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//===-- APFloat.cpp - Implement APFloat class -----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a class to represent arbitrary precision floating
// point values and provide a variety of arithmetic operations on them.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <cstring>
#include <limits.h>
#define APFLOAT_DISPATCH_ON_SEMANTICS(METHOD_CALL) \
do { \
if (usesLayout<IEEEFloat>(getSemantics())) \
return U.IEEE.METHOD_CALL; \
if (usesLayout<DoubleAPFloat>(getSemantics())) \
return U.Double.METHOD_CALL; \
llvm_unreachable("Unexpected semantics"); \
} while (false)
using namespace llvm;
/// A macro used to combine two fcCategory enums into one key which can be used
/// in a switch statement to classify how the interaction of two APFloat's
/// categories affects an operation.
///
/// TODO: If clang source code is ever allowed to use constexpr in its own
/// codebase, change this into a static inline function.
#define PackCategoriesIntoKey(_lhs, _rhs) ((_lhs) * 4 + (_rhs))
/* Assumed in hexadecimal significand parsing, and conversion to
hexadecimal strings. */
static_assert(APFloatBase::integerPartWidth % 4 == 0, "Part width must be divisible by 4!");
namespace llvm {
/* Represents floating point arithmetic semantics. */
struct fltSemantics {
/* The largest E such that 2^E is representable; this matches the
definition of IEEE 754. */
APFloatBase::ExponentType maxExponent;
/* The smallest E such that 2^E is a normalized number; this
matches the definition of IEEE 754. */
APFloatBase::ExponentType minExponent;
/* Number of bits in the significand. This includes the integer
bit. */
unsigned int precision;
/* Number of bits actually used in the semantics. */
unsigned int sizeInBits;
};
static const fltSemantics semIEEEhalf = {15, -14, 11, 16};
static const fltSemantics semIEEEsingle = {127, -126, 24, 32};
static const fltSemantics semIEEEdouble = {1023, -1022, 53, 64};
static const fltSemantics semIEEEquad = {16383, -16382, 113, 128};
static const fltSemantics semX87DoubleExtended = {16383, -16382, 64, 80};
static const fltSemantics semBogus = {0, 0, 0, 0};
/* The IBM double-double semantics. Such a number consists of a pair of IEEE
64-bit doubles (Hi, Lo), where |Hi| > |Lo|, and if normal,
(double)(Hi + Lo) == Hi. The numeric value it's modeling is Hi + Lo.
Therefore it has two 53-bit mantissa parts that aren't necessarily adjacent
to each other, and two 11-bit exponents.
Note: we need to make the value different from semBogus as otherwise
an unsafe optimization may collapse both values to a single address,
and we heavily rely on them having distinct addresses. */
static const fltSemantics semPPCDoubleDouble = {-1, 0, 0, 0};
/* These are legacy semantics for the fallback, inaccrurate implementation of
IBM double-double, if the accurate semPPCDoubleDouble doesn't handle the
operation. It's equivalent to having an IEEE number with consecutive 106
bits of mantissa and 11 bits of exponent.
It's not equivalent to IBM double-double. For example, a legit IBM
double-double, 1 + epsilon:
1 + epsilon = 1 + (1 >> 1076)
is not representable by a consecutive 106 bits of mantissa.
Currently, these semantics are used in the following way:
semPPCDoubleDouble -> (IEEEdouble, IEEEdouble) ->
(64-bit APInt, 64-bit APInt) -> (128-bit APInt) ->
semPPCDoubleDoubleLegacy -> IEEE operations
We use bitcastToAPInt() to get the bit representation (in APInt) of the
underlying IEEEdouble, then use the APInt constructor to construct the
legacy IEEE float.
TODO: Implement all operations in semPPCDoubleDouble, and delete these
semantics. */
static const fltSemantics semPPCDoubleDoubleLegacy = {1023, -1022 + 53,
53 + 53, 128};
const fltSemantics &APFloatBase::IEEEhalf() {
return semIEEEhalf;
}
const fltSemantics &APFloatBase::IEEEsingle() {
return semIEEEsingle;
}
const fltSemantics &APFloatBase::IEEEdouble() {
return semIEEEdouble;
}
const fltSemantics &APFloatBase::IEEEquad() {
return semIEEEquad;
}
const fltSemantics &APFloatBase::x87DoubleExtended() {
return semX87DoubleExtended;
}
const fltSemantics &APFloatBase::Bogus() {
return semBogus;
}
const fltSemantics &APFloatBase::PPCDoubleDouble() {
return semPPCDoubleDouble;
}
/* A tight upper bound on number of parts required to hold the value
pow(5, power) is
power * 815 / (351 * integerPartWidth) + 1
However, whilst the result may require only this many parts,
because we are multiplying two values to get it, the
multiplication may require an extra part with the excess part
being zero (consider the trivial case of 1 * 1, tcFullMultiply
requires two parts to hold the single-part result). So we add an
extra one to guarantee enough space whilst multiplying. */
const unsigned int maxExponent = 16383;
const unsigned int maxPrecision = 113;
const unsigned int maxPowerOfFiveExponent = maxExponent + maxPrecision - 1;
const unsigned int maxPowerOfFiveParts = 2 + ((maxPowerOfFiveExponent * 815) / (351 * APFloatBase::integerPartWidth));
unsigned int APFloatBase::semanticsPrecision(const fltSemantics &semantics) {
return semantics.precision;
}
APFloatBase::ExponentType
APFloatBase::semanticsMaxExponent(const fltSemantics &semantics) {
return semantics.maxExponent;
}
APFloatBase::ExponentType
APFloatBase::semanticsMinExponent(const fltSemantics &semantics) {
return semantics.minExponent;
}
unsigned int APFloatBase::semanticsSizeInBits(const fltSemantics &semantics) {
return semantics.sizeInBits;
}
unsigned APFloatBase::getSizeInBits(const fltSemantics &Sem) {
return Sem.sizeInBits;
}
/* A bunch of private, handy routines. */
static inline unsigned int
partCountForBits(unsigned int bits)
{
return ((bits) + APFloatBase::integerPartWidth - 1) / APFloatBase::integerPartWidth;
}
/* Returns 0U-9U. Return values >= 10U are not digits. */
static inline unsigned int
decDigitValue(unsigned int c)
{
return c - '0';
}
/* Return the value of a decimal exponent of the form
[+-]ddddddd.
If the exponent overflows, returns a large exponent with the
appropriate sign. */
static int
readExponent(StringRef::iterator begin, StringRef::iterator end)
{
bool isNegative;
unsigned int absExponent;
const unsigned int overlargeExponent = 24000; /* FIXME. */
StringRef::iterator p = begin;
assert(p != end && "Exponent has no digits");
isNegative = (*p == '-');
if (*p == '-' || *p == '+') {
p++;
assert(p != end && "Exponent has no digits");
}
absExponent = decDigitValue(*p++);
assert(absExponent < 10U && "Invalid character in exponent");
for (; p != end; ++p) {
unsigned int value;
value = decDigitValue(*p);
assert(value < 10U && "Invalid character in exponent");
value += absExponent * 10;
if (absExponent >= overlargeExponent) {
absExponent = overlargeExponent;
p = end; /* outwit assert below */
break;
}
absExponent = value;
}
assert(p == end && "Invalid exponent in exponent");
if (isNegative)
return -(int) absExponent;
else
return (int) absExponent;
}
/* This is ugly and needs cleaning up, but I don't immediately see
how whilst remaining safe. */
static int
totalExponent(StringRef::iterator p, StringRef::iterator end,
int exponentAdjustment)
{
int unsignedExponent;
bool negative, overflow;
int exponent = 0;
assert(p != end && "Exponent has no digits");
negative = *p == '-';
if (*p == '-' || *p == '+') {
p++;
assert(p != end && "Exponent has no digits");
}
unsignedExponent = 0;
overflow = false;
for (; p != end; ++p) {
unsigned int value;
value = decDigitValue(*p);
assert(value < 10U && "Invalid character in exponent");
unsignedExponent = unsignedExponent * 10 + value;
if (unsignedExponent > 32767) {
overflow = true;
break;
}
}
if (exponentAdjustment > 32767 || exponentAdjustment < -32768)
overflow = true;
if (!overflow) {
exponent = unsignedExponent;
if (negative)
exponent = -exponent;
exponent += exponentAdjustment;
if (exponent > 32767 || exponent < -32768)
overflow = true;
}
if (overflow)
exponent = negative ? -32768: 32767;
return exponent;
}
static StringRef::iterator
skipLeadingZeroesAndAnyDot(StringRef::iterator begin, StringRef::iterator end,
StringRef::iterator *dot)
{
StringRef::iterator p = begin;
*dot = end;
while (p != end && *p == '0')
p++;
if (p != end && *p == '.') {
*dot = p++;
assert(end - begin != 1 && "Significand has no digits");
while (p != end && *p == '0')
p++;
}
return p;
}
/* Given a normal decimal floating point number of the form
dddd.dddd[eE][+-]ddd
where the decimal point and exponent are optional, fill out the
structure D. Exponent is appropriate if the significand is
treated as an integer, and normalizedExponent if the significand
is taken to have the decimal point after a single leading
non-zero digit.
If the value is zero, V->firstSigDigit points to a non-digit, and
the return exponent is zero.
*/
struct decimalInfo {
const char *firstSigDigit;
const char *lastSigDigit;
int exponent;
int normalizedExponent;
};
static void
interpretDecimal(StringRef::iterator begin, StringRef::iterator end,
decimalInfo *D)
{
StringRef::iterator dot = end;
StringRef::iterator p = skipLeadingZeroesAndAnyDot (begin, end, &dot);
D->firstSigDigit = p;
D->exponent = 0;
D->normalizedExponent = 0;
for (; p != end; ++p) {
if (*p == '.') {
assert(dot == end && "String contains multiple dots");
dot = p++;
if (p == end)
break;
}
if (decDigitValue(*p) >= 10U)
break;
}
if (p != end) {
assert((*p == 'e' || *p == 'E') && "Invalid character in significand");
assert(p != begin && "Significand has no digits");
assert((dot == end || p - begin != 1) && "Significand has no digits");
/* p points to the first non-digit in the string */
D->exponent = readExponent(p + 1, end);
/* Implied decimal point? */
if (dot == end)
dot = p;
}
/* If number is all zeroes accept any exponent. */
if (p != D->firstSigDigit) {
/* Drop insignificant trailing zeroes. */
if (p != begin) {
do
do
p--;
while (p != begin && *p == '0');
while (p != begin && *p == '.');
}
/* Adjust the exponents for any decimal point. */
D->exponent += static_cast<APFloat::ExponentType>((dot - p) - (dot > p));
D->normalizedExponent = (D->exponent +
static_cast<APFloat::ExponentType>((p - D->firstSigDigit)
- (dot > D->firstSigDigit && dot < p)));
}
D->lastSigDigit = p;
}
/* Return the trailing fraction of a hexadecimal number.
