android: Allow running some singletons in parallel.

Many of the singletons are trivial and can be run in parallel, improving
the performance during analysis.

Bug: 281536768
Test: manual, presubmit
Change-Id: I989333e2ff3fe71783601f27bf5e0732a1b4ea61
diff --git a/android/register.go b/android/register.go
index 1a3db9d..c57964c 100644
--- a/android/register.go
+++ b/android/register.go
@@ -65,16 +65,19 @@
 	// True if this should be registered as a pre-singleton, false otherwise.
 	pre bool
 
+	// True if this should be registered as a parallel singleton.
+	parallel bool
+
 	name    string
 	factory SingletonFactory
 }
 
-func newSingleton(name string, factory SingletonFactory) singleton {
-	return singleton{false, name, factory}
+func newSingleton(name string, factory SingletonFactory, parallel bool) singleton {
+	return singleton{pre: false, parallel: parallel, name: name, factory: factory}
 }
 
 func newPreSingleton(name string, factory SingletonFactory) singleton {
-	return singleton{true, name, factory}
+	return singleton{pre: true, parallel: false, name: name, factory: factory}
 }
 
 func (s singleton) componentName() string {
@@ -86,7 +89,7 @@
 	if s.pre {
 		ctx.RegisterPreSingletonType(s.name, adaptor)
 	} else {
-		ctx.RegisterSingletonType(s.name, adaptor)
+		ctx.RegisterSingletonType(s.name, adaptor, s.parallel)
 	}
 }
 
@@ -145,8 +148,16 @@
 	moduleTypeByFactory[factory] = name
 }
 
+func registerSingletonType(name string, factory SingletonFactory, parallel bool) {
+	singletons = append(singletons, newSingleton(name, factory, parallel))
+}
+
 func RegisterSingletonType(name string, factory SingletonFactory) {
-	singletons = append(singletons, newSingleton(name, factory))
+	registerSingletonType(name, factory, false)
+}
+
+func RegisterParallelSingletonType(name string, factory SingletonFactory) {
+	registerSingletonType(name, factory, true)
 }
 
 func RegisterPreSingletonType(name string, factory SingletonFactory) {
@@ -220,17 +231,17 @@
 func collateGloballyRegisteredSingletons() sortableComponents {
 	allSingletons := append(sortableComponents(nil), singletons...)
 	allSingletons = append(allSingletons,
-		singleton{false, "bazeldeps", BazelSingleton},
+		singleton{pre: false, parallel: false, name: "bazeldeps", factory: BazelSingleton},
 
 		// Register phony just before makevars so it can write out its phony rules as Make rules
-		singleton{false, "phony", phonySingletonFactory},
+		singleton{pre: false, parallel: false, name: "phony", factory: phonySingletonFactory},
 
 		// Register makevars after other singletons so they can export values through makevars
-		singleton{false, "makevars", makeVarsSingletonFunc},
+		singleton{pre: false, parallel: false, name: "makevars", factory: makeVarsSingletonFunc},
 
 		// Register env and ninjadeps last so that they can track all used environment variables and
 		// Ninja file dependencies stored in the config.
-		singleton{false, "ninjadeps", ninjaDepsSingletonFactory},
+		singleton{pre: false, parallel: false, name: "ninjadeps", factory: ninjaDepsSingletonFactory},
 	)
 
 	return allSingletons
@@ -259,7 +270,9 @@
 type RegistrationContext interface {
 	RegisterModuleType(name string, factory ModuleFactory)
 	RegisterSingletonModuleType(name string, factory SingletonModuleFactory)
+	RegisterParallelSingletonModuleType(name string, factory SingletonModuleFactory)
 	RegisterPreSingletonType(name string, factory SingletonFactory)
+	RegisterParallelSingletonType(name string, factory SingletonFactory)
 	RegisterSingletonType(name string, factory SingletonFactory)
 	PreArchMutators(f RegisterMutatorFunc)
 
@@ -315,8 +328,15 @@
 }
 
 func (ctx *initRegistrationContext) RegisterSingletonModuleType(name string, factory SingletonModuleFactory) {
+	ctx.registerSingletonModuleType(name, factory, false)
+}
+func (ctx *initRegistrationContext) RegisterParallelSingletonModuleType(name string, factory SingletonModuleFactory) {
+	ctx.registerSingletonModuleType(name, factory, true)
+}
+
+func (ctx *initRegistrationContext) registerSingletonModuleType(name string, factory SingletonModuleFactory, parallel bool) {
 	s, m := SingletonModuleFactoryAdaptor(name, factory)
-	ctx.RegisterSingletonType(name, s)
+	ctx.registerSingletonType(name, s, parallel)
 	ctx.RegisterModuleType(name, m)
 	// Overwrite moduleTypesForDocs with the original factory instead of the lambda returned by
 	// SingletonModuleFactoryAdaptor so that docs can find the module type documentation on the
@@ -324,12 +344,20 @@
 	RegisterModuleTypeForDocs(name, reflect.ValueOf(factory))
 }
 
-func (ctx *initRegistrationContext) RegisterSingletonType(name string, factory SingletonFactory) {
+func (ctx *initRegistrationContext) registerSingletonType(name string, factory SingletonFactory, parallel bool) {
 	if _, present := ctx.singletonTypes[name]; present {
 		panic(fmt.Sprintf("singleton type %q is already registered", name))
 	}
 	ctx.singletonTypes[name] = factory
-	RegisterSingletonType(name, factory)
+	registerSingletonType(name, factory, parallel)
+}
+
+func (ctx *initRegistrationContext) RegisterSingletonType(name string, factory SingletonFactory) {
+	ctx.registerSingletonType(name, factory, false)
+}
+
+func (ctx *initRegistrationContext) RegisterParallelSingletonType(name string, factory SingletonFactory) {
+	ctx.registerSingletonType(name, factory, true)
 }
 
 func (ctx *initRegistrationContext) RegisterPreSingletonType(name string, factory SingletonFactory) {