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LibJS: Optimize the CalendarDateUntil AO for large year differences

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For example, consider the following operation:

    const instance = new Temporal.PlainDate(2000, 5, 2);
    instance.until("-271821-04-19");

The spec would have us enter a loop to compute the difference between
these dates by incrementing an intermediate date one day at a time.
Instead, we can do some math to skip ahead much closer to the desired
date.
This commit is contained in:
Timothy Flynn 2024-11-22 12:50:52 -05:00 • committed by Andreas Kling
parent f280a96e35
commit b319d45566
Notes: github-actions[bot] 2024-11-23 13:47:59 +00:00
1 changed files with 33 additions and 53 deletions
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86
Libraries/LibJS/Runtime/Temporal/Calendar.cpp
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@ -9,6 +9,7 @@
#include <AK/NonnullRawPtr.h>
#include <AK/QuickSort.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/Temporal/Calendar.h>
#include <LibJS/Runtime/Temporal/DateEquations.h>
#include <LibJS/Runtime/Temporal/Duration.h>
@ -361,12 +362,22 @@ DateDuration calendar_date_until(VM& vm, StringView calendar, ISODate const& one
// c. Let years be 0.
double years = 0;
// d. If largestUnit is YEAR, then
if (largest_unit == Unit::Year) {
// i. Let candidateYears be sign.
double candidate_years = sign;
// e. Let months be 0.
double months = 0;
// ii. Repeat, while ISODateSurpasses(sign, one.[[Year]] + candidateYears, one.[[Month]], one.[[Day]], two) is false,
// OPTIMIZATION: If the largestUnit is MONTH, we want to skip ahead to the correct year. If implemented in exact
// accordance with the spec, we could enter the second ISODateSurpasses loop below with a very large
// number of months to traverse.
// d. If largestUnit is YEAR, then
// f. If largestUnit is YEAR or largestUnit is MONTH, then
if (largest_unit == Unit::Year || largest_unit == Unit::Month) {
// d.i. Let candidateYears be sign.
auto candidate_years = two.year - one.year;
if (candidate_years != 0)
candidate_years -= sign;
// d.ii. Repeat, while ISODateSurpasses(sign, one.[[Year]] + candidateYears, one.[[Month]], one.[[Day]], two) is false,
while (!iso_date_surpasses(sign, static_cast<double>(one.year) + candidate_years, one.month, one.day, two)) {
// 1. Set years to candidateYears.
years = candidate_years;
@ -374,20 +385,14 @@ DateDuration calendar_date_until(VM& vm, StringView calendar, ISODate const& one
// 2. Set candidateYears to candidateYears + sign.
candidate_years += sign;
}
}
// e. Let months be 0.
double months = 0;
// f. If largestUnit is YEAR or largestUnit is MONTH, then
if (largest_unit == Unit::Year || largest_unit == Unit::Month) {
// i. Let candidateMonths be sign.
// f.i. Let candidateMonths be sign.
double candidate_months = sign;
// ii. Let intermediate be BalanceISOYearMonth(one.[[Year]] + years, one.[[Month]] + candidateMonths).
// f.ii. Let intermediate be BalanceISOYearMonth(one.[[Year]] + years, one.[[Month]] + candidateMonths).
auto intermediate = balance_iso_year_month(static_cast<double>(one.year) + years, static_cast<double>(one.month) + candidate_months);
// iii. Repeat, while ISODateSurpasses(sign, intermediate.[[Year]], intermediate.[[Month]], one.[[Day]], two) is false,
// f.iii. Repeat, while ISODateSurpasses(sign, intermediate.[[Year]], intermediate.[[Month]], one.[[Day]], two) is false,
while (!iso_date_surpasses(sign, intermediate.year, intermediate.month, one.day, two)) {
// 1. Set months to candidateMonths.
months = candidate_months;
@ -398,6 +403,11 @@ DateDuration calendar_date_until(VM& vm, StringView calendar, ISODate const& one
// 3. Set intermediate to BalanceISOYearMonth(intermediate.[[Year]], intermediate.[[Month]] + sign).
intermediate = balance_iso_year_month(intermediate.year, static_cast<double>(intermediate.month) + sign);
}
if (largest_unit == Unit::Month) {
months += years * 12.0;
years = 0.0;
}
}
// g. Set intermediate to BalanceISOYearMonth(one.[[Year]] + years, one.[[Month]] + months).
@ -409,46 +419,16 @@ DateDuration calendar_date_until(VM& vm, StringView calendar, ISODate const& one
// i. Let weeks be 0.
double weeks = 0;
// j. If largestUnit is WEEK, then
// OPTIMIZATION: If the largestUnit is DAY, we do not want to enter an ISODateSurpasses loop. The loop would have
// us increment the intermediate ISOYearMonth one day at time, which will take an extremely long
// time if the difference is a large number of years. Instead, we can compute the day difference,
// and convert to weeks if needed.
auto days = iso_date_to_epoch_days(two.year, two.month - 1, two.day) - iso_date_to_epoch_days(constrained.year, constrained.month - 1, constrained.day);
if (largest_unit == Unit::Week) {
// i. Let candidateWeeks be sign.
double candidate_weeks = sign;
// ii. Set intermediate to BalanceISODate(constrained.[[Year]], constrained.[[Month]], constrained.[[Day]] + 7 × candidateWeeks).
auto intermediate = balance_iso_date(constrained.year, constrained.month, static_cast<double>(constrained.day) + (7.0 * candidate_weeks));
// iii. Repeat, while ISODateSurpasses(sign, intermediate.[[Year]], intermediate.[[Month]], intermediate.[[Day]], two) is false,
while (!iso_date_surpasses(sign, intermediate.year, intermediate.month, intermediate.day, two)) {
// 1. Set weeks to candidateWeeks.
weeks = candidate_weeks;
// 2. Set candidateWeeks to candidateWeeks + sign.
candidate_weeks += sign;
// 3. Set intermediate to BalanceISODate(intermediate.[[Year]], intermediate.[[Month]], intermediate.[[Day]] + 7 × sign).
intermediate = balance_iso_date(intermediate.year, intermediate.month, static_cast<double>(intermediate.day) + (7.0 * sign));
}
}
// k. Let days be 0.
double days = 0;
// l. Let candidateDays be sign.
double candidate_days = sign;
// m. Set intermediate to BalanceISODate(constrained.[[Year]], constrained.[[Month]], constrained.[[Day]] + 7 × weeks + candidateDays).
auto intermediate_date = balance_iso_date(constrained.year, constrained.month, static_cast<double>(constrained.day) + (7.0 * weeks) + candidate_days);
// n. Repeat, while ISODateSurpasses(sign, intermediate.[[Year]], intermediate.[[Month]], intermediate.[[Day]], two) is false,
while (!iso_date_surpasses(sign, intermediate_date.year, intermediate_date.month, intermediate_date.day, two)) {
// i. Set days to candidateDays.
days = candidate_days;
// ii. Set candidateDays to candidateDays + sign.
candidate_days += sign;
// iii. Set intermediate to BalanceISODate(intermediate.[[Year]], intermediate.[[Month]], intermediate.[[Day]] + sign).
intermediate_date = balance_iso_date(intermediate_date.year, intermediate_date.month, static_cast<double>(intermediate_date.day) + sign);
weeks = trunc(days / 7.0);
days = fmod(days, 7.0);
}
// o. Return ! CreateDateDurationRecord(years, months, weeks, days).