SILGen: Refactor key path component lowering.

include/swift/AST/Expr.h

@@ -4909,7 +4909,7 @@ class KeyPathExpr : public Expr {
       case Kind::OptionalForce:
       case Kind::UnresolvedProperty:
       case Kind::Property:
-        llvm_unreachable("no index expr for this kind");
+        return nullptr;
       }
     }
 
@@ -4942,7 +4942,7 @@ class KeyPathExpr : public Expr {
       case Kind::OptionalForce:
       case Kind::UnresolvedProperty:
       case Kind::Property:
-        llvm_unreachable("no hashable conformances for this kind");
+        return {};
       }
     }
 

lib/SILGen/SILGen.cpp

@@ -1158,6 +1158,53 @@ void SILGenModule::visitVarDecl(VarDecl *vd) {
     if (auto setter = vd->getSetter())
       emitFunction(setter);
   }
+
+  tryEmitPropertyDescriptor(vd);
+}
+
+static bool doesPropertyNeedDescriptor(AbstractStorageDecl *decl) {
+  // The storage needs a descriptor if it sits at a module's ABI boundary,
+  // meaning it has public linkage.
+
+  // Any property that's potentially resilient should have accessors
+  // synthesized.
+  if (!decl->getGetter())
+    return false;
+
+  // TODO: If previous versions of an ABI-stable binary needed the descriptor,
+  // then we still do.
+
+  auto getter = SILDeclRef(decl->getGetter());
+  auto getterLinkage = getter.getLinkage(ForDefinition);
+
+  switch (getterLinkage) {
+  case SILLinkage::Public:
+  case SILLinkage::PublicNonABI:
+    // We may need a descriptor.
+    break;
+
+  case SILLinkage::Shared:
+  case SILLinkage::Private:
+  case SILLinkage::Hidden:
+    // Don't need a public descriptor.
+    return false;
+
+  case SILLinkage::HiddenExternal:
+  case SILLinkage::PrivateExternal:
+  case SILLinkage::PublicExternal:
+  case SILLinkage::SharedExternal:
+    llvm_unreachable("should be definition linkage?");
+  }
+
+  // TODO: We might be able to avoid a descriptor if the property is committed
+  // to being implemented a certain way, such as if it's promised to remain
+  // stored, or is computed with inlinable accessors, and can't change its
+  // mutability (because it's already promised to be mutable or fully immutable).
+  return true;
+}
+
+void SILGenModule::tryEmitPropertyDescriptor(AbstractStorageDecl *decl) {
+  // TODO
 }
 
 void SILGenModule::emitPropertyBehavior(VarDecl *vd) {

lib/SILGen/SILGen.h

@@ -333,6 +333,12 @@ class LLVM_LIBRARY_VISIBILITY SILGenModule : public ASTVisitor<SILGenModule> {
   /// Emit a global initialization.
   void emitGlobalInitialization(PatternBindingDecl *initializer, unsigned elt);
 
+  SILDeclRef getGetterDeclRef(AbstractStorageDecl *decl);
+  SILDeclRef getSetterDeclRef(AbstractStorageDecl *decl);
+  SILDeclRef getAddressorDeclRef(AbstractStorageDecl *decl,
+                                 AccessKind accessKind);
+  SILDeclRef getMaterializeForSetDeclRef(AbstractStorageDecl *decl);
+
   /// Known functions for bridging.
   SILDeclRef getStringToNSStringFn();
   SILDeclRef getNSStringToStringFn();
@@ -421,6 +427,9 @@ class LLVM_LIBRARY_VISIBILITY SILGenModule : public ASTVisitor<SILGenModule> {
   SubstitutionList
   getNonMemberVarDeclSubstitutions(VarDecl *var);
 
+  /// Emit a property descriptor for the given storage decl if it needs one.
+  void tryEmitPropertyDescriptor(AbstractStorageDecl *decl);
+
 private:
   /// Emit the deallocator for a class that uses the objc allocator.
   void emitObjCAllocatorDestructor(ClassDecl *cd, DestructorDecl *dd);

lib/SILGen/SILGenApply.cpp

@@ -5015,7 +5015,7 @@ ArgumentSource SILGenFunction::prepareAccessorBaseArg(SILLocation loc,
   return Preparer.prepare();
 }
 
-SILDeclRef SILGenFunction::getGetterDeclRef(AbstractStorageDecl *storage) {
+SILDeclRef SILGenModule::getGetterDeclRef(AbstractStorageDecl *storage) {
   auto *getter = storage->getGetter();
   return SILDeclRef(getter, SILDeclRef::Kind::Func)
     .asForeign(requiresForeignEntryPoint(getter));
@@ -5054,7 +5054,7 @@ emitGetAccessor(SILLocation loc, SILDeclRef get,
   return emission.apply(c);
 }
 
-SILDeclRef SILGenFunction::getSetterDeclRef(AbstractStorageDecl *storage) {
+SILDeclRef SILGenModule::getSetterDeclRef(AbstractStorageDecl *storage) {
   auto *setter = storage->getSetter();
   return SILDeclRef(setter, SILDeclRef::Kind::Func)
     .asForeign(requiresForeignEntryPoint(setter));
@@ -5120,7 +5120,7 @@ void SILGenFunction::emitSetAccessor(SILLocation loc, SILDeclRef set,
 }
 
 SILDeclRef
-SILGenFunction::getMaterializeForSetDeclRef(AbstractStorageDecl *storage) {
+SILGenModule::getMaterializeForSetDeclRef(AbstractStorageDecl *storage) {
   return SILDeclRef(storage->getMaterializeForSetFunc(),
                     SILDeclRef::Kind::Func);
 }
@@ -5197,8 +5197,8 @@ emitMaterializeForSetAccessor(SILLocation loc, SILDeclRef materializeForSet,
                             optionalCallback, callbackStorage);
 }
 
-SILDeclRef SILGenFunction::getAddressorDeclRef(AbstractStorageDecl *storage,
-                                               AccessKind accessKind) {
+SILDeclRef SILGenModule::getAddressorDeclRef(AbstractStorageDecl *storage,
+                                             AccessKind accessKind) {
   FuncDecl *addressorFunc = storage->getAddressorForAccess(accessKind);
   return SILDeclRef(addressorFunc, SILDeclRef::Kind::Func);
 }