DIGITVALUE is the first hex digit of the fraction, P points to
the next digit. */
static lostFraction
trailingHexadecimalFraction(StringRef::iterator p, StringRef::iterator end,
unsigned int digitValue)
{
unsigned int hexDigit;
/* If the first trailing digit isn't 0 or 8 we can work out the
fraction immediately. */
if (digitValue > 8)
return lfMoreThanHalf;
else if (digitValue < 8 && digitValue > 0)
return lfLessThanHalf;
// Otherwise we need to find the first non-zero digit.
while (p != end && (*p == '0' || *p == '.'))
p++;
assert(p != end && "Invalid trailing hexadecimal fraction!");
hexDigit = hexDigitValue(*p);
/* If we ran off the end it is exactly zero or one-half, otherwise
a little more. */
if (hexDigit == -1U)
return digitValue == 0 ? lfExactlyZero: lfExactlyHalf;
else
return digitValue == 0 ? lfLessThanHalf: lfMoreThanHalf;
}
/* Return the fraction lost were a bignum truncated losing the least
significant BITS bits. */
static lostFraction
lostFractionThroughTruncation(const APFloatBase::integerPart *parts,
unsigned int partCount,
unsigned int bits)
{
unsigned int lsb;
lsb = APInt::tcLSB(parts, partCount);
/* Note this is guaranteed true if bits == 0, or LSB == -1U. */
if (bits <= lsb)
return lfExactlyZero;
if (bits == lsb + 1)
return lfExactlyHalf;
if (bits <= partCount * APFloatBase::integerPartWidth &&
APInt::tcExtractBit(parts, bits - 1))
return lfMoreThanHalf;
return lfLessThanHalf;
}
/* Shift DST right BITS bits noting lost fraction. */
static lostFraction
shiftRight(APFloatBase::integerPart *dst, unsigned int parts, unsigned int bits)
{
lostFraction lost_fraction;
lost_fraction = lostFractionThroughTruncation(dst, parts, bits);
APInt::tcShiftRight(dst, parts, bits);
return lost_fraction;
}
/* Combine the effect of two lost fractions. */
static lostFraction
combineLostFractions(lostFraction moreSignificant,
lostFraction lessSignificant)
{
if (lessSignificant != lfExactlyZero) {
if (moreSignificant == lfExactlyZero)
moreSignificant = lfLessThanHalf;
else if (moreSignificant == lfExactlyHalf)
moreSignificant = lfMoreThanHalf;
}
return moreSignificant;
}
/* The error from the true value, in half-ulps, on multiplying two
floating point numbers, which differ from the value they
approximate by at most HUE1 and HUE2 half-ulps, is strictly less
than the returned value.
See "How to Read Floating Point Numbers Accurately" by William D
Clinger. */
static unsigned int
HUerrBound(bool inexactMultiply, unsigned int HUerr1, unsigned int HUerr2)
{
assert(HUerr1 < 2 || HUerr2 < 2 || (HUerr1 + HUerr2 < 8));
if (HUerr1 + HUerr2 == 0)
return inexactMultiply * 2; /* <= inexactMultiply half-ulps. */
else
return inexactMultiply + 2 * (HUerr1 + HUerr2);
}
/* The number of ulps from the boundary (zero, or half if ISNEAREST)
when the least significant BITS are truncated. BITS cannot be
zero. */
static APFloatBase::integerPart
ulpsFromBoundary(const APFloatBase::integerPart *parts, unsigned int bits,
bool isNearest) {
unsigned int count, partBits;
APFloatBase::integerPart part, boundary;
assert(bits != 0);
bits--;
count = bits / APFloatBase::integerPartWidth;
partBits = bits % APFloatBase::integerPartWidth + 1;
part = parts[count] & (~(APFloatBase::integerPart) 0 >> (APFloatBase::integerPartWidth - partBits));
if (isNearest)
boundary = (APFloatBase::integerPart) 1 << (partBits - 1);
else
boundary = 0;
if (count == 0) {
if (part - boundary <= boundary - part)
return part - boundary;
else
return boundary - part;
}
if (part == boundary) {
while (--count)
if (parts[count])
return ~(APFloatBase::integerPart) 0; /* A lot. */
return parts[0];
} else if (part == boundary - 1) {
while (--count)
if (~parts[count])
return ~(APFloatBase::integerPart) 0; /* A lot. */
return -parts[0];
}
return ~(APFloatBase::integerPart) 0; /* A lot. */
}
/* Place pow(5, power) in DST, and return the number of parts used.
DST must be at least one part larger than size of the answer. */
static unsigned int
powerOf5(APFloatBase::integerPart *dst, unsigned int power) {
static const APFloatBase::integerPart firstEightPowers[] = { 1, 5, 25, 125, 625, 3125, 15625, 78125 };
APFloatBase::integerPart pow5s[maxPowerOfFiveParts * 2 + 5];
pow5s[0] = 78125 * 5;
unsigned int partsCount[16] = { 1 };
APFloatBase::integerPart scratch[maxPowerOfFiveParts], *p1, *p2, *pow5;
unsigned int result;
assert(power <= maxExponent);
p1 = dst;
p2 = scratch;
*p1 = firstEightPowers[power & 7];
power >>= 3;
result = 1;
pow5 = pow5s;
for (unsigned int n = 0; power; power >>= 1, n++) {
unsigned int pc;
pc = partsCount[n];
/* Calculate pow(5,pow(2,n+3)) if we haven't yet. */
if (pc == 0) {
pc = partsCount[n - 1];
APInt::tcFullMultiply(pow5, pow5 - pc, pow5 - pc, pc, pc);
pc *= 2;
if (pow5[pc - 1] == 0)
pc--;
partsCount[n] = pc;
}
if (power & 1) {
APFloatBase::integerPart *tmp;
APInt::tcFullMultiply(p2, p1, pow5, result, pc);
result += pc;
if (p2[result - 1] == 0)
result--;
/* Now result is in p1 with partsCount parts and p2 is scratch
space. */
tmp = p1;
p1 = p2;
p2 = tmp;
}
pow5 += pc;
}
if (p1 != dst)
APInt::tcAssign(dst, p1, result);
return result;
}
/* Zero at the end to avoid modular arithmetic when adding one; used
when rounding up during hexadecimal output. */
static const char hexDigitsLower[] = "0123456789abcdef0";
static const char hexDigitsUpper[] = "0123456789ABCDEF0";
static const char infinityL[] = "infinity";
static const char infinityU[] = "INFINITY";
static const char NaNL[] = "nan";
static const char NaNU[] = "NAN";
/* Write out an integerPart in hexadecimal, starting with the most
significant nibble. Write out exactly COUNT hexdigits, return
COUNT. */
static unsigned int
partAsHex (char *dst, APFloatBase::integerPart part, unsigned int count,
const char *hexDigitChars)
{
unsigned int result = count;
assert(count != 0 && count <= APFloatBase::integerPartWidth / 4);
part >>= (APFloatBase::integerPartWidth - 4 * count);
while (count--) {
dst[count] = hexDigitChars[part & 0xf];
part >>= 4;
}
return result;
}
/* Write out an unsigned decimal integer. */
static char *
writeUnsignedDecimal (char *dst, unsigned int n)
{
char buff[40], *p;
p = buff;
do
*p++ = '0' + n % 10;
while (n /= 10);
do
*dst++ = *--p;
while (p != buff);
return dst;
}
/* Write out a signed decimal integer. */
static char *
writeSignedDecimal (char *dst, int value)
{
if (value < 0) {
*dst++ = '-';
dst = writeUnsignedDecimal(dst, -(unsigned) value);
} else
dst = writeUnsignedDecimal(dst, value);
return dst;
}
namespace detail {
/* Constructors. */
void IEEEFloat::initialize(const fltSemantics *ourSemantics) {
unsigned int count;
semantics = ourSemantics;
count = partCount();
if (count > 1)
significand.parts = new integerPart[count];
}
void IEEEFloat::freeSignificand() {
if (needsCleanup())
delete [] significand.parts;
}
void IEEEFloat::assign(const IEEEFloat &rhs) {
assert(semantics == rhs.semantics);
sign = rhs.sign;
category = rhs.category;
exponent = rhs.exponent;
if (isFiniteNonZero() || category == fcNaN)
copySignificand(rhs);
}
void IEEEFloat::copySignificand(const IEEEFloat &rhs) {
assert(isFiniteNonZero() || category == fcNaN);
assert(rhs.partCount() >= partCount());
APInt::tcAssign(significandParts(), rhs.significandParts(),
partCount());
}
/* Make this number a NaN, with an arbitrary but deterministic value
for the significand. If double or longer, this is a signalling NaN,
which may not be ideal. If float, this is QNaN(0). */
void IEEEFloat::makeNaN(bool SNaN, bool Negative, const APInt *fill) {
category = fcNaN;
sign = Negative;
integerPart *significand = significandParts();
unsigned numParts = partCount();
// Set the significand bits to the fill.
if (!fill || fill->getNumWords() < numParts)
APInt::tcSet(significand, 0, numParts);
if (fill) {
APInt::tcAssign(significand, fill->getRawData(),
std::min(fill->getNumWords(), numParts));
// Zero out the excess bits of the significand.
unsigned bitsToPreserve = semantics->precision - 1;
unsigned part = bitsToPreserve / 64;
bitsToPreserve %= 64;
significand[part] &= ((1ULL << bitsToPreserve) - 1);
for (part++; part != numParts; ++part)
significand[part] = 0;
}
unsigned QNaNBit = semantics->precision - 2;
if (SNaN) {
// We always have to clear the QNaN bit to make it an SNaN.
APInt::tcClearBit(significand, QNaNBit);
// If there are no bits set in the payload, we have to set
// *something* to make it a NaN instead of an infinity;
// conventionally, this is the next bit down from the QNaN bit.
if (APInt::tcIsZero(significand, numParts))
APInt::tcSetBit(significand, QNaNBit - 1);
} else {
// We always have to set the QNaN bit to make it a QNaN.
