Merge pull request #18100 from jckarter/keypath-external-irgen

IRGen and runtime support for key path resilience.

Author: jckarter

include/swift/ABI/KeyPath.h

@@ -190,7 +190,7 @@ class KeyPathComponentHeader {
                       bool resolvedID) {
     return KeyPathComponentHeader(
       (_SwiftKeyPathComponentHeader_ComputedTag
-      << _SwiftKeyPathComponentHeader_DiscriminatorShift)
+        << _SwiftKeyPathComponentHeader_DiscriminatorShift)
       | (kind != GetOnly
            ? _SwiftKeyPathComponentHeader_ComputedSettableFlag : 0)
       | (kind == SettableMutating
@@ -205,10 +205,14 @@ class KeyPathComponentHeader {
   }
 
   constexpr static KeyPathComponentHeader
-  forExternalComponent() {
-    return KeyPathComponentHeader(
-      _SwiftKeyPathComponentHeader_ExternalTag
-      << _SwiftKeyPathComponentHeader_DiscriminatorShift);
+  forExternalComponent(unsigned numSubstitutions) {
+    return assert(numSubstitutions <
+        (1u << _SwiftKeyPathComponentHeader_DiscriminatorShift) - 1u
+        && "too many substitutions"),
+      KeyPathComponentHeader(
+        (_SwiftKeyPathComponentHeader_ExternalTag
+          << _SwiftKeyPathComponentHeader_DiscriminatorShift)
+        | numSubstitutions);
   }
 
   constexpr uint32_t getData() const { return Data; }

include/swift/AST/Decl.h

@@ -4438,6 +4438,10 @@ class AbstractStorageDecl : public ValueDecl {
   BehaviorRecord *getMutableBehavior() {
     return BehaviorInfo.getPointer();
   }
+  
+  /// True if the storage exports a property descriptor for key paths in
+  /// other modules.
+  bool exportsPropertyDescriptor() const;
 
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) {

lib/IRGen/GenKeyPath.cpp

@@ -702,6 +702,27 @@ emitMetadataGeneratorForKeyPath(IRGenModule &IGM,
     });
 };
 
+static llvm::Function *
+emitWitnessTableGeneratorForKeyPath(IRGenModule &IGM,
+                                    CanType type,
+                                    ProtocolConformanceRef conformance,
+                                    GenericEnvironment *genericEnv,
+                                    ArrayRef<GenericRequirement> requirements) {
+  // TODO: Use the standard conformance accessor when there are no arguments
+  // and the conformance accessor is defined.
+  return emitGeneratorForKeyPath(IGM, "keypath_get_witness_table", type,
+    IGM.WitnessTablePtrTy,
+    genericEnv, requirements,
+    [&](IRGenFunction &IGF, CanType substType) {
+      if (type->hasTypeParameter())
+        conformance = conformance.subst(type,
+          QueryInterfaceTypeSubstitutions(genericEnv),
+          LookUpConformanceInSignature(*genericEnv->getGenericSignature()));
+      auto ret = emitWitnessTableRef(IGF, substType, conformance);
+      IGF.Builder.CreateRet(ret);
+    });
+}
+
 static void
 emitKeyPathComponent(IRGenModule &IGM,
                      ConstantStructBuilder &fields,
@@ -815,6 +836,46 @@ emitKeyPathComponent(IRGenModule &IGM,
   }
   case KeyPathPatternComponent::Kind::GettableProperty:
   case KeyPathPatternComponent::Kind::SettableProperty: {
+    // If the component references an external property, encode that in a
+    // header before the local attempt header, so that we can consult the
+    // external descriptor at instantiation time.
+    if (auto externalDecl = component.getExternalDecl()) {
+      SmallVector<llvm::Constant *, 4> externalSubArgs;
+      auto componentSig = externalDecl->getInnermostDeclContext()
+        ->getGenericSignatureOfContext();
+      auto subs = component.getExternalSubstitutions();
+      if (!subs.empty()) {
+        enumerateGenericSignatureRequirements(
+          componentSig->getCanonicalSignature(),
+          [&](GenericRequirement reqt) {
+            auto substType = reqt.TypeParameter.subst(subs)
+              ->getCanonicalType();
+            if (!reqt.Protocol) {
+              // Type requirement.
+              externalSubArgs.push_back(
+                emitMetadataGeneratorForKeyPath(IGM, substType,
+                                                genericEnv, requirements));
+            } else {
+              // Protocol requirement.
+              auto conformance = subs.lookupConformance(
+                           reqt.TypeParameter->getCanonicalType(), reqt.Protocol);
+              externalSubArgs.push_back(
+                emitWitnessTableGeneratorForKeyPath(IGM, substType,
+                                                    *conformance,
+                                                    genericEnv, requirements));
+            }
+          });
+      }
+      fields.addInt32(
+        KeyPathComponentHeader::forExternalComponent(externalSubArgs.size())
+          .getData());
+      fields.addAlignmentPadding(IGM.getPointerAlignment());
+      auto descriptor = IGM.getAddrOfPropertyDescriptor(externalDecl);
+      fields.add(descriptor);
+      for (auto *arg : externalSubArgs)
+        fields.add(arg);
+    }
+  
     // Encode the settability.
     bool settable = kind == KeyPathPatternComponent::Kind::SettableProperty;
     KeyPathComponentHeader::ComputedPropertyKind componentKind;

