libc/test/utils/FPUtil/x86_long_double_test.cpp

   1 //===-- Unittests for x86 long double -------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "src/__support/FPUtil/FPBits.h"
  10 #include "test/UnitTest/Test.h"
  11
  12 #include <math.h>
  13
  14 using FPBits = LIBC_NAMESPACE::fputil::FPBits<long double>;
  15
  16 TEST(LlvmLibcX86LongDoubleTest, is_nan) {
  17   // In the nan checks below, we use the macro isnan from math.h to ensure that
  18   // a number is actually a NaN. The isnan macro resolves to the compiler
  19   // builtin function. Hence, matching LLVM-libc's notion of NaN with the
  20   // isnan result ensures that LLVM-libc's behavior matches the compiler's
  21   // behavior.
  22   constexpr uint32_t COUNT = 100'000;
  23
  24   FPBits bits(0.0l);
  25   bits.set_unbiased_exponent(FPBits::MAX_EXPONENT);
  26   for (unsigned int i = 0; i < COUNT; ++i) {
  27     // If exponent has the max value and the implicit bit is 0,
  28     // then the number is a NaN for all values of mantissa.
  29     bits.set_mantissa(i);
  30     long double nan = bits;
  31     ASSERT_NE(static_cast<int>(isnan(nan)), 0);
  32     ASSERT_TRUE(bits.is_nan());
  33   }
  34
  35   bits.set_implicit_bit(1);
  36   for (unsigned int i = 1; i < COUNT; ++i) {
  37     // If exponent has the max value and the implicit bit is 1,
  38     // then the number is a NaN for all non-zero values of mantissa.
  39     // Note the initial value of |i| of 1 to avoid a zero mantissa.
  40     bits.set_mantissa(i);
  41     long double nan = bits;
  42     ASSERT_NE(static_cast<int>(isnan(nan)), 0);
  43     ASSERT_TRUE(bits.is_nan());
  44   }
  45
  46   bits.set_unbiased_exponent(1);
  47   bits.set_implicit_bit(0);
  48   for (unsigned int i = 0; i < COUNT; ++i) {
  49     // If exponent is non-zero and also not max, and the implicit bit is 0,
  50     // then the number is a NaN for all values of mantissa.
  51     bits.set_mantissa(i);
  52     long double nan = bits;
  53     ASSERT_NE(static_cast<int>(isnan(nan)), 0);
  54     ASSERT_TRUE(bits.is_nan());
  55   }
  56
  57   bits.set_unbiased_exponent(1);
  58   bits.set_implicit_bit(1);
  59   for (unsigned int i = 0; i < COUNT; ++i) {
  60     // If exponent is non-zero and also not max, and the implicit bit is 1,
  61     // then the number is normal value for all values of mantissa.
  62     bits.set_mantissa(i);
  63     long double valid = bits;
  64     ASSERT_EQ(static_cast<int>(isnan(valid)), 0);
  65     ASSERT_FALSE(bits.is_nan());
  66   }
  67
  68   bits.set_unbiased_exponent(0);
  69   bits.set_implicit_bit(1);
  70   for (unsigned int i = 0; i < COUNT; ++i) {
  71     // If exponent is zero, then the number is a valid but denormal value.
  72     bits.set_mantissa(i);
  73     long double valid = bits;
  74     ASSERT_EQ(static_cast<int>(isnan(valid)), 0);
  75     ASSERT_FALSE(bits.is_nan());
  76   }
  77
  78   bits.set_unbiased_exponent(0);
  79   bits.set_implicit_bit(0);
  80   for (unsigned int i = 0; i < COUNT; ++i) {
  81     // If exponent is zero, then the number is a valid but denormal value.
  82     bits.set_mantissa(i);
  83     long double valid = bits;
  84     ASSERT_EQ(static_cast<int>(isnan(valid)), 0);
  85     ASSERT_FALSE(bits.is_nan());
  86   }
  87 }