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Properly clear all the extra bits in a significand when making a NaN from an 

APInt.  Be certain to set the integer bit in an x87 extended-precision
significand so that we don't accidentally make a pseudo-NaN.

llvm-svn: 97382
This commit is contained in:
John McCall 2010-02-28 12:49:50 +00:00
parent 512b650210
commit c12b133d00
1 changed files with 28 additions and 8 deletions
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36
llvm/lib/Support/APFloat.cpp
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@ -631,25 +631,45 @@ void APFloat::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() < partCount())
APInt::tcSet(significandParts(), 0, partCount());
if (fill)
APInt::tcAssign(significandParts(), fill->getRawData(), partCount());
if (!fill || fill->getNumWords() < numParts)
APInt::tcSet(significand, 0, numParts);
if (fill) {
APInt::tcAssign(significand, fill->getRawData(), partCount());
// 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(significandParts(), semantics->precision - 2);
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(significandParts(), partCount()))
APInt::tcSetBit(significandParts(), semantics->precision - 3);
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(significandParts(), semantics->precision - 2);
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 == &APFloat::x87DoubleExtended)
APInt::tcSetBit(significand, QNaNBit + 1);
}
APFloat APFloat::makeNaN(const fltSemantics &Sem, bool SNaN, bool Negative,