[5.0] Fix a race condition with the initialization of class metadata

include/swift/Runtime/RuntimeFunctions.def

@@ -780,7 +780,6 @@ FUNCTION(RelocateClassMetadata,
          ARGS(TypeContextDescriptorPtrTy, Int8PtrTy),
          ATTRS(NoUnwind))
 
-// struct FieldInfo { size_t Size; size_t AlignMask; };
 // void swift_initClassMetadata(Metadata *self,
 //                              ClassLayoutFlags flags,
 //                              size_t numFields,
@@ -794,7 +793,6 @@ FUNCTION(InitClassMetadata,
               SizeTy->getPointerTo()),
          ATTRS(NoUnwind))
 
-// struct FieldInfo { size_t Size; size_t AlignMask; };
 // void swift_updateClassMetadata(Metadata *self,
 //                                ClassLayoutFlags flags,
 //                                size_t numFields,
@@ -808,7 +806,6 @@ FUNCTION(UpdateClassMetadata,
               SizeTy->getPointerTo()),
          ATTRS(NoUnwind))
 
-// struct FieldInfo { size_t Size; size_t AlignMask; };
 // MetadataDependency swift_initClassMetadata2(Metadata *self,
 //                                             ClassLayoutFlags flags,
 //                                             size_t numFields,
@@ -822,7 +819,6 @@ FUNCTION(InitClassMetadata2,
               SizeTy->getPointerTo()),
          ATTRS(NoUnwind))
 
-// struct FieldInfo { size_t Size; size_t AlignMask; };
 // MetadataDependency swift_updateClassMetadata2(Metadata *self,
 //                                               ClassLayoutFlags flags,
 //                                               size_t numFields,

lib/IRGen/GenMeta.cpp

@@ -1815,24 +1815,33 @@ static void emitInitializeFieldOffsetVector(IRGenFunction &IGF,
     if (!doesClassMetadataRequireRelocation(IGM, classDecl))
       flags |= ClassLayoutFlags::HasStaticVTable;
 
+    llvm::Value *dependency;
     if (doesClassMetadataRequireInitialization(IGM, classDecl)) {
       // Call swift_initClassMetadata().
-      IGF.Builder.CreateCall(IGM.getInitClassMetadataFn(),
-                             {metadata,
-                              IGM.getSize(Size(uintptr_t(flags))),
-                              numFields, fields.getAddress(), fieldVector});
+      dependency =
+        IGF.Builder.CreateCall(IGM.getInitClassMetadata2Fn(),
+                               {metadata,
+                                IGM.getSize(Size(uintptr_t(flags))),
+                                numFields, fields.getAddress(), fieldVector});
     } else {
       assert(doesClassMetadataRequireUpdate(IGM, classDecl));
       assert(IGM.Context.LangOpts.EnableObjCInterop);
 
       // Call swift_updateClassMetadata(). Note that the static metadata
       // already references the superclass in this case, but we still want
       // to ensure the superclass metadata is initialized first.
-      IGF.Builder.CreateCall(IGM.getUpdateClassMetadataFn(),
-                             {metadata,
-                              IGM.getSize(Size(uintptr_t(flags))),
-                              numFields, fields.getAddress(), fieldVector});
+      dependency =
+        IGF.Builder.CreateCall(IGM.getUpdateClassMetadata2Fn(),
+                               {metadata,
+                                IGM.getSize(Size(uintptr_t(flags))),
+                                numFields, fields.getAddress(), fieldVector});
     }
+
+    // Collect any possible dependency from initializing the class; generally
+    // this involves the superclass.
+    assert(collector);
+    collector->collect(IGF, dependency);
+
   } else {
     assert(isa<StructDecl>(target));
 

lib/IRGen/MetadataRequest.cpp

@@ -162,29 +162,57 @@ void MetadataDependencyCollector::checkDependency(IRGenFunction &IGF,
 