APInt::tcSetBit(significand, QNaNBit);
}
// For x87 extended precision, we want to make a NaN, not a
// pseudo-NaN. Maybe we should expose the ability to make
// pseudo-NaNs?
if (semantics == &semX87DoubleExtended)
APInt::tcSetBit(significand, QNaNBit + 1);
}
IEEEFloat &IEEEFloat::operator=(const IEEEFloat &rhs) {
if (this != &rhs) {
if (semantics != rhs.semantics) {
freeSignificand();
initialize(rhs.semantics);
}
assign(rhs);
}
return *this;
}
IEEEFloat &IEEEFloat::operator=(IEEEFloat &&rhs) {
freeSignificand();
semantics = rhs.semantics;
significand = rhs.significand;
exponent = rhs.exponent;
category = rhs.category;
sign = rhs.sign;
rhs.semantics = &semBogus;
return *this;
}
bool IEEEFloat::isDenormal() const {
return isFiniteNonZero() && (exponent == semantics->minExponent) &&
(APInt::tcExtractBit(significandParts(),
semantics->precision - 1) == 0);
}
bool IEEEFloat::isSmallest() const {
// The smallest number by magnitude in our format will be the smallest
// denormal, i.e. the floating point number with exponent being minimum
// exponent and significand bitwise equal to 1 (i.e. with MSB equal to 0).
return isFiniteNonZero() && exponent == semantics->minExponent &&
significandMSB() == 0;
}
bool IEEEFloat::isSignificandAllOnes() const {
// Test if the significand excluding the integral bit is all ones. This allows
// us to test for binade boundaries.
const integerPart *Parts = significandParts();
const unsigned PartCount = partCount();
for (unsigned i = 0; i < PartCount - 1; i++)
if (~Parts[i])
return false;
// Set the unused high bits to all ones when we compare.
const unsigned NumHighBits =
PartCount*integerPartWidth - semantics->precision + 1;
assert(NumHighBits <= integerPartWidth && "Can not have more high bits to "
"fill than integerPartWidth");
const integerPart HighBitFill =
~integerPart(0) << (integerPartWidth - NumHighBits);
if (~(Parts[PartCount - 1] | HighBitFill))
return false;
return true;
}
bool IEEEFloat::isSignificandAllZeros() const {
// Test if the significand excluding the integral bit is all zeros. This
// allows us to test for binade boundaries.
const integerPart *Parts = significandParts();
const unsigned PartCount = partCount();
for (unsigned i = 0; i < PartCount - 1; i++)
if (Parts[i])
return false;
const unsigned NumHighBits =
PartCount*integerPartWidth - semantics->precision + 1;
assert(NumHighBits <= integerPartWidth && "Can not have more high bits to "
"clear than integerPartWidth");
const integerPart HighBitMask = ~integerPart(0) >> NumHighBits;
if (Parts[PartCount - 1] & HighBitMask)
return false;
return true;
}
bool IEEEFloat::isLargest() const {
// The largest number by magnitude in our format will be the floating point
// number with maximum exponent and with significand that is all ones.
return isFiniteNonZero() && exponent == semantics->maxExponent
&& isSignificandAllOnes();
}
bool IEEEFloat::isInteger() const {
// This could be made more efficient; I'm going for obviously correct.
if (!isFinite()) return false;
IEEEFloat truncated = *this;
truncated.roundToIntegral(rmTowardZero);
return compare(truncated) == cmpEqual;
}
bool IEEEFloat::bitwiseIsEqual(const IEEEFloat &rhs) const {
if (this == &rhs)
return true;
if (semantics != rhs.semantics ||
category != rhs.category ||
sign != rhs.sign)
return false;
if (category==fcZero || category==fcInfinity)
return true;
if (isFiniteNonZero() && exponent != rhs.exponent)
return false;
return std::equal(significandParts(), significandParts() + partCount(),
rhs.significandParts());
}
IEEEFloat::IEEEFloat(const fltSemantics &ourSemantics, integerPart value) {
initialize(&ourSemantics);
sign = 0;
category = fcNormal;
zeroSignificand();
exponent = ourSemantics.precision - 1;
significandParts()[0] = value;
normalize(rmNearestTiesToEven, lfExactlyZero);
}
IEEEFloat::IEEEFloat(const fltSemantics &ourSemantics) {
initialize(&ourSemantics);
category = fcZero;
sign = false;
}
// Delegate to the previous constructor, because later copy constructor may
// actually inspects category, which can't be garbage.
IEEEFloat::IEEEFloat(const fltSemantics &ourSemantics, uninitializedTag tag)
: IEEEFloat(ourSemantics) {}
IEEEFloat::IEEEFloat(const IEEEFloat &rhs) {
initialize(rhs.semantics);
assign(rhs);
}
IEEEFloat::IEEEFloat(IEEEFloat &&rhs) : semantics(&semBogus) {
*this = std::move(rhs);
}
IEEEFloat::~IEEEFloat() { freeSignificand(); }
unsigned int IEEEFloat::partCount() const {
return partCountForBits(semantics->precision + 1);
}
const IEEEFloat::integerPart *IEEEFloat::significandParts() const {
return const_cast<IEEEFloat *>(this)->significandParts();
}
IEEEFloat::integerPart *IEEEFloat::significandParts() {
if (partCount() > 1)
return significand.parts;
else
return &significand.part;
}
void IEEEFloat::zeroSignificand() {
APInt::tcSet(significandParts(), 0, partCount());
}
/* Increment an fcNormal floating point number's significand. */
void IEEEFloat::incrementSignificand() {
integerPart carry;
carry = APInt::tcIncrement(significandParts(), partCount());
/* Our callers should never cause us to overflow. */
assert(carry == 0);
(void)carry;
}
/* Add the significand of the RHS. Returns the carry flag. */
IEEEFloat::integerPart IEEEFloat::addSignificand(const IEEEFloat &rhs) {
integerPart *parts;
parts = significandParts();
assert(semantics == rhs.semantics);
assert(exponent == rhs.exponent);
return APInt::tcAdd(parts, rhs.significandParts(), 0, partCount());
}
/* Subtract the significand of the RHS with a borrow flag. Returns
the borrow flag. */
IEEEFloat::integerPart IEEEFloat::subtractSignificand(const IEEEFloat &rhs,
integerPart borrow) {
integerPart *parts;
parts = significandParts();
assert(semantics == rhs.semantics);
assert(exponent == rhs.exponent);
return APInt::tcSubtract(parts, rhs.significandParts(), borrow,
partCount());
}
/* Multiply the significand of the RHS. If ADDEND is non-NULL, add it
on to the full-precision result of the multiplication. Returns the
lost fraction. */
lostFraction IEEEFloat::multiplySignificand(const IEEEFloat &rhs,
const IEEEFloat *addend) {
unsigned int omsb; // One, not zero, based MSB.
unsigned int partsCount, newPartsCount, precision;
integerPart *lhsSignificand;
integerPart scratch[4];
integerPart *fullSignificand;
lostFraction lost_fraction;
bool ignored;
assert(semantics == rhs.semantics);
precision = semantics->precision;
// Allocate space for twice as many bits as the original significand, plus one
// extra bit for the addition to overflow into.
newPartsCount = partCountForBits(precision * 2 + 1);
if (newPartsCount > 4)
fullSignificand = new integerPart[newPartsCount];
else
fullSignificand = scratch;
lhsSignificand = significandParts();
partsCount = partCount();
APInt::tcFullMultiply(fullSignificand, lhsSignificand,
rhs.significandParts(), partsCount, partsCount);
lost_fraction = lfExactlyZero;
omsb = APInt::tcMSB(fullSignificand, newPartsCount) + 1;
exponent += rhs.exponent;
// Assume the operands involved in the multiplication are single-precision
// FP, and the two multiplicants are:
// *this = a23 . a22 ... a0 * 2^e1
// rhs = b23 . b22 ... b0 * 2^e2
// the result of multiplication is:
// *this = c48 c47 c46 . c45 ... c0 * 2^(e1+e2)
// Note that there are three significant bits at the left-hand side of the
// radix point: two for the multiplication, and an overflow bit for the
// addition (that will always be zero at this point). Move the radix point
// toward left by two bits, and adjust exponent accordingly.
exponent += 2;
if (addend && addend->isNonZero()) {
// The intermediate result of the multiplication has "2 * precision"
// signicant bit; adjust the addend to be consistent with mul result.
//
Significand savedSignificand = significand;
const fltSemantics *savedSemantics = semantics;
fltSemantics extendedSemantics;
opStatus status;
unsigned int extendedPrecision;
// Normalize our MSB to one below the top bit to allow for overflow.
extendedPrecision = 2 * precision + 1;
if (omsb != extendedPrecision - 1) {
assert(extendedPrecision > omsb);
APInt::tcShiftLeft(fullSignificand, newPartsCount,
(extendedPrecision - 1) - omsb);
exponent -= (extendedPrecision - 1) - omsb;
}
/* Create new semantics. */
extendedSemantics = *semantics;
extendedSemantics.precision = extendedPrecision;
if (newPartsCount == 1)
significand.part = fullSignificand[0];
else
significand.parts = fullSignificand;
semantics = &extendedSemantics;
IEEEFloat extendedAddend(*addend);
status = extendedAddend.convert(extendedSemantics, rmTowardZero, &ignored);
assert(status == opOK);
(void)status;
// Shift the significand of the addend right by one bit. This guarantees
// that the high bit of the significand is zero (same as fullSignificand),
// so the addition will overflow (if it does overflow at all) into the top bit.
lost_fraction = extendedAddend.shiftSignificandRight(1);
assert(lost_fraction == lfExactlyZero &&
"Lost precision while shifting addend for fused-multiply-add.");
lost_fraction = addOrSubtractSignificand(extendedAddend, false);
/* Restore our state. */
if (newPartsCount == 1)
fullSignificand[0] = significand.part;
significand = savedSignificand;
semantics = savedSemantics;
omsb = APInt::tcMSB(fullSignificand, newPartsCount) + 1;
}
// Convert the result having "2 * precision" significant-bits back to the one
// having "precision" significant-bits. First, move the radix point from
// poision "2*precision - 1" to "precision - 1". The exponent need to be
// adjusted by "2*precision - 1" - "precision - 1" = "precision".
exponent -= precision + 1;
// In case MSB resides at the left-hand side of radix point, shift the
// mantissa right by some amount to make sure the MSB reside right before
// the radix point (i.e. "MSB . rest-significant-bits").
