1 //===-- lib/fp_lib.h - Floating-point utilities -------------------*- C -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is dual licensed under the MIT and the University of Illinois Open 6 // Source Licenses. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file is a configuration header for soft-float routines in compiler-rt. 11 // This file does not provide any part of the compiler-rt interface, but defines 12 // many useful constants and utility routines that are used in the 13 // implementation of the soft-float routines in compiler-rt. 14 // 15 // Assumes that float and double correspond to the IEEE-754 binary32 and 16 // binary64 types, respectively, and that integer endianness matches floating 17 // point endianness on the target platform. 18 // 19 //===----------------------------------------------------------------------===// 20 21 #ifndef FP_LIB_HEADER 22 #define FP_LIB_HEADER 23 24 #include <stdint.h> 25 #include <stdbool.h> 26 #include <limits.h> 27 #include "int_lib.h" 28 29 #if defined SINGLE_PRECISION 30 31 typedef uint32_t rep_t; 32 typedef int32_t srep_t; 33 typedef float fp_t; 34 #define REP_C UINT32_C 35 #define significandBits 23 36 37 static inline int rep_clz(rep_t a) { 38 return __builtin_clz(a); 39 } 40 41 // 32x32 --> 64 bit multiply 42 static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) { 43 const uint64_t product = (uint64_t)a*b; 44 *hi = product >> 32; 45 *lo = product; 46 } 47 48 #elif defined DOUBLE_PRECISION 49 50 typedef uint64_t rep_t; 51 typedef int64_t srep_t; 52 typedef double fp_t; 53 #define REP_C UINT64_C 54 #define significandBits 52 55 56 static inline int rep_clz(rep_t a) { 57 #if defined __LP64__ 58 return __builtin_clzl(a); 59 #else 60 if (a & REP_C(0xffffffff00000000)) 61 return __builtin_clz(a >> 32); 62 else 63 return 32 + __builtin_clz(a & REP_C(0xffffffff)); 64 #endif 65 } 66 67 #define loWord(a) (a & 0xffffffffU) 68 #define hiWord(a) (a >> 32) 69 70 // 64x64 -> 128 wide multiply for platforms that don't have such an operation; 71 // many 64-bit platforms have this operation, but they tend to have hardware 72 // floating-point, so we don't bother with a special case for them here. 73 static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) { 74 // Each of the component 32x32 -> 64 products 75 const uint64_t plolo = loWord(a) * loWord(b); 76 const uint64_t plohi = loWord(a) * hiWord(b); 77 const uint64_t philo = hiWord(a) * loWord(b); 78 const uint64_t phihi = hiWord(a) * hiWord(b); 79 // Sum terms that contribute to lo in a way that allows us to get the carry 80 const uint64_t r0 = loWord(plolo); 81 const uint64_t r1 = hiWord(plolo) + loWord(plohi) + loWord(philo); 82 *lo = r0 + (r1 << 32); 83 // Sum terms contributing to hi with the carry from lo 84 *hi = hiWord(plohi) + hiWord(philo) + hiWord(r1) + phihi; 85 } 86 #undef loWord 87 #undef hiWord 88 89 #else 90 #error Either SINGLE_PRECISION or DOUBLE_PRECISION must be defined. 91 #endif 92 93 #define typeWidth (sizeof(rep_t)*CHAR_BIT) 94 #define exponentBits (typeWidth - significandBits - 1) 95 #define maxExponent ((1 << exponentBits) - 1) 96 #define exponentBias (maxExponent >> 1) 97 98 #define implicitBit (REP_C(1) << significandBits) 99 #define significandMask (implicitBit - 1U) 100 #define signBit (REP_C(1) << (significandBits + exponentBits)) 101 #define absMask (signBit - 1U) 102 #define exponentMask (absMask ^ significandMask) 103 #define oneRep ((rep_t)exponentBias << significandBits) 104 #define infRep exponentMask 105 #define quietBit (implicitBit >> 1) 106 #define qnanRep (exponentMask | quietBit) 107 108 static inline rep_t toRep(fp_t x) { 109 const union { fp_t f; rep_t i; } rep = {.f = x}; 110 return rep.i; 111 } 112 113 static inline fp_t fromRep(rep_t x) { 114 const union { fp_t f; rep_t i; } rep = {.i = x}; 115 return rep.f; 116 } 117 118 static inline int normalize(rep_t *significand) { 119 const int shift = rep_clz(*significand) - rep_clz(implicitBit); 120 *significand <<= shift; 121 return 1 - shift; 122 } 123 124 static inline void wideLeftShift(rep_t *hi, rep_t *lo, int count) { 125 *hi = *hi << count | *lo >> (typeWidth - count); 126 *lo = *lo << count; 127 } 128 129 static inline void wideRightShiftWithSticky(rep_t *hi, rep_t *lo, unsigned int count) { 130 if (count < typeWidth) { 131 const bool sticky = *lo << (typeWidth - count); 132 *lo = *hi << (typeWidth - count) | *lo >> count | sticky; 133 *hi = *hi >> count; 134 } 135 else if (count < 2*typeWidth) { 136 const bool sticky = *hi << (2*typeWidth - count) | *lo; 137 *lo = *hi >> (count - typeWidth) | sticky; 138 *hi = 0; 139 } else { 140 const bool sticky = *hi | *lo; 141 *lo = sticky; 142 *hi = 0; 143 } 144 } 145 146 #endif // FP_LIB_HEADER 147