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Shift amount corrections (alpha & beta) are now done in std::uint_fas…
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…t8_t
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@jk-jeon
jk-jeon committed May 4, 2024
1 parent 9cba70c commit bde5ab8
Showing 1 changed file with 67 additions and 44 deletions.
111 changes: 67 additions & 44 deletions include/dragonbox/dragonbox.h
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Original file line number Diff line number Diff line change
Expand Up @@ -228,6 +228,7 @@ namespace jkj {
using JKJ_STD_REPLACEMENT_NAMESPACE::uint_least16_t;
using JKJ_STD_REPLACEMENT_NAMESPACE::uint_least32_t;
using JKJ_STD_REPLACEMENT_NAMESPACE::uint_least64_t;
using JKJ_STD_REPLACEMENT_NAMESPACE::uint_fast8_t;
using JKJ_STD_REPLACEMENT_NAMESPACE::uint_fast16_t;
using JKJ_STD_REPLACEMENT_NAMESPACE::uint_fast32_t;
// We need INT32_C, UINT32_C and UINT64_C macros too, but again there is nothing to do
Expand Down Expand Up @@ -2107,8 +2108,9 @@ namespace jkj {
}
else {
// Compute the required amount of bit-shift.
auto const alpha = detail::log::floor_log2_pow10<min_k, max_k>(k) -
detail::log::floor_log2_pow10<min_k, max_k>(kb) - offset;
auto const alpha = detail::stdr::uint_fast8_t(
detail::log::floor_log2_pow10<min_k, max_k>(k) -
detail::log::floor_log2_pow10<min_k, max_k>(kb) - offset);
assert(alpha > 0 && alpha < 64);

// Try to recover the real cache.
Expand All @@ -2119,7 +2121,9 @@ namespace jkj {
: detail::stdr::uint_least32_t(pow5_table[offset]);
auto mul_result = detail::wuint::umul128(base_cache, pow5);
auto const recovered_cache = cache_entry_type(
(((mul_result.high() << (64 - alpha)) | (mul_result.low() >> alpha)) + 1) &
(((mul_result.high() << detail::stdr::uint_fast8_t(64 - alpha)) |
(mul_result.low() >> alpha)) +
1) &
UINT64_C(0xffffffffffffffff));
assert(recovered_cache != 0);

Expand Down Expand Up @@ -2202,8 +2206,9 @@ namespace jkj {
}
else {
// Compute the required amount of bit-shift.
auto const alpha = detail::log::floor_log2_pow10<min_k, max_k>(k) -
detail::log::floor_log2_pow10<min_k, max_k>(kb) - offset;
auto const alpha = detail::stdr::uint_fast8_t(
detail::log::floor_log2_pow10<min_k, max_k>(k) -
detail::log::floor_log2_pow10<min_k, max_k>(kb) - offset);
assert(alpha > 0 && alpha < 64);

// Try to recover the real cache.
Expand All @@ -2214,9 +2219,11 @@ namespace jkj {
recovered_cache += middle_low.high();

auto const high_to_middle = detail::stdr::uint_least64_t(
(recovered_cache.high() << (64 - alpha)) & UINT64_C(0xffffffffffffffff));
(recovered_cache.high() << detail::stdr::uint_fast8_t(64 - alpha)) &
UINT64_C(0xffffffffffffffff));
auto const middle_to_low = detail::stdr::uint_least64_t(
(recovered_cache.low() << (64 - alpha)) & UINT64_C(0xffffffffffffffff));
(recovered_cache.low() << detail::stdr::uint_fast8_t(64 - alpha)) &
UINT64_C(0xffffffffffffffff));

recovered_cache = {(recovered_cache.low() >> alpha) | high_to_middle,
((middle_low.low() >> alpha) | middle_to_low)};
Expand Down Expand Up @@ -3002,39 +3009,46 @@ namespace jkj {
return {carrier_uint(r >> 32), carrier_uint(r) == 0};
}