//
// Note that the result is not normalized when "omsb < precision". So, the
// caller needs to call IEEEFloat::normalize() if normalized value is
// expected.
if (omsb > precision) {
unsigned int bits, significantParts;
lostFraction lf;
bits = omsb - precision;
significantParts = partCountForBits(omsb);
lf = shiftRight(fullSignificand, significantParts, bits);
lost_fraction = combineLostFractions(lf, lost_fraction);
exponent += bits;
}
APInt::tcAssign(lhsSignificand, fullSignificand, partsCount);
if (newPartsCount > 4)
delete [] fullSignificand;
return lost_fraction;
}
/* Multiply the significands of LHS and RHS to DST. */
lostFraction IEEEFloat::divideSignificand(const IEEEFloat &rhs) {
unsigned int bit, i, partsCount;
const integerPart *rhsSignificand;
integerPart *lhsSignificand, *dividend, *divisor;
integerPart scratch[4];
lostFraction lost_fraction;
assert(semantics == rhs.semantics);
lhsSignificand = significandParts();
rhsSignificand = rhs.significandParts();
partsCount = partCount();
if (partsCount > 2)
dividend = new integerPart[partsCount * 2];
else
dividend = scratch;
divisor = dividend + partsCount;
/* Copy the dividend and divisor as they will be modified in-place. */
for (i = 0; i < partsCount; i++) {
dividend[i] = lhsSignificand[i];
divisor[i] = rhsSignificand[i];
lhsSignificand[i] = 0;
}
exponent -= rhs.exponent;
unsigned int precision = semantics->precision;
/* Normalize the divisor. */
bit = precision - APInt::tcMSB(divisor, partsCount) - 1;
if (bit) {
exponent += bit;
APInt::tcShiftLeft(divisor, partsCount, bit);
}
/* Normalize the dividend. */
bit = precision - APInt::tcMSB(dividend, partsCount) - 1;
if (bit) {
exponent -= bit;
APInt::tcShiftLeft(dividend, partsCount, bit);
}
/* Ensure the dividend >= divisor initially for the loop below.
Incidentally, this means that the division loop below is
guaranteed to set the integer bit to one. */
if (APInt::tcCompare(dividend, divisor, partsCount) < 0) {
exponent--;
APInt::tcShiftLeft(dividend, partsCount, 1);
assert(APInt::tcCompare(dividend, divisor, partsCount) >= 0);
}
/* Long division. */
for (bit = precision; bit; bit -= 1) {
if (APInt::tcCompare(dividend, divisor, partsCount) >= 0) {
APInt::tcSubtract(dividend, divisor, 0, partsCount);
APInt::tcSetBit(lhsSignificand, bit - 1);
}
APInt::tcShiftLeft(dividend, partsCount, 1);
}
/* Figure out the lost fraction. */
int cmp = APInt::tcCompare(dividend, divisor, partsCount);
if (cmp > 0)
lost_fraction = lfMoreThanHalf;
else if (cmp == 0)
lost_fraction = lfExactlyHalf;
else if (APInt::tcIsZero(dividend, partsCount))
lost_fraction = lfExactlyZero;
else
lost_fraction = lfLessThanHalf;
if (partsCount > 2)
delete [] dividend;
return lost_fraction;
}
unsigned int IEEEFloat::significandMSB() const {
return APInt::tcMSB(significandParts(), partCount());
}
unsigned int IEEEFloat::significandLSB() const {
return APInt::tcLSB(significandParts(), partCount());
}
/* Note that a zero result is NOT normalized to fcZero. */
lostFraction IEEEFloat::shiftSignificandRight(unsigned int bits) {
/* Our exponent should not overflow. */
assert((ExponentType) (exponent + bits) >= exponent);
exponent += bits;
return shiftRight(significandParts(), partCount(), bits);
}
/* Shift the significand left BITS bits, subtract BITS from its exponent. */
void IEEEFloat::shiftSignificandLeft(unsigned int bits) {
assert(bits < semantics->precision);
if (bits) {
unsigned int partsCount = partCount();
APInt::tcShiftLeft(significandParts(), partsCount, bits);
exponent -= bits;
assert(!APInt::tcIsZero(significandParts(), partsCount));
}
}
IEEEFloat::cmpResult
IEEEFloat::compareAbsoluteValue(const IEEEFloat &rhs) const {
int compare;
assert(semantics == rhs.semantics);
assert(isFiniteNonZero());
assert(rhs.isFiniteNonZero());
compare = exponent - rhs.exponent;
/* If exponents are equal, do an unsigned bignum comparison of the
significands. */
if (compare == 0)
compare = APInt::tcCompare(significandParts(), rhs.significandParts(),
partCount());
if (compare > 0)
return cmpGreaterThan;
else if (compare < 0)
return cmpLessThan;
else
return cmpEqual;
}
/* Handle overflow. Sign is preserved. We either become infinity or
the largest finite number. */
IEEEFloat::opStatus IEEEFloat::handleOverflow(roundingMode rounding_mode) {
/* Infinity? */
if (rounding_mode == rmNearestTiesToEven ||
rounding_mode == rmNearestTiesToAway ||
(rounding_mode == rmTowardPositive && !sign) ||
(rounding_mode == rmTowardNegative && sign)) {
category = fcInfinity;
return (opStatus) (opOverflow | opInexact);
}
/* Otherwise we become the largest finite number. */
category = fcNormal;
exponent = semantics->maxExponent;
APInt::tcSetLeastSignificantBits(significandParts(), partCount(),
semantics->precision);
return opInexact;
}
/* Returns TRUE if, when truncating the current number, with BIT the
new LSB, with the given lost fraction and rounding mode, the result
would need to be rounded away from zero (i.e., by increasing the
signficand). This routine must work for fcZero of both signs, and
fcNormal numbers. */
bool IEEEFloat::roundAwayFromZero(roundingMode rounding_mode,
lostFraction lost_fraction,
unsigned int bit) const {
/* NaNs and infinities should not have lost fractions. */
assert(isFiniteNonZero() || category == fcZero);
/* Current callers never pass this so we don't handle it. */
assert(lost_fraction != lfExactlyZero);
switch (rounding_mode) {
case rmNearestTiesToAway:
return lost_fraction == lfExactlyHalf || lost_fraction == lfMoreThanHalf;
case rmNearestTiesToEven:
if (lost_fraction == lfMoreThanHalf)
return true;
/* Our zeroes don't have a significand to test. */
if (lost_fraction == lfExactlyHalf && category != fcZero)
return APInt::tcExtractBit(significandParts(), bit);
return false;
case rmTowardZero:
return false;
case rmTowardPositive:
return !sign;
case rmTowardNegative:
return sign;
}
llvm_unreachable("Invalid rounding mode found");
}
IEEEFloat::opStatus IEEEFloat::normalize(roundingMode rounding_mode,
lostFraction lost_fraction) {
unsigned int omsb; /* One, not zero, based MSB. */
int exponentChange;
if (!isFiniteNonZero())
return opOK;
/* Before rounding normalize the exponent of fcNormal numbers. */
omsb = significandMSB() + 1;
if (omsb) {
/* OMSB is numbered from 1. We want to place it in the integer
bit numbered PRECISION if possible, with a compensating change in
the exponent. */
exponentChange = omsb - semantics->precision;
/* If the resulting exponent is too high, overflow according to
the rounding mode. */
if (exponent + exponentChange > semantics->maxExponent)
return handleOverflow(rounding_mode);
/* Subnormal numbers have exponent minExponent, and their MSB
is forced based on that. */
if (exponent + exponentChange < semantics->minExponent)
exponentChange = semantics->minExponent - exponent;
/* Shifting left is easy as we don't lose precision. */
if (exponentChange < 0) {
assert(lost_fraction == lfExactlyZero);
shiftSignificandLeft(-exponentChange);
return opOK;
}
if (exponentChange > 0) {
lostFraction lf;
/* Shift right and capture any new lost fraction. */
lf = shiftSignificandRight(exponentChange);
lost_fraction = combineLostFractions(lf, lost_fraction);
/* Keep OMSB up-to-date. */
if (omsb > (unsigned) exponentChange)
omsb -= exponentChange;
else
omsb = 0;
}
}
/* Now round the number according to rounding_mode given the lost
fraction. */
/* As specified in IEEE 754, since we do not trap we do not report
underflow for exact results. */
if (lost_fraction == lfExactlyZero) {
/* Canonicalize zeroes. */
if (omsb == 0)
category = fcZero;
return opOK;
}
/* Increment the significand if we're rounding away from zero. */
if (roundAwayFromZero(rounding_mode, lost_fraction, 0)) {
if (omsb == 0)
exponent = semantics->minExponent;
incrementSignificand();
omsb = significandMSB() + 1;
/* Did the significand increment overflow? */
if (omsb == (unsigned) semantics->precision + 1) {
/* Renormalize by incrementing the exponent and shifting our
significand right one. However if we already have the
maximum exponent we overflow to infinity. */
if (exponent == semantics->maxExponent) {
category = fcInfinity;
return (opStatus) (opOverflow | opInexact);
}
shiftSignificandRight(1);
return opInexact;
}
}
/* The normal case - we were and are not denormal, and any
significand increment above didn't overflow. */
if (omsb == semantics->precision)
return opInexact;
/* We have a non-zero denormal. */
assert(omsb < semantics->precision);
/* Canonicalize zeroes. */
if (omsb == 0)
category = fcZero;
/* The fcZero case is a denormal that underflowed to zero. */
return (opStatus) (opUnderflow | opInexact);
}
IEEEFloat::opStatus IEEEFloat::addOrSubtractSpecials(const IEEEFloat &rhs,
bool subtract) {
switch (PackCategoriesIntoKey(category, rhs.category)) {
default:
llvm_unreachable(nullptr);
case PackCategoriesIntoKey(fcNaN, fcZero):
case PackCategoriesIntoKey(fcNaN, fcNormal):
case PackCategoriesIntoKey(fcNaN, fcInfinity):
case PackCategoriesIntoKey(fcNaN, fcNaN):
case PackCategoriesIntoKey(fcNormal, fcZero):
case PackCategoriesIntoKey(fcInfinity, fcNormal):
case PackCategoriesIntoKey(fcInfinity, fcZero):
return opOK;
case PackCategoriesIntoKey(fcZero, fcNaN):
case PackCategoriesIntoKey(fcNormal, fcNaN):
case PackCategoriesIntoKey(fcInfinity, fcNaN):
// We need to be sure to flip the sign here for subtraction because we
// don't have a separate negate operation so -NaN becomes 0 - NaN here.
