Optimize QDate by shortcutting some gregorian calendar methods

Add some static methods to QGregorianCalendar, some of which serve to
implement its methods, that QDate can use to bypass vtables and
exploit fixed truths of the Gregorian calendar in its default
handling.

Change-Id: Iec191cdf4d52945dbd5679e609180cb4fe59b5fd
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 38 insertions, 1 deletions

diff --git a/src/corelib/time/qgregoriancalendar.cpp b/src/corelib/time/qgregoriancalendar.cpp
index d3db572aa7..447185d124 100644
--- a/src/corelib/time/qgregoriancalendar.cpp
+++ b/src/corelib/time/qgregoriancalendar.cpp
@@ -78,6 +78,11 @@ QCalendar::System QGregorianCalendar::calendarSystem() const
 
 bool QGregorianCalendar::isLeapYear(int year) const
 {
+    return leapTest(year);
+}
+
+bool QGregorianCalendar::leapTest(int year)
+{
     if (year == QCalendar::Unspecified)
         return false;
 
@@ -88,10 +93,37 @@ bool QGregorianCalendar::isLeapYear(int year) const
     return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
 }
 
+// Duplicating code from QRomanCalendar, but inlining isLeapYear() as leapTest():
+int QGregorianCalendar::monthLength(int month, int year)
+{
+    if (month < 1 || month > 12)
+        return 0;
+
+    if (month == 2)
+        return leapTest(year) ? 29 : 28;
+
+    return 30 | ((month & 1) ^ (month >> 3));
+}
+
+bool QGregorianCalendar::validParts(int year, int month, int day)
+{
+    return year && 0 < day && day <= monthLength(month, year);
+}
+
+int QGregorianCalendar::weekDayOfJulian(qint64 jd)
+{
+    return qMod(jd, 7) + 1;
+}
+
 bool QGregorianCalendar::dateToJulianDay(int year, int month, int day, qint64 *jd) const
 {
+    return julianFromParts(year, month, day, jd);
+}
+
+bool QGregorianCalendar::julianFromParts(int year, int month, int day, qint64 *jd)
+{
     Q_ASSERT(jd);
-    if (!isDateValid(year, month, day))
+    if (!validParts(year, month, day))
         return false;
 
     if (year < 0)
@@ -112,6 +144,11 @@ bool QGregorianCalendar::dateToJulianDay(int year, int month, int day, qint64 *j
 
 QCalendar::YearMonthDay QGregorianCalendar::julianDayToDate(qint64 jd) const
 {
+    return partsFromJulian(jd);
+}
+
+QCalendar::YearMonthDay QGregorianCalendar::partsFromJulian(qint64 jd)
+{
     /*
      * Math from The Calendar FAQ at http://www.tondering.dk/claus/cal/julperiod.php
      * This formula is correct for all julian days, when using mathematical integer