Convert ActorIsolationRequest to use split caching

Author: slavapestov

include/swift/AST/Decl.h

@@ -2820,6 +2820,10 @@ class ValueDecl : public Decl {
     /// Whether this declaration produces an implicitly unwrapped
     /// optional result.
     unsigned isIUO : 1;
+
+    /// Whether we're in the common case where the ActorIsolationRequest
+    /// request returned ActorIsolation::forUnspecified().
+    unsigned noActorIsolation : 1;
   } LazySemanticInfo = { };
 
   friend class DynamicallyReplacedDeclRequest;
@@ -2830,6 +2834,7 @@ class ValueDecl : public Decl {
   friend class IsImplicitlyUnwrappedOptionalRequest;
   friend class InterfaceTypeRequest;
   friend class CheckRedeclarationRequest;
+  friend class ActorIsolationRequest;
   friend class Decl;
   SourceLoc getLocFromSource() const { return NameLoc; }
 protected:

include/swift/AST/TypeCheckRequests.h

@@ -1534,7 +1534,8 @@ class GlobalActorAttributeRequest
 class ActorIsolationRequest :
     public SimpleRequest<ActorIsolationRequest,
                          ActorIsolation(ValueDecl *),
-                         RequestFlags::Cached> {
+                         RequestFlags::SeparatelyCached |
+                         RequestFlags::SplitCached> {
 public:
   using SimpleRequest::SimpleRequest;
 
@@ -1544,8 +1545,10 @@ class ActorIsolationRequest :
   ActorIsolation evaluate(Evaluator &evaluator, ValueDecl *value) const;
 
 public:
-  // Caching
+  // Separate.
   bool isCached() const { return true; }
+  std::optional<ActorIsolation> getCachedResult() const;
+  void cacheResult(ActorIsolation value) const;
 };
 
 /// Determine whether the given function should have an isolated 'self'.

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -177,7 +177,7 @@ SWIFT_REQUEST(TypeChecker, GlobalActorAttributeRequest,
               SeparatelyCached | SplitCached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, ActorIsolationRequest,
               ActorIsolationState(ValueDecl *),
-              Cached, NoLocationInfo)
+              SeparatelyCached | SplitCached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, HasIsolatedSelfRequest,
               bool(ValueDecl *),
               Uncached, NoLocationInfo)

lib/AST/TypeCheckRequests.cpp

@@ -1943,6 +1943,28 @@ GlobalActorAttributeRequest::cacheResult(std::optional<CustomAttrNominalPair> va
   }
 }
 
+//----------------------------------------------------------------------------//
+// ActorIsolationRequest computation.
+//----------------------------------------------------------------------------//
+
+std::optional<ActorIsolation> ActorIsolationRequest::getCachedResult() const {
+  auto *decl = std::get<0>(getStorage());
+  if (decl->LazySemanticInfo.noActorIsolation)
+    return ActorIsolation::forUnspecified();
+
+  return decl->getASTContext().evaluator.getCachedNonEmptyOutput(*this);
+}
+
+void ActorIsolationRequest::cacheResult(ActorIsolation value) const {
+  auto *decl = std::get<0>(getStorage());
+  if (value.isUnspecified()) {
+    decl->LazySemanticInfo.noActorIsolation = 1;
+    return;
+  }
+
+  decl->getASTContext().evaluator.cacheNonEmptyOutput(*this, std::move(value));
+}
+
 //----------------------------------------------------------------------------//
 // ResolveMacroRequest computation.
 //----------------------------------------------------------------------------//