static constexpr detail::stdr::uint_least64_t compute_delta(cache_entry_type const& cache,
int beta) noexcept {
return detail::stdr::uint_least64_t(cache >> (cache_bits - 1 - beta));
static constexpr detail::stdr::uint_least64_t
compute_delta(cache_entry_type const& cache, detail::stdr::uint_fast8_t beta) noexcept {
return detail::stdr::uint_least64_t(cache >>
detail::stdr::uint_fast8_t(cache_bits - 1 - beta));
}

static JKJ_CONSTEXPR20 compute_mul_parity_result
compute_mul_parity(carrier_uint two_f, cache_entry_type const& cache, int beta) noexcept {
compute_mul_parity(carrier_uint two_f, cache_entry_type const& cache,
detail::stdr::uint_fast8_t beta) noexcept {
assert(beta >= 1);
assert(beta <= 32);

auto const r = detail::wuint::umul96_lower64(two_f, cache);
return {((r >> (64 - beta)) & 1) != 0,
(UINT32_C(0xffffffff) & (r >> (32 - beta))) == 0};
return {((r >> detail::stdr::uint_fast8_t(64 - beta)) & 1) != 0,
(UINT32_C(0xffffffff) & (r >> detail::stdr::uint_fast8_t(32 - beta))) == 0};
}

static constexpr carrier_uint
compute_left_endpoint_for_shorter_interval_case(cache_entry_type const& cache,
int beta) noexcept {
return carrier_uint((cache - (cache >> (significand_bits + 2))) >>
(cache_bits - significand_bits - 1 - beta));
detail::stdr::uint_fast8_t beta) noexcept {
return carrier_uint(
(cache - (cache >> (significand_bits + 2))) >>
detail::stdr::uint_fast8_t(cache_bits - significand_bits - 1 - beta));
}

static constexpr carrier_uint
compute_right_endpoint_for_shorter_interval_case(cache_entry_type const& cache,
int beta) noexcept {
return carrier_uint((cache + (cache >> (significand_bits + 1))) >>
(cache_bits - significand_bits - 1 - beta));
detail::stdr::uint_fast8_t beta) noexcept {
return carrier_uint(
(cache + (cache >> (significand_bits + 1))) >>
detail::stdr::uint_fast8_t(cache_bits - significand_bits - 1 - beta));
}

static constexpr carrier_uint
compute_round_up_for_shorter_interval_case(cache_entry_type const& cache,
int beta) noexcept {
return (carrier_uint(cache >> (cache_bits - significand_bits - 2 - beta)) + 1) / 2;
detail::stdr::uint_fast8_t beta) noexcept {
return (carrier_uint(cache >> detail::stdr::uint_fast8_t(cache_bits - significand_bits -
2 - beta)) +
1) /
2;
}
};

Expand All @@ -3051,40 +3065,45 @@ namespace jkj {
return {r.high(), r.low() == 0};
}

static constexpr detail::stdr::uint_least64_t compute_delta(cache_entry_type const& cache,
int beta) noexcept {
return detail::stdr::uint_least64_t(cache.high() >> (total_bits - 1 - beta));
static constexpr detail::stdr::uint_least64_t
compute_delta(cache_entry_type const& cache, detail::stdr::uint_fast8_t beta) noexcept {
return detail::stdr::uint_least64_t(cache.high() >>
detail::stdr::uint_fast8_t(total_bits - 1 - beta));
}

static JKJ_CONSTEXPR20 compute_mul_parity_result
compute_mul_parity(carrier_uint two_f, cache_entry_type const& cache, int beta) noexcept {
compute_mul_parity(carrier_uint two_f, cache_entry_type const& cache,
detail::stdr::uint_fast8_t beta) noexcept {
assert(beta >= 1);
assert(beta < 64);

auto const r = detail::wuint::umul192_lower128(two_f, cache);
return {((r.high() >> (64 - beta)) & 1) != 0,
return {((r.high() >> detail::stdr::uint_fast8_t(64 - beta)) & 1) != 0,
(((r.high() << beta) & UINT64_C(0xffffffffffffffff)) |
(r.low() >> (64 - beta))) == 0};
(r.low() >> detail::stdr::uint_fast8_t(64 - beta))) == 0};
}

