TBD: Use SILWitnessVisitor instead of baking in knowledge of witness table layout

Author: slavapestov

include/swift/SIL/SILWitnessVisitor.h

@@ -38,10 +38,12 @@ namespace swift {
 /// physical projection (if we decide to support that).
 ///
 /// You must override the following methods:
+/// - addProtocolConformanceDescriptor()
 /// - addOutOfLineBaseProtocol()
-/// - addMethod()
-/// - addConstructor()
 /// - addAssociatedType()
+/// - addAssociatedConformance()
+/// - addMethod()
+/// - addPlaceholder()
 
 template <class T> class SILWitnessVisitor : public ASTVisitor<T> {
   T &asDerived() { return *static_cast<T*>(this); }

lib/TBDGen/TBDGen.cpp

@@ -28,6 +28,7 @@
 #include "swift/SIL/SILModule.h"
 #include "swift/SIL/SILVTableVisitor.h"
 #include "swift/SIL/SILWitnessTable.h"
+#include "swift/SIL/SILWitnessVisitor.h"
 #include "swift/SIL/TypeLowering.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Error.h"
@@ -280,7 +281,7 @@ void TBDGenVisitor::visitAbstractStorageDecl(AbstractStorageDecl *ASD) {
 
   // Explicitly look at each accessor here: see visitAccessorDecl.
   for (auto accessor : ASD->getAllAccessors()) {
-    visitAbstractFunctionDecl(accessor);
+    visitFuncDecl(accessor);
   }
 }
 
@@ -365,16 +366,8 @@ void TBDGenVisitor::visitClassDecl(ClassDecl *CD) {
 
   // Some members of classes get extra handling, beyond members of struct/enums,
   // so let's walk over them manually.
-  for (auto *member : CD->getMembers()) {
-    auto value = dyn_cast<ValueDecl>(member);
-    if (!value)
-      continue;
-
-    auto var = dyn_cast<VarDecl>(value);
-    auto hasFieldOffset = var && var->hasStorage() && !var->isStatic();
-    if (hasFieldOffset)
-      addSymbol(LinkEntity::forFieldOffset(var));
-  }
+  for (auto *var : CD->getStoredProperties())
+    addSymbol(LinkEntity::forFieldOffset(var));
 
   visitNominalTypeDecl(CD);
 
@@ -465,28 +458,6 @@ void TBDGenVisitor::visitExtensionDecl(ExtensionDecl *ED) {
     visit(member);
 }
 
-/// Determine whether the protocol descriptor for the given protocol will
-/// contain any protocol requirements.
-static bool protocolDescriptorHasRequirements(ProtocolDecl *proto) {
-  if (!proto->getRequirementSignature().empty())
-    return true;
-
-  for (auto *member : proto->getMembers()) {
-    if (auto func = dyn_cast<AbstractFunctionDecl>(member)) {
-      if (SILDeclRef::requiresNewWitnessTableEntry(func))
-        return true;
-    }
-
-    if (auto assocType = dyn_cast<AssociatedTypeDecl>(member)) {
-      if (assocType->getOverriddenDecls().empty()) {
-        return true;
-      }
-    }
-  }
-
-  return false;
-}
-
 #ifndef NDEBUG
 static bool isValidProtocolMemberForTBDGen(const Decl *D) {
   switch (D->getKind()) {
@@ -530,45 +501,45 @@ void TBDGenVisitor::visitProtocolDecl(ProtocolDecl *PD) {
   if (!PD->isObjC()) {
     addSymbol(LinkEntity::forProtocolDescriptor(PD));
 
-    // If there are any requirements, emit a requirements base descriptor.
-    if (protocolDescriptorHasRequirements(PD))
-      addProtocolRequirementsBaseDescriptor(PD);
-
-    for (const auto &req : PD->getRequirementSignature()) {
-      if (req.getKind() != RequirementKind::Conformance)
-        continue;
-
-      if (req.getFirstType()->isEqual(PD->getSelfInterfaceType())) {
-        BaseConformance conformance(
-          PD,
-          req.getSecondType()->castTo<ProtocolType>()->getDecl());
-        addBaseConformanceDescriptor(conformance);
-      } else {
-        AssociatedConformance conformance(
-          PD,
-          req.getFirstType()->getCanonicalType(),
-          req.getSecondType()->castTo<ProtocolType>()->getDecl());
-        addAssociatedConformanceDescriptor(conformance);
-      }
-    }
+    struct WitnessVisitor : public SILWitnessVisitor<WitnessVisitor> {
+      TBDGenVisitor &TBD;
+      ProtocolDecl *PD;
 
-    for (auto *member : PD->getMembers()) {
-      if (PD->isResilient()) {
-        if (auto *funcDecl = dyn_cast<AbstractFunctionDecl>(member)) {
-          if (SILDeclRef::requiresNewWitnessTableEntry(funcDecl)) {
-            addDispatchThunk(SILDeclRef(funcDecl));
-            addMethodDescriptor(SILDeclRef(funcDecl));
-          }
+    public:
+      WitnessVisitor(TBDGenVisitor &TBD, ProtocolDecl *PD)
+          : TBD(TBD), PD(PD) {}
+
+      void addMethod(SILDeclRef declRef) {
+        if (PD->isResilient()) {
+          TBD.addDispatchThunk(declRef);
+          TBD.addMethodDescriptor(declRef);
         }
       }
 
-      // Always produce associated type descriptors, because they can
-      // be referenced by generic signatures.
-      if (auto *assocType = dyn_cast<AssociatedTypeDecl>(member)) {
-        if (assocType->getOverriddenDecls().empty())
-          addAssociatedTypeDescriptor(assocType);
+      void addAssociatedType(AssociatedType associatedType) {
+        TBD.addAssociatedTypeDescriptor(associatedType.getAssociation());
       }
-    }
+
+      void addProtocolConformanceDescriptor() {
+        TBD.addProtocolRequirementsBaseDescriptor(PD);
+      }
+
+      void addOutOfLineBaseProtocol(ProtocolDecl *proto) {
+        TBD.addBaseConformanceDescriptor(BaseConformance(PD, proto));
+      }
+
+      void addAssociatedConformance(AssociatedConformance associatedConf) {
+        TBD.addAssociatedConformanceDescriptor(associatedConf);
+      }
+
+      void addPlaceholder(MissingMemberDecl *decl) {}
+
+      void doIt() {
+        visitProtocolDecl(PD);
+      }
+    };
+
+    WitnessVisitor(*this, PD).doIt();
 
     // Include the self-conformance.
     addConformances(PD);