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 "hdr/math_macros.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_biased_exponent(FPBits::MAX_BIASED_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     ASSERT_TRUE(bits.is_nan());
  31   }
  32
  33   bits.set_implicit_bit(1);
  34   for (unsigned int i = 1; i < COUNT; ++i) {
  35     // If exponent has the max value and the implicit bit is 1,
  36     // then the number is a NaN for all non-zero values of mantissa.
  37     // Note the initial value of |i| of 1 to avoid a zero mantissa.
  38     bits.set_mantissa(i);
  39     ASSERT_TRUE(bits.is_nan());
  40   }
  41
  42   bits.set_biased_exponent(1);
  43   bits.set_implicit_bit(0);
  44   for (unsigned int i = 0; i < COUNT; ++i) {
  45     // If exponent is non-zero and also not max, and the implicit bit is 0,
  46     // then the number is a NaN for all values of mantissa.
  47     bits.set_mantissa(i);
  48     ASSERT_TRUE(bits.is_nan());
  49   }
  50
  51   bits.set_biased_exponent(1);
  52   bits.set_implicit_bit(1);
  53   for (unsigned int i = 0; i < COUNT; ++i) {
  54     // If exponent is non-zero and also not max, and the implicit bit is 1,
  55     // then the number is normal value for all values of mantissa.
  56     bits.set_mantissa(i);
  57     ASSERT_FALSE(bits.is_nan());
  58   }
  59
  60   bits.set_biased_exponent(0);
  61   bits.set_implicit_bit(1);
  62   for (unsigned int i = 0; i < COUNT; ++i) {
  63     // If exponent is zero, then the number is a valid but denormal value.
  64     bits.set_mantissa(i);
  65     ASSERT_FALSE(bits.is_nan());
  66   }
  67
  68   bits.set_biased_exponent(0);
  69   bits.set_implicit_bit(0);
  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     ASSERT_FALSE(bits.is_nan());
  74   }
  75 }