   // Otherwise, we need to pull out the response state and compare it against
   // the request state.
+  llvm::Value *requiredState = request.getRequiredState(IGF);
+
+  // More advanced metadata states are lower numbers.
+  static_assert(MetadataStateIsReverseOrdered,
+                "relying on the ordering of MetadataState here");
+  auto satisfied = IGF.Builder.CreateICmpULE(metadataState, requiredState);
+
+  emitCheckBranch(IGF, satisfied, metadata, requiredState);
+}
+
+void MetadataDependencyCollector::collect(IRGenFunction &IGF,
+                                          llvm::Value *dependency) {
+  // Having either both or neither of the PHIs is normal.
+  // Having just RequiredState means that we already finalized this collector
+  // and shouldn't be using it anymore.
+  assert((!RequiredMetadata || RequiredState) &&
+         "checking dependencies on a finished collector");
+
+  assert(dependency->getType() == IGF.IGM.TypeMetadataDependencyTy);
 
-  // Lazily create the continuation block and phis.
+  // Split the dependency.
+  auto metadata = IGF.Builder.CreateExtractValue(dependency, 0);
+  auto requiredState = IGF.Builder.CreateExtractValue(dependency, 1);
+
+  // We have a dependency if the metadata is non-null; otherwise we're
+  // satisfied and can continue.
+  auto satisfied = IGF.Builder.CreateIsNull(metadata);
+  emitCheckBranch(IGF, satisfied, metadata, requiredState);
+}
+
+void MetadataDependencyCollector::emitCheckBranch(IRGenFunction &IGF,
+                                                  llvm::Value *satisfied,
+                                                  llvm::Value *metadata,
+                                                  llvm::Value *requiredState) {
+  // Lazily create the final continuation block and phis.
   if (!RequiredMetadata) {
     auto contBB = IGF.createBasicBlock("metadata-dependencies.cont");
     RequiredMetadata =
       llvm::PHINode::Create(IGF.IGM.TypeMetadataPtrTy, 4, "", contBB);
     RequiredState = llvm::PHINode::Create(IGF.IGM.SizeTy, 4, "", contBB);
   }
 
-  llvm::Value *requiredState = request.getRequiredState(IGF);
-
-  // More advanced metadata states are lower numbers.
-  static_assert(MetadataStateIsReverseOrdered,
-                "relying on the ordering of MetadataState here");
-  auto satisfied = IGF.Builder.CreateICmpULE(metadataState, requiredState);
-
+  // Conditionally branch to the final continuation block.
   auto satisfiedBB = IGF.createBasicBlock("dependency-satisfied");
   auto curBB = IGF.Builder.GetInsertBlock();
   RequiredMetadata->addIncoming(metadata, curBB);
   RequiredState->addIncoming(requiredState, curBB);
   IGF.Builder.CreateCondBr(satisfied, satisfiedBB,
                            RequiredMetadata->getParent());
 
+  // Otherwise resume emitting code on the main path.
   IGF.Builder.emitBlock(satisfiedBB);
 }
 

lib/IRGen/MetadataRequest.h

@@ -430,14 +430,27 @@ class MetadataDependencyCollector {
            "failed to finish MetadataDependencyCollector");
   }
 
-  /// Check the dependency.  This takes a metadata and state separately
-  /// instead of taking a MetadataResponse because it's quite important
-  /// that we not rely on anything from MetadataResponse that might assume
-  /// that we've already done dependency collection.
+  /// Given the result of fetching metadata, check whether it creates a
+  /// metadata dependency, and branch if so.
+  ///
+  /// This takes a metadata and state separately instead of taking a
+  /// MetadataResponse pair because it's quite important that we not rely on
+  /// anything from MetadataResponse that might assume that we've already
+  /// done dependency collection.
   void checkDependency(IRGenFunction &IGF, DynamicMetadataRequest request,
                        llvm::Value *metadata, llvm::Value *state);
 
+  /// Given an optional MetadataDependency value (e.g. the result of calling
+  /// a dependency-returning function, in which a dependency is signalled
+  /// by a non-null metadata value), check whether it indicates a dependency
+  /// and branch if so.
+  void collect(IRGenFunction &IGF, llvm::Value *dependencyPair);
+
   MetadataDependency finish(IRGenFunction &IGF);
+
+private:
+  void emitCheckBranch(IRGenFunction &IGF, llvm::Value *satisfied,
+                       llvm::Value *metadata, llvm::Value *requiredState);
 };
 
 enum class MetadataAccessStrategy {

stdlib/public/runtime/ProtocolConformance.cpp

@@ -689,7 +689,7 @@ bool swift::_checkGenericRequirements(
     case GenericRequirementKind::BaseClass: {
       // Demangle the base type under the given substitutions.
       auto baseType =
-        swift_getTypeByMangledName(MetadataState::Complete,
+        swift_getTypeByMangledName(MetadataState::Abstract,
                                    req.getMangledTypeName(), substGenericParam,
                                    substWitnessTable).getMetadata();
       if (!baseType) return true;

test/IRGen/class_resilience.swift

@@ -400,7 +400,13 @@ extension ResilientGenericOutsideParent {
 // CHECK: dependency-satisfied:
 
