Merge pull request #29345 from nate-chandler/generic-metadata-prespecialization-components/enums

Generic metadata prespecialization: enums

Author: nate-chandler

include/swift/ABI/Metadata.h

@@ -1426,6 +1426,32 @@ struct TargetEnumMetadata : public TargetValueMetadata<Runtime> {
     return *asWords;
   }
 
+  bool isCanonicalStaticallySpecializedGenericMetadata() const {
+    auto *description = getDescription();
+    if (!description->isGeneric())
+      return false;
+
+    auto *trailingFlags = getTrailingFlags();
+    if (trailingFlags == nullptr)
+      return false;
+
+    return trailingFlags->isCanonicalStaticSpecialization();
+  }
+
+  const MetadataTrailingFlags *getTrailingFlags() const {
+    auto description = getDescription();
+    auto flags = description->getFullGenericContextHeader()
+                     .DefaultInstantiationPattern->PatternFlags;
+    if (!flags.hasTrailingFlags())
+      return nullptr;
+    auto offset =
+        getGenericArgumentOffset() +
+        description->getFullGenericContextHeader().Base.getNumArguments() +
+        (hasPayloadSize() ? 1 : 0);
+    auto asWords = reinterpret_cast<const void *const *>(this);
+    return reinterpret_cast<const MetadataTrailingFlags *>(asWords + offset);
+  }
+
   static constexpr int32_t getGenericArgumentOffset() {
     return sizeof(TargetEnumMetadata<Runtime>) / sizeof(StoredPointer);
   }

lib/IRGen/EnumMetadataVisitor.h

@@ -62,6 +62,14 @@ template <class Impl> class EnumMetadataVisitor
            Target->getDeclaredTypeInContext()->getCanonicalType());
     if (strategy.needsPayloadSizeInMetadata())
       asImpl().addPayloadSize();
+
+    if (asImpl().hasTrailingFlags())
+      asImpl().addTrailingFlags();
+  }
+
+  bool hasTrailingFlags() {
+    return Target->isGenericContext() &&
+           IGM.shouldPrespecializeGenericMetadata();
   }
 };
 
@@ -86,6 +94,7 @@ class EnumMetadataScanner : public EnumMetadataVisitor<Impl> {
   void addGenericWitnessTable(GenericRequirement requirement) { addPointer(); }
   void addPayloadSize() { addPointer(); }
   void noteStartOfTypeSpecificMembers() {}
+  void addTrailingFlags() { addPointer(); }
 
 private:
   void addPointer() {