Optimize Date construction and string concatenation with...

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 29 matching lines @@
 // changes to these properties.
 const $Date = global.Date;
 
 // Helper function to throw error.
 function ThrowDateTypeError() {
   throw new $TypeError('this is not a Date object.');
 }
 
 // ECMA 262 - 15.9.1.2
 function Day(time) {
-  return FLOOR(time/msPerDay);
+  return FLOOR(time / msPerDay);
 }
 
 
 // ECMA 262 - 5.2
 function Modulo(value, remainder) {
   var mod = value % remainder;
   // Guard against returning -0.
   if (mod == 0) return 0;
   return mod >= 0 ? mod : mod + remainder;
 }
@@ skipping 360 matching lines @@
 
 // ECMA 262 - 15.9.1.14
 function TimeClip(time) {
   if (!$isFinite(time)) return $NaN;
   if ($abs(time) > 8.64E15) return $NaN;
   return TO_INTEGER(time);
 }
 
 
 %SetCode($Date, function(year, month, date, hours, minutes, seconds, ms) {
-  if (%_IsConstructCall()) {
-    // ECMA 262 - 15.9.3
-    var argc = %_ArgumentsLength();
-    if (argc == 0) {
-      %_SetValueOf(this, %DateCurrentTime());
-      return;
+  if (!%_IsConstructCall()) {
+    // ECMA 262 - 15.9.2
+    return (new $Date()).toString();
+  }
+
+  // ECMA 262 - 15.9.3
+  var argc = %_ArgumentsLength();
+  var value;
+  if (argc == 0) {
+    value = %DateCurrentTime();
+
+  } else if (argc == 1) {
+    if (IS_NUMBER(year)) {
+      value = TimeClip(year);
+    } else {
+      // According to ECMA 262, no hint should be given for this
+      // conversion. However, ToPrimitive defaults to STRING_HINT for
+      // Date objects which will lose precision when the Date
+      // constructor is called with another Date object as its
+      // argument. We therefore use NUMBER_HINT for the conversion,
+      // which is the default for everything else than Date objects.
+      // This makes us behave like KJS and SpiderMonkey.
+      var time = ToPrimitive(year, NUMBER_HINT);
+      value = IS_STRING(time) ? DateParse(time) : TimeClip(ToNumber(time));
     }
-    if (argc == 1) {
-      // According to ECMA 262, no hint should be given for this
-      // conversion.  However, ToPrimitive defaults to String Hint
-      // for Date objects which will lose precision when the Date
-      // constructor is called with another Date object as its
-      // argument.  We therefore use Number Hint for the conversion
-      // (which is the default for everything else than Date
-      // objects).  This makes us behave like KJS and SpiderMonkey.
-      var time = ToPrimitive(year, NUMBER_HINT);
-      if (IS_STRING(time)) {
-        %_SetValueOf(this, DateParse(time));
-      } else {
-        %_SetValueOf(this, TimeClip(ToNumber(time)));
-      }
-      return;
-    }
+
+  } else {
     year = ToNumber(year);
     month = ToNumber(month);
     date = argc > 2 ? ToNumber(date) : 1;
     hours = argc > 3 ? ToNumber(hours) : 0;
     minutes = argc > 4 ? ToNumber(minutes) : 0;
     seconds = argc > 5 ? ToNumber(seconds) : 0;
     ms = argc > 6 ? ToNumber(ms) : 0;
     year = (!NUMBER_IS_NAN(year) && 0 <= TO_INTEGER(year) && TO_INTEGER(year) <= 99)
         ? 1900 + TO_INTEGER(year) : year;
     var day = MakeDay(year, month, date);
     var time = MakeTime(hours, minutes, seconds, ms);
-    %_SetValueOf(this, TimeClip(UTC(MakeDate(day, time))));
-  } else {
-    // ECMA 262 - 15.9.2
-    return (new $Date()).toString();
+    value = TimeClip(UTC(MakeDate(day, time)));
   }
+  %_SetValueOf(this, value);
 });
 
 
 // Helper functions.
 function GetTimeFrom(aDate) {
   return DATE_VALUE(aDate);
 }
 
 
 function GetMillisecondsFrom(aDate) {
@@ skipping 648 matching lines @@
     "toGMTString", DateToGMTString,
     "toUTCString", DateToUTCString,
     "getYear", DateGetYear,
     "setYear", DateSetYear,
     "toISOString", DateToISOString,
     "toJSON", DateToJSON
   ));
 }
 
 SetupDate();