 // -- ClassLayoutFlags = 0x100 (HasStaticVTable)
-// CHECK:      void @swift_initClassMetadata(%swift.type* %0, [[INT]] 256, [[INT]] 3, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK:      [[T0:%.*]] = call swiftcc %swift.metadata_response @swift_initClassMetadata2(%swift.type* %0, [[INT]] 256, [[INT]] 3, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK-NEXT: [[INITDEP_METADATA:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
+// CHECK-NEXT: [[INITDEP_STATUS:%.*]] = extractvalue %swift.metadata_response [[T0]], 1
+// CHECK-NEXT: [[INITDEP_PRESENT:%.*]] = icmp eq %swift.type* [[INITDEP_METADATA]], null
+// CHECK-NEXT: br i1 [[INITDEP_PRESENT]], label %dependency-satisfied1, label %metadata-dependencies.cont
+
+// CHECK: dependency-satisfied1:
 
 // CHECK-native:      [[FIELD_OFFSET:%.*]] = load [[INT]], [[INT]]* {{.*}}
 // CHECK-native-NEXT: store [[INT]] [[FIELD_OFFSET]], [[INT]]* @"$s16class_resilience26ClassWithResilientPropertyC1s16resilient_struct4SizeVvpWvd"
@@ -412,8 +418,8 @@ extension ResilientGenericOutsideParent {
 
 // CHECK: metadata-dependencies.cont:
 
-// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[SIZE_METADATA]], %entry ], [ null, %dependency-satisfied ]
-// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ 63, %entry ], [ 0, %dependency-satisfied ]
+// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[SIZE_METADATA]], %entry ], [ [[INITDEP_METADATA]], %dependency-satisfied ], [ null, %dependency-satisfied1 ]
+// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ 63, %entry ], [ [[INITDEP_STATUS]], %dependency-satisfied ], [ 0, %dependency-satisfied1 ]
 // CHECK-NEXT: [[T0:%.*]] = insertvalue %swift.metadata_response undef, %swift.type* [[PENDING_METADATA]], 0
 // CHECK-NEXT: [[T1:%.*]] = insertvalue %swift.metadata_response [[T0]], [[INT]] [[NEW_STATUS]], 1
 // CHECK-NEXT: ret %swift.metadata_response [[T1]]
@@ -448,7 +454,13 @@ extension ResilientGenericOutsideParent {
 // CHECK: dependency-satisfied:
 
 // -- ClassLayoutFlags = 0x100 (HasStaticVTable)
-// CHECK:      call void @swift_initClassMetadata(%swift.type* %0, [[INT]] 256, [[INT]] 2, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK:      [[T0:%.*]] = call swiftcc %swift.metadata_response @swift_initClassMetadata2(%swift.type* %0, [[INT]] 256, [[INT]] 2, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK-NEXT: [[INITDEP_METADATA:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
+// CHECK-NEXT: [[INITDEP_STATUS:%.*]] = extractvalue %swift.metadata_response [[T0]], 1
+// CHECK-NEXT: [[INITDEP_PRESENT:%.*]] = icmp eq %swift.type* [[INITDEP_METADATA]], null
+// CHECK-NEXT: br i1 [[INITDEP_PRESENT]], label %dependency-satisfied1, label %metadata-dependencies.cont
+
+// CHECK: dependency-satisfied1:
 
 // CHECK-native:      [[FIELD_OFFSET:%.*]] = load [[INT]], [[INT]]* {{.*}}
 // CHECK-native-NEXT: store [[INT]] [[FIELD_OFFSET]], [[INT]]* @"$s16class_resilience33ClassWithResilientlySizedPropertyC1r16resilient_struct9RectangleVvpWvd"
@@ -460,8 +472,8 @@ extension ResilientGenericOutsideParent {
 
