Drop size of hello world to 745 kB

src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/MethodTable.Runtime.cs

@@ -37,7 +37,7 @@ internal bool IsEnum
 
                 // Generic type definitions that return true for IsPrimitive are type definitions of generic enums.
                 // Otherwise check the base type.
-                return IsPrimitive && (IsGenericTypeDefinition || NonArrayBaseType == MethodTable.Of<Enum>());
+                return IsPrimitive && (IsGenericTypeDefinition || NonArrayBaseType != MethodTable.Of<ValueType>());
             }
         }
 

src/coreclr/nativeaot/System.Private.CoreLib/src/System/GC.NativeAot.cs

@@ -764,7 +764,7 @@ public static long GetTotalAllocatedBytes(bool precise = false)
 
         /// <summary>Gets garbage collection memory information.</summary>
         /// <returns>An object that contains information about the garbage collector's memory usage.</returns>
-        public static GCMemoryInfo GetGCMemoryInfo() => GetGCMemoryInfo(GCKind.Any);
+        public static GCMemoryInfo GetGCMemoryInfo() => GetGCMemoryInfoUnchecked(GCKind.Any);
 
         /// <summary>Gets garbage collection memory information.</summary>
         /// <param name="kind">The kind of collection for which to retrieve memory information.</param>
@@ -780,6 +780,11 @@ public static GCMemoryInfo GetGCMemoryInfo(GCKind kind)
                                           GCKind.Background));
             }
 
+            return GetGCMemoryInfoUnchecked(kind);
+        }
+
+        private static GCMemoryInfo GetGCMemoryInfoUnchecked(GCKind kind)
+        {
             var data = new GCMemoryInfoData();
             RuntimeImports.RhGetMemoryInfo(ref data.GetRawData(), kind);
             return new GCMemoryInfo(data);

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Threading/Thread.NativeAot.Windows.cs

@@ -289,7 +289,14 @@ private bool SetApartmentStateUnchecked(ApartmentState state, bool throwOnError)
             {
                 if (throwOnError)
                 {
-                    string msg = SR.Format(SR.Thread_ApartmentState_ChangeFailed, retState);
+                    // NOTE: We do the enum stringification manually to avoid introducing a dependency
+                    // on enum stringification in small apps. We set apartment state in the startup path.
+                    string msg = SR.Format(SR.Thread_ApartmentState_ChangeFailed, retState switch
+                    {
+                        ApartmentState.MTA => "MTA",
+                        ApartmentState.STA => "STA",
+                        _ => "Unknown"
+                    });
                     throw new InvalidOperationException(msg);
                 }
 

src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.cs

@@ -625,15 +625,11 @@ private static CultureData CreateCultureWithInvariantData()
             invariant._iFirstDayOfWeek = 0;                      // first day of week
             invariant._iFirstWeekOfYear = 0;                      // first week of year
 
-            // all available calendar type(s).  The first one is the default calendar
-            invariant._waCalendars = [CalendarId.GREGORIAN];
-
-            if (!GlobalizationMode.InvariantNoLoad)
-            {
-                // Store for specific data about each calendar
-                invariant._calendars = new CalendarData[CalendarData.MAX_CALENDARS];
-                invariant._calendars[0] = CalendarData.Invariant;
-            }
+            // Calendar information is expensive size-wise, especially for AOT.
+            // CalendarData.Invariant is special cased in _waCalendars and _calendars
+            // accessors and gets initialized lazily.
+            // invariant._waCalendars
+            // invariant._calendars
 
