8 files changed, 195 insertions, 1 deletions
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 2d2d528..b3f54ab 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -1679,6 +1679,17 @@ add_fp_unittest(
 )
 
 add_fp_unittest(
+  rsqrtf_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    rsqrtf_test.cpp
+  DEPENDS
+    libc.src.math.rsqrtf
+)
+
+add_fp_unittest(
   rsqrtf16_test
   NEED_MPFR
   SUITE
diff --git a/libc/test/src/math/RsqrtTest.h b/libc/test/src/math/RsqrtTest.h
new file mode 100644
index 0000000..d11d708
--- /dev/null
+++ b/libc/test/src/math/RsqrtTest.h
@@ -0,0 +1,74 @@
+//===-- Utility class to test rsqrt[f|l] ------------------------*- 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_TEST_SRC_MATH_RSQRTTEST_H
+#define LLVM_LIBC_TEST_SRC_MATH_RSQRTTEST_H
+
+#include "test/UnitTest/FEnvSafeTest.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+template <typename OutType, typename InType = OutType>
+class RsqrtTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
+
+  DECLARE_SPECIAL_CONSTANTS(InType)
+
+  static constexpr StorageType HIDDEN_BIT =
+      StorageType(1) << LIBC_NAMESPACE::fputil::FPBits<InType>::FRACTION_LEN;
+
+public:
+  using RsqrtFunc = OutType (*)(InType);
+
+  // Subnormal inputs: probe both power-of-two mantissas and an even sampling
+  // across the subnormal range.
+  void test_denormal_values(RsqrtFunc func) {
+    // Powers of two in the subnormal mantissa space.
+    for (StorageType mant = 1; mant < HIDDEN_BIT; mant <<= 1) {
+      FPBits denormal(zero);
+      denormal.set_mantissa(mant);
+      InType x = denormal.get_val();
+      ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Rsqrt, x, func(x), 0.5);
+    }
+
+    // Even sampling across all subnormals.
+    constexpr StorageType COUNT = 200'001;
+    constexpr StorageType STEP = HIDDEN_BIT / COUNT;
+    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
+      InType x = FPBits(i).get_val();
+      ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Rsqrt, x, func(x), 0.5);
+    }
+  }
+
+  // Positive normal range sampling: skip NaNs and negative values.
+  void test_normal_range(RsqrtFunc func) {
+    constexpr StorageType COUNT = 200'001;
+    constexpr StorageType STEP = STORAGE_MAX / COUNT;
+    for (StorageType i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
+      FPBits x_bits(v);
+      InType x = x_bits.get_val();
+      if (x_bits.is_nan() || x_bits.is_neg())
+        continue;
+      ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Rsqrt, x, func(x), 0.5);
+    }
+  }
+};
+
+#define LIST_RSQRT_TESTS(T, func)                                              \
+  using LlvmLibcRsqrtTest = RsqrtTest<T, T>;                                   \
+  TEST_F(LlvmLibcRsqrtTest, DenormalValues) { test_denormal_values(&func); }   \
+  TEST_F(LlvmLibcRsqrtTest, NormalRange) { test_normal_range(&func); }
+
+#define LIST_NARROWING_RSQRT_TESTS(OutType, InType, func)                      \
+  using LlvmLibcRsqrtTest = RsqrtTest<OutType, InType>;                        \
+  TEST_F(LlvmLibcRsqrtTest, DenormalValues) { test_denormal_values(&func); }   \
+  TEST_F(LlvmLibcRsqrtTest, NormalRange) { test_normal_range(&func); }
+
+#endif // LLVM_LIBC_TEST_SRC_MATH_RSQRTTEST_H
diff --git a/libc/test/src/math/exhaustive/CMakeLists.txt b/libc/test/src/math/exhaustive/CMakeLists.txt
index 07c36f424..1583ab6 100644
--- a/libc/test/src/math/exhaustive/CMakeLists.txt
+++ b/libc/test/src/math/exhaustive/CMakeLists.txt
@@ -27,6 +27,21 @@ add_fp_unittest(
 )
 