sign = rhs.sign ^ subtract;
category = fcNaN;
copySignificand(rhs);
return opOK;
case PackCategoriesIntoKey(fcNormal, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcInfinity):
category = fcInfinity;
sign = rhs.sign ^ subtract;
return opOK;
case PackCategoriesIntoKey(fcZero, fcNormal):
assign(rhs);
sign = rhs.sign ^ subtract;
return opOK;
case PackCategoriesIntoKey(fcZero, fcZero):
/* Sign depends on rounding mode; handled by caller. */
return opOK;
case PackCategoriesIntoKey(fcInfinity, fcInfinity):
/* Differently signed infinities can only be validly
subtracted. */
if (((sign ^ rhs.sign)!=0) != subtract) {
makeNaN();
return opInvalidOp;
}
return opOK;
case PackCategoriesIntoKey(fcNormal, fcNormal):
return opDivByZero;
}
}
/* Add or subtract two normal numbers. */
lostFraction IEEEFloat::addOrSubtractSignificand(const IEEEFloat &rhs,
bool subtract) {
integerPart carry;
lostFraction lost_fraction;
int bits;
/* Determine if the operation on the absolute values is effectively
an addition or subtraction. */
subtract ^= static_cast<bool>(sign ^ rhs.sign);
/* Are we bigger exponent-wise than the RHS? */
bits = exponent - rhs.exponent;
/* Subtraction is more subtle than one might naively expect. */
if (subtract) {
IEEEFloat temp_rhs(rhs);
bool reverse;
if (bits == 0) {
reverse = compareAbsoluteValue(temp_rhs) == cmpLessThan;
lost_fraction = lfExactlyZero;
} else if (bits > 0) {
lost_fraction = temp_rhs.shiftSignificandRight(bits - 1);
shiftSignificandLeft(1);
reverse = false;
} else {
lost_fraction = shiftSignificandRight(-bits - 1);
temp_rhs.shiftSignificandLeft(1);
reverse = true;
}
if (reverse) {
carry = temp_rhs.subtractSignificand
(*this, lost_fraction != lfExactlyZero);
copySignificand(temp_rhs);
sign = !sign;
} else {
carry = subtractSignificand
(temp_rhs, lost_fraction != lfExactlyZero);
}
/* Invert the lost fraction - it was on the RHS and
subtracted. */
if (lost_fraction == lfLessThanHalf)
lost_fraction = lfMoreThanHalf;
else if (lost_fraction == lfMoreThanHalf)
lost_fraction = lfLessThanHalf;
/* The code above is intended to ensure that no borrow is
necessary. */
assert(!carry);
(void)carry;
} else {
if (bits > 0) {
IEEEFloat temp_rhs(rhs);
lost_fraction = temp_rhs.shiftSignificandRight(bits);
carry = addSignificand(temp_rhs);
} else {
lost_fraction = shiftSignificandRight(-bits);
carry = addSignificand(rhs);
}
/* We have a guard bit; generating a carry cannot happen. */
assert(!carry);
(void)carry;
}
return lost_fraction;
}
IEEEFloat::opStatus IEEEFloat::multiplySpecials(const IEEEFloat &rhs) {
switch (PackCategoriesIntoKey(category, rhs.category)) {
default:
llvm_unreachable(nullptr);
case PackCategoriesIntoKey(fcNaN, fcZero):
case PackCategoriesIntoKey(fcNaN, fcNormal):
case PackCategoriesIntoKey(fcNaN, fcInfinity):
case PackCategoriesIntoKey(fcNaN, fcNaN):
sign = false;
return opOK;
case PackCategoriesIntoKey(fcZero, fcNaN):
case PackCategoriesIntoKey(fcNormal, fcNaN):
case PackCategoriesIntoKey(fcInfinity, fcNaN):
sign = false;
category = fcNaN;
copySignificand(rhs);
return opOK;
case PackCategoriesIntoKey(fcNormal, fcInfinity):
case PackCategoriesIntoKey(fcInfinity, fcNormal):
case PackCategoriesIntoKey(fcInfinity, fcInfinity):
category = fcInfinity;
return opOK;
case PackCategoriesIntoKey(fcZero, fcNormal):
case PackCategoriesIntoKey(fcNormal, fcZero):
case PackCategoriesIntoKey(fcZero, fcZero):
category = fcZero;
return opOK;
case PackCategoriesIntoKey(fcZero, fcInfinity):
case PackCategoriesIntoKey(fcInfinity, fcZero):
makeNaN();
return opInvalidOp;
case PackCategoriesIntoKey(fcNormal, fcNormal):
return opOK;
}
}
IEEEFloat::opStatus IEEEFloat::divideSpecials(const IEEEFloat &rhs) {
switch (PackCategoriesIntoKey(category, rhs.category)) {
default:
llvm_unreachable(nullptr);
case PackCategoriesIntoKey(fcZero, fcNaN):
case PackCategoriesIntoKey(fcNormal, fcNaN):
case PackCategoriesIntoKey(fcInfinity, fcNaN):
category = fcNaN;
copySignificand(rhs);
LLVM_FALLTHROUGH;
case PackCategoriesIntoKey(fcNaN, fcZero):
case PackCategoriesIntoKey(fcNaN, fcNormal):
case PackCategoriesIntoKey(fcNaN, fcInfinity):
case PackCategoriesIntoKey(fcNaN, fcNaN):
sign = false;
LLVM_FALLTHROUGH;
case PackCategoriesIntoKey(fcInfinity, fcZero):
case PackCategoriesIntoKey(fcInfinity, fcNormal):
case PackCategoriesIntoKey(fcZero, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcNormal):
return opOK;
case PackCategoriesIntoKey(fcNormal, fcInfinity):
category = fcZero;
return opOK;
case PackCategoriesIntoKey(fcNormal, fcZero):
category = fcInfinity;
return opDivByZero;
case PackCategoriesIntoKey(fcInfinity, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcZero):
makeNaN();
return opInvalidOp;
case PackCategoriesIntoKey(fcNormal, fcNormal):
return opOK;
}
}
IEEEFloat::opStatus IEEEFloat::modSpecials(const IEEEFloat &rhs) {
switch (PackCategoriesIntoKey(category, rhs.category)) {
default:
llvm_unreachable(nullptr);
case PackCategoriesIntoKey(fcNaN, fcZero):
case PackCategoriesIntoKey(fcNaN, fcNormal):
case PackCategoriesIntoKey(fcNaN, fcInfinity):
case PackCategoriesIntoKey(fcNaN, fcNaN):
case PackCategoriesIntoKey(fcZero, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcNormal):
case PackCategoriesIntoKey(fcNormal, fcInfinity):
return opOK;
case PackCategoriesIntoKey(fcZero, fcNaN):
case PackCategoriesIntoKey(fcNormal, fcNaN):
case PackCategoriesIntoKey(fcInfinity, fcNaN):
sign = false;
category = fcNaN;
copySignificand(rhs);
return opOK;
case PackCategoriesIntoKey(fcNormal, fcZero):
case PackCategoriesIntoKey(fcInfinity, fcZero):
case PackCategoriesIntoKey(fcInfinity, fcNormal):
case PackCategoriesIntoKey(fcInfinity, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcZero):
makeNaN();
return opInvalidOp;
case PackCategoriesIntoKey(fcNormal, fcNormal):
return opOK;
}
}
/* Change sign. */
void IEEEFloat::changeSign() {
/* Look mummy, this one's easy. */
sign = !sign;
}
/* Normalized addition or subtraction. */
IEEEFloat::opStatus IEEEFloat::addOrSubtract(const IEEEFloat &rhs,
roundingMode rounding_mode,
bool subtract) {
opStatus fs;
fs = addOrSubtractSpecials(rhs, subtract);
/* This return code means it was not a simple case. */
if (fs == opDivByZero) {
lostFraction lost_fraction;
lost_fraction = addOrSubtractSignificand(rhs, subtract);
fs = normalize(rounding_mode, lost_fraction);
/* Can only be zero if we lost no fraction. */
assert(category != fcZero || lost_fraction == lfExactlyZero);
}
/* If two numbers add (exactly) to zero, IEEE 754 decrees it is a
positive zero unless rounding to minus infinity, except that
adding two like-signed zeroes gives that zero. */
if (category == fcZero) {
if (rhs.category != fcZero || (sign == rhs.sign) == subtract)
sign = (rounding_mode == rmTowardNegative);
}
return fs;
}
/* Normalized addition. */
IEEEFloat::opStatus IEEEFloat::add(const IEEEFloat &rhs,
roundingMode rounding_mode) {
return addOrSubtract(rhs, rounding_mode, false);
}
/* Normalized subtraction. */
IEEEFloat::opStatus IEEEFloat::subtract(const IEEEFloat &rhs,
roundingMode rounding_mode) {
return addOrSubtract(rhs, rounding_mode, true);
}
/* Normalized multiply. */
IEEEFloat::opStatus IEEEFloat::multiply(const IEEEFloat &rhs,
roundingMode rounding_mode) {
opStatus fs;
sign ^= rhs.sign;
fs = multiplySpecials(rhs);
if (isFiniteNonZero()) {
lostFraction lost_fraction = multiplySignificand(rhs, nullptr);
fs = normalize(rounding_mode, lost_fraction);
if (lost_fraction != lfExactlyZero)
fs = (opStatus) (fs | opInexact);
}
return fs;
}
/* Normalized divide. */
IEEEFloat::opStatus IEEEFloat::divide(const IEEEFloat &rhs,
roundingMode rounding_mode) {
opStatus fs;
sign ^= rhs.sign;
fs = divideSpecials(rhs);
if (isFiniteNonZero()) {
lostFraction lost_fraction = divideSignificand(rhs);
fs = normalize(rounding_mode, lost_fraction);
if (lost_fraction != lfExactlyZero)
fs = (opStatus) (fs | opInexact);
}
return fs;
}
/* Normalized remainder. This is not currently correct in all cases. */
IEEEFloat::opStatus IEEEFloat::remainder(const IEEEFloat &rhs) {
opStatus fs;
IEEEFloat V = *this;
unsigned int origSign = sign;
fs = V.divide(rhs, rmNearestTiesToEven);
if (fs == opDivByZero)
return fs;
int parts = partCount();
integerPart *x = new integerPart[parts];
bool ignored;
fs = V.convertToInteger(makeMutableArrayRef(x, parts),
parts * integerPartWidth, true, rmNearestTiesToEven,
&ignored);
if (fs == opInvalidOp) {
delete[] x;
return fs;
}
fs = V.convertFromZeroExtendedInteger(x, parts * integerPartWidth, true,
rmNearestTiesToEven);
assert(fs==opOK); // should always work
fs = V.multiply(rhs, rmNearestTiesToEven);
assert(fs==opOK || fs==opInexact); // should not overflow or underflow
fs = subtract(V, rmNearestTiesToEven);
assert(fs==opOK || fs==opInexact); // likewise
if (isZero())
sign = origSign; // IEEE754 requires this
delete[] x;
return fs;
}
/* Normalized llvm frem (C fmod). */
IEEEFloat::opStatus IEEEFloat::mod(const IEEEFloat &rhs) {
opStatus fs;
fs = modSpecials(rhs);
unsigned int origSign = sign;
while (isFiniteNonZero() && rhs.isFiniteNonZero() &&
compareAbsoluteValue(rhs) != cmpLessThan) {
IEEEFloat V = scalbn(rhs, ilogb(*this) - ilogb(rhs), rmNearestTiesToEven);
if (compareAbsoluteValue(V) == cmpLessThan)
V = scalbn(V, -1, rmNearestTiesToEven);
V.sign = sign;
fs = subtract(V, rmNearestTiesToEven);
assert(fs==opOK);
}
if (isZero())
sign = origSign; // fmod requires this
return fs;
}
/* Normalized fused-multiply-add. */
IEEEFloat::opStatus IEEEFloat::fusedMultiplyAdd(const IEEEFloat &multiplicand,
const IEEEFloat &addend,
roundingMode rounding_mode) {
opStatus fs;
/* Post-multiplication sign, before addition. */
sign ^= multiplicand.sign;
/* If and only if all arguments are normal do we need to do an
extended-precision calculation. */
if (isFiniteNonZero() &&
multiplicand.isFiniteNonZero() &&
addend.isFinite()) {
lostFraction lost_fraction;
lost_fraction = multiplySignificand(multiplicand, &addend);
fs = normalize(rounding_mode, lost_fraction);
if (lost_fraction != lfExactlyZero)
fs = (opStatus) (fs | opInexact);
/* If two numbers add (exactly) to zero, IEEE 754 decrees it is a
positive zero unless rounding to minus infinity, except that
adding two like-signed zeroes gives that zero. */
if (category == fcZero && !(fs & opUnderflow) && sign != addend.sign)
sign = (rounding_mode == rmTowardNegative);
} else {
fs = multiplySpecials(multiplicand);
/* FS can only be opOK or opInvalidOp. There is no more work
to do in the latter case. The IEEE-754R standard says it is
implementation-defined in this case whether, if ADDEND is a
quiet NaN, we raise invalid op; this implementation does so.