lib/SIL/SIL.cpp

@@ -208,3 +208,49 @@ bool SILModule::isTypeABIAccessible(SILType type) {
   // Otherwise, we need to be able to fetch layout-metadata for the type.
   return isTypeMetadataForLayoutAccessible(*this, type);
 }
+
+bool AbstractStorageDecl::exportsPropertyDescriptor() const {
+  // The storage needs a descriptor if it sits at a module's ABI boundary,
+  // meaning it has public linkage.
+  
+  // TODO: Global and static properties ought to eventually be referenceable
+  // as key paths from () or T.Type too.
+  if (!getDeclContext()->isTypeContext() || isStatic())
+    return false;
+  
+  // Any property that's potentially resilient should have accessors
+  // synthesized.
+  if (!getGetter())
+    return false;
+
+  // If the getter is mutating, we cannot form a keypath to it at all.
+  if (isGetterMutating())
+    return false;
+
+  // TODO: If previous versions of an ABI-stable binary needed the descriptor,
+  // then we still do.
+
+  auto getter = SILDeclRef(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?");
+  }
+
+  return true;
+}

lib/SIL/SILDeclRef.cpp

@@ -314,8 +314,19 @@ SILLinkage SILDeclRef::getLinkage(ForDefinition_t forDefinition) const {
       neverPublic = true;
     }
   }
+  
+  auto effectiveAccess = d->getEffectiveAccess();
+  
+  // Private setter implementations for an internal storage declaration should
+  // be internal as well, so that a dynamically-writable
+  // keypath can be formed from other files.
+  if (auto accessor = dyn_cast<AccessorDecl>(d)) {
+    if (accessor->isSetter()
+       && accessor->getStorage()->getEffectiveAccess() == AccessLevel::Internal)
+      effectiveAccess = AccessLevel::Internal;
+  }
 
-  switch (d->getEffectiveAccess()) {
+  switch (effectiveAccess) {
   case AccessLevel::Private:
   case AccessLevel::FilePrivate:
     return maybeAddExternal(SILLinkage::Private);

lib/SIL/SILVerifier.cpp

@@ -232,11 +232,15 @@ void verifyKeyPathComponent(SILModule &M,
               && !component.getSubscriptIndexEquals()
               && !component.getSubscriptIndexHash(),
               "property descriptor should not have index information");
+      
+      require(component.getExternalDecl() == nullptr
+              && component.getExternalSubstitutions().empty(),
+              "property descriptor should not refer to another external decl");
     } else {
       require(hasIndices == !component.getSubscriptIndices().empty(),
               "component for subscript should have indices");
     }
-  
+    
     ParameterConvention normalArgConvention;
     if (M.getOptions().EnableGuaranteedNormalArguments)
       normalArgConvention = ParameterConvention::Indirect_In_Guaranteed;

lib/SILGen/SILGen.cpp

@@ -1228,47 +1228,6 @@ TypeConverter::canStorageUseStoredKeyPathComponent(AbstractStorageDecl *decl) {
   }
 }
 
-static bool doesStorageNeedDescriptor(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;
-
-  // If the getter is mutating, we cannot form a keypath to it at all.
-  if (decl->isGetterMutating())
-    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?");
-  }
-
-  return true;
-}
-
 static bool canStorageUseTrivialDescriptor(SILModule &M,
                                            AbstractStorageDecl *decl) {
   // A property can use a trivial property descriptor if the key path component
@@ -1322,7 +1281,7 @@ void SILGenModule::tryEmitPropertyDescriptor(AbstractStorageDecl *decl) {
   if (!SILModuleConventions(M).useLoweredAddresses())
     return;
 
