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 "hdr/math_macros.h"
20#include <stdint.h>
21
22using LIBC_NAMESPACE::Sign;
23
24template <typename T>
25class LdExpTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
26 using FPBits = LIBC_NAMESPACE::fputil::FPBits<T>;
27 using NormalFloat = LIBC_NAMESPACE::fputil::NormalFloat<T>;
28 using StorageType = typename FPBits::StorageType;
29
30 const T inf = FPBits::inf(Sign::POS).get_val();
31 const T neg_inf = FPBits::inf(Sign::NEG).get_val();
32 const T zero = FPBits::zero(Sign::POS).get_val();
33 const T neg_zero = FPBits::zero(Sign::NEG).get_val();
34 const T nan = FPBits::quiet_nan().get_val();
35
36 // A normalized mantissa to be used with tests.
37 static constexpr StorageType MANTISSA = NormalFloat::ONE + 0x1234;
38
39public:
40 typedef T (*LdExpFunc)(T, int);
41
42 void testSpecialNumbers(LdExpFunc func) {
43 int exp_array[5] = {-INT_MAX - 1, -10, 0, 10, INT_MAX};
44 for (int exp : exp_array) {
45 ASSERT_FP_EQ(zero, func(zero, exp));
46 ASSERT_FP_EQ(neg_zero, func(neg_zero, exp));
47 ASSERT_FP_EQ(inf, func(inf, exp));
48 ASSERT_FP_EQ(neg_inf, func(neg_inf, exp));
49 ASSERT_FP_EQ(nan, func(nan, exp));
50 }
51 }
52
53 void testPowersOfTwo(LdExpFunc func) {
54 int32_t exp_array[5] = {1, 2, 3, 4, 5};
55 int32_t val_array[6] = {1, 2, 4, 8, 16, 32};
56 for (int32_t exp : exp_array) {
57 for (int32_t val : val_array) {
58 ASSERT_FP_EQ(T(val << exp), func(T(val), exp));
59 ASSERT_FP_EQ(T(-1 * (val << exp)), func(T(-val), exp));
60 }
61 }
62 }
63
64 void testOverflow(LdExpFunc func) {
65 NormalFloat x(Sign::POS, FPBits::MAX_BIASED_EXPONENT - 10,
66 NormalFloat::ONE + 0xF00BA);
67 for (int32_t exp = 10; exp < 100; ++exp) {
68 ASSERT_FP_EQ(inf, func(T(x), exp));
69 ASSERT_FP_EQ(neg_inf, func(-T(x), exp));
70 }
71 }
72
73 void testUnderflowToZeroOnNormal(LdExpFunc func) {
74 // In this test, we pass a normal nubmer to func and expect zero
75 // to be returned due to underflow.
76 int32_t base_exponent = FPBits::EXP_BIAS + FPBits::FRACTION_LEN;
77 int32_t exp_array[] = {base_exponent + 5, base_exponent + 4,
78 base_exponent + 3, base_exponent + 2,
79 base_exponent + 1};
80 T x = NormalFloat(Sign::POS, 0, MANTISSA);
81 for (int32_t exp : exp_array) {
82 ASSERT_FP_EQ(func(x, -exp), x > 0 ? zero : neg_zero);
83 }
84 }
85
86 void testUnderflowToZeroOnSubnormal(LdExpFunc func) {
87 // In this test, we pass a normal nubmer to func and expect zero
88 // to be returned due to underflow.
89 int32_t base_exponent = FPBits::EXP_BIAS + FPBits::FRACTION_LEN;
90 int32_t exp_array[] = {base_exponent + 5, base_exponent + 4,
91 base_exponent + 3, base_exponent + 2,
92 base_exponent + 1};
93 T x = NormalFloat(Sign::POS, -FPBits::EXP_BIAS, MANTISSA);
94 for (int32_t exp : exp_array) {
95 ASSERT_FP_EQ(func(x, -exp), x > 0 ? zero : neg_zero);
96 }
97 }
98
99 void testNormalOperation(LdExpFunc func) {
100 T val_array[] = {// Normal numbers
101 NormalFloat(Sign::POS, 100, MANTISSA),
102 NormalFloat(Sign::POS, -100, MANTISSA),
103 NormalFloat(Sign::NEG, 100, MANTISSA),
104 NormalFloat(Sign::NEG, -100, MANTISSA),
105 // Subnormal numbers
106 NormalFloat(Sign::POS, -FPBits::EXP_BIAS, MANTISSA),
107 NormalFloat(Sign::NEG, -FPBits::EXP_BIAS, MANTISSA)};
108 for (int32_t exp = 0; exp <= FPBits::FRACTION_LEN; ++exp) {
109 for (T x : val_array) {
110 // We compare the result of ldexp with the result
111 // of the native multiplication/division instruction.
