[IRGen] Remove lazy field type accessor functions

All of their usages have been replaced with new runtime
`swift_getFieldAt` method.

Author: xedin

include/swift/Runtime/Metadata.h

@@ -1289,16 +1289,6 @@ struct TargetClassMetadata : public TargetHeapMetadata<Runtime> {
     auto asWords = reinterpret_cast<const void * const*>(this);
     return reinterpret_cast<const StoredPointer *>(asWords + offset);
   }
-  
-  /// Get a pointer to the field type vector, if present, or null.
-  const FieldType *getFieldTypes() const {
-    assert(isTypeMetadata());
-    auto *getter = getDescription()->GetFieldTypes.get();
-    if (!getter)
-      return nullptr;
-    
-    return getter(this);
-  }
 
   uint32_t getSizeInWords() const {
     assert(isTypeMetadata());
@@ -1571,15 +1561,6 @@ struct TargetStructMetadata : public TargetValueMetadata<Runtime> {
     auto asWords = reinterpret_cast<const void * const*>(this);
     return reinterpret_cast<const StoredPointer *>(asWords + offset);
   }
-  
-  /// Get a pointer to the field type vector, if present, or null.
-  const FieldType *getFieldTypes() const {
-    auto *getter = getDescription()->GetFieldTypes.get();
-    if (!getter)
-      return nullptr;
-    
-    return getter(this);
-  }
 
   static bool classof(const TargetMetadata<Runtime> *metadata) {
     return metadata->getKind() == MetadataKind::Struct;
@@ -3177,12 +3158,6 @@ class TargetClassDescriptor final
   /// length and order is consistent with that of the field offset vector.
   RelativeDirectPointer<const char, /*nullable*/ true> FieldNames;
 
-  /// The field type vector accessor. Returns a pointer to an array of
-  /// type metadata references whose order is consistent with that of the
-  /// field offset vector.
-  RelativeDirectPointer<const FieldType *
-    (const TargetMetadata<Runtime> *)> GetFieldTypes;
-
   /// True if metadata records for this type have a field offset vector for
   /// its stored properties.
   bool hasFieldOffsetVector() const { return FieldOffsetVectorOffset != 0; }
@@ -3286,12 +3261,6 @@ class TargetStructDescriptor final
   /// The field names. A doubly-null-terminated list of strings, whose
   /// length and order is consistent with that of the field offset vector.
   RelativeDirectPointer<const char, /*nullable*/ true> FieldNames;
-  
-  /// The field type vector accessor. Returns a pointer to an array of
-  /// type metadata references whose order is consistent with that of the
-  /// field offset vector.
-  RelativeDirectPointer<const FieldType *
-    (const TargetMetadata<Runtime> *)> GetFieldTypes;
 
   /// True if metadata records for this type have a field offset vector for
   /// its stored properties.
@@ -3340,13 +3309,6 @@ class TargetEnumDescriptor final
   /// tag order, non-empty cases first, followed by empty cases.
   RelativeDirectPointer<const char, /*nullable*/ true> CaseNames;
 
-  /// The field type vector accessor. Returns a pointer to an array of
-  /// type metadata references whose order is consistent with that of the
-  /// CaseNames. Only types for payload cases are provided.
-  RelativeDirectPointer<
-    const FieldType * (const TargetMetadata<Runtime> *)>
-    GetCaseTypes;
-
   uint32_t getNumPayloadCases() const {
     return NumPayloadCasesAndPayloadSizeOffset & 0x00FFFFFFU;
   }

lib/IRGen/GenDecl.cpp

@@ -1151,7 +1151,7 @@ void IRGenerator::emitLazyDefinitions() {
   while (!LazyMetadata.empty() ||
          !LazyTypeContextDescriptors.empty() ||
          !LazyFunctionDefinitions.empty() ||
-         !LazyFieldTypeAccessors.empty() ||
+         !LazyFieldTypes.empty() ||
          !LazyWitnessTables.empty()) {
 
     // Emit any lazy type metadata we require.
@@ -1171,10 +1171,20 @@ void IRGenerator::emitLazyDefinitions() {
         emitLazyTypeContextDescriptor(*IGM.get(), Nominal);
       }
     }
-    while (!LazyFieldTypeAccessors.empty()) {
-      auto accessor = LazyFieldTypeAccessors.pop_back_val();
-      emitFieldTypeAccessor(*accessor.IGM, accessor.type, accessor.fn,
-                            accessor.fieldTypes);
+    while (!LazyFieldTypes.empty()) {
+      auto info = LazyFieldTypes.pop_back_val();
+      auto &IGM = *info.IGM;
+
+      for (auto fieldType : info.fieldTypes) {
+        if (fieldType->isAnyExistentialType())
+          continue;
+
+        // Ensure that all of the foreign metadata is forced, otherwise
+        // there might be a problem when fields are accessed through
+        // reflection.
+        if (IGM.requiresForeignTypeMetadata(fieldType))
+          (void)IGM.getAddrOfForeignTypeMetadataCandidate(fieldType);
+      }
     }
     while (!LazyWitnessTables.empty()) {
       SILWitnessTable *wt = LazyWitnessTables.pop_back_val();