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

@@ -543,7 +543,34 @@ internal static CultureInfo[] GetCultures(CultureTypes types)
             return GlobalizationMode.UseNls ? NlsEnumCultures(types) : IcuEnumCultures(types);
         }
 
+        private static CalendarId[] GetInvariantCalendarIdArray() => [CalendarId.GREGORIAN];
+        private static CalendarData[] GetInvariantCalendarDataArray()
+        {
+            var calendars = new CalendarData[CalendarData.MAX_CALENDARS];
+            calendars[0] = CalendarData.Invariant;
+            return calendars;
+        }
+
         private static CultureData CreateCultureWithInvariantData()
+        {
+            CultureData invariant = CreateCultureWithInvariantDataWithoutCalendars();
+
+            // all available calendar type(s).  The first one is the default calendar
+            invariant._waCalendars = GetInvariantCalendarIdArray();
+
+            if (!GlobalizationMode.InvariantNoLoad)
+            {
+                invariant._calendars = GetInvariantCalendarDataArray();
+            }
+
+            return invariant;
+        }
+
+        // Calendar information is expensive size-wise, especially for AOT.
+        // CalendarData.Invariant is special cased in _waCalendars and _calendars
+        // accessors and gets initialized lazily. All other uses should use
+        // CreateCultureWithInvariantData above that populates calendars too.
+        private static CultureData CreateCultureWithInvariantDataWithoutCalendars()
         {
             // Make a new culturedata
             CultureData invariant = new CultureData();
@@ -625,16 +652,6 @@ 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;
-            }
-
             // Text information
             invariant._iReadingLayout = 0;
 
@@ -658,7 +675,7 @@ private static CultureData CreateCultureWithInvariantData()
         /// Build our invariant information
         /// We need an invariant instance, which we build hard-coded
         /// </summary>
-        internal static CultureData Invariant => field ??= CreateCultureWithInvariantData();
+        internal static CultureData Invariant => field ??= CreateCultureWithInvariantDataWithoutCalendars();
 
         // Cache of cultures we've already looked up
         private static volatile Dictionary<string, CultureData>? s_cachedCultures;
@@ -1647,7 +1664,13 @@ internal CalendarId[] CalendarIds
         {
             get
             {
-                if (_waCalendars == null && !GlobalizationMode.Invariant)
+                if (_waCalendars == null && this == Invariant)
+                {
+                    // 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 = GetInvariantCalendarIdArray();
+                }
+                else if (_waCalendars == null && !GlobalizationMode.Invariant)
                 {
                     // 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.
@@ -1660,8 +1683,8 @@ internal CalendarId[] CalendarIds
                     // See if we had a calendar to add.
                     if (count == 0)
                     {
-                        // Failed for some reason, just grab Gregorian from Invariant
-                        _waCalendars = Invariant._waCalendars!;
+                        // Failed for some reason, just use Gregorian
+                        _waCalendars = GetInvariantCalendarIdArray();
                     }
                     else
                     {
@@ -1727,6 +1750,13 @@ internal CalendarData GetCalendar(CalendarId calendarId)
             // arrays are 0 based, calendarIds are 1 based
             int calendarIndex = (int)calendarId - 1;
 
+            if (_calendars == null && this == Invariant)
+            {
+                // We do this lazily as opposed in CreateCultureWithInvariantData to avoid introducing
+                // invariant calendar data into apps that don't even need calendar.
+                _calendars = GetInvariantCalendarDataArray();
+            }
+
             // Have to have calendars
             _calendars ??= new CalendarData[CalendarData.MAX_CALENDARS];