IRGen: add forceShared flag to LinkeEntity for type metadata

Author: eeckstein

include/swift/IRGen/Linking.h

@@ -127,6 +127,9 @@ class LinkEntity {
     // This field appears in the TypeMetadata and ObjCResilientClassStub kinds.
     MetadataAddressShift = 8, MetadataAddressMask = 0x0300,
 
+    // This field appears in the TypeMetadata kind.
+    ForceSharedShift = 12, ForceSharedMask = 0x1000,
+
     // This field appears in associated type access functions.
     AssociatedTypeIndexShift = 8, AssociatedTypeIndexMask = ~KindMask,
 
@@ -847,12 +850,14 @@ class LinkEntity {
   }
 
   static LinkEntity forTypeMetadata(CanType concreteType,
-                                    TypeMetadataAddress addr) {
+                                    TypeMetadataAddress addr,
+                                    bool forceShared = false) {
     assert(!isObjCImplementation(concreteType));
     assert(!isEmbedded(concreteType) || isMetadataAllowedInEmbedded(concreteType));
     LinkEntity entity;
     entity.setForType(Kind::TypeMetadata, concreteType);
     entity.Data |= LINKENTITY_SET_FIELD(MetadataAddress, unsigned(addr));
+    entity.Data |= LINKENTITY_SET_FIELD(ForceShared, unsigned(forceShared));
     return entity;
   }
 
@@ -1584,6 +1589,10 @@ class LinkEntity {
            getKind() == Kind::ObjCResilientClassStub);
     return (TypeMetadataAddress)LINKENTITY_GET_FIELD(Data, MetadataAddress);
   }
+  bool isForcedShared() const {
+    assert(getKind() == Kind::TypeMetadata);
+    return (bool)LINKENTITY_GET_FIELD(Data, ForceShared);
+  }
   bool isObjCClassRef() const {
     return getKind() == Kind::ObjCClassRef;
   }

lib/IRGen/Linking.cpp

@@ -642,6 +642,9 @@ SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
     return SILLinkage::Shared;
 
   case Kind::TypeMetadata: {
+    if (isForcedShared())
+      return SILLinkage::Shared;
+
     auto *nominal = getType().getAnyNominal();
     switch (getMetadataAddress()) {
     case TypeMetadataAddress::FullMetadata: