Reapply "[DebugInfo] Make DIArgList inherit from Metadata and always unique"

This reverts commit 0fd5dc94380d5fe666dc6c603b4bb782cef743e7.

The original commit removed DIArgLists from being in an MDNode map, but did
not insert a new `delete` in the LLVMContextImpl destructor. This
reapply adds that call to delete, preventing a memory leak.

1 files changed, 27 insertions, 35 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 927aefb..c507346 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -2115,11 +2115,14 @@ DIMacroFile *DIMacroFile::getImpl(LLVMContext &Context, unsigned MIType,
   DEFINE_GETIMPL_STORE(DIMacroFile, (MIType, Line), Ops);
 }
 
-DIArgList *DIArgList::getImpl(LLVMContext &Context,
-                              ArrayRef<ValueAsMetadata *> Args,
-                              StorageType Storage, bool ShouldCreate) {
-  DEFINE_GETIMPL_LOOKUP(DIArgList, (Args));
-  DEFINE_GETIMPL_STORE_NO_OPS(DIArgList, (Args));
+DIArgList *DIArgList::get(LLVMContext &Context,
+                          ArrayRef<ValueAsMetadata *> Args) {
+  auto ExistingIt = Context.pImpl->DIArgLists.find_as(DIArgListKeyInfo(Args));
+  if (ExistingIt != Context.pImpl->DIArgLists.end())
+    return *ExistingIt;
+  DIArgList *NewArgList = new DIArgList(Context, Args);
+  Context.pImpl->DIArgLists.insert(NewArgList);
+  return NewArgList;
 }
 
 void DIArgList::handleChangedOperand(void *Ref, Metadata *New) {
@@ -2127,12 +2130,9 @@ void DIArgList::handleChangedOperand(void *Ref, Metadata *New) {
   assert((!New || isa<ValueAsMetadata>(New)) &&
          "DIArgList must be passed a ValueAsMetadata");
   untrack();
-  bool Uniq = isUniqued();
-  if (Uniq) {
-    // We need to update the uniqueness once the Args are updated since they
-    // form the key to the DIArgLists store.
-    eraseFromStore();
-  }
+  // We need to update the set storage once the Args are updated since they
+  // form the key to the DIArgLists store.
+  getContext().pImpl->DIArgLists.erase(this);
   ValueAsMetadata *NewVM = cast_or_null<ValueAsMetadata>(New);
   for (ValueAsMetadata *&VM : Args) {
     if (&VM == OldVMPtr) {
@@ -2142,28 +2142,19 @@ void DIArgList::handleChangedOperand(void *Ref, Metadata *New) {
         VM = ValueAsMetadata::get(PoisonValue::get(VM->getValue()->getType()));
     }
   }
-  if (Uniq) {
-    // In the RemoveDIs project (eliminating debug-info-intrinsics), DIArgLists
-    // can be referred to by DebugValueUser objects, which necessitates them
-    // being unique and replaceable metadata. This causes a slight
-    // performance regression that's to be avoided during the early stages of
-    // the RemoveDIs prototype, see D154080.
-#ifdef EXPERIMENTAL_DEBUGINFO_ITERATORS
-    MDNode *UniqueArgList = uniquify();
-    if (UniqueArgList != this) {
-      replaceAllUsesWith(UniqueArgList);
-      // Clear this here so we don't try to untrack in the destructor.
-      Args.clear();
-      delete this;
-      return;
-    }
-#else
-    // Otherwise, don't fully unique, become distinct instead. See D108968,
-    // there's a latent bug that presents here as nondeterminism otherwise.
-    if (uniquify() != this)
-      storeDistinctInContext();
-#endif
+  // We've changed the contents of this DIArgList, and the set storage may
+  // already contain a DIArgList with our new set of args; if it does, then we
+  // must RAUW this with the existing DIArgList, otherwise we simply insert this
+  // back into the set storage.
+  DIArgList *ExistingArgList = getUniqued(getContext().pImpl->DIArgLists, this);
+  if (ExistingArgList) {
+    replaceAllUsesWith(ExistingArgList);
+    // Clear this here so we don't try to untrack in the destructor.
+    Args.clear();
+    delete this;
+    return;
   }
+  getContext().pImpl->DIArgLists.insert(this);
   track();
 }
 void DIArgList::track() {
@@ -2176,8 +2167,9 @@ void DIArgList::untrack() {
     if (VAM)
       MetadataTracking::untrack(&VAM, *VAM);
 }
-void DIArgList::dropAllReferences() {
-  untrack();
+void DIArgList::dropAllReferences(bool Untrack) {
+  if (Untrack)
+    untrack();
   Args.clear();
-  MDNode::dropAllReferences();
+  ReplaceableMetadataImpl::resolveAllUses(/* ResolveUsers */ false);
 }