 add_fp_unittest(
+  rsqrtf_test
+  NO_RUN_POSTBUILD
+  NEED_MPFR
+  SUITE
+    libc_math_exhaustive_tests
+  SRCS
+    rsqrtf_test.cpp
+  DEPENDS
+    .exhaustive_test
+    libc.src.math.rsqrtf
+  LINK_LIBRARIES
+    -lpthread
+)
+
+add_fp_unittest(
   sinf_test
   NO_RUN_POSTBUILD
   NEED_MPFR
diff --git a/libc/test/src/math/exhaustive/rsqrtf_test.cpp b/libc/test/src/math/exhaustive/rsqrtf_test.cpp
new file mode 100644
index 0000000..803c9b4
--- /dev/null
+++ b/libc/test/src/math/exhaustive/rsqrtf_test.cpp
@@ -0,0 +1,27 @@
+//===-- Exhaustive test for rsqrtf ----------------------------------------===//
+//
+// 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 "exhaustive_test.h"
+#include "src/math/rsqrtf.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcRsqrtfTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+using LlvmLibcRsqrtfExhaustiveTest =
+    LlvmLibcUnaryOpExhaustiveMathTest<float, mpfr::Operation::Rsqrt,
+                                      LIBC_NAMESPACE::rsqrtf>;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+// Range: [0, Inf]
+static constexpr uint32_t POS_START = 0x0000'0000U;
+static constexpr uint32_t POS_STOP = 0x7f80'0000U;
+
+TEST_F(LlvmLibcRsqrtfExhaustiveTest, PositiveRange) {
+  test_full_range_all_roundings(POS_START, POS_STOP);
+}
diff --git a/libc/test/src/math/rsqrtf_test.cpp b/libc/test/src/math/rsqrtf_test.cpp
new file mode 100644
index 0000000..4e476c0
--- /dev/null
+++ b/libc/test/src/math/rsqrtf_test.cpp
@@ -0,0 +1,12 @@
+//===-- Unittests for rsqrtf ----------------------------------------------===//
+// 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 "RsqrtTest.h"
+
+#include "src/math/rsqrtf.h"
+
+LIST_RSQRT_TESTS(float, LIBC_NAMESPACE::rsqrtf)
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 42a97ba..5afd3a9 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -3503,14 +3503,27 @@ add_fp_unittest(
 )
 
 add_fp_unittest(
+  rsqrtf_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    rsqrtf_test.cpp
+  DEPENDS
+    libc.hdr.errno_macros  
+    libc.hdr.fenv_macros  
+    libc.src.math.rsqrtf 
+)
+
+add_fp_unittest(
   rsqrtf16_test
   SUITE
     libc-math-smoke-tests
   SRCS
     rsqrtf16_test.cpp
   DEPENDS
+    libc.hdr.errno_macros  
+    libc.hdr.fenv_macros 
     libc.src.math.rsqrtf16
-    libc.hdr.errno_macros
 )
 
 add_fp_unittest(
diff --git a/libc/test/src/math/smoke/rsqrtf16_test.cpp b/libc/test/src/math/smoke/rsqrtf16_test.cpp
index e103e73..13d9a33 100644
--- a/libc/test/src/math/smoke/rsqrtf16_test.cpp
+++ b/libc/test/src/math/smoke/rsqrtf16_test.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
 #include "src/__support/FPUtil/cast.h"
 #include "src/__support/macros/properties/architectures.h"
 #include "src/math/rsqrtf16.h"
diff --git a/libc/test/src/math/smoke/rsqrtf_test.cpp b/libc/test/src/math/smoke/rsqrtf_test.cpp
new file mode 100644
index 0000000..d71b82c
--- /dev/null
+++ b/libc/test/src/math/smoke/rsqrtf_test.cpp
@@ -0,0 +1,41 @@
+//===-- Unittests for rsqrtf --------------------------------------------===//
+//
+// 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 "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
+#include "src/math/rsqrtf.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcRsqrtfTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+TEST_F(LlvmLibcRsqrtfTest, SpecialNumbers) {
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::rsqrtf(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_IS_NAN_WITH_EXCEPTION(LIBC_NAMESPACE::rsqrtf(sNaN), FE_INVALID);
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(inf, LIBC_NAMESPACE::rsqrtf(zero));
+  EXPECT_MATH_ERRNO(ERANGE);
+
+  EXPECT_FP_EQ(neg_inf, LIBC_NAMESPACE::rsqrtf(neg_zero));
+  EXPECT_MATH_ERRNO(ERANGE);
+
+  EXPECT_FP_EQ(1.0f, LIBC_NAMESPACE::rsqrtf(1.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::rsqrtf(inf));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::rsqrtf(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::rsqrtf(-2.0f));
+  EXPECT_MATH_ERRNO(EDOM);
+}