[mono] Perform the class init at runtime when static fields of BEFORE_FIELD_INIT type are accessed

src/mono/mono/mini/method-to-ir.c

@@ -4190,11 +4190,6 @@ mini_field_access_needs_cctor_run (MonoCompile *cfg, MonoMethod *method, MonoCla
 			return FALSE;
 	}
 
-	if (mono_class_is_before_field_init (klass)) {
-		if (cfg->method == method)
-			return FALSE;
-	}
-
 	if (!mono_class_needs_cctor_run (klass, method))
 		return FALSE;
 

src/mono/mono/mini/mini-runtime.c

@@ -1565,7 +1565,7 @@ mono_resolve_patch_target_ext (MonoMemoryManager *mem_manager, MonoMethod *metho
 			return addr;
 		}
 
-		if (!vtable->initialized && !mono_class_is_before_field_init (vtable->klass) && (!method || mono_class_needs_cctor_run (vtable->klass, method)))
+		if (!vtable->initialized && (!method || mono_class_needs_cctor_run (vtable->klass, method)))
 			/* Done by the generated code */
 			;
 		else {

src/tests/JIT/Methodical/beforefieldinit/StaticFieldInit.cs

@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+
+static class C
+{
+    public static int retVal = 100;
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    public static int TestMethod(bool cond)
+    {
+        if (cond)
+        {
+            // never invoked in this program
+            return ClassB.X;
+        }
+        // always taken
+        return 0;
+    }
+}
+
+public class ClassB
+{
+    public static readonly int X = GetX();
+
+    static int GetX()
+    {
+        Console.WriteLine("GetX call!..."); // not expected to be invoked in this program
+        C.retVal = 42;
+        return 42;
+    }
+}
+
+public class StaticFieldInit
+{
+    public static int Main () {
+        C.TestMethod(false);
+
+        return C.retVal;
+    }
+}

src/tests/JIT/Methodical/beforefieldinit/StaticFieldInit.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>PdbOnly</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="StaticFieldInit.cs" />
+  </ItemGroup>
+</Project>