[RemoteMirror] Optimize brute-force search in getCaptureDescriptor()

Author: bentroller

include/swift/RemoteInspection/TypeRefBuilder.h

@@ -534,6 +534,12 @@ class TypeRefBuilder {
     /// Indexes of Reflection Infos we've already processed.
     llvm::DenseSet<size_t> ProcessedReflectionInfoIndexes;
 
+    /// Cache for capture descriptor lookups.
+    std::unordered_map<uint64_t /* remote address*/,
+                       RemoteRef<CaptureDescriptor>>
+        CaptureDescriptorsByAddress;
+    uint32_t CaptureDescriptorsByAddressLastReflectionInfoCache = 0;
+
     /// Cache for field info lookups.
     std::unordered_map<std::string, RemoteRef<FieldDescriptor>>
         FieldTypeInfoCache;

stdlib/public/RemoteInspection/TypeRefBuilder.cpp

@@ -684,15 +684,24 @@ TypeRefBuilder::getMultiPayloadEnumDescriptor(const TypeRef *TR) {
 RemoteRef<CaptureDescriptor>
 TypeRefBuilder::ReflectionTypeDescriptorFinder::getCaptureDescriptor(
     uint64_t RemoteAddress) {
-  for (auto Info : ReflectionInfos) {
-    for (auto CD : Info.Capture) {
-      if (RemoteAddress == CD.getAddressData()) {
-        return CD;
-      }
+
+  for (; CaptureDescriptorsByAddressLastReflectionInfoCache <
+         ReflectionInfos.size();
+       CaptureDescriptorsByAddressLastReflectionInfoCache++) {
+    for (const auto &CD :
+         ReflectionInfos[CaptureDescriptorsByAddressLastReflectionInfoCache]
+             .Capture) {
+      CaptureDescriptorsByAddress.emplace(
+          std::make_pair(CD.getAddressData(), CD));
     }
   }
 
-  return nullptr;
+  const auto found = CaptureDescriptorsByAddress.find(RemoteAddress);
+  if (found == CaptureDescriptorsByAddress.end()) {
+    return nullptr;
+  }
+
+  return found->second;
 }
 
 /// Get the unsubstituted capture types for a closure context.