1//===-- Utility class to test different flavors of ldexp --------*- C++ -*-===//
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#ifndef LLVM_LIBC_TEST_SRC_MATH_LDEXPTEST_H
10#define LLVM_LIBC_TEST_SRC_MATH_LDEXPTEST_H
11
12#include "src/__support/CPP/limits.h" // INT_MAX
13#include "src/__support/FPUtil/FPBits.h"
14#include "src/__support/FPUtil/NormalFloat.h"
15#include "test/UnitTest/FEnvSafeTest.h"
16#include "test/UnitTest/FPMatcher.h"
17#include "test/UnitTest/Test.h"
18
19#include <stdint.h>
20
21using LIBC_NAMESPACE::Sign;
22
23template <typename T, typename U = int>
24class LdExpTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
25 using FPBits = LIBC_NAMESPACE::fputil::FPBits<T>;
26 using NormalFloat = LIBC_NAMESPACE::fputil::NormalFloat<T>;
27 using StorageType = typename FPBits::StorageType;
28
29 const T inf = FPBits::inf(Sign::POS).get_val();
30 const T neg_inf = FPBits::inf(Sign::NEG).get_val();
31 const T zero = FPBits::zero(Sign::POS).get_val();
32 const T neg_zero = FPBits::zero(Sign::NEG).get_val();
33 const T nan = FPBits::quiet_nan().get_val();
34
35 // A normalized mantissa to be used with tests.
36 static constexpr StorageType MANTISSA = NormalFloat::ONE + 0x123;
37
38public:
39 typedef T (*LdExpFunc)(T, U);
40
41 void testSpecialNumbers(LdExpFunc func) {
42 int exp_array[5] = {INT_MIN, -10, 0, 10, INT_MAX};
43 for (int exp : exp_array) {
44 ASSERT_FP_EQ(zero, func(zero, exp));
45 ASSERT_FP_EQ(neg_zero, func(neg_zero, exp));
46 ASSERT_FP_EQ(inf, func(inf, exp));
47 ASSERT_FP_EQ(neg_inf, func(neg_inf, exp));
48 ASSERT_FP_EQ(nan, func(nan, exp));
49 }
50
51 if constexpr (sizeof(U) < sizeof(long) || sizeof(long) == sizeof(int))
52 return;
53 long long_exp_array[4] = {LONG_MIN, static_cast<long>(INT_MIN - 1LL),
54 static_cast<long>(INT_MAX + 1LL), LONG_MAX};
55 for (long exp : long_exp_array) {
56 ASSERT_FP_EQ(zero, func(zero, exp));
57 ASSERT_FP_EQ(neg_zero, func(neg_zero, exp));
58 ASSERT_FP_EQ(inf, func(inf, exp));
59 ASSERT_FP_EQ(neg_inf, func(neg_inf, exp));
60 ASSERT_FP_EQ(nan, func(nan, exp));
61 }
62 }
63
64 void testPowersOfTwo(LdExpFunc func) {
65 int32_t exp_array[5] = {1, 2, 3, 4, 5};
66 int32_t val_array[6] = {1, 2, 4, 8, 16, 32};
67 for (int32_t exp : exp_array) {
68 for (int32_t val : val_array) {
69 ASSERT_FP_EQ(T(val << exp), func(T(val), exp));
70 ASSERT_FP_EQ(T(-1 * (val << exp)), func(T(-val), exp));
71 }
72 }
73 }
74
75 void testOverflow(LdExpFunc func) {
76 NormalFloat x(Sign::POS, FPBits::MAX_BIASED_EXPONENT - 10,
77 NormalFloat::ONE + 0xFB);
78 for (int32_t exp = 10; exp < 100; ++exp) {
79 ASSERT_FP_EQ(inf, func(T(x), exp));
80 ASSERT_FP_EQ(neg_inf, func(-T(x), exp));
81 }
82 }
83
84 void testUnderflowToZeroOnNormal(LdExpFunc func) {
85 // In this test, we pass a normal nubmer to func and expect zero
86 // to be returned due to underflow.
87 int32_t base_exponent = FPBits::EXP_BIAS + FPBits::FRACTION_LEN;
88 int32_t exp_array[] = {base_exponent + 5, base_exponent + 4,
89 base_exponent + 3, base_exponent + 2,
90 base_exponent + 1};
91 T x = NormalFloat(Sign::POS, 0, MANTISSA);
92 for (int32_t exp : exp_array) {
93 ASSERT_FP_EQ(func(x, -exp), x > 0 ? zero : neg_zero);
94 }
95 }
96
97 void testUnderflowToZeroOnSubnormal(LdExpFunc func) {
98 // In this test, we pass a normal nubmer to func and expect zero
99 // to be returned due to underflow.
