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 22 using LIBC_NAMESPACE::Sign; 23 24 template <typename T> 25 class 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 39 public: 40 typedef T (*LdExpFunc)(T, int); 41 testSpecialNumbers(LdExpFunc func)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 testPowersOfTwo(LdExpFunc func)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 testOverflow(LdExpFunc func)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 testUnderflowToZeroOnNormal(LdExpFunc func)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 testUnderflowToZeroOnSubnormal(LdExpFunc func)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 testNormalOperation(LdExpFunc func)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