 // CHECK: metadata-dependencies.cont:
 
-// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[SIZE_METADATA]], %entry ], [ null, %dependency-satisfied ]
-// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ 63, %entry ], [ 0, %dependency-satisfied ]
+// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[SIZE_METADATA]], %entry ], [ [[INITDEP_METADATA]], %dependency-satisfied ], [ null, %dependency-satisfied1 ]
+// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ 63, %entry ], [ [[INITDEP_STATUS]], %dependency-satisfied ], [ 0, %dependency-satisfied1 ]
 // CHECK-NEXT: [[T0:%.*]] = insertvalue %swift.metadata_response undef, %swift.type* [[PENDING_METADATA]], 0
 // CHECK-NEXT: [[T1:%.*]] = insertvalue %swift.metadata_response [[T0]], [[INT]] [[NEW_STATUS]], 1
 // CHECK-NEXT: ret %swift.metadata_response [[T1]]
@@ -481,7 +493,7 @@ extension ResilientGenericOutsideParent {
 // CHECK-LABEL: define internal swiftcc %swift.metadata_response @"$s16class_resilience14ResilientChildCMr"(%swift.type*, i8*, i8**)
 
 // Initialize field offset vector...
-// CHECK:      call void @swift_initClassMetadata(%swift.type* %0, [[INT]] 0, [[INT]] 1, i8*** {{.*}}, [[INT]]* {{.*}})
+// CHECK:      call swiftcc %swift.metadata_response @swift_initClassMetadata2(%swift.type* %0, [[INT]] 0, [[INT]] 1, i8*** {{.*}}, [[INT]]* {{.*}})
 
 // CHECK: ret %swift.metadata_response
 
@@ -519,7 +531,7 @@ extension ResilientGenericOutsideParent {
 // CHECK-LABEL: define internal swiftcc %swift.metadata_response @"$s16class_resilience21ResilientGenericChildCMr"
 // CHECK-SAME:    (%swift.type* [[METADATA:%.*]], i8*, i8**)
 
-// CHECK:              call void @swift_initClassMetadata(%swift.type* [[METADATA]], [[INT]] 0,
+// CHECK:              call swiftcc %swift.metadata_response @swift_initClassMetadata2(%swift.type* [[METADATA]], [[INT]] 0,
 // CHECK:              ret %swift.metadata_response
 
 

test/IRGen/completely_fragile_class_layout.sil

@@ -209,7 +209,7 @@ bb0(%0 : @guaranteed $ClassWithResilientField):
 // CHECK-NEXT: ret %objc_class* [[RESULT]]
 
 
-// Metadata initialization function for ClassWithResilientField calls swift_updateClassMetadata():
+// Metadata initialization function for ClassWithResilientField calls swift_updateClassMetadata2():
 
 // CHECK-LABEL: define internal swiftcc %swift.metadata_response @"$s31completely_fragile_class_layout23ClassWithResilientFieldCMr"(%swift.type*, i8*, i8**)
 
@@ -230,7 +230,13 @@ bb0(%0 : @guaranteed $ClassWithResilientField):
 // CHECK: dependency-satisfied:
 
 // -- ClassLayoutFlags = 0x100 (HasStaticVTable)
-// CHECK:      void @swift_updateClassMetadata(%swift.type* %0, [[INT]] 256, [[INT]] 3, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK:      [[T0:%.*]] = call swiftcc %swift.metadata_response @swift_updateClassMetadata2(%swift.type* %0, [[INT]] 256, [[INT]] 3, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK-NEXT: [[INITDEP_METADATA:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
+// CHECK-NEXT: [[INITDEP_STATUS:%.*]] = extractvalue %swift.metadata_response [[T0]], 1
+// CHECK-NEXT: [[INITDEP_PRESENT:%.*]] = icmp eq %swift.type* [[INITDEP_METADATA]], null
+// CHECK-NEXT: br i1 [[INITDEP_PRESENT]], label %dependency-satisfied1, label %metadata-dependencies.cont
+
+// CHECK: dependency-satisfied1:
 
