Rewrite MakeDay function from JS to C++.

src/date-delay.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 95 matching lines @@
 
 function EquivalentTime(t) {
   // The issue here is that some library calls don't work right for dates
   // that cannot be represented using a non-negative signed 32 bit integer
   // (measured in whole seconds based on the 1970 epoch).
   // We solve this by mapping the time to a year with same leap-year-ness
   // and same starting day for the year.  The ECMAscript specification says
   // we must do this, but for compatibility with other browsers, we use
   // the actual year if it is in the range 1970..2037
   if (t >= 0 && t <= 2.1e12) return t;
-  var day = MakeDay(EquivalentYear(YEAR_FROM_TIME(t)), MONTH_FROM_TIME(t), DATE_FROM_TIME(t));
-  return TimeClip(MakeDate(day, TimeWithinDay(t)));
+
+  // We call function from runtime.cc to avoid extra checks which are unneeded.
+  var day = %DateMakeDay(EquivalentYear(YEAR_FROM_TIME(t)),
+                         MONTH_FROM_TIME(t),
+                         DATE_FROM_TIME(t));
+  return MakeDate(day, TimeWithinDay(t));
 }
 
 
 // Because computing the DST offset is a pretty expensive operation
 // we keep a cache of last computed offset along with a time interval
 // where we know the cache is valid.
 var DST_offset_cache = {
   // Cached DST offset.
   offset: 0,
   // Time interval where the cached offset is valid.
@@ skipping 122 matching lines @@
       + TO_INTEGER(ms);
 }
 
 
 // ECMA 262 - 15.9.1.12
 function TimeInYear(year) {
   return DaysInYear(year) * msPerDay;
 }
 
 
-// Compute modified Julian day from year, month, date.
-function ToJulianDay(year, month, date) {
-  var jy = (month > 1) ? year : year - 1;
-  var jm = (month > 1) ? month + 2 : month + 14;
-  var ja = FLOOR(jy / 100);
-  return FLOOR(FLOOR(365.25*jy) + FLOOR(30.6001*jm) + date + 1720995) + 2 - ja + FLOOR(0.25*ja);
-}
-
 var four_year_cycle_table = CalculateDateTable();
 
 
 function CalculateDateTable() {
   var month_lengths = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
   var four_year_cycle_table = new $Array(1461);
 
   var cumulative = 0;
   var position = 0;
   var leap_position = 0;
@@ skipping 74 matching lines @@
 
 // Compute number of days given a year, month, date.
 // Note that month and date can lie outside the normal range.
 //   For example:
 //     MakeDay(2007, -4, 20) --> MakeDay(2006, 8, 20)
 //     MakeDay(2007, -33, 1) --> MakeDay(2004, 3, 1)
 //     MakeDay(2007, 14, -50) --> MakeDay(2007, 8, 11)
 function MakeDay(year, month, date) {
   if (!$isFinite(year) || !$isFinite(month) || !$isFinite(date)) return $NaN;
 
-  // Conversion to integers.
   year = TO_INTEGER(year);
   month = TO_INTEGER(month);
   date = TO_INTEGER(date);
 
-  // Overflow months into year.
-  year = year + FLOOR(month/12);
-  month = month % 12;
-  if (month < 0) {
-    month += 12;
+  if (year < kMinYear || year > kMaxYear ||
+      month < kMinMonth || month > kMaxMonth ||
+      date < kMinDate || date > kMaxDate) {
+    return $NaN;
   }
 
-  // Return days relative to Jan 1 1970.
-  return ToJulianDay(year, month, date) - kDayZeroInJulianDay;
+  // Now we presume that year, month and date are actually SMIs.

[Mads Ager (chromium), 2010/03/02 13:04:08]

Since the runtime function probably relies on year, month and date being Smis,
we have to be 100% sure that they are.  Could you update the comment explaining
why they have to be Smis?

[Oleg Eterevsky, 2010/03/02 13:28:23]

Done.

+  return %DateMakeDay(year, month, date);
 }
 
 
 // ECMA 262 - 15.9.1.13
 function MakeDate(day, time) {
   if (!$isFinite(day)) return $NaN;
   if (!$isFinite(time)) return $NaN;
   return day * msPerDay + time;
 }
 
@@ skipping 743 matching lines @@
     "toGMTString", DateToGMTString,
     "toUTCString", DateToUTCString,
     "getYear", DateGetYear,
     "setYear", DateSetYear,
     "toISOString", DateToISOString,
     "toJSON", DateToJSON
   ));
 }
 
 SetupDate();