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Add comments to double.h.

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Review URL: http://codereview.chromium.org/4687001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5789 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
floitschV8@gmail.com 2010-11-08 15:40:28 +00:00
parent 0c200bec48
commit c86e548e1d
1 changed files with 11 additions and 3 deletions
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14
src/double.h
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@ -54,18 +54,20 @@ class Double {
explicit Double(DiyFp diy_fp)
: d64_(DiyFpToUint64(diy_fp)) {}
// The value encoded by this Double must be greater or equal to +0.0.
// It must not be special (infinity, or NaN).
DiyFp AsDiyFp() const {
ASSERT(Sign() > 0);
ASSERT(!IsSpecial());
return DiyFp(Significand(), Exponent());
}
// this->Significand() must not be 0.
// The value encoded by this Double must be strictly greater than 0.
DiyFp AsNormalizedDiyFp() const {
ASSERT(value() > 0.0);
uint64_t f = Significand();
int e = Exponent();
ASSERT(f != 0);
// The current double could be a denormal.
while ((f & kHiddenBit) == 0) {
f <<= 1;
@ -82,6 +84,7 @@ class Double {
return d64_;
}
// Returns the next greater double. Returns +infinity on input +infinity.
double NextDouble() const {
if (d64_ == kInfinity) return Double(kInfinity).value();
if (Sign() < 0 && Significand() == 0) {
@ -144,14 +147,19 @@ class Double {
return (d64 & kSignMask) == 0? 1: -1;
}
// Precondition: the value encoded by this Double must be greater or equal
// than +0.0.
DiyFp UpperBoundary() const {
ASSERT(Sign() > 0);
return DiyFp(Significand() * 2 + 1, Exponent() - 1);
}
// Returns the two boundaries of this.
// The bigger boundary (m_plus) is normalized. The lower boundary has the same
// exponent as m_plus.
// Precondition: the value encoded by this Double must be greater than 0.
void NormalizedBoundaries(DiyFp* out_m_minus, DiyFp* out_m_plus) const {
ASSERT(value() > 0.0);
DiyFp v = this->AsDiyFp();
bool significand_is_zero = (v.f() == kHiddenBit);
DiyFp m_plus = DiyFp::Normalize(DiyFp((v.f() << 1) + 1, v.e() - 1));