Make caching the typeref builder cache lazier

Author: augusto2112

include/swift/Reflection/TypeRefBuilder.h

@@ -643,6 +643,10 @@ class TypeRefBuilder {
 
 private:
   std::vector<ReflectionInfo> ReflectionInfos;
+
+  /// Index of the next Reflection Info that should be processed.
+  /// This assumes that Reflection Infos are never removed from the vector.
+  size_t FirstUnprocessedReflectionInfoIndex = 0;
 
   llvm::Optional<std::string> normalizeReflectionName(RemoteRef<char> name);
   bool reflectionNameMatches(RemoteRef<char> reflectionName,

stdlib/public/Reflection/TypeRefBuilder.cpp

@@ -201,22 +201,25 @@ TypeRefBuilder::getFieldTypeInfo(const TypeRef *TR) {
   if (Found != FieldTypeInfoCache.end())
     return Found->second;
 
-  // On failure, fill out the cache with everything we know about.
-  std::vector<std::pair<std::string, const TypeRef *>> Fields;
-  for (auto &Info : ReflectionInfos) {
+  // On failure, fill out the cache, ReflectionInfo by ReflectionInfo,
+  // until we find the field desciptor we're looking for.
+  while (FirstUnprocessedReflectionInfoIndex < ReflectionInfos.size()) {
+    auto &Info = ReflectionInfos[FirstUnprocessedReflectionInfoIndex];
     for (auto FD : Info.Field) {
       if (!FD->hasMangledTypeName())
         continue;
       auto CandidateMangledName = readTypeRef(FD, FD->MangledTypeName);
       if (auto NormalizedName = normalizeReflectionName(CandidateMangledName))
         FieldTypeInfoCache[*NormalizedName] = FD;
     }
-  }
 
-  // We've filled the cache with everything we know about now. Try the cache again.
-  Found = FieldTypeInfoCache.find(MangledName);
-  if (Found != FieldTypeInfoCache.end())
-    return Found->second;
+    // Since we're done with the current ReflectionInfo, increment early in
+    // case we get a cache hit.
+    ++FirstUnprocessedReflectionInfoIndex;
+    Found = FieldTypeInfoCache.find(MangledName);
+    if (Found != FieldTypeInfoCache.end())
+      return Found->second;
+  }
 
   return nullptr;
 }