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MathExtras: MulOverflow: use builtin when available (NFC) #95046

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Merged
merged 1 commit into from
Jun 11, 2024
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MathExtras: MulOverflow: use builtin when available (NFC) #95046

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4 changes: 4 additions & 0 deletions llvm/include/llvm/Support/MathExtras.h
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Original file line number Diff line number Diff line change
Expand Up @@ -635,6 +635,9 @@ std::enable_if_t<std::is_signed_v<T>, T> SubOverflow(T X, T Y, T &Result) {
/// result, returning true if an overflow ocurred.
template <typename T>
std::enable_if_t<std::is_signed_v<T>, T> MulOverflow(T X, T Y, T &Result) {
#if __has_builtin(__builtin_mul_overflow)
return __builtin_mul_overflow(X, Y, &Result);
#else
// Perform the unsigned multiplication on absolute values.
using U = std::make_unsigned_t<T>;
const U UX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
Expand All @@ -656,6 +659,7 @@ std::enable_if_t<std::is_signed_v<T>, T> MulOverflow(T X, T Y, T &Result) {
return UX > (static_cast<U>(std::numeric_limits<T>::max()) + U(1)) / UY;
else
return UX > (static_cast<U>(std::numeric_limits<T>::max())) / UY;
#endif
}

} // namespace llvm
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