[llvm] [CGData] Lazy loading support for stable function map (PR #151660)

[Ellis Hoag via llvm-commits]

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@@ -114,25 +117,63 @@ size_t StableFunctionMap::size(SizeType Type) const {
   case UniqueHashCount:
     return HashToFuncs.size();
   case TotalFunctionCount: {
+    deserializeLazyLoadingEntries();
     size_t Count = 0;
     for (auto &Funcs : HashToFuncs)
-      Count += Funcs.second.size();
+      Count += Funcs.second.Entries.size();
     return Count;
   }
   case MergeableFunctionCount: {
+    deserializeLazyLoadingEntries();
     size_t Count = 0;
     for (auto &[Hash, Funcs] : HashToFuncs)
-      if (Funcs.size() >= 2)
-        Count += Funcs.size();
+      if (Funcs.Entries.size() >= 2)
+        Count += Funcs.Entries.size();
     return Count;
   }
   }
   llvm_unreachable("Unhandled size type");
 }
 
+const StableFunctionMap::StableFunctionEntries &
+StableFunctionMap::at(HashFuncsMapType::key_type FunctionHash) const {
+  auto It = HashToFuncs.find(FunctionHash);
+  if (isLazilyLoaded())
+    deserializeLazyLoadingEntry(It);
+  return It->second.Entries;
+}
+
+void StableFunctionMap::deserializeLazyLoadingEntry(
+    HashFuncsMapType::iterator It) const {
+  assert(isLazilyLoaded() && "Cannot deserialize non-lazily-loaded map");
+  auto &[Hash, Storage] = *It;
+  std::call_once(Storage.LazyLoadFlag,
+                 [this, HashArg = Hash, &StorageArg = Storage]() {
+                   for (auto Offset : StorageArg.Offsets)
+                     StableFunctionMapRecord::deserializeEntry(
+                         reinterpret_cast<const unsigned char *>(Offset),
+                         HashArg, const_cast<StableFunctionMap *>(this));
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ellishg wrote:

Yeah I agree that would be weird

https://github.com/llvm/llvm-project/pull/151660