[libc] Fuzz tests for acos and atan (#147843)

created fuzz tests for acos and atan

---------

Co-authored-by: Sriya Pratipati <sriyap@google.com>

Author: sribee8

libc/fuzzing/math/CMakeLists.txt

@@ -71,6 +71,15 @@ add_libc_fuzzer(
     libc.src.math.sin
 )
 
+add_libc_fuzzer(
+  acos_fuzz
+  NEED_MPFR
+  SRCS
+    acos_fuzz.cpp
+  DEPENDS
+    libc.src.math.acos
+)
+
 add_libc_fuzzer(
   cos_fuzz
   NEED_MPFR
@@ -80,6 +89,15 @@ add_libc_fuzzer(
     libc.src.math.cos
 )
 
+add_libc_fuzzer(
+  atan_fuzz
+  NEED_MPFR
+  SRCS
+    atan_fuzz.cpp
+  DEPENDS
+    libc.src.math.atan
+)
+
 add_libc_fuzzer(
   tan_fuzz
   NEED_MPFR

libc/fuzzing/math/acos_fuzz.cpp

@@ -0,0 +1,38 @@
+//===-- acos_fuzz.cpp -----------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// Fuzzing test for llvm-libc acos implementation.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/math/acos.h"
+#include "utils/MPFRWrapper/mpfr_inc.h"
+#include <math.h>
+
+extern "C" int LLVMFuzzerTestOneInput(double x) {
+  // remove NaN and inf and values outside accepted range
+  if (isnan(x) || isinf(x) || x > 1 || x < -1)
+    return 0;
+  // signed zeros already tested in unit tests
+  if (signbit(x) && x == 0.0)
+    return 0;
+  mpfr_t input;
+  mpfr_init2(input, 53);
+  mpfr_set_d(input, x, MPFR_RNDN);
+  int output = mpfr_acos(input, input, MPFR_RNDN);
+  mpfr_subnormalize(input, output, MPFR_RNDN);
+  double to_compare = mpfr_get_d(input, MPFR_RNDN);
+
+  double result = LIBC_NAMESPACE::acos(x);
+
+  if (result != to_compare)
+    __builtin_trap();
+
+  mpfr_clear(input);
+  return 0;
+}

libc/fuzzing/math/atan_fuzz.cpp

@@ -0,0 +1,38 @@
+//===-- atan_fuzz.cpp -----------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// Fuzzing test for llvm-libc atan implementation.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/math/atan.h"
+#include "utils/MPFRWrapper/mpfr_inc.h"
+#include <math.h>
+
+extern "C" int LLVMFuzzerTestOneInput(double x) {
+  // remove NaN and inf
+  if (isnan(x) || isinf(x))
+    return 0;
+  // signed zeros already tested in unit tests
+  if (signbit(x) && x == 0.0)
+    return 0;
+  mpfr_t input;
+  mpfr_init2(input, 53);
+  mpfr_set_d(input, x, MPFR_RNDN);
+  int output = mpfr_atan(input, input, MPFR_RNDN);
+  mpfr_subnormalize(input, output, MPFR_RNDN);
+  double to_compare = mpfr_get_d(input, MPFR_RNDN);
+
+  double result = LIBC_NAMESPACE::atan(x);
+
+  if (result != to_compare)
+    __builtin_trap();
+
+  mpfr_clear(input);
+  return 0;
+}