Wasm: Enable field reflection (#7022)

Fixes #6944  

This change enables reflection on fields and in doing so fixes some gaps in the `ExternalReferencesTableNode` which fixes reflecting on some types that were not previously caught in the tests.

src/ILCompiler.WebAssembly/src/CodeGen/WebAssemblyObjectWriter.cs

@@ -6,19 +6,15 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Diagnostics;
-using System.Runtime.InteropServices;
 
 using ILCompiler.DependencyAnalysisFramework;
 
 using Internal.Text;
 using Internal.TypeSystem;
-using Internal.TypeSystem.TypesDebugInfo;
 using ObjectData = ILCompiler.DependencyAnalysis.ObjectNode.ObjectData;
 
 using LLVMSharp;
 using ILCompiler.CodeGen;
-using System.Linq;
-using Internal.IL;
 
 namespace ILCompiler.DependencyAnalysis
 {
@@ -36,7 +32,6 @@ namespace ILCompiler.DependencyAnalysis
 
             if (symbol is ObjectNode)
             {
-                ObjectNode objNode = (ObjectNode)symbol;
                 ISymbolDefinitionNode symbolDefNode = (ISymbolDefinitionNode)symbol;
                 if (symbolDefNode.Offset == 0)
                 {
@@ -387,16 +382,8 @@ namespace ILCompiler.DependencyAnalysis
                     if (ObjectSymbolRefs.TryGetValue(curOffset, out symbolRef))
                     {
                         LLVMValueRef pointedAtValue = symbolRef.ToLLVMValueRef(module);
-                        //TODO: why did this come back null
-                        if (pointedAtValue.Pointer != IntPtr.Zero)
-                        {
-                            var ptrValue = LLVM.ConstBitCast(pointedAtValue, intPtrType);
-                            entries.Add(ptrValue);
-                        }
-                        else
-                        {
-                            entries.Add(LLVM.ConstPointerNull(intPtrType));
-                        }
+                        var ptrValue = LLVM.ConstBitCast(pointedAtValue, intPtrType);
+                        entries.Add(ptrValue);
                     }
                     else
                     {
@@ -424,7 +411,6 @@ namespace ILCompiler.DependencyAnalysis
 
         public void DoneObjectNode()
         {
-            int pointerSize = _nodeFactory.Target.PointerSize;
             EmitAlignment(_nodeFactory.Target.PointerSize);
             Debug.Assert(_nodeFactory.Target.PointerSize == 4);
             int countOfPointerSizedElements = _currentObjectData.Count / _nodeFactory.Target.PointerSize;
@@ -837,7 +823,17 @@ namespace ILCompiler.DependencyAnalysis
                                     delta = Relocation.ReadValue(reloc.RelocType, location);
                                 }
                             }
-                            int size = objectWriter.EmitSymbolReference(reloc.Target, (int)delta, reloc.RelocType);
+                            ISymbolNode symbolToWrite = reloc.Target;
+                            var eeTypeNode = reloc.Target as EETypeNode;
+                            if (eeTypeNode != null)
+                            {
+                                if (eeTypeNode.ShouldSkipEmittingObjectNode(factory))
+                                {
+                                    symbolToWrite = factory.ConstructedTypeSymbol(eeTypeNode.Type);
+                                }
+                            }
+
+                            int size = objectWriter.EmitSymbolReference(symbolToWrite, (int)delta, reloc.RelocType);
 
                             /*
                              WebAssembly has no thumb 

src/ILCompiler.WebAssembly/src/Compiler/WebAssemblyMetadataBlockingPolicy.cs

@@ -21,7 +21,7 @@ namespace ILCompiler
 
         public override bool IsBlocked(FieldDesc field)
         {
-            return true;
+            return false;
         }
     }
 }

tests/src/Simple/HelloWasm/Program.cs

@@ -6,6 +6,8 @@ using System;
 using System.Threading;
 using System.Runtime.InteropServices;
 using System.Collections.Generic;
+using System.Reflection;
+
 #if PLATFORM_WINDOWS
 using CpObj;
 #endif
@@ -734,6 +736,7 @@ internal static class Program
 
     [System.Runtime.InteropServices.DllImport("*")]
     private static extern void CallMe(int x);
+
     private static void TestMetaData()
     {
 
@@ -754,15 +757,15 @@ internal static class Program
         var typeofChar = typeof(Char);
         if (typeofChar == null)
         {
-            PrintLine("type == null.  Simple class metadata test: Failed");
+            PrintLine("type == null.  Simple struct metadata test: Failed");
         }
         else
         {
             if (typeofChar.FullName != "System.Char")
             {
-                PrintLine("type != System.Char.  Simple class metadata test: Failed");
+                PrintLine("type != System.Char.  Simple struct metadata test: Failed");
             }
-            else PrintLine("Simple class metadata test (typeof(Char)): Ok.");
+            else PrintLine("Simple struct metadata test (typeof(Char)): Ok.");
         }
 
         var gentT = new Gen<int>();
@@ -801,8 +804,124 @@ internal static class Program
         {
             PrintLine("Ok.");
         }
+
+        PrintString("Type GetFields length: ");
+        var x = new ClassForMetaTests();
+        var s = x.StringField;  
+        var i = x.IntField;
+        var fieldClassType = typeof(ClassForMetaTests);
+        FieldInfo[] fields = fieldClassType.GetFields();
+        if (fields.Length == 3)
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine(" Failed.");
+        }
+
+        PrintString("Type get string field via reflection: ");
+        var stringFieldInfo = fieldClassType.GetField("StringField");
+        if ((string)stringFieldInfo.GetValue(x) == s)
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
+        PrintString("Type get int field via reflection: ");
+        var intFieldInfo = fieldClassType.GetField("IntField");
+        if ((int)intFieldInfo.GetValue(x) == i)
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
+
+        PrintString("Type get static int field via reflection: ");
+        var staticIntFieldInfo = fieldClassType.GetField("StaticIntField");
+        if ((int)staticIntFieldInfo.GetValue(x) == 23)
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
+
+        PrintString("Type set string field via reflection: ");
+        stringFieldInfo.SetValue(x, "bcd");
+        if (x.StringField == "bcd")
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
+
+        PrintString("Type set int field via reflection: ");
+        intFieldInfo.SetValue(x, 456);
+        if (x.IntField == 456)
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
+
+        PrintString("Type set static int field via reflection: ");
+        staticIntFieldInfo.SetValue(x, 987);
+        if (ClassForMetaTests.StaticIntField == 987)
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
+        var st = new StructForMetaTests();
+        st.StringField = "xyz";
+        var fieldStructType = typeof(StructForMetaTests);
+        var structStringFieldInfo = fieldStructType.GetField("StringField");
+        PrintString("Struct get string field via reflection: ");
+        if ((string)structStringFieldInfo.GetValue(st) == "xyz")
+        {
+            PrintLine("Ok.");
+        }
+        else
+        {
+            PrintLine("Failed.");
+        }
     }
 
+    public class ClassForMetaTests
+    {
+        // used via reflection
+#pragma warning disable 0169
+        public int IntField;
+        public string StringField;
+#pragma warning restore 0169
+        public static int StaticIntField;
+
+        public ClassForMetaTests()
+        {
+            StringField = "ab";
+            IntField = 12;
+            StaticIntField = 23;
+        }
+    }
+
+    public struct StructForMetaTests
+    {
+        public string StringField;
+    }
+
+
     /// <summary>
     /// Ensures all of the blocks of a try/finally function are hit when there aren't exceptions
     /// </summary>