100 int32_t base_exponent = FPBits::EXP_BIAS + FPBits::FRACTION_LEN;
101 int32_t exp_array[] = {base_exponent + 5, base_exponent + 4,
102 base_exponent + 3, base_exponent + 2,
103 base_exponent + 1};
104 T x = NormalFloat(Sign::POS, -FPBits::EXP_BIAS, MANTISSA);
105 for (int32_t exp : exp_array) {
106 ASSERT_FP_EQ(func(x, -exp), x > 0 ? zero : neg_zero);
107 }
108 }
109
110 void testNormalOperation(LdExpFunc func) {
111 T val_array[] = {// Normal numbers
112 NormalFloat(Sign::POS, 10, MANTISSA),
113 NormalFloat(Sign::POS, -10, MANTISSA),
114 NormalFloat(Sign::NEG, 10, MANTISSA),
115 NormalFloat(Sign::NEG, -10, MANTISSA),
116 // Subnormal numbers
117 NormalFloat(Sign::POS, -FPBits::EXP_BIAS, MANTISSA),
118 NormalFloat(Sign::NEG, -FPBits::EXP_BIAS, MANTISSA)};
119 for (int32_t exp = 0; exp <= FPBits::FRACTION_LEN; ++exp) {
120 for (T x : val_array) {
121 // We compare the result of ldexp with the result
122 // of the native multiplication/division instruction.
123
124 // We need to use a NormalFloat here (instead of 1 << exp), because
125 // there are 32 bit systems that don't support 128bit long ints but
126 // support long doubles. This test can do 1 << 64, which would fail
127 // in these systems.
128 NormalFloat two_to_exp = NormalFloat(static_cast<T>(1.L));
129 two_to_exp = two_to_exp.mul2(exp);
130
131 ASSERT_FP_EQ(func(x, exp), x * static_cast<T>(two_to_exp));
132 ASSERT_FP_EQ(func(x, -exp), x / static_cast<T>(two_to_exp));
133 }
134 }
135
136 // Normal which trigger mantissa overflow.
137 T x = NormalFloat(Sign::POS, -FPBits::EXP_BIAS + 1,
138 StorageType(2) * NormalFloat::ONE - StorageType(1));
139 ASSERT_FP_EQ(func(x, -1), x / 2);
140 ASSERT_FP_EQ(func(-x, -1), -x / 2);
141
142 // Start with a normal number high exponent but pass a very low number for
143 // exp. The result should be a subnormal number.
144 x = NormalFloat(Sign::POS, FPBits::EXP_BIAS, NormalFloat::ONE);
145 int exp = -FPBits::MAX_BIASED_EXPONENT - 5;
146 T result = func(x, exp);
147 FPBits result_bits(result);
148 ASSERT_FALSE(result_bits.is_zero());
149 // Verify that the result is indeed subnormal.
150 ASSERT_EQ(result_bits.get_biased_exponent(), uint16_t(0));
151 // But if the exp is so less that normalization leads to zero, then
152 // the result should be zero.
153 result = func(x, -FPBits::MAX_BIASED_EXPONENT - FPBits::FRACTION_LEN - 5);
154 ASSERT_TRUE(FPBits(result).is_zero());
155
156 // Start with a subnormal number but pass a very high number for exponent.
157 // The result should not be infinity.
158 x = NormalFloat(Sign::POS, -FPBits::EXP_BIAS + 1, NormalFloat::ONE >> 10);
159 exp = FPBits::MAX_BIASED_EXPONENT + 5;
160 ASSERT_FALSE(FPBits(func(x, exp)).is_inf());
161 // But if the exp is large enough to oversome than the normalization shift,
162 // then it should result in infinity.
163 exp = FPBits::MAX_BIASED_EXPONENT + 15;
164 ASSERT_FP_EQ(func(x, exp), inf);
165 }
166};
167
168#define LIST_LDEXP_TESTS(T, func) \
169 using LlvmLibcLdExpTest = LdExpTestTemplate<T>; \
170 TEST_F(LlvmLibcLdExpTest, SpecialNumbers) { testSpecialNumbers(&func); } \
171 TEST_F(LlvmLibcLdExpTest, PowersOfTwo) { testPowersOfTwo(&func); } \
172 TEST_F(LlvmLibcLdExpTest, OverFlow) { testOverflow(&func); } \
173 TEST_F(LlvmLibcLdExpTest, UnderflowToZeroOnNormal) { \
174 testUnderflowToZeroOnNormal(&func); \
175 } \
176 TEST_F(LlvmLibcLdExpTest, UnderflowToZeroOnSubnormal) { \
177 testUnderflowToZeroOnSubnormal(&func); \
178 } \
179 TEST_F(LlvmLibcLdExpTest, NormalOperation) { testNormalOperation(&func); } \
180 static_assert(true)
181
182#endif // LLVM_LIBC_TEST_SRC_MATH_LDEXPTEST_H
183

source code of libc/test/src/math/smoke/LdExpTest.h