T x = xbits.get_val();
+      if (xbits.is_inf_or_nan())
         continue;
 
       ASSERT_MPFR_MATCH(mpfr::Operation::RoundEven, x, func(x), 0.0);
diff --git a/libc/test/src/math/RoundTest.h b/libc/test/src/math/RoundTest.h
index 2a31df3..d571d5d 100644
--- a/libc/test/src/math/RoundTest.h
+++ b/libc/test/src/math/RoundTest.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_TEST_SRC_MATH_ROUNDTEST_H
 #define LLVM_LIBC_TEST_SRC_MATH_ROUNDTEST_H
 
+#include "src/__support/CPP/algorithm.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -62,18 +63,21 @@ public:
     EXPECT_FP_EQ(T(-10.0), func(T(-10.32)));
     EXPECT_FP_EQ(T(11.0), func(T(10.65)));
     EXPECT_FP_EQ(T(-11.0), func(T(-10.65)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1234.38)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1234.38)));
-    EXPECT_FP_EQ(T(1235.0), func(T(1234.96)));
-    EXPECT_FP_EQ(T(-1235.0), func(T(-1234.96)));
+    EXPECT_FP_EQ(T(123.0), func(T(123.38)));
+    EXPECT_FP_EQ(T(-123.0), func(T(-123.38)));
+    EXPECT_FP_EQ(T(124.0), func(T(123.96)));
+    EXPECT_FP_EQ(T(-124.0), func(T(-123.96)));
   }
 
   void testRange(RoundFunc func) {
-    constexpr StorageType COUNT = 100'000;
-    constexpr StorageType STEP = STORAGE_MAX / COUNT;
-    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
-      T x = FPBits(v).get_val();
-      if (isnan(x) || isinf(x))
+    constexpr int COUNT = 100'000;
+    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
+        static_cast<StorageType>(STORAGE_MAX / COUNT), StorageType(1));
+    StorageType v = 0;
+    for (int i = 0; i <= COUNT; ++i, v += STEP) {
+      FPBits xbits(v);
+      T x = xbits.get_val();
+      if (xbits.is_inf_or_nan())
         continue;
 
       ASSERT_MPFR_MATCH(mpfr::Operation::Round, x, func(x), 0.0);
diff --git a/libc/test/src/math/TruncTest.h b/libc/test/src/math/TruncTest.h
index bc5b761..76c9740 100644
--- a/libc/test/src/math/TruncTest.h
+++ b/libc/test/src/math/TruncTest.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_TEST_SRC_MATH_TRUNCTEST_H
 #define LLVM_LIBC_TEST_SRC_MATH_TRUNCTEST_H
 
+#include "src/__support/CPP/algorithm.h"
 #include "test/UnitTest/FEnvSafeTest.h"
 #include "test/UnitTest/FPMatcher.h"
 #include "test/UnitTest/Test.h"
@@ -62,18 +63,21 @@ public:
     EXPECT_FP_EQ(T(-10.0), func(T(-10.32)));
     EXPECT_FP_EQ(T(10.0), func(T(10.65)));
     EXPECT_FP_EQ(T(-10.0), func(T(-10.65)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1234.38)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1234.38)));
-    EXPECT_FP_EQ(T(1234.0), func(T(1234.96)));
-    EXPECT_FP_EQ(T(-1234.0), func(T(-1234.96)));
+    EXPECT_FP_EQ(T(123.0), func(T(123.38)));
+    EXPECT_FP_EQ(T(-123.0), func(T(-123.38)));
+    EXPECT_FP_EQ(T(123.0), func(T(123.96)));
+    EXPECT_FP_EQ(T(-123.0), func(T(-123.96)));
   }
 
   void testRange(TruncFunc func) {
-    constexpr StorageType COUNT = 100'000;
-    constexpr StorageType STEP = STORAGE_MAX / COUNT;
-    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
-      T x = FPBits(v).get_val();
-      if (isnan(x) || isinf(x))
+    constexpr int COUNT = 100'000;
+    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
+        static_cast<StorageType>(STORAGE_MAX / COUNT), StorageType(1));
+    StorageType v = 0;
+    for (int i = 0; i <= COUNT; ++i, v += STEP) {
+      FPBits xbits(v);
+      T x = xbits.get_val();
+      if (xbits.is_inf_or_nan())
         continue;
 
