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Fixes for proper handling of IEEE Section 7.2 #1136

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Merged
merged 11 commits into from
Oct 16, 2025
Merged

Fixes for proper handling of IEEE Section 7.2 #1136

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d1086c2
Add first case to test set
mborland Oct 15, 2025
a765f2b
Handle 7.2.d
mborland Oct 16, 2025
2653ea3
Add 7.2.b test case
mborland Oct 16, 2025
77aaa67
Fix handling of comparisons to zero
mborland Oct 16, 2025
2a66705
Implement support for 7.2.b
mborland Oct 16, 2025
0956d71
Add test for 7.2.e
mborland Oct 16, 2025
6b86049
Implement support for 7.2.e
mborland Oct 16, 2025
5aaa62d
Add 7.2.f test set
mborland Oct 16, 2025
5d212c8
Fix missing operator++
mborland Oct 16, 2025
78b2313
Remove/disable incorrect tests
mborland Oct 16, 2025
7a30129
Re-order location of comparison operators for old clang
mborland Oct 16, 2025
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54 changes: 41 additions & 13 deletions include/boost/decimal/decimal128_t.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1429,8 +1429,8 @@ constexpr auto d128_div_impl(const decimal128_t& lhs, const decimal128_t& rhs, d
#ifndef BOOST_DECIMAL_FAST_MATH
// Check pre-conditions
constexpr decimal128_t zero {0, 0};
constexpr decimal128_t nan {boost::decimal::from_bits(boost::decimal::detail::d128_snan_mask)};
constexpr decimal128_t inf {boost::decimal::from_bits(boost::decimal::detail::d128_inf_mask)};
constexpr decimal128_t nan {from_bits(detail::d128_nan_mask)};
constexpr decimal128_t inf {from_bits(detail::d128_inf_mask)};

const bool sign {lhs.isneg() != rhs.isneg()};

Expand All @@ -1447,12 +1447,28 @@ constexpr auto d128_div_impl(const decimal128_t& lhs, const decimal128_t& rhs, d
switch (lhs_fp)
{
case FP_INFINITE:
q = sign ? -inf : inf;
r = zero;
if (rhs_fp == FP_INFINITE)
{
q = nan;
r = nan;
}
else
{
q = sign ? -inf : inf;
r = zero;
}
return;
case FP_ZERO:
q = sign ? -zero : zero;
r = sign ? -zero : zero;
if (rhs_fp == FP_ZERO)
{
q = nan;
r = nan;
}
else
{
q = sign ? -zero : zero;
r = sign ? -zero : zero;
}
return;
default:
static_cast<void>(lhs);
Expand Down Expand Up @@ -1509,6 +1525,11 @@ constexpr auto operator+(const decimal128_t& lhs, const decimal128_t& rhs) noexc
#ifndef BOOST_DECIMAL_FAST_MATH
if (not_finite(lhs) || not_finite(rhs))
{
if (isinf(lhs) && isinf(rhs) && signbit(lhs) != signbit(rhs))
{
return from_bits(detail::d128_nan_mask);
}

return detail::check_non_finite(lhs, rhs);
}
#endif
Expand Down Expand Up @@ -1567,6 +1588,11 @@ constexpr auto operator-(const decimal128_t& lhs, const decimal128_t& rhs) noexc
#ifndef BOOST_DECIMAL_FAST_MATH
if (not_finite(lhs) || not_finite(rhs))
{
if (isinf(lhs) && isinf(rhs) && signbit(lhs) == signbit(rhs))
{
return from_bits(detail::d128_nan_mask);
}

return detail::check_non_finite(lhs, rhs);
}
#endif
Expand Down Expand Up @@ -1648,19 +1674,21 @@ constexpr auto operator*(const decimal128_t& lhs, const decimal128_t& rhs) noexc
#ifndef BOOST_DECIMAL_FAST_MATH
if (not_finite(lhs) || not_finite(rhs))
{
if ((isinf(lhs) && rhs == 0) || (isinf(rhs) && lhs == 0))
{
return from_bits(detail::d128_nan_mask);
}