 // CHECK-native:      [[FIELD_OFFSET:%.*]] = load [[INT]], [[INT]]* {{.*}}
 // CHECK-native-NEXT: store [[INT]] [[FIELD_OFFSET]], [[INT]]* @"$s31completely_fragile_class_layout23ClassWithResilientFieldC1s16resilient_struct4SizeVvpWvd"
@@ -242,8 +248,8 @@ bb0(%0 : @guaranteed $ClassWithResilientField):
 
 // CHECK: metadata-dependencies.cont:
 
-// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[SIZE_METADATA]], %entry ], [ null, %dependency-satisfied ]
-// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ 63, %entry ], [ 0, %dependency-satisfied ]
+// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[SIZE_METADATA]], %entry ], [ [[INITDEP_METADATA]], %dependency-satisfied ], [ null, %dependency-satisfied1 ]
+// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ 63, %entry ], [ [[INITDEP_STATUS]], %dependency-satisfied ], [ 0, %dependency-satisfied1 ]
 // CHECK-NEXT: [[T0:%.*]] = insertvalue %swift.metadata_response undef, %swift.type* [[PENDING_METADATA]], 0
 // CHECK-NEXT: [[T1:%.*]] = insertvalue %swift.metadata_response [[T0]], [[INT]] [[NEW_STATUS]], 1
 // CHECK-NEXT: ret %swift.metadata_response [[T1]]
@@ -262,9 +268,21 @@ bb0(%0 : @guaranteed $ClassWithResilientField):
 // CHECK-NEXT: [[FIELDS_PTR:%.*]] = getelementptr inbounds [0 x i8**], [0 x i8**]* [[FIELDS]], i32 0, i32 0
 
 // -- ClassLayoutFlags = 0x100 (HasStaticVTable)
-// CHECK:      void @swift_updateClassMetadata(%swift.type* %0, [[INT]] 256, [[INT]] 0, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK:      [[T0:%.*]] = call swiftcc %swift.metadata_response @swift_updateClassMetadata2(%swift.type* %0, [[INT]] 256, [[INT]] 0, i8*** [[FIELDS_PTR]], [[INT]]* [[FIELDS_DEST]])
+// CHECK-NEXT: [[INITDEP_METADATA:%.*]] = extractvalue %swift.metadata_response [[T0]], 0
+// CHECK-NEXT: [[INITDEP_STATUS:%.*]] = extractvalue %swift.metadata_response [[T0]], 1
+// CHECK-NEXT: [[INITDEP_PRESENT:%.*]] = icmp eq %swift.type* [[INITDEP_METADATA]], null
+// CHECK-NEXT: br i1 [[INITDEP_PRESENT]], label %dependency-satisfied, label %metadata-dependencies.cont
+
+// CHECK: dependency-satisfied:
+// CHECK:      br label %metadata-dependencies.cont
 
-// CHECK: ret %swift.metadata_response zeroinitializer
+// CHECK: metadata-dependencies.cont:
+// CHECK-NEXT: [[PENDING_METADATA:%.*]] = phi %swift.type* [ [[INITDEP_METADATA]], %entry ], [ null, %dependency-satisfied ]
+// CHECK-NEXT: [[NEW_STATUS:%.*]] = phi [[INT]] [ [[INITDEP_STATUS]], %entry ], [ 0, %dependency-satisfied ]
+// CHECK-NEXT: [[T0:%.*]] = insertvalue %swift.metadata_response undef, %swift.type* [[PENDING_METADATA]], 0
+// CHECK-NEXT: [[T1:%.*]] = insertvalue %swift.metadata_response [[T0]], [[INT]] [[NEW_STATUS]], 1
+// CHECK-NEXT: ret %swift.metadata_response [[T1]]
 
 // Metadata accessor for ClassWithResilientEnum looks like singleton initialization:
 

test/IRGen/concrete_inherits_generic_base.swift

@@ -83,4 +83,4 @@ presentBase(Base(x: 2))
 
 // CHECK-LABEL: define internal swiftcc %swift.metadata_response @"$s3foo12SuperDerivedCMr"(%swift.type*, i8*, i8**)
 // -- ClassLayoutFlags = 0x100 (HasStaticVTable)
-// CHECK:         call void @swift_initClassMetadata(%swift.type* %0, [[INT]] 256, {{.*}})
+// CHECK:         call swiftcc %swift.metadata_response @swift_initClassMetadata2(%swift.type* %0, [[INT]] 256, {{.*}})