[NativeAOT] Respect Align8 flag for thread statics (#105905)

* Respect Align8 flag for thread statics

* Port WASM test

Co-authored-by: yowl <scott.waye@hubse.com>

---------

Co-authored-by: yowl <scott.waye@hubse.com>

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

@@ -137,7 +137,15 @@ private static unsafe object AllocateThreadStaticStorageForType(TypeManagerHandl
                 gcDesc = Internal.Runtime.Augments.RuntimeAugments.TypeLoaderCallbacks.GetThreadStaticGCDescForDynamicType(typeManager, typeTlsIndex);
             }
 
-            return RuntimeImports.RhNewObject((MethodTable*)gcDesc);
+            MethodTable *pMethodTable = (MethodTable*)gcDesc;
+#if FEATURE_64BIT_ALIGNMENT
+            if (pMethodTable->RequiresAlign8)
+            {
+                return InternalCalls.RhpNewFastAlign8(pMethodTable);
+            }
+#endif
+
+            return RuntimeImports.RhNewObject(pMethodTable);
         }
     }
 }

src/tests/nativeaot/SmokeTests/UnitTests/BasicThreading.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -18,6 +19,9 @@ internal static int Run()
 
         ThreadStaticsTestWithTasks.Run();
 
+        if (ThreadStaticAlignmentTest.Run() != Pass)
+            return Fail;
+
         if (ThreadTest.Run() != Pass)
             return Fail;
 
@@ -187,6 +191,59 @@ public static void Run()
     }
 }
 
+class ThreadStaticAlignmentTest
+{
+    public static int Run()
+    {
+        // Check for 8-byte alignment requirement
+        if (RuntimeInformation.ProcessArchitecture is Architecture.Arm or Architecture.Wasm)
+        {
+            // Assume that these are allocated sequentially, use a padding object of size 12 (mod 8 is not 0)
+            // to move the alignment of the second AddressOfReturnArea in case the first is coincidentally aligned 8.
+            var ts1Addr = ThreadStaticAlignCheck1.returnArea.AddressOfReturnArea();
+            var p = new Padder();
+            var ts2Addr = ThreadStaticAlignCheck2.returnArea.AddressOfReturnArea();
+
+            if (((nint)ts1Addr) % 8 != 0)
+                return BasicThreading.Fail;
+            if (((nint)ts2Addr) % 8 != 0)
+                return BasicThreading.Fail;
+        }
+
+        return BasicThreading.Pass;
+    }
+
+    [InlineArray(3)]
+    private struct ReturnArea
+    {
+        private ulong buffer;
+
+        internal unsafe nint AddressOfReturnArea()
+        {
+            return (nint)Unsafe.AsPointer(ref buffer);
+        }
+    }
+
+    private class ThreadStaticAlignCheck1
+    {
+        [ThreadStatic]
+        [FixedAddressValueType]
+        internal static ReturnArea returnArea = default;
+    }
+
+    private class Padder
+    {
+        private object o1;
+    }
+
+    private class ThreadStaticAlignCheck2
+    {
+        [ThreadStatic]
+        [FixedAddressValueType]
+        internal static ReturnArea returnArea = default;
+    }
+}
+
 class ThreadTest
 {
     private static readonly List<Thread> s_startedThreads = new List<Thread>();