return detail::check_non_finite(lhs, rhs);
}
#endif

const auto lhs_sig {lhs.full_significand()};
const auto lhs_exp {lhs.biased_exponent()};

const auto rhs_sig {rhs.full_significand()};
const auto rhs_exp {rhs.biased_exponent()};
const auto lhs_components {lhs.to_components()};
const auto rhs_components {rhs.to_components()};

return detail::d128_mul_impl<decimal128_t>(
lhs_sig, lhs_exp, lhs.isneg(),
rhs_sig, rhs_exp, rhs.isneg());
lhs_components.sig, lhs_components.exp, lhs_components.sign,
rhs_components.sig, rhs_components.exp, rhs_components.sign);
}

template <typename Integer>
Expand Down
45 changes: 39 additions & 6 deletions include/boost/decimal/decimal32_t.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -875,6 +875,12 @@ constexpr auto operator+(const decimal32_t lhs, const decimal32_t rhs) noexcept
#ifndef BOOST_DECIMAL_FAST_MATH
if (!isfinite(lhs) || !isfinite(rhs))
{
// Case from 7.2.d
if (isinf(lhs) && isinf(rhs) && signbit(lhs) != signbit(rhs))
{
return from_bits(detail::d32_nan_mask);
}

return detail::check_non_finite(lhs, rhs);
}
#endif
Expand Down Expand Up @@ -968,6 +974,12 @@ constexpr auto operator-(const decimal32_t lhs, const decimal32_t rhs) noexcept
#ifndef BOOST_DECIMAL_FAST_MATH
if (!isfinite(lhs) || !isfinite(rhs))
{
// Case from 7.2.d
if (isinf(lhs) && isinf(rhs) && signbit(lhs) == signbit(rhs))
{
return from_bits(detail::d32_nan_mask);
}

return detail::check_non_finite(lhs, rhs);
}
#endif
Expand Down Expand Up @@ -1645,6 +1657,11 @@ constexpr auto operator*(const decimal32_t lhs, const decimal32_t rhs) noexcept
#ifndef BOOST_DECIMAL_FAST_MATH
if (!isfinite(lhs) || !isfinite(rhs))
{
if ((isinf(lhs) && rhs == 0) || (isinf(rhs) && lhs == 0))
{
return from_bits(detail::d32_nan_mask);
}

return detail::check_non_finite(lhs, rhs);
}
#endif
Expand Down Expand Up @@ -1716,8 +1733,8 @@ constexpr auto div_impl(const decimal32_t lhs, const decimal32_t rhs, decimal32_
#ifndef BOOST_DECIMAL_FAST_MATH
// Check pre-conditions
constexpr decimal32_t zero {0, 0};
constexpr decimal32_t nan {boost::decimal::from_bits(boost::decimal::detail::d32_snan_mask)};
constexpr decimal32_t inf {boost::decimal::from_bits(boost::decimal::detail::d32_inf_mask)};
constexpr decimal32_t nan {from_bits(detail::d32_nan_mask)};
constexpr decimal32_t inf {from_bits(detail::d32_inf_mask)};

const bool sign {lhs.isneg() != rhs.isneg()};

Expand All @@ -1734,12 +1751,28 @@ constexpr auto div_impl(const decimal32_t lhs, const decimal32_t rhs, decimal32_
switch (lhs_fp)
{
case FP_INFINITE:
q = sign ? -inf : inf;
r = zero;
if (rhs_fp == FP_INFINITE)
{
q = nan;
r = nan;
}
else
{
q = sign ? -inf : inf;
r = zero;
}
return;
case FP_ZERO:
q = sign ? -zero : zero;
r = sign ? -zero : zero;
if (rhs_fp == FP_ZERO)
{
q = nan;
r = nan;
}
else
{
q = sign ? -zero : zero;
r = sign ? -zero : zero;
}
return;
default:
static_cast<void>(lhs);
Expand Down
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