If we need to do the addition we can do so with normal
precision. */
if (fs == opOK)
fs = addOrSubtract(addend, rounding_mode, false);
}
return fs;
}
/* Rounding-mode corrrect round to integral value. */
IEEEFloat::opStatus IEEEFloat::roundToIntegral(roundingMode rounding_mode) {
opStatus fs;
// If the exponent is large enough, we know that this value is already
// integral, and the arithmetic below would potentially cause it to saturate
// to +/-Inf. Bail out early instead.
if (isFiniteNonZero() && exponent+1 >= (int)semanticsPrecision(*semantics))
return opOK;
// The algorithm here is quite simple: we add 2^(p-1), where p is the
// precision of our format, and then subtract it back off again. The choice
// of rounding modes for the addition/subtraction determines the rounding mode
// for our integral rounding as well.
// NOTE: When the input value is negative, we do subtraction followed by
// addition instead.
APInt IntegerConstant(NextPowerOf2(semanticsPrecision(*semantics)), 1);
IntegerConstant <<= semanticsPrecision(*semantics)-1;
IEEEFloat MagicConstant(*semantics);
fs = MagicConstant.convertFromAPInt(IntegerConstant, false,
rmNearestTiesToEven);
MagicConstant.sign = sign;
if (fs != opOK)
return fs;
// Preserve the input sign so that we can handle 0.0/-0.0 cases correctly.
bool inputSign = isNegative();
fs = add(MagicConstant, rounding_mode);
if (fs != opOK && fs != opInexact)
return fs;
fs = subtract(MagicConstant, rounding_mode);
// Restore the input sign.
if (inputSign != isNegative())
changeSign();
return fs;
}
/* Comparison requires normalized numbers. */
IEEEFloat::cmpResult IEEEFloat::compare(const IEEEFloat &rhs) const {
cmpResult result;
assert(semantics == rhs.semantics);
switch (PackCategoriesIntoKey(category, rhs.category)) {
default:
llvm_unreachable(nullptr);
case PackCategoriesIntoKey(fcNaN, fcZero):
case PackCategoriesIntoKey(fcNaN, fcNormal):
case PackCategoriesIntoKey(fcNaN, fcInfinity):
case PackCategoriesIntoKey(fcNaN, fcNaN):
case PackCategoriesIntoKey(fcZero, fcNaN):
case PackCategoriesIntoKey(fcNormal, fcNaN):
case PackCategoriesIntoKey(fcInfinity, fcNaN):
return cmpUnordered;
case PackCategoriesIntoKey(fcInfinity, fcNormal):
case PackCategoriesIntoKey(fcInfinity, fcZero):
case PackCategoriesIntoKey(fcNormal, fcZero):
if (sign)
return cmpLessThan;
else
return cmpGreaterThan;
case PackCategoriesIntoKey(fcNormal, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcInfinity):
case PackCategoriesIntoKey(fcZero, fcNormal):
if (rhs.sign)
return cmpGreaterThan;
else
return cmpLessThan;
case PackCategoriesIntoKey(fcInfinity, fcInfinity):
if (sign == rhs.sign)
return cmpEqual;
else if (sign)
return cmpLessThan;
else
return cmpGreaterThan;
case PackCategoriesIntoKey(fcZero, fcZero):
return cmpEqual;
case PackCategoriesIntoKey(fcNormal, fcNormal):
break;
}
/* Two normal numbers. Do they have the same sign? */
if (sign != rhs.sign) {
if (sign)
result = cmpLessThan;
else
result = cmpGreaterThan;
} else {
/* Compare absolute values; invert result if negative. */
result = compareAbsoluteValue(rhs);
if (sign) {
if (result == cmpLessThan)
result = cmpGreaterThan;
else if (result == cmpGreaterThan)
result = cmpLessThan;
}
}
return result;
}
/// IEEEFloat::convert - convert a value of one floating point type to another.
/// The return value corresponds to the IEEE754 exceptions. *losesInfo
/// records whether the transformation lost information, i.e. whether
/// converting the result back to the original type will produce the
/// original value (this is almost the same as return value==fsOK, but there
/// are edge cases where this is not so).
IEEEFloat::opStatus IEEEFloat::convert(const fltSemantics &toSemantics,
roundingMode rounding_mode,
bool *losesInfo) {
lostFraction lostFraction;
unsigned int newPartCount, oldPartCount;
opStatus fs;
int shift;
const fltSemantics &fromSemantics = *semantics;
lostFraction = lfExactlyZero;
newPartCount = partCountForBits(toSemantics.precision + 1);
oldPartCount = partCount();
shift = toSemantics.precision - fromSemantics.precision;
bool X86SpecialNan = false;
if (&fromSemantics == &semX87DoubleExtended &&
&toSemantics != &semX87DoubleExtended && category == fcNaN &&
(!(*significandParts() & 0x8000000000000000ULL) ||
!(*significandParts() & 0x4000000000000000ULL))) {
// x86 has some unusual NaNs which cannot be represented in any other
// format; note them here.
X86SpecialNan = true;
}
// If this is a truncation of a denormal number, and the target semantics
// has larger exponent range than the source semantics (this can happen
// when truncating from PowerPC double-double to double format), the
// right shift could lose result mantissa bits. Adjust exponent instead
// of performing excessive shift.
if (shift < 0 && isFiniteNonZero()) {
int exponentChange = significandMSB() + 1 - fromSemantics.precision;
if (exponent + exponentChange < toSemantics.minExponent)
exponentChange = toSemantics.minExponent - exponent;
if (exponentChange < shift)
exponentChange = shift;
if (exponentChange < 0) {
shift -= exponentChange;
exponent += exponentChange;
}
}
// If this is a truncation, perform the shift before we narrow the storage.
if (shift < 0 && (isFiniteNonZero() || category==fcNaN))
lostFraction = shiftRight(significandParts(), oldPartCount, -shift);
// Fix the storage so it can hold to new value.
if (newPartCount > oldPartCount) {
// The new type requires more storage; make it available.
integerPart *newParts;
newParts = new integerPart[newPartCount];
APInt::tcSet(newParts, 0, newPartCount);
if (isFiniteNonZero() || category==fcNaN)
APInt::tcAssign(newParts, significandParts(), oldPartCount);
freeSignificand();
significand.parts = newParts;
} else if (newPartCount == 1 && oldPartCount != 1) {
// Switch to built-in storage for a single part.
integerPart newPart = 0;
if (isFiniteNonZero() || category==fcNaN)
newPart = significandParts()[0];
freeSignificand();
significand.part = newPart;
}
// Now that we have the right storage, switch the semantics.
semantics = &toSemantics;
// If this is an extension, perform the shift now that the storage is
// available.
if (shift > 0 && (isFiniteNonZero() || category==fcNaN))
APInt::tcShiftLeft(significandParts(), newPartCount, shift);
if (isFiniteNonZero()) {
fs = normalize(rounding_mode, lostFraction);
*losesInfo = (fs != opOK);
} else if (category == fcNaN) {
*losesInfo = lostFraction != lfExactlyZero || X86SpecialNan;
// For x87 extended precision, we want to make a NaN, not a special NaN if
// the input wasn't special either.
if (!X86SpecialNan && semantics == &semX87DoubleExtended)
APInt::tcSetBit(significandParts(), semantics->precision - 1);
// gcc forces the Quiet bit on, which means (float)(double)(float_sNan)
// does not give you back the same bits. This is dubious, and we
// don't currently do it. You're really supposed to get
// an invalid operation signal at runtime, but nobody does that.
fs = opOK;
} else {
*losesInfo = false;
fs = opOK;
}
return fs;
}
/* Convert a floating point number to an integer according to the
rounding mode. If the rounded integer value is out of range this
returns an invalid operation exception and the contents of the
destination parts are unspecified. If the rounded value is in
range but the floating point number is not the exact integer, the C
standard doesn't require an inexact exception to be raised. IEEE
854 does require it so we do that.
Note that for conversions to integer type the C standard requires
round-to-zero to always be used. */
IEEEFloat::opStatus IEEEFloat::convertToSignExtendedInteger(
MutableArrayRef<integerPart> parts, unsigned int width, bool isSigned,
roundingMode rounding_mode, bool *isExact) const {
lostFraction lost_fraction;
const integerPart *src;
unsigned int dstPartsCount, truncatedBits;
*isExact = false;
/* Handle the three special cases first. */
if (category == fcInfinity || category == fcNaN)
return opInvalidOp;
dstPartsCount = partCountForBits(width);
assert(dstPartsCount <= parts.size() && "Integer too big");
if (category == fcZero) {
APInt::tcSet(parts.data(), 0, dstPartsCount);
// Negative zero can't be represented as an int.
*isExact = !sign;
return opOK;
}
src = significandParts();
/* Step 1: place our absolute value, with any fraction truncated, in
the destination. */
if (exponent < 0) {
/* Our absolute value is less than one; truncate everything. */
APInt::tcSet(parts.data(), 0, dstPartsCount);
/* For exponent -1 the integer bit represents .5, look at that.
