forked from OSchip/llvm-project
145 lines
4.6 KiB
C
145 lines
4.6 KiB
C
//===-- lib/fp_lib.h - Floating-point utilities -------------------*- C -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a configuration header for soft-float routines in compiler-rt.
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// This file does not provide any part of the compiler-rt interface, but defines
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// many useful constants and utility routines that are used in the
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// implementation of the soft-float routines in compiler-rt.
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//
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// Assumes that float and double correspond to the IEEE-754 binary32 and
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// binary64 types, respectively, and that integer endianness matches floating
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// point endianness on the target platform.
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//
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//===----------------------------------------------------------------------===//
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#ifndef FP_LIB_HEADER
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#define FP_LIB_HEADER
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#include <stdint.h>
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#include <stdbool.h>
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#include <limits.h>
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#include "int_lib.h"
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#if defined SINGLE_PRECISION
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typedef uint32_t rep_t;
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typedef int32_t srep_t;
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typedef float fp_t;
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#define REP_C UINT32_C
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#define significandBits 23
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static inline int rep_clz(rep_t a) {
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return __builtin_clz(a);
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}
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// 32x32 --> 64 bit multiply
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static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
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const uint64_t product = (uint64_t)a*b;
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*hi = product >> 32;
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*lo = product;
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}
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#elif defined DOUBLE_PRECISION
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typedef uint64_t rep_t;
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typedef int64_t srep_t;
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typedef double fp_t;
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#define REP_C UINT64_C
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#define significandBits 52
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static inline int rep_clz(rep_t a) {
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#if defined __LP64__
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return __builtin_clzl(a);
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#else
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if (a & REP_C(0xffffffff00000000))
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return __builtin_clz(a >> 32);
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else
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return 32 + __builtin_clz(a & REP_C(0xffffffff));
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#endif
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}
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#define loWord(a) (a & 0xffffffffU)
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#define hiWord(a) (a >> 32)
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// 64x64 -> 128 wide multiply for platforms that don't have such an operation;
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// many 64-bit platforms have this operation, but they tend to have hardware
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// floating-point, so we don't bother with a special case for them here.
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static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
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// Each of the component 32x32 -> 64 products
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const uint64_t plolo = loWord(a) * loWord(b);
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const uint64_t plohi = loWord(a) * hiWord(b);
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const uint64_t philo = hiWord(a) * loWord(b);
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const uint64_t phihi = hiWord(a) * hiWord(b);
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// Sum terms that contribute to lo in a way that allows us to get the carry
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const uint64_t r0 = loWord(plolo);
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const uint64_t r1 = hiWord(plolo) + loWord(plohi) + loWord(philo);
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*lo = r0 + (r1 << 32);
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// Sum terms contributing to hi with the carry from lo
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*hi = hiWord(plohi) + hiWord(philo) + hiWord(r1) + phihi;
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}
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#else
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#error Either SINGLE_PRECISION or DOUBLE_PRECISION must be defined.
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#endif
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#define typeWidth (sizeof(rep_t)*CHAR_BIT)
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#define exponentBits (typeWidth - significandBits - 1)
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#define maxExponent ((1 << exponentBits) - 1)
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#define exponentBias (maxExponent >> 1)
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#define implicitBit (REP_C(1) << significandBits)
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#define significandMask (implicitBit - 1U)
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#define signBit (REP_C(1) << (significandBits + exponentBits))
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#define absMask (signBit - 1U)
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#define exponentMask (absMask ^ significandMask)
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#define oneRep ((rep_t)exponentBias << significandBits)
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#define infRep exponentMask
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#define quietBit (implicitBit >> 1)
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#define qnanRep (exponentMask | quietBit)
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static inline rep_t toRep(fp_t x) {
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const union { fp_t f; rep_t i; } rep = {.f = x};
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return rep.i;
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}
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static inline fp_t fromRep(rep_t x) {
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const union { fp_t f; rep_t i; } rep = {.i = x};
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return rep.f;
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}
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static inline int normalize(rep_t *significand) {
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const int shift = rep_clz(*significand) - rep_clz(implicitBit);
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*significand <<= shift;
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return 1 - shift;
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}
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static inline void wideLeftShift(rep_t *hi, rep_t *lo, int count) {
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*hi = *hi << count | *lo >> (typeWidth - count);
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*lo = *lo << count;
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}
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static inline void wideRightShiftWithSticky(rep_t *hi, rep_t *lo, int count) {
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if (count < typeWidth) {
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const bool sticky = *lo << (typeWidth - count);
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*lo = *hi << (typeWidth - count) | *lo >> count | sticky;
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*hi = *hi >> count;
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}
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else if (count < 2*typeWidth) {
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const bool sticky = *hi << (2*typeWidth - count) | *lo;
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*lo = *hi >> (count - typeWidth) | sticky;
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*hi = 0;
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} else {
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const bool sticky = *hi | *lo;
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*lo = sticky;
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*hi = 0;
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}
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}
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#endif // FP_LIB_HEADER
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