[mtouch] Give BuildTasks enough information to determine if the task is up-to-date or not.

tools/common/BuildTasks.cs

@@ -40,6 +40,9 @@ namespace Xamarin.Bundler
 		public IEnumerable<BuildTask> NextTasks;
 
 		protected abstract void Execute ();
+		
+		// A list of input files (not a list of all the dependencies that would make this task rebuild).
+		public abstract IEnumerable<string> Inputs { get; }
 
 		public IEnumerable<BuildTask> Run ()
 		{
@@ -47,9 +50,21 @@ namespace Xamarin.Bundler
 			return NextTasks;
 		}
 
-		public virtual bool IsUptodate ()
-		{
-			return false;
+		public virtual bool IsUptodate {
+			get {
+				return Application.IsUptodate (FileDependencies, Outputs);
+			}
 		}
+
+		// A list of all the files that causes the task to rebuild.
+		// This should at least include all the 'Inputs', and potentially other files as well.
+		public virtual IEnumerable<string> FileDependencies {
+			get {
+				return Inputs;
+			}
+		}
+
+		// A list of files that this task outputs.
+		public abstract IEnumerable<string> Outputs { get; }
 	}
 }

tools/common/CompilerFlags.cs

@@ -299,5 +299,12 @@ namespace Xamarin.Utils
 			WriteArguments (args);
 			return args.ToString ();
 		}
+
+		public void PopulateInputs ()
+		{
+			var args = new StringBuilder ();
+			Inputs = new List<string> ();
+			WriteArguments (args);
+		}
 	}
 }

tools/mtouch/Assembly.cs

@@ -282,8 +282,10 @@ namespace Xamarin.Bundler {
 
 			return new BuildTask [] { new AOTTask ()
 				{
+					Assembly = this,
 					AssemblyName = s,
 					AddBitcodeMarkerSection = App.FastDev && App.EnableMarkerOnlyBitCode,
+					AotOutputs = outputs,
 					AssemblyPath = asm,
 					ProcessStartInfo = Driver.CreateStartInfo (App, aotCompiler, aotArgs, Path.GetDirectoryName (s)),
 					NextTasks = nextTasks

tools/mtouch/BuildTasks.mtouch.cs

@@ -88,13 +88,19 @@ namespace Xamarin.Bundler
 		public string MainM;
 		public IList<string> RegistrationMethods;
 
-		public IEnumerable<string> Inputs {
+		public override IEnumerable<string> Inputs {
 			get {
 				foreach (var asm in Target.Assemblies)
 					yield return asm.FullPath;
 			}
 		}
 
+		public override IEnumerable<string> Outputs {
+			get {
+				yield return MainM;
+			}
+		}
+
 		protected override void Execute ()
 		{
 			Driver.GenerateMain (Target.App, Target.Assemblies, Target.App.AssemblyName, Abi, MainM, RegistrationMethods);
@@ -123,6 +129,20 @@ namespace Xamarin.Bundler
 		public string RegistrarM;
 		public string RegistrarH;
 
+		public override IEnumerable<string> Inputs {
+			get {
+				foreach (var asm in Target.Assemblies)
+					yield return asm.FullPath;
+			}
+		}
+
+		public override IEnumerable<string> Outputs {
+			get {
+				yield return RegistrarH;
+				yield return RegistrarM;
+			}
+		}
+
 		protected override void Execute ()
 		{
 			Target.StaticRegistrar.Generate (Target.Assemblies.Select ((a) => a.AssemblyDefinition), RegistrarH, RegistrarM);
@@ -131,6 +151,16 @@ namespace Xamarin.Bundler
 
 	class CompileRegistrarTask : CompileTask
 	{
+		public string RegistrarM;
+		public string RegistrarH;
+
+		public override IEnumerable<string> Inputs {
+			get {
+				yield return RegistrarH;
+				yield return RegistrarM;
+			}
+		}
+
 		protected override void CompilationFailed (int exitCode)
 		{
 			throw ErrorHelper.CreateError (4109, "Failed to compile the generated registrar code. Please file a bug report at http://bugzilla.xamarin.com");
@@ -139,9 +169,44 @@ namespace Xamarin.Bundler
 
 	public class AOTTask : ProcessTask
 	{
+		public Assembly Assembly;
 		public string AssemblyName;
 		public bool AddBitcodeMarkerSection;
 		public string AssemblyPath; // path to the .s file.
+		List<string> inputs;
+		public IEnumerable<string> AotOutputs;
+
+		public override IEnumerable<string> Outputs {
+			get {
+				return AotOutputs;
+			}
+		}
+
+		public override IEnumerable<string> Inputs {
+			get {
+				yield return Assembly.FullPath;
+			}
+		}
+
+		public override IEnumerable<string> FileDependencies {
+			get {
+				if (inputs == null) {
+					inputs = new List<string> ();
+					if (Assembly.HasDependencyMap)
+						inputs.AddRange (Assembly.DependencyMap);
+					inputs.Add (AssemblyName);
+					inputs.Add (Driver.GetAotCompiler (Assembly.App, Assembly.Target.Is64Build));
+				}
+				return inputs;
+			}
+		}
+
+		public override bool IsUptodate {
+			get {
+				// We can only check dependencies if we know the assemblies this assembly depend on (otherwise always rebuild).
+				return Assembly.HasDependencyMap && base.IsUptodate;
+			}
+		}
 
 		// executed with Parallel.ForEach
 		protected override void Execute ()
@@ -181,6 +246,19 @@ namespace Xamarin.Bundler
 		public string OutputFile;
 		public CompilerFlags CompilerFlags;
 
+		public override IEnumerable<string> Inputs {
+			get {
+				CompilerFlags.PopulateInputs ();
+				return CompilerFlags.Inputs;
+			}
+		}
+
+		public override IEnumerable<string> Outputs {
+			get {
+				yield return OutputFile;
+			}
+		}
+
 		protected override void Execute ()
 		{
 			// always show the native linker warnings since many of them turn out to be very important
@@ -245,6 +323,19 @@ namespace Xamarin.Bundler
 		public string InstallName;
 		public string Language;
 
+		public override IEnumerable<string> Inputs {
+			get {
+				CompilerFlags.PopulateInputs ();
+				return CompilerFlags.Inputs;
+			}
+		}
+
+		public override IEnumerable<string> Outputs {
+			get {
+				yield return OutputFile;
+			}
+		}
+
 		public bool IsAssembler {
 			get {
 				return Language == "assembler";
@@ -414,6 +505,18 @@ namespace Xamarin.Bundler
 		public Abi Abi { get; set; }
 		public Version DeploymentTarget { get; set; }
 
+		public override IEnumerable<string> Inputs {
+			get {
+				yield return Input;
+			}
+		}
+
+		public override IEnumerable<string> Outputs {
+			get {
+				yield return OutputFile;
+			}
+		}
+
 		protected override void Execute ()
 		{
 			new BitcodeConverter (Input, OutputFile, Platform, Abi, DeploymentTarget).Convert ();

tools/mtouch/Target.cs

@@ -724,6 +724,8 @@ namespace Xamarin.Bundler
 							Abi = abi,
 							InputFile = registrar_m,
 							OutputFile = ofile,
+							RegistrarM = registrar_m,
+							RegistrarH = registrar_h,
 							SharedLibrary = false,
 							Language = "objective-c++",
 						};