-  if (!doesStorageNeedDescriptor(decl))
+  if (!decl->exportsPropertyDescriptor())
     return;
 
   Type baseTy;

lib/SILGen/SILGenExpr.cpp

@@ -3679,6 +3679,16 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
       }
     }
   }
+  
+  auto isSettableInComponent = [&]() -> bool {
+    // For storage we reference by a property descriptor, the descriptor will
+    // supply the settability if needed. We only reference it here if the
+    // setter is public.
+    if (shouldUseExternalKeyPathComponent())
+      return storage->isSettable(M.getSwiftModule())
+        && storage->isSetterAccessibleFrom(M.getSwiftModule());
+    return storage->isSettable(storage->getDeclContext());
+  };
 
   if (auto var = dyn_cast<VarDecl>(storage)) {
     CanType componentTy;
@@ -3729,7 +3739,7 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
                {},
                baseTy, componentTy);
 
-      if (var->isSettable(var->getDeclContext())) {
+      if (isSettableInComponent()) {
         auto setter = getOrCreateKeyPathSetter(*this, loc,
                var, subs,
                needsGenericContext ? genericEnv : nullptr,
@@ -3783,7 +3793,7 @@ SILGenModule::emitKeyPathComponentForDecl(SILLocation loc,
              baseTy, componentTy);
 
     auto indexPatternsCopy = getASTContext().AllocateCopy(indexPatterns);
-    if (decl->isSettable()) {
+    if (isSettableInComponent()) {
       auto setter = getOrCreateKeyPathSetter(*this, loc,
              decl, subs,
              needsGenericContext ? genericEnv : nullptr,

lib/TBDGen/TBDGen.cpp

@@ -156,6 +156,12 @@ void TBDGenVisitor::visitAccessorDecl(AccessorDecl *AD) {
 }
 
 void TBDGenVisitor::visitAbstractStorageDecl(AbstractStorageDecl *ASD) {
+  // Add the property descriptor if the decl needs it.
+  if (SwiftModule->getASTContext().LangOpts.EnableKeyPathResilience
+      && ASD->exportsPropertyDescriptor()) {
+    addSymbol(LinkEntity::forPropertyDescriptor(ASD));
+  }
+
   // Explicitly look at each accessor here: see visitAccessorDecl.
   for (auto accessor : ASD->getAllAccessors()) {
     visitAbstractFunctionDecl(accessor);

stdlib/public/SwiftShims/KeyPath.h

@@ -46,18 +46,18 @@ static const __swift_uint32_t _SwiftKeyPathComponentHeader_DiscriminatorShift
   = 24;
 
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_StructTag
-  = 0;
-static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedTag
   = 1;
-static const __swift_uint32_t _SwiftKeyPathComponentHeader_ClassTag
+static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedTag
   = 2;
-static const __swift_uint32_t _SwiftKeyPathComponentHeader_OptionalTag
+static const __swift_uint32_t _SwiftKeyPathComponentHeader_ClassTag
   = 3;
+static const __swift_uint32_t _SwiftKeyPathComponentHeader_OptionalTag
+  = 4;
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_ExternalTag
-  = 0x7F;
+  = 0;
 
 static const __swift_uint32_t
-_SwiftKeyPathComponentHeader_TrivialPropertyDescriptorMarker = 0xFFFFFFFFU;
+_SwiftKeyPathComponentHeader_TrivialPropertyDescriptorMarker = 0U;
 
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_MaximumOffsetPayload
   = 0x00FFFFFCU;
@@ -91,13 +91,21 @@ static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedIDByVTableOff
   = 0x00100000U;
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedHasArgumentsFlag
   = 0x00080000U;
+// Not ABI, used internally by key path runtime implementation
+static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedInstantiatedFromExternalWithArgumentsFlag
+  = 0x00000010U;
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedIDResolutionMask
   = 0x0000000FU;
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedIDResolved
   = 0x00000000U;
 static const __swift_uint32_t _SwiftKeyPathComponentHeader_ComputedIDUnresolvedIndirectPointer
   = 0x00000002U;
 
+extern void *(swift_keyPathGenericWitnessTable[]);
+
+static inline void *__swift_keyPathGenericWitnessTable_addr(void) {
+  return swift_keyPathGenericWitnessTable;
+}
 
 #ifdef __cplusplus
 } // extern "C"