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[flang][runtime] Add limit check to MOD/MODULO #80026

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Merged
merged 1 commit into from
Jan 31, 2024
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[flang][runtime] Add limit check to MOD/MODULO #80026

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24 changes: 14 additions & 10 deletions flang/runtime/numeric.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -145,14 +145,19 @@ inline RT_API_ATTRS T RealMod(
} else if (std::isinf(p)) {
return a;
}
if (auto aInt{static_cast<std::int64_t>(a)}; a == aInt) {
if (auto pInt{static_cast<std::int64_t>(p)}; p == pInt) {
// Fast exact case for integer operands
auto mod{aInt - (aInt / pInt) * pInt};
if (IS_MODULO && (aInt > 0) != (pInt > 0)) {
mod += pInt;
T aAbs{std::abs(a)};
T pAbs{std::abs(p)};
if (aAbs <= static_cast<T>(std::numeric_limits<std::int64_t>::max()) &&
pAbs <= static_cast<T>(std::numeric_limits<std::int64_t>::max())) {
if (auto aInt{static_cast<std::int64_t>(a)}; a == aInt) {
if (auto pInt{static_cast<std::int64_t>(p)}; p == pInt) {
// Fast exact case for integer operands
auto mod{aInt - (aInt / pInt) * pInt};
if (IS_MODULO && (aInt > 0) != (pInt > 0)) {
mod += pInt;
}
return static_cast<T>(mod);
}
return static_cast<T>(mod);
}
}
if constexpr (std::is_same_v<T, float> || std::is_same_v<T, double> ||
Expand Down Expand Up @@ -183,9 +188,8 @@ inline RT_API_ATTRS T RealMod(
// what's left is the desired remainder. This is basically
// the same algorithm as arbitrary precision binary long division,
// discarding the quotient.
T tmp{std::abs(a)};
T pAbs{std::abs(p)};
for (T adj{SetExponent(pAbs, Exponent<int>(tmp))}; tmp >= pAbs; adj /= 2) {
T tmp{aAbs};
for (T adj{SetExponent(pAbs, Exponent<int>(aAbs))}; tmp >= pAbs; adj /= 2) {
if (tmp >= adj) {
tmp -= adj;
if (tmp == 0) {
Expand Down