1 //===-- lib/fp_lib.h - Floating-point utilities -------------------*- C -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
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.
19 //===----------------------------------------------------------------------===//
28 #if defined SINGLE_PRECISION
30 typedef uint32_t rep_t;
31 typedef int32_t srep_t;
33 #define REP_C UINT32_C
34 #define significandBits 23
36 static inline int rep_clz(rep_t a) {
37 return __builtin_clz(a);
40 // 32x32 --> 64 bit multiply
41 static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
42 const uint64_t product = (uint64_t)a*b;
47 #elif defined DOUBLE_PRECISION
49 typedef uint64_t rep_t;
50 typedef int64_t srep_t;
52 #define REP_C UINT64_C
53 #define significandBits 52
55 static inline int rep_clz(rep_t a) {
57 return __builtin_clzl(a);
59 if (a & REP_C(0xffffffff00000000))
60 return __builtin_clz(a >> 32);
62 return 32 + __builtin_clz(a & REP_C(0xffffffff));
66 #define loWord(a) (a & 0xffffffffU)
67 #define hiWord(a) (a >> 32)
69 // 64x64 -> 128 wide multiply for platforms that don't have such an operation;
70 // many 64-bit platforms have this operation, but they tend to have hardware
71 // floating-point, so we don't bother with a special case for them here.
72 static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
73 // Each of the component 32x32 -> 64 products
74 const uint64_t plolo = loWord(a) * loWord(b);
75 const uint64_t plohi = loWord(a) * hiWord(b);
76 const uint64_t philo = hiWord(a) * loWord(b);
77 const uint64_t phihi = hiWord(a) * hiWord(b);
78 // Sum terms that contribute to lo in a way that allows us to get the carry
79 const uint64_t r0 = loWord(plolo);
80 const uint64_t r1 = hiWord(plolo) + loWord(plohi) + loWord(philo);
81 *lo = r0 + (r1 << 32);
82 // Sum terms contributing to hi with the carry from lo
83 *hi = hiWord(plohi) + hiWord(philo) + hiWord(r1) + phihi;
87 #error Either SINGLE_PRECISION or DOUBLE_PRECISION must be defined.
90 #define typeWidth (sizeof(rep_t)*CHAR_BIT)
91 #define exponentBits (typeWidth - significandBits - 1)
92 #define maxExponent ((1 << exponentBits) - 1)
93 #define exponentBias (maxExponent >> 1)
95 #define implicitBit (REP_C(1) << significandBits)
96 #define significandMask (implicitBit - 1U)
97 #define signBit (REP_C(1) << (significandBits + exponentBits))
98 #define absMask (signBit - 1U)
99 #define exponentMask (absMask ^ significandMask)
100 #define oneRep ((rep_t)exponentBias << significandBits)
101 #define infRep exponentMask
102 #define quietBit (implicitBit >> 1)
103 #define qnanRep (exponentMask | quietBit)
105 static inline rep_t toRep(fp_t x) {
106 const union { fp_t f; rep_t i; } rep = {.f = x};
110 static inline fp_t fromRep(rep_t x) {
111 const union { fp_t f; rep_t i; } rep = {.i = x};
115 static inline int normalize(rep_t *significand) {
116 const int shift = rep_clz(*significand) - rep_clz(implicitBit);
117 *significand <<= shift;
121 static inline void wideLeftShift(rep_t *hi, rep_t *lo, int count) {
122 *hi = *hi << count | *lo >> (typeWidth - count);
126 static inline void wideRightShiftWithSticky(rep_t *hi, rep_t *lo, int count) {
127 if (count < typeWidth) {
128 const bool sticky = *lo << (typeWidth - count);
129 *lo = *hi << (typeWidth - count) | *lo >> count | sticky;
132 else if (count < 2*typeWidth) {
133 const bool sticky = *hi << (2*typeWidth - count) | *lo;
134 *lo = *hi >> (count - typeWidth) | sticky;
137 const bool sticky = *hi | *lo;
143 #endif // FP_LIB_HEADER