Fix performance of AddXmlDocumentationTransform

ICSharpCode.Decompiler/CSharp/Transforms/AddXmlDocumentationTransform.cs

@@ -34,6 +34,9 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 		{
 			if (!context.Settings.ShowXmlDocumentation)
 				return;
+			var xmldoc = XmlDocLoader.LoadDocumentation(context.TypeSystem.ModuleDefinition);
+			if (xmldoc == null)
+				return;
 			foreach (var entity in rootNode.DescendantsAndSelf.OfType<EntityDeclaration>()) {
 				var symbol = entity.GetSymbol();
 				Mono.Cecil.MemberReference mr;
@@ -47,14 +50,9 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					default:
 						continue;
 				}
-				if (mr != null && mr.Module != null) {
+				string doc = xmldoc.GetDocumentation(XmlDocKeyProvider.GetKey(mr));
-					var xmldoc = XmlDocLoader.LoadDocumentation(mr.Module);
+				if (doc != null) {
-					if (xmldoc != null) {
+					InsertXmlDocumentation(entity, new StringReader(doc));
-						string doc = xmldoc.GetDocumentation(XmlDocKeyProvider.GetKey(mr));
-						if (doc != null) {
-							InsertXmlDocumentation(entity, new StringReader(doc));
-						}
-					}
 				}
 			}
 		}

ICSharpCode.Decompiler/Documentation/XmlDocLoader.cs

@@ -62,6 +62,7 @@ namespace ICSharpCode.Decompiler.Documentation
 						xmlDoc = new XmlDocumentationProvider(xmlDocFile);
 						cache.Add(module, xmlDoc);
 					} else {
+						cache.Add(module, null); // add missing documentation files as well
 						xmlDoc = null;
 					}
 				}