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Handle storage complications of float->float conversions. 

llvm-svn: 42220
This commit is contained in:
Neil Booth 2007-09-22 02:56:19 +00:00
parent cf3e26fff2
commit a8d7269269
1 changed files with 23 additions and 18 deletions
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41
llvm/lib/Support/APFloat.cpp
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@ -1318,39 +1318,44 @@ APFloat::opStatus
APFloat::convert(const fltSemantics &toSemantics,
roundingMode rounding_mode)
{
unsigned int newPartCount;
lostFraction lostFraction;
unsigned int newPartCount, oldPartCount;
opStatus fs;
lostFraction = lfExactlyZero;
newPartCount = partCountForBits(toSemantics.precision + 1);
oldPartCount = partCount();
/* If our new form is wider, re-allocate our bit pattern into wider
storage.
If we're narrowing from multiple words to 1 words, copy to the single
word. If we are losing information by doing this, we would have to
worry about rounding; right now the only case is f80 -> shorter
conversion, and we are keeping all 64 significant bits, so it's OK. */
if(newPartCount > partCount()) {
/* Handle storage complications. If our new form is wider,
re-allocate our bit pattern into wider storage. If it is
narrower, we ignore the excess parts, but if narrowing to a
single part we need to free the old storage. */
if (newPartCount > oldPartCount) {
integerPart *newParts;
newParts = new integerPart[newPartCount];
APInt::tcSet(newParts, 0, newPartCount);
APInt::tcAssign(newParts, significandParts(), partCount());
APInt::tcAssign(newParts, significandParts(), oldPartCount);
freeSignificand();
significand.parts = newParts;
} else if (newPartCount==1 && newPartCount < partCount()) {
integerPart newPart;
APInt::tcSet(&newPart, 0, newPartCount);
APInt::tcAssign(&newPart, significandParts(), partCount());
freeSignificand();
significand.part = newPart;
} else if (newPartCount < oldPartCount) {
/* Capture any lost fraction through truncation of parts so we get
correct rounding whilst normalizing. */
lostFraction = lostFractionThroughTruncation
(significandParts(), oldPartCount, toSemantics.precision);
if (newPartCount == 1)
{
integerPart newPart = significandParts()[0];
freeSignificand();
significand.part = newPart;
}
}
if(category == fcNormal) {
/* Re-interpret our bit-pattern. */
exponent += toSemantics.precision - semantics->precision;
semantics = &toSemantics;
fs = normalize(rounding_mode, lfExactlyZero);
fs = normalize(rounding_mode, lostFraction);
} else {
semantics = &toSemantics;
fs = opOK;