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 21 template <typename T> 22 class 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 36 public: 37 typedef T (*LdExpFunc)(T, int); 38 testSpecialNumbers(LdExpFunc func)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 testPowersOfTwo(LdExpFunc func)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 testOverflow(LdExpFunc func)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 testUnderflowToZeroOnNormal(LdExpFunc func)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 testUnderflowToZeroOnSubnormal(LdExpFunc func)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 testNormalOperation(LdExpFunc func)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