For smaller exponents leftmost truncated bit is 0. */
truncatedBits = semantics->precision -1U - exponent;
} else {
/* We want the most significant (exponent + 1) bits; the rest are
truncated. */
unsigned int bits = exponent + 1U;
/* Hopelessly large in magnitude? */
if (bits > width)
return opInvalidOp;
if (bits < semantics->precision) {
/* We truncate (semantics->precision - bits) bits. */
truncatedBits = semantics->precision - bits;
APInt::tcExtract(parts.data(), dstPartsCount, src, bits, truncatedBits);
} else {
/* We want at least as many bits as are available. */
APInt::tcExtract(parts.data(), dstPartsCount, src, semantics->precision,
0);
APInt::tcShiftLeft(parts.data(), dstPartsCount,
bits - semantics->precision);
truncatedBits = 0;
}
}
/* Step 2: work out any lost fraction, and increment the absolute
value if we would round away from zero. */
if (truncatedBits) {
lost_fraction = lostFractionThroughTruncation(src, partCount(),
truncatedBits);
if (lost_fraction != lfExactlyZero &&
roundAwayFromZero(rounding_mode, lost_fraction, truncatedBits)) {
if (APInt::tcIncrement(parts.data(), dstPartsCount))
return opInvalidOp; /* Overflow. */
}
} else {
lost_fraction = lfExactlyZero;
}
/* Step 3: check if we fit in the destination. */
unsigned int omsb = APInt::tcMSB(parts.data(), dstPartsCount) + 1;
if (sign) {
if (!isSigned) {
/* Negative numbers cannot be represented as unsigned. */
if (omsb != 0)
return opInvalidOp;
} else {
/* It takes omsb bits to represent the unsigned integer value.
We lose a bit for the sign, but care is needed as the
maximally negative integer is a special case. */
if (omsb == width &&
APInt::tcLSB(parts.data(), dstPartsCount) + 1 != omsb)
return opInvalidOp;
/* This case can happen because of rounding. */
if (omsb > width)
return opInvalidOp;
}
APInt::tcNegate (parts.data(), dstPartsCount);
} else {
if (omsb >= width + !isSigned)
return opInvalidOp;
}
if (lost_fraction == lfExactlyZero) {
*isExact = true;
return opOK;
} else
return opInexact;
}
/* Same as convertToSignExtendedInteger, except we provide
deterministic values in case of an invalid operation exception,
namely zero for NaNs and the minimal or maximal value respectively
for underflow or overflow.
The *isExact output tells whether the result is exact, in the sense
that converting it back to the original floating point type produces
the original value. This is almost equivalent to result==opOK,
except for negative zeroes.
*/
IEEEFloat::opStatus
IEEEFloat::convertToInteger(MutableArrayRef<integerPart> parts,
unsigned int width, bool isSigned,
roundingMode rounding_mode, bool *isExact) const {
opStatus fs;
fs = convertToSignExtendedInteger(parts, width, isSigned, rounding_mode,
isExact);
if (fs == opInvalidOp) {
unsigned int bits, dstPartsCount;
dstPartsCount = partCountForBits(width);
assert(dstPartsCount <= parts.size() && "Integer too big");
if (category == fcNaN)
bits = 0;
else if (sign)
bits = isSigned;
else
bits = width - isSigned;
APInt::tcSetLeastSignificantBits(parts.data(), dstPartsCount, bits);
if (sign && isSigned)
APInt::tcShiftLeft(parts.data(), dstPartsCount, width - 1);
}
return fs;
}
/* Convert an unsigned integer SRC to a floating point number,
rounding according to ROUNDING_MODE. The sign of the floating
point number is not modified. */
IEEEFloat::opStatus IEEEFloat::convertFromUnsignedParts(
const integerPart *src, unsigned int srcCount, roundingMode rounding_mode) {
unsigned int omsb, precision, dstCount;
integerPart *dst;
lostFraction lost_fraction;
category = fcNormal;
omsb = APInt::tcMSB(src, srcCount) + 1;
dst = significandParts();
dstCount = partCount();
precision = semantics->precision;
/* We want the most significant PRECISION bits of SRC. There may not
be that many; extract what we can. */
if (precision <= omsb) {
exponent = omsb - 1;
lost_fraction = lostFractionThroughTruncation(src, srcCount,
omsb - precision);
APInt::tcExtract(dst, dstCount, src, precision, omsb - precision);
} else {
exponent = precision - 1;
lost_fraction = lfExactlyZero;
APInt::tcExtract(dst, dstCount, src, omsb, 0);
}
return normalize(rounding_mode, lost_fraction);
}
IEEEFloat::opStatus IEEEFloat::convertFromAPInt(const APInt &Val, bool isSigned,
roundingMode rounding_mode) {
unsigned int partCount = Val.getNumWords();
APInt api = Val;
sign = false;
if (isSigned && api.isNegative()) {
sign = true;
api = -api;
}
return convertFromUnsignedParts(api.getRawData(), partCount, rounding_mode);
}
/* Convert a two's complement integer SRC to a floating point number,
rounding according to ROUNDING_MODE. ISSIGNED is true if the
integer is signed, in which case it must be sign-extended. */
IEEEFloat::opStatus
IEEEFloat::convertFromSignExtendedInteger(const integerPart *src,
unsigned int srcCount, bool isSigned,
roundingMode rounding_mode) {
opStatus status;
if (isSigned &&
APInt::tcExtractBit(src, srcCount * integerPartWidth - 1)) {
integerPart *copy;
/* If we're signed and negative negate a copy. */
sign = true;
copy = new integerPart[srcCount];
APInt::tcAssign(copy, src, srcCount);
APInt::tcNegate(copy, srcCount);
status = convertFromUnsignedParts(copy, srcCount, rounding_mode);
delete [] copy;
} else {
sign = false;
status = convertFromUnsignedParts(src, srcCount, rounding_mode);
}
return status;
}
/* FIXME: should this just take a const APInt reference? */
IEEEFloat::opStatus
IEEEFloat::convertFromZeroExtendedInteger(const integerPart *parts,
unsigned int width, bool isSigned,
roundingMode rounding_mode) {
unsigned int partCount = partCountForBits(width);
APInt api = APInt(width, makeArrayRef(parts, partCount));
sign = false;
if (isSigned && APInt::tcExtractBit(parts, width - 1)) {
sign = true;
api = -api;
}
return convertFromUnsignedParts(api.getRawData(), partCount, rounding_mode);
}
IEEEFloat::opStatus
IEEEFloat::convertFromHexadecimalString(StringRef s,
roundingMode rounding_mode) {
lostFraction lost_fraction = lfExactlyZero;
category = fcNormal;
zeroSignificand();
exponent = 0;
integerPart *significand = significandParts();
unsigned partsCount = partCount();
unsigned bitPos = partsCount * integerPartWidth;
bool computedTrailingFraction = false;
// Skip leading zeroes and any (hexa)decimal point.
StringRef::iterator begin = s.begin();
StringRef::iterator end = s.end();
StringRef::iterator dot;
StringRef::iterator p = skipLeadingZeroesAndAnyDot(begin, end, &dot);
StringRef::iterator firstSignificantDigit = p;
while (p != end) {
integerPart hex_value;
if (*p == '.') {
assert(dot == end && "String contains multiple dots");
dot = p++;
continue;
}
hex_value = hexDigitValue(*p);
if (hex_value == -1U)
break;
p++;
// Store the number while we have space.
if (bitPos) {
bitPos -= 4;
hex_value <<= bitPos % integerPartWidth;
significand[bitPos / integerPartWidth] |= hex_value;
} else if (!computedTrailingFraction) {
lost_fraction = trailingHexadecimalFraction(p, end, hex_value);
computedTrailingFraction = true;
}
}
/* Hex floats require an exponent but not a hexadecimal point. */
assert(p != end && "Hex strings require an exponent");
assert((*p == 'p' || *p == 'P') && "Invalid character in significand");
assert(p != begin && "Significand has no digits");
assert((dot == end || p - begin != 1) && "Significand has no digits");
/* Ignore the exponent if we are zero. */
if (p != firstSignificantDigit) {
int expAdjustment;
/* Implicit hexadecimal point? */
if (dot == end)
dot = p;
/* Calculate the exponent adjustment implicit in the number of
significant digits. */
expAdjustment = static_cast<int>(dot - firstSignificantDigit);
if (expAdjustment < 0)
expAdjustment++;
expAdjustment = expAdjustment * 4 - 1;
/* Adjust for writing the significand starting at the most
significant nibble. */
expAdjustment += semantics->precision;
expAdjustment -= partsCount * integerPartWidth;
/* Adjust for the given exponent. */
exponent = totalExponent(p + 1, end, expAdjustment);
}
return normalize(rounding_mode, lost_fraction);
}
IEEEFloat::opStatus
IEEEFloat::roundSignificandWithExponent(const integerPart *decSigParts,
unsigned sigPartCount, int exp,
roundingMode rounding_mode) {
unsigned int parts, pow5PartCount;
fltSemantics calcSemantics = { 32767, -32767, 0, 0 };
integerPart pow5Parts[maxPowerOfFiveParts];
bool isNearest;
isNearest = (rounding_mode == rmNearestTiesToEven ||
rounding_mode == rmNearestTiesToAway);
parts = partCountForBits(semantics->precision + 11);
/* Calculate pow(5, abs(exp)). */
pow5PartCount = powerOf5(pow5Parts, exp >= 0 ? exp: -exp);
for (;; parts *= 2) {
opStatus sigStatus, powStatus;
unsigned int excessPrecision, truncatedBits;
calcSemantics.precision = parts * integerPartWidth - 1;
excessPrecision = calcSemantics.precision - semantics->precision;
truncatedBits = excessPrecision;
IEEEFloat decSig(calcSemantics, uninitialized);
decSig.makeZero(sign);
IEEEFloat pow5(calcSemantics);
sigStatus = decSig.convertFromUnsignedParts(decSigParts, sigPartCount,
rmNearestTiesToEven);
powStatus = pow5.convertFromUnsignedParts(pow5Parts, pow5PartCount,
rmNearestTiesToEven);
/* Add exp, as 10^n = 5^n * 2^n. */
decSig.exponent += exp;
lostFraction calcLostFraction;
integerPart HUerr, HUdistance;
unsigned int powHUerr;
if (exp >= 0) {
/* multiplySignificand leaves the precision-th bit set to 1. */
calcLostFraction = decSig.multiplySignificand(pow5, nullptr);
powHUerr = powStatus != opOK;
} else {
calcLostFraction = decSig.divideSignificand(pow5);
/* Denormal numbers have less precision. */
if (decSig.exponent < semantics->minExponent) {
excessPrecision += (semantics->minExponent - decSig.exponent);
truncatedBits = excessPrecision;
if (excessPrecision > calcSemantics.precision)
excessPrecision = calcSemantics.precision;
}
/* Extra half-ulp lost in reciprocal of exponent. */
powHUerr = (powStatus == opOK && calcLostFraction == lfExactlyZero) ? 0:2;
}
/* Both multiplySignificand and divideSignificand return the
result with the integer bit set. */
assert(APInt::tcExtractBit
(decSig.significandParts(), calcSemantics.precision - 1) == 1);
HUerr = HUerrBound(calcLostFraction != lfExactlyZero, sigStatus != opOK,
powHUerr);
HUdistance = 2 * ulpsFromBoundary(decSig.significandParts(),
excessPrecision, isNearest);
/* Are we guaranteed to round correctly if we truncate? */
if (HUdistance >= HUerr) {
APInt::tcExtract(significandParts(), partCount(), decSig.significandParts(),
calcSemantics.precision - excessPrecision,
excessPrecision);
/* Take the exponent of decSig. If we tcExtract-ed less bits
above we must adjust our exponent to compensate for the
implicit right shift. */
exponent = (decSig.exponent + semantics->precision
- (calcSemantics.precision - excessPrecision));
calcLostFraction = lostFractionThroughTruncation(decSig.significandParts(),
decSig.partCount(),
truncatedBits);
return normalize(rounding_mode, calcLostFraction);
}
}
}
IEEEFloat::opStatus
IEEEFloat::convertFromDecimalString(StringRef str, roundingMode rounding_mode) {
decimalInfo D;
opStatus fs;
/* Scan the text. */
StringRef::iterator p = str.begin();
interpretDecimal(p, str.end(), &D);
/* Handle the quick cases. First the case of no significant digits,
i.e. zero, and then exponents that are obviously too large or too
small. Writing L for log 10 / log 2, a number d.ddddd*10^exp
definitely overflows if
(exp - 1) * L >= maxExponent
and definitely underflows to zero where
(exp + 1) * L <= minExponent - precision
With integer arithmetic the tightest bounds for L are
93/28 < L < 196/59 [ numerator <= 256 ]
42039/12655 < L < 28738/8651 [ numerator <= 65536 ]
*/
// Test if we have a zero number allowing for strings with no null terminators
// and zero decimals with non-zero exponents.
