Convert DynamicallyReplacedDeclRequest to use split caching

Author: slavapestov

include/swift/AST/Decl.h

@@ -2807,6 +2807,10 @@ class ValueDecl : public Decl {
     /// allows the entity to be replaced at runtime.
     unsigned isDynamic : 1;
 
+    /// Whether the DynamicallyReplacedDeclRequest request was evaluated and
+    /// output a null pointer.
+    unsigned noDynamicallyReplacedDecl : 1;
+
     /// Whether the "isFinal" bit has been computed yet.
     unsigned isFinalComputed : 1;
 
@@ -2835,6 +2839,7 @@ class ValueDecl : public Decl {
   friend class InterfaceTypeRequest;
   friend class CheckRedeclarationRequest;
   friend class ActorIsolationRequest;
+  friend class DynamicallyReplacedDeclRequest;
   friend class Decl;
   SourceLoc getLocFromSource() const { return NameLoc; }
 protected:

include/swift/AST/TypeCheckRequests.h

@@ -3270,7 +3270,9 @@ class CallerSideDefaultArgExprRequest
 
 class DynamicallyReplacedDeclRequest
     : public SimpleRequest<DynamicallyReplacedDeclRequest,
-                           ValueDecl *(ValueDecl *), RequestFlags::Cached> {
+                           ValueDecl *(ValueDecl *),
+                           RequestFlags::SeparatelyCached |
+                           RequestFlags::SplitCached> {
 public:
   using SimpleRequest::SimpleRequest;
 
@@ -3281,8 +3283,11 @@ class DynamicallyReplacedDeclRequest
   ValueDecl * evaluate(Evaluator &evaluator, ValueDecl *VD) const;
 
 public:
-  // Caching.
+  // Separate caching.
   bool isCached() const { return true; }
+  std::optional<ValueDecl *> getCachedResult() const;
+  void cacheResult(ValueDecl *result) const;
+
 };
 
 class SpecializeAttrTargetDeclRequest

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -86,7 +86,7 @@ SWIFT_REQUEST(TypeChecker, TypeEraserHasViableInitRequest,
               Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, DynamicallyReplacedDeclRequest,
               ValueDecl *(ValueDecl *),
-              Cached, NoLocationInfo)
+              SeparatelyCached | SplitCached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, ABIMembersRequest,
               ArrayRef<Decl *>(IterableDeclContext *), Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, AllMembersRequest,

lib/AST/TypeCheckRequests.cpp

@@ -351,6 +351,31 @@ void IsDynamicRequest::cacheResult(bool value) const {
     decl->getAttrs().add(new (decl->getASTContext()) DynamicAttr(/*Implicit=*/true));
 }
 
+//----------------------------------------------------------------------------//
+// DynamicallyReplacedDeclRequest computation.
+//----------------------------------------------------------------------------//
+
+std::optional<ValueDecl *> DynamicallyReplacedDeclRequest::getCachedResult() const {
+  auto *decl = std::get<0>(getStorage());
+
+  if (decl->LazySemanticInfo.noDynamicallyReplacedDecl)
+    return std::optional(nullptr);
+
+  return decl->getASTContext().evaluator.getCachedNonEmptyOutput(*this);
+}
+
+
+void DynamicallyReplacedDeclRequest::cacheResult(ValueDecl *result) const {
+  auto *decl = std::get<0>(getStorage());
+
+  if (!result) {
+    decl->LazySemanticInfo.noDynamicallyReplacedDecl = 1;
+    return;
+  }
+
+  decl->getASTContext().evaluator.cacheNonEmptyOutput(*this, std::move(result));
+}
+
 //----------------------------------------------------------------------------//
 // RequirementSignatureRequest computation.
 //----------------------------------------------------------------------------//