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Optimize bigint division for fast path #2039

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Optimize bigint division for fast path #2039

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17 changes: 17 additions & 0 deletions lib/Support/BigIntSupport.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1777,6 +1777,23 @@ static OperationStatus compute(
return OperationStatus::DIVISION_BY_ZERO;
}

// Fast path: if lhs < rhs (in absolute value), then quotient is 0 and
// remainder is lhs. This avoids expensive division computation.
if (lhs.numDigits < rhs.numDigits) {
// Quotient is 0
if (quoc.digits != nullptr) {
quoc.numDigits = 1;
quoc.digits[0] = 0;
}
// Remainder is lhs (with sign preserved)
if (rem.digits != nullptr) {
auto res = initNonCanonicalWithReadOnlyBigInt(rem, lhs);
assert(res == OperationStatus::RETURNED && "rem array is too small");
(void)res;
}
return OperationStatus::RETURNED;
}

// tcDivide operates on unsigned number, so just like multiply, the operands
// must be negated (and the result as well, if appropriate) if they are
// negative.
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