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blockfreq: Defer to BranchProbability::scale()

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`BlockMass` can now defer to `BranchProbability::scale()`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207547 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
2014-04-29 16:20:05 +00:00
parent 81566c52fd
commit 6919443535
2 changed files with 4 additions and 51 deletions
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26
lib/Analysis/BlockFrequencyInfoImpl.cpp
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@ -311,32 +311,6 @@ std::pair<uint64_t, int16_t> UnsignedFloatBase::multiply64(uint64_t L,
// BlockMass implementation.
//
//===----------------------------------------------------------------------===//
BlockMass &BlockMass::operator*=(const BranchProbability &P) {
uint32_t N = P.getNumerator(), D = P.getDenominator();
assert(D && "divide by 0");
assert(N <= D && "fraction greater than 1");
// Fast path for multiplying by 1.0.
if (!Mass || N == D)
return *this;
// Get as much precision as we can.
int Shift = countLeadingZeros(Mass);
uint64_t ShiftedQuotient = (Mass << Shift) / D;
uint64_t Product = ShiftedQuotient * N >> Shift;
// Now check for what's lost.
uint64_t Left = ShiftedQuotient * (D - N) >> Shift;
uint64_t Lost = Mass - Product - Left;
// TODO: prove this assertion.
assert(Lost <= UINT32_MAX);
// Take the product plus a portion of the spoils.
Mass = Product + Lost * N / D;
return *this;
}
UnsignedFloat<uint64_t> BlockMass::toFloat() const {
if (isFull())
return UnsignedFloat<uint64_t>(1, 0);