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[Flang] Shift the data from lower to higher order bits in the big endian environment #73670

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Merged
merged 4 commits into from
Dec 28, 2023
Merged

[Flang] Shift the data from lower to higher order bits in the big endian environment #73670

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e5639ec
[Flang] Shift the data from lower to higher order bits in the big end…
Nov 28, 2023
0c25a34
swap two halves in Int128 in big endian
kkwli Dec 12, 2023
96a3678
address review comments
kkwli Dec 19, 2023
ef72557
add comment to explain the logic
kkwli Dec 19, 2023
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32 changes: 22 additions & 10 deletions flang/include/flang/Common/uint128.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,15 +33,18 @@ template <bool IS_SIGNED = false> class Int128 {
constexpr Int128(unsigned n) : low_{n} {}
constexpr Int128(unsigned long n) : low_{n} {}
constexpr Int128(unsigned long long n) : low_{n} {}
constexpr Int128(int n)
: low_{static_cast<std::uint64_t>(n)}, high_{-static_cast<std::uint64_t>(
n < 0)} {}
constexpr Int128(long n)
: low_{static_cast<std::uint64_t>(n)}, high_{-static_cast<std::uint64_t>(
n < 0)} {}
constexpr Int128(long long n)
: low_{static_cast<std::uint64_t>(n)}, high_{-static_cast<std::uint64_t>(
n < 0)} {}
constexpr Int128(int n) {
low_ = static_cast<std::uint64_t>(n);
high_ = -static_cast<std::uint64_t>(n < 0);
}
constexpr Int128(long n) {
low_ = static_cast<std::uint64_t>(n);
high_ = -static_cast<std::uint64_t>(n < 0);
}
constexpr Int128(long long n) {
low_ = static_cast<std::uint64_t>(n);
high_ = -static_cast<std::uint64_t>(n < 0);
}
constexpr Int128(const Int128 &) = default;
constexpr Int128(Int128 &&) = default;
constexpr Int128 &operator=(const Int128 &) = default;
Expand Down Expand Up @@ -246,7 +249,10 @@ template <bool IS_SIGNED = false> class Int128 {
}

private:
constexpr Int128(std::uint64_t hi, std::uint64_t lo) : low_{lo}, high_{hi} {}
constexpr Int128(std::uint64_t hi, std::uint64_t lo) {
low_ = lo;
high_ = hi;
}
constexpr int LeadingZeroes() const {
if (high_ == 0) {
return 64 + LeadingZeroBitCount(low_);
Expand All @@ -255,7 +261,13 @@ template <bool IS_SIGNED = false> class Int128 {
}
}
static constexpr std::uint64_t topBit{std::uint64_t{1} << 63};
#if FLANG_LITTLE_ENDIAN
std::uint64_t low_{0}, high_{0};
#elif FLANG_BIG_ENDIAN
std::uint64_t high_{0}, low_{0};
#else
#error host endianness is not known
#endif
};

using UnsignedInt128 = Int128<false>;
Expand Down
11 changes: 10 additions & 1 deletion flang/runtime/edit-input.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -244,7 +244,16 @@ bool EditIntegerInput(
value = -value;
}
if (any || !io.GetConnectionState().IsAtEOF()) {
std::memcpy(n, &value, kind); // a blank field means zero
// The value is stored in the lower order bits on big endian platform.
// When memcpy, shift the value to the higher order bit.
auto shft{static_cast<int>(sizeof(value.low())) - kind};
// For kind==8 (i.e. shft==0), the value is stored in low_ in big endian.
if (!isHostLittleEndian && shft >= 0) {
auto l{value.low() << (8 * shft)};
std::memcpy(n, &l, kind);
} else {
std::memcpy(n, &value, kind); // a blank field means zero
}
}
return any;
}
Expand Down