//
// We computed firstSigDigit by ignoring all zeros and dots. Thus if
// D->firstSigDigit equals str.end(), every digit must be a zero and there can
// be at most one dot. On the other hand, if we have a zero with a non-zero
// exponent, then we know that D.firstSigDigit will be non-numeric.
if (D.firstSigDigit == str.end() || decDigitValue(*D.firstSigDigit) >= 10U) {
category = fcZero;
fs = opOK;
/* Check whether the normalized exponent is high enough to overflow
max during the log-rebasing in the max-exponent check below. */
} else if (D.normalizedExponent - 1 > INT_MAX / 42039) {
fs = handleOverflow(rounding_mode);
/* If it wasn't, then it also wasn't high enough to overflow max
during the log-rebasing in the min-exponent check. Check that it
won't overflow min in either check, then perform the min-exponent
check. */
} else if (D.normalizedExponent - 1 < INT_MIN / 42039 ||
(D.normalizedExponent + 1) * 28738 <=
8651 * (semantics->minExponent - (int) semantics->precision)) {
/* Underflow to zero and round. */
category = fcNormal;
zeroSignificand();
fs = normalize(rounding_mode, lfLessThanHalf);
/* We can finally safely perform the max-exponent check. */
} else if ((D.normalizedExponent - 1) * 42039
>= 12655 * semantics->maxExponent) {
/* Overflow and round. */
fs = handleOverflow(rounding_mode);
} else {
integerPart *decSignificand;
unsigned int partCount;
/* A tight upper bound on number of bits required to hold an
N-digit decimal integer is N * 196 / 59. Allocate enough space
to hold the full significand, and an extra part required by
tcMultiplyPart. */
partCount = static_cast<unsigned int>(D.lastSigDigit - D.firstSigDigit) + 1;
partCount = partCountForBits(1 + 196 * partCount / 59);
decSignificand = new integerPart[partCount + 1];
partCount = 0;
/* Convert to binary efficiently - we do almost all multiplication
in an integerPart. When this would overflow do we do a single
bignum multiplication, and then revert again to multiplication
in an integerPart. */
do {
integerPart decValue, val, multiplier;
val = 0;
multiplier = 1;
do {
if (*p == '.') {
p++;
if (p == str.end()) {
break;
}
}
decValue = decDigitValue(*p++);
assert(decValue < 10U && "Invalid character in significand");
multiplier *= 10;
val = val * 10 + decValue;
/* The maximum number that can be multiplied by ten with any
digit added without overflowing an integerPart. */
} while (p <= D.lastSigDigit && multiplier <= (~ (integerPart) 0 - 9) / 10);
/* Multiply out the current part. */
APInt::tcMultiplyPart(decSignificand, decSignificand, multiplier, val,
partCount, partCount + 1, false);
/* If we used another part (likely but not guaranteed), increase
the count. */
if (decSignificand[partCount])
partCount++;
} while (p <= D.lastSigDigit);
category = fcNormal;
fs = roundSignificandWithExponent(decSignificand, partCount,
D.exponent, rounding_mode);
delete [] decSignificand;
}
return fs;
}
bool IEEEFloat::convertFromStringSpecials(StringRef str) {
if (str.equals("inf") || str.equals("INFINITY") || str.equals("+Inf")) {
makeInf(false);
return true;
}
if (str.equals("-inf") || str.equals("-INFINITY") || str.equals("-Inf")) {
makeInf(true);
return true;
}
if (str.equals("nan") || str.equals("NaN")) {
makeNaN(false, false);
return true;
}
if (str.equals("-nan") || str.equals("-NaN")) {
makeNaN(false, true);
return true;
}
return false;
}
IEEEFloat::opStatus IEEEFloat::convertFromString(StringRef str,
roundingMode rounding_mode) {
assert(!str.empty() && "Invalid string length");
// Handle special cases.
if (convertFromStringSpecials(str))
return opOK;
/* Handle a leading minus sign. */
StringRef::iterator p = str.begin();
size_t slen = str.size();
sign = *p == '-' ? 1 : 0;
if (*p == '-' || *p == '+') {
p++;
slen--;
assert(slen && "String has no digits");
}
if (slen >= 2 && p[0] == '0' && (p[1] == 'x' || p[1] == 'X')) {
assert(slen - 2 && "Invalid string");
return convertFromHexadecimalString(StringRef(p + 2, slen - 2),
rounding_mode);
}
return convertFromDecimalString(StringRef(p, slen), rounding_mode);
}
/* Write out a hexadecimal representation of the floating point value
to DST, which must be of sufficient size, in the C99 form
[-]0xh.hhhhp[+-]d. Return the number of characters written,
excluding the terminating NUL.
If UPPERCASE, the output is in upper case, otherwise in lower case.
HEXDIGITS digits appear altogether, rounding the value if
necessary. If HEXDIGITS is 0, the minimal precision to display the
number precisely is used instead. If nothing would appear after
the decimal point it is suppressed.
The decimal exponent is always printed and has at least one digit.
Zero values display an exponent of zero. Infinities and NaNs
appear as "infinity" or "nan" respectively.
The above rules are as specified by C99. There is ambiguity about
what the leading hexadecimal digit should be. This implementation
uses whatever is necessary so that the exponent is displayed as
stored. This implies the exponent will fall within the IEEE format
range, and the leading hexadecimal digit will be 0 (for denormals),
1 (normal numbers) or 2 (normal numbers rounded-away-from-zero with
any other digits zero).
*/
unsigned int IEEEFloat::convertToHexString(char *dst, unsigned int hexDigits,
bool upperCase,
roundingMode rounding_mode) const {
char *p;
p = dst;
if (sign)
*dst++ = '-';
switch (category) {
case fcInfinity:
memcpy (dst, upperCase ? infinityU: infinityL, sizeof infinityU - 1);
dst += sizeof infinityL - 1;
break;
case fcNaN:
memcpy (dst, upperCase ? NaNU: NaNL, sizeof NaNU - 1);
dst += sizeof NaNU - 1;
break;
case fcZero:
*dst++ = '0';
*dst++ = upperCase ? 'X': 'x';
*dst++ = '0';
if (hexDigits > 1) {
*dst++ = '.';
memset (dst, '0', hexDigits - 1);
dst += hexDigits - 1;
}
*dst++ = upperCase ? 'P': 'p';
*dst++ = '0';
break;
case fcNormal:
dst = convertNormalToHexString (dst, hexDigits, upperCase, rounding_mode);
break;
}
*dst = 0;
return static_cast<unsigned int>(dst - p);
}
/* Does the hard work of outputting the correctly rounded hexadecimal
form of a normal floating point number with the specified number of
hexadecimal digits. If HEXDIGITS is zero the minimum number of
digits necessary to print the value precisely is output. */
char *IEEEFloat::convertNormalToHexString(char *dst, unsigned int hexDigits,
bool upperCase,
roundingMode rounding_mode) const {
unsigned int count, valueBits, shift, partsCount, outputDigits;
const char *hexDigitChars;
const integerPart *significand;
char *p;
bool roundUp;
*dst++ = '0';
*dst++ = upperCase ? 'X': 'x';
roundUp = false;
hexDigitChars = upperCase ? hexDigitsUpper: hexDigitsLower;
significand = significandParts();
partsCount = partCount();
/* +3 because the first digit only uses the single integer bit, so
we have 3 virtual zero most-significant-bits. */
valueBits = semantics->precision + 3;
shift = integerPartWidth - valueBits % integerPartWidth;
/* The natural number of digits required ignoring trailing
insignificant zeroes. */
outputDigits = (valueBits - significandLSB () + 3) / 4;
/* hexDigits of zero means use the required number for the
precision. Otherwise, see if we are truncating. If we are,
find out if we need to round away from zero. */
if (hexDigits) {
if (hexDigits < outputDigits) {
/* We are dropping non-zero bits, so need to check how to round.
"bits" is the number of dropped bits. */
unsigned int bits;
lostFraction fraction;
bits = valueBits - hexDigits * 4;
fraction = lostFractionThroughTruncation (significand, partsCount, bits);
roundUp = roundAwayFromZero(rounding_mode, fraction, bits);
}
outputDigits = hexDigits;
}
/* Write the digits consecutively, and start writing in the location
of the hexadecimal point. We move the most significant digit
left and add the hexadecimal point later. */
p = ++dst;
count = (valueBits + integerPartWidth - 1) / integerPartWidth;
while (outputDigits && count)