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 "utils/UnitTest/Test.h"
11 
12 #include <math.h>
13 
14 using FPBits = __llvm_libc::fputil::FPBits<long double>;
15 
16 TEST(X86LongDoubleTest, 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 
23   FPBits bits(0.0l);
24   bits.exponent = FPBits::MAX_EXPONENT;
25   for (unsigned int i = 0; i < 1000000; ++i) {
26     // If exponent has the max value and the implicit bit is 0,
27     // then the number is a NaN for all values of mantissa.
28     bits.mantissa = i;
29     long double nan = bits;
30     ASSERT_NE(isnan(nan), 0);
31     ASSERT_TRUE(bits.is_nan());
32   }
33 
34   bits.implicitBit = 1;
35   for (unsigned int i = 1; i < 1000000; ++i) {
36     // If exponent has the max value and the implicit bit is 1,
37     // then the number is a NaN for all non-zero values of mantissa.
38     // Note the initial value of |i| of 1 to avoid a zero mantissa.
39     bits.mantissa = i;
40     long double nan = bits;
41     ASSERT_NE(isnan(nan), 0);
42     ASSERT_TRUE(bits.is_nan());
43   }
44 
45   bits.exponent = 1;
46   bits.implicitBit = 0;
47   for (unsigned int i = 0; i < 1000000; ++i) {
48     // If exponent is non-zero and also not max, and the implicit bit is 0,
49     // then the number is a NaN for all values of mantissa.
50     bits.mantissa = i;
51     long double nan = bits;
52     ASSERT_NE(isnan(nan), 0);
53     ASSERT_TRUE(bits.is_nan());
54   }
55 
56   bits.exponent = 1;
57   bits.implicitBit = 1;
58   for (unsigned int i = 0; i < 1000000; ++i) {
59     // If exponent is non-zero and also not max, and the implicit bit is 1,
60     // then the number is normal value for all values of mantissa.
61     bits.mantissa = i;
62     long double valid = bits;
63     ASSERT_EQ(isnan(valid), 0);
64     ASSERT_FALSE(bits.is_nan());
65   }
66 
67   bits.exponent = 0;
68   bits.implicitBit = 1;
69   for (unsigned int i = 0; i < 1000000; ++i) {
70     // If exponent is zero, then the number is a valid but denormal value.
71     bits.mantissa = i;
72     long double valid = bits;
73     ASSERT_EQ(isnan(valid), 0);
74     ASSERT_FALSE(bits.is_nan());
75   }
76 
77   bits.exponent = 0;
78   bits.implicitBit = 0;
79   for (unsigned int i = 0; i < 1000000; ++i) {
80     // If exponent is zero, then the number is a valid but denormal value.
81     bits.mantissa = i;
82     long double valid = bits;
83     ASSERT_EQ(isnan(valid), 0);
84     ASSERT_FALSE(bits.is_nan());
85   }
86 }
87