112
113 // We need to use a NormalFloat here (instead of 1 << exp), because
114 // there are 32 bit systems that don't support 128bit long ints but
115 // support long doubles. This test can do 1 << 64, which would fail
116 // in these systems.
117 NormalFloat two_to_exp = NormalFloat(static_cast<T>(1.L));
118 two_to_exp = two_to_exp.mul2(exp);
119
120 ASSERT_FP_EQ(func(x, exp), x * two_to_exp);
121 ASSERT_FP_EQ(func(x, -exp), x / two_to_exp);
122 }
123 }
124
125 // Normal which trigger mantissa overflow.
126 T x = NormalFloat(Sign::POS, -FPBits::EXP_BIAS + 1,
127 StorageType(2) * NormalFloat::ONE - StorageType(1));
128 ASSERT_FP_EQ(func(x, -1), x / 2);
129 ASSERT_FP_EQ(func(-x, -1), -x / 2);
130
131 // Start with a normal number high exponent but pass a very low number for
132 // exp. The result should be a subnormal number.
133 x = NormalFloat(Sign::POS, FPBits::EXP_BIAS, NormalFloat::ONE);
134 int exp = -FPBits::MAX_BIASED_EXPONENT - 5;
135 T result = func(x, exp);
136 FPBits result_bits(result);
137 ASSERT_FALSE(result_bits.is_zero());
138 // Verify that the result is indeed subnormal.
139 ASSERT_EQ(result_bits.get_biased_exponent(), uint16_t(0));
140 // But if the exp is so less that normalization leads to zero, then
141 // the result should be zero.
142 result = func(x, -FPBits::MAX_BIASED_EXPONENT - FPBits::FRACTION_LEN - 5);
143 ASSERT_TRUE(FPBits(result).is_zero());
144
145 // Start with a subnormal number but pass a very high number for exponent.
146 // The result should not be infinity.
147 x = NormalFloat(Sign::POS, -FPBits::EXP_BIAS + 1, NormalFloat::ONE >> 10);
148 exp = FPBits::MAX_BIASED_EXPONENT + 5;
149 ASSERT_FALSE(FPBits(func(x, exp)).is_inf());
150 // But if the exp is large enough to oversome than the normalization shift,
151 // then it should result in infinity.
152 exp = FPBits::MAX_BIASED_EXPONENT + 15;
153 ASSERT_FP_EQ(func(x, exp), inf);
154 }
155};
156
157#define LIST_LDEXP_TESTS(T, func) \
158 using LlvmLibcLdExpTest = LdExpTestTemplate<T>; \
159 TEST_F(LlvmLibcLdExpTest, SpecialNumbers) { testSpecialNumbers(&func); } \
160 TEST_F(LlvmLibcLdExpTest, PowersOfTwo) { testPowersOfTwo(&func); } \
161 TEST_F(LlvmLibcLdExpTest, OverFlow) { testOverflow(&func); } \
162 TEST_F(LlvmLibcLdExpTest, UnderflowToZeroOnNormal) { \
163 testUnderflowToZeroOnNormal(&func); \
164 } \
165 TEST_F(LlvmLibcLdExpTest, UnderflowToZeroOnSubnormal) { \
166 testUnderflowToZeroOnSubnormal(&func); \
167 } \
168 TEST_F(LlvmLibcLdExpTest, NormalOperation) { testNormalOperation(&func); }
169
170#endif // LLVM_LIBC_TEST_SRC_MATH_LDEXPTEST_H
171

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