             // Text information
             invariant._iReadingLayout = 0;
@@ -1647,61 +1643,68 @@ internal CalendarId[] CalendarIds
         {
             get
             {
-                if (_waCalendars == null && !GlobalizationMode.Invariant)
+                if (_waCalendars == null)
                 {
-                    // We pass in an array of ints, and native side fills it up with count calendars.
-                    // We then have to copy that list to a new array of the right size.
-                    // Default calendar should be first
-                    CalendarId[] calendars = new CalendarId[23];
-                    Debug.Assert(_sWindowsName != null, "[CultureData.CalendarIds] Expected _sWindowsName to be populated by already");
-
-                    int count = CalendarData.GetCalendarsCore(_sWindowsName, _bUseOverrides, calendars);
-
-                    // See if we had a calendar to add.
-                    if (count == 0)
+                    if (GlobalizationMode.Invariant || IsInvariantCulture)
                     {
-                        // Failed for some reason, just grab Gregorian from Invariant
-                        _waCalendars = Invariant._waCalendars!;
+                        // We do this lazily as opposed in CreateCultureWithInvariantData to avoid introducing
+                        // enum arrays into apps that otherwise wouldn't have them. This helps with size in AOT.
+                        _waCalendars = [CalendarId.GREGORIAN];
                     }
                     else
                     {
-                        // The OS may not return calendar 4 for zh-TW, but we've always allowed it.
-                        // TODO: Is this hack necessary long-term?
-                        if (_sWindowsName == "zh-TW")
-                        {
-                            bool found = false;
+                        // We pass in an array of ints, and native side fills it up with count calendars.
+                        // We then have to copy that list to a new array of the right size.
+                        // Default calendar should be first
+                        CalendarId[] calendars = new CalendarId[23];
+                        Debug.Assert(_sWindowsName != null, "[CultureData.CalendarIds] Expected _sWindowsName to be populated by already");
+
+                        int count = CalendarData.GetCalendarsCore(_sWindowsName, _bUseOverrides, calendars);
 
-                            // Do we need to insert calendar 4?
-                            for (int i = 0; i < count; i++)
+                        // See if we had a calendar to add.
+                        if (count == 0)
+                        {
+                            // Failed for some reason, just use Gregorian
+                            _waCalendars = Invariant.CalendarIds;
+                        }
+                        else
+                        {
+                            // The OS may not return calendar 4 for zh-TW, but we've always allowed it.
+                            // TODO: Is this hack necessary long-term?
+                            if (_sWindowsName == "zh-TW")
                             {
-                                // Stop if we found calendar four
-                                if (calendars[i] == CalendarId.TAIWAN)
+                                bool found = false;
+
+                                // Do we need to insert calendar 4?
+                                for (int i = 0; i < count; i++)
                                 {
-                                    found = true;
-                                    break;
+                                    // Stop if we found calendar four
+                                    if (calendars[i] == CalendarId.TAIWAN)
+                                    {
+                                        found = true;
+                                        break;
+                                    }
                                 }
-                            }
 
-                            // If not found then insert it
-                            if (!found)
-                            {
-                                // Insert it as the 2nd calendar
-                                count++;
-                                // Copy them from the 2nd position to the end, -1 for skipping 1st, -1 for one being added.
-                                Array.Copy(calendars, 1, calendars, 2, 23 - 1 - 1);
-                                calendars[1] = CalendarId.TAIWAN;
+                                // If not found then insert it
+                                if (!found)
+                                {
+                                    // Insert it as the 2nd calendar
+                                    count++;
+                                    // Copy them from the 2nd position to the end, -1 for skipping 1st, -1 for one being added.
+                                    Array.Copy(calendars, 1, calendars, 2, 23 - 1 - 1);
+                                    calendars[1] = CalendarId.TAIWAN;
+                                }
                             }
-                        }
-
-                        // It worked, remember the list
-                        CalendarId[] temp = new CalendarId[count];
-                        Array.Copy(calendars, temp, count);
 
-                        _waCalendars = temp;
+                            // It worked, remember the list
+                            CalendarId[] temp = new CalendarId[count];
+                            Array.Copy(calendars, temp, count);
+                            _waCalendars = temp;
+                        }
                     }
                 }
-
-                return _waCalendars!;
+                return _waCalendars;
             }
         }
 
@@ -1737,8 +1740,17 @@ internal CalendarData GetCalendar(CalendarId calendarId)
             // Make sure that calendar has data
             if (calendarData == null)
             {
-                Debug.Assert(_sWindowsName != null, "[CultureData.GetCalendar] Expected _sWindowsName to be populated by already");
-                calendarData = new CalendarData(_sWindowsName, calendarId, _bUseOverrides);
+                if (calendarIndex == 0 && IsInvariantCulture)
+                {
+                    // We do this lazily as opposed in CreateCultureWithInvariantData to avoid introducing
+                    // invariant calendar data into apps that don't even need calendar.
+                    calendarData = CalendarData.Invariant;
+                }
+                else
+                {
+                    Debug.Assert(_sWindowsName != null, "[CultureData.GetCalendar] Expected _sWindowsName to be populated by already");
+                    calendarData = new CalendarData(_sWindowsName, calendarId, _bUseOverrides);
+                }
                 _calendars[calendarIndex] = calendarData;
             }