static constexpr carrier_uint
compute_left_endpoint_for_shorter_interval_case(cache_entry_type const& cache,
int beta) noexcept {
detail::stdr::uint_fast8_t beta) noexcept {
return (cache.high() - (cache.high() >> (significand_bits + 2))) >>
(total_bits - significand_bits - 1 - beta);
detail::stdr::uint_fast8_t(total_bits - significand_bits - 1 - beta);
}

static constexpr carrier_uint
compute_right_endpoint_for_shorter_interval_case(cache_entry_type const& cache,
int beta) noexcept {
detail::stdr::uint_fast8_t beta) noexcept {
return (cache.high() + (cache.high() >> (significand_bits + 1))) >>
(total_bits - significand_bits - 1 - beta);
detail::stdr::uint_fast8_t(total_bits - significand_bits - 1 - beta);
}

static constexpr carrier_uint
compute_round_up_for_shorter_interval_case(cache_entry_type const& cache,
int beta) noexcept {
return ((cache.high() >> (total_bits - significand_bits - 2 - beta)) + 1) / 2;
detail::stdr::uint_fast8_t beta) noexcept {
return ((cache.high() >>
detail::stdr::uint_fast8_t(total_bits - significand_bits - 2 - beta)) +
1) /
2;
}
};

Expand Down Expand Up @@ -3229,8 +3248,9 @@ namespace jkj {
min_exponent - format::significand_bits,
max_exponent - format::significand_bits, decimal_exponent_type_>(
binary_exponent);
auto const beta = binary_exponent + log::floor_log2_pow10<min_k, max_k>(
decimal_exponent_type_(-minus_k));
auto const beta = stdr::uint_fast8_t(
binary_exponent +
log::floor_log2_pow10<min_k, max_k>(decimal_exponent_type_(-minus_k)));

// Compute xi and zi.
auto const cache = CachePolicy::template get_cache<format>(
Expand Down Expand Up @@ -3315,8 +3335,9 @@ namespace jkj {
kappa);
auto const cache =
CachePolicy::template get_cache<format>(decimal_exponent_type_(-minus_k));
auto const beta = binary_exponent + log::floor_log2_pow10<min_k, max_k>(
decimal_exponent_type_(-minus_k));
auto const beta =
stdr::uint_fast8_t(binary_exponent + log::floor_log2_pow10<min_k, max_k>(
decimal_exponent_type_(-minus_k)));

// Compute zi and deltai.
// 10^kappa <= deltai < 10^(kappa + 1)
Expand Down Expand Up @@ -3507,8 +3528,9 @@ namespace jkj {
kappa);
auto const cache =
CachePolicy::template get_cache<format>(decimal_exponent_type_(-minus_k));
int const beta = binary_exponent + log::floor_log2_pow10<min_k, max_k>(
decimal_exponent_type_(-minus_k));
auto const beta =
stdr::uint_fast8_t(binary_exponent + log::floor_log2_pow10<min_k, max_k>(
decimal_exponent_type_(-minus_k)));

// Compute xi and deltai.
// 10^kappa <= deltai < 10^(kappa + 1)
Expand Down Expand Up @@ -3648,14 +3670,15 @@ namespace jkj {
(shorter_interval ? 1 : 0)) -
kappa);
auto const cache =
CachePolicy::template get_cache<format>(deicmal_exponent_type(-minus_k));
int const beta =
binary_exponent + log::floor_log2_pow10(deicmal_exponent_type(-minus_k));
CachePolicy::template get_cache<format>(decimal_exponent_type(-minus_k));
auto const beta = stdr::uint_fast8_t(
binary_exponent + log::floor_log2_pow10(decimal_exponent_type(-minus_k)));

// Compute zi and deltai.
// 10^kappa <= deltai < 10^(kappa + 1)
auto const deltai = static_cast<remainder_type_>(
multiplication_traits_::compute_delta(cache, beta - shorter_interval ? 1 : 0));
auto const deltai =
static_cast<remainder_type_>(multiplication_traits_::compute_delta(
cache, stdr::uint_fast8_t(beta - shorter_interval ? 1 : 0)));
carrier_uint const zi =
multiplication_traits_::compute_mul(two_fc << beta, cache).integer_part;

Expand Down

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