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

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