Runtime: Remove old 'default requirements at the end' mechanism

Author: slavapestov

stdlib/public/runtime/Metadata.cpp

@@ -3169,22 +3169,26 @@ static GenericWitnessTableCache &getCache(GenericWitnessTable *gen) {
 /// If there's no initializer, no private storage, and all requirements
 /// are present, we don't have to instantiate anything; just return the
 /// witness table template.
-///
-/// Most of the time IRGen should be able to determine this statically;
-/// the one case is with resilient conformances, where the resilient
-/// protocol has not yet changed in a way that's incompatible with the
-/// conformance.
 static bool doesNotRequireInstantiation(GenericWitnessTable *genericTable) {
-  if (genericTable->Instantiator.isNull() &&
-      genericTable->ResilientWitnesses.isNull() &&
-      genericTable->WitnessTablePrivateSizeInWords == 0 &&
-      genericTable->WitnessTableSizeInWords ==
-        (genericTable->Protocol->NumRequirements +
-           WitnessTableFirstRequirementOffset)) {
-    return true;
+  // If we have resilient witnesses, we require instantiation.
+  if (!genericTable->ResilientWitnesses.isNull()) {
+    return false;
   }
 
-  return false;
+  // If we don't have resilient witnesses, the template must provide
+  // everything.
+  assert (genericTable->WitnessTableSizeInWords ==
+          (genericTable->Protocol->NumRequirements +
+           WitnessTableFirstRequirementOffset));
+
+  // If we have an instantiation function or private data, we require
+  // instantiation.
+  if (!genericTable->Instantiator.isNull() ||
+      genericTable->WitnessTablePrivateSizeInWords > 0) {
+    return false;
+  }
+
+  return true;
 }
 
 /// Initialize witness table entries from order independent resilient
@@ -3260,7 +3264,6 @@ WitnessTableCacheEntry::allocate(GenericWitnessTable *genericTable,
   // negative offsets.
   auto table = fullTable + privateSizeInWords;
   auto pattern = reinterpret_cast<void * const *>(&*genericTable->Pattern);
-  auto requirements = protocol->Requirements.get();
 
   // Fill in the provided part of the requirements from the pattern.
   for (size_t i = 0, e = numPatternWitnesses; i < e; ++i) {
@@ -3270,16 +3273,6 @@ WitnessTableCacheEntry::allocate(GenericWitnessTable *genericTable,
   // Fill in any default requirements.
   if (genericTable->ResilientWitnesses)
     initializeResilientWitnessTable(genericTable, table);
-  else {
-    for (size_t i = numPatternWitnesses, e = numRequirements; i < e; ++i) {
-      size_t requirementIndex = i - WitnessTableFirstRequirementOffset;
-      void *defaultImpl =
-        requirements[requirementIndex].DefaultImplementation.get();
-      assert(defaultImpl &&
-             "no default implementation for missing requirement");
-      table[i] = defaultImpl;
-    }
-  }
 
   auto castTable = reinterpret_cast<WitnessTable*>(table);