       ASSERT_MPFR_MATCH(mpfr::Operation::Trunc, x, func(x), 0.0);
diff --git a/libc/test/src/math/ceilf16_test.cpp b/libc/test/src/math/ceilf16_test.cpp
new file mode 100644
index 0000000..a6ec922
--- /dev/null
+++ b/libc/test/src/math/ceilf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for ceilf16 ---------------------------------------------===//
+//
+// 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 "CeilTest.h"
+
+#include "src/math/ceilf16.h"
+
+LIST_CEIL_TESTS(float16, LIBC_NAMESPACE::ceilf16)
diff --git a/libc/test/src/math/floorf16_test.cpp b/libc/test/src/math/floorf16_test.cpp
new file mode 100644
index 0000000..ca5160e
--- /dev/null
+++ b/libc/test/src/math/floorf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for floorf16 --------------------------------------------===//
+//
+// 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 "FloorTest.h"
+
+#include "src/math/floorf16.h"
+
+LIST_FLOOR_TESTS(float16, LIBC_NAMESPACE::floorf16)
diff --git a/libc/test/src/math/roundevenf16_test.cpp b/libc/test/src/math/roundevenf16_test.cpp
new file mode 100644
index 0000000..911a32c
--- /dev/null
+++ b/libc/test/src/math/roundevenf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for roundevenf16 ----------------------------------------===//
+//
+// 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 "RoundEvenTest.h"
+
+#include "src/math/roundevenf16.h"
+
+LIST_ROUNDEVEN_TESTS(float16, LIBC_NAMESPACE::roundevenf16)
diff --git a/libc/test/src/math/roundf16_test.cpp b/libc/test/src/math/roundf16_test.cpp
new file mode 100644
index 0000000..54ead85
--- /dev/null
+++ b/libc/test/src/math/roundf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for roundf16 --------------------------------------------===//
+//
+// 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 "RoundTest.h"
+
+#include "src/math/roundf16.h"
+
+LIST_ROUND_TESTS(float16, LIBC_NAMESPACE::roundf16)
diff --git a/libc/test/src/math/truncf16_test.cpp b/libc/test/src/math/truncf16_test.cpp
new file mode 100644
index 0000000..832d88e
--- /dev/null
+++ b/libc/test/src/math/truncf16_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for truncf16 --------------------------------------------===//
+//
+// 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 "TruncTest.h"
+
+#include "src/math/truncf16.h"
+
+LIST_TRUNC_TESTS(float16, LIBC_NAMESPACE::truncf16)
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
index 18a8ac0..a9177fa 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.cpp
+++ b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -12,6 +12,7 @@
 #include "src/__support/CPP/string_view.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/fpbits_str.h"
+#include "src/__support/macros/properties/types.h"
 #include "test/UnitTest/FPMatcher.h"
 
 #include "hdr/math_macros.h"
@@ -30,6 +31,12 @@ namespace mpfr {
 // precision compared to the floating point precision.
 template <typename T> struct ExtraPrecision;
 
+#ifdef LIBC_TYPES_HAS_FLOAT16
+template <> struct ExtraPrecision<float16> {
+  static constexpr unsigned int VALUE = 128;
+};
+#endif
+
 template <> struct ExtraPrecision<float> {
   static constexpr unsigned int VALUE = 128;
 };
@@ -85,9 +92,16 @@ public:
 
   // We use explicit EnableIf specializations to disallow implicit
   // conversions. Implicit conversions can potentially lead to loss of
-  // precision.
+  // precision. We exceptionally allow implicit conversions from float16
+  // to float, as the MPFR API does not support float16, thus requiring
+  // conversion to a higher-precision format.
   template <typename XType,
-            cpp::enable_if_t<cpp::is_same_v<float, XType>, int> = 0>
+            cpp::enable_if_t<cpp::is_same_v<float, XType>
+#ifdef LIBC_TYPES_HAS_FLOAT16
+                                 || cpp::is_same_v<float16, XType>
+#endif
+                             ,
+                             int> = 0>
   explicit MPFRNumber(XType x,
                       unsigned int precision = ExtraPrecision<XType>::VALUE,
                       RoundingMode rounding = RoundingMode::Nearest)
@@ -529,8 +543,8 @@ public:
     // If the control reaches here, it means that this number and input are
     // of the same sign but different exponent. In such a case, ULP error is
     // calculated as sum of two parts.
-    thisAsT = std::abs(thisAsT);
-    input = std::abs(input);
+    thisAsT = FPBits<T>(thisAsT).abs().get_val();
+    input = FPBits<T>(input).abs().get_val();
     T min = thisAsT > input ? input : thisAsT;
     T max = thisAsT > input ? thisAsT : input;
     int minExponent = FPBits<T>(min).get_exponent();
@@ -585,6 +599,14 @@ template <> long double MPFRNumber::as<long double>() const {
   return mpfr_get_ld(value, mpfr_rounding);
 }
 
+#ifdef LIBC_TYPES_HAS_FLOAT16
+template <> float16 MPFRNumber::as<float16>() const {
+  // TODO: Either prove that this cast won't cause double-rounding errors, or
+  // find a better way to get a float16.
+  return static_cast<float16>(mpfr_get_d(value, mpfr_rounding));
+}
+#endif
+
 namespace internal {
 
 template <typename InputType>
@@ -763,6 +785,10 @@ template void explain_unary_operation_single_output_error<double>(
     Operation op, double, double, double, RoundingMode);
 template void explain_unary_operation_single_output_error<long double>(
     Operation op, long double, long double, double, RoundingMode);
+#ifdef LIBC_TYPES_HAS_FLOAT16
+template void explain_unary_operation_single_output_error<float16>(
+    Operation op, float16, float16, double, RoundingMode);
+#endif
 
 template <typename T>
 void explain_unary_operation_two_outputs_error(
@@ -942,6 +968,11 @@ template bool compare_unary_operation_single_output<double>(Operation, double,
                                                             RoundingMode);
 template bool compare_unary_operation_single_output<long double>(
     Operation, long double, long double, double, RoundingMode);
+#ifdef LIBC_TYPES_HAS_FLOAT16
+template bool compare_unary_operation_single_output<float16>(Operation, float16,
+                                                             float16, double,
+                                                             RoundingMode);
+#endif
 
 template <typename T>
 bool compare_unary_operation_two_outputs(Operation op, T input,