[DIBuilder] Add a more fine-grained finalization method

Summary:
Clang wants to clone a function before it is done building the entire
compilation unit. As of now, there is no good way to do that, because
CloneFunction doesn't like dealing with temporary metadata. However,
as long as clang doesn't want to add any variables to this SP, it
should be fine to just prematurely finalize it. Add an API to allow this.

This is done in preparation of a clang commit to fix the assertion that
necessitated the revert of D33655.

Reviewers: aprantl, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33704

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304467 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/DIBuilder.h

@@ -86,6 +86,10 @@ namespace llvm {
     /// Construct any deferred debug info descriptors.
     void finalize();
 
+    /// Finalize a specific subprogram - no new variables may be added to this
+    /// subprogram afterwards.
+    void finalizeSubprogram(DISubprogram *SP);
+
     /// A CompileUnit provides an anchor for all debugging
     /// information generated during this instance of compilation.
     /// \param Lang          Source programming language, eg. dwarf::DW_LANG_C99

lib/IR/DIBuilder.cpp

@@ -39,6 +39,21 @@ void DIBuilder::trackIfUnresolved(MDNode *N) {
   UnresolvedNodes.emplace_back(N);
 }
 
+void DIBuilder::finalizeSubprogram(DISubprogram *SP) {
+  MDTuple *Temp = SP->getVariables().get();
+  if (!Temp || !Temp->isTemporary())
+    return;
+
+  SmallVector<Metadata *, 4> Variables;
+
+  auto PV = PreservedVariables.find(SP);
+  if (PV != PreservedVariables.end())
+    Variables.append(PV->second.begin(), PV->second.end());
+
+  DINodeArray AV = getOrCreateArray(Variables);
+  TempMDTuple(Temp)->replaceAllUsesWith(AV.get());
+}
+
 void DIBuilder::finalize() {
   if (!CUNode) {
     assert(!AllowUnresolvedNodes &&
@@ -62,25 +77,11 @@ void DIBuilder::finalize() {
     CUNode->replaceRetainedTypes(MDTuple::get(VMContext, RetainValues));
 
   DISubprogramArray SPs = MDTuple::get(VMContext, AllSubprograms);
-  auto resolveVariables = [&](DISubprogram *SP) {
-    MDTuple *Temp = SP->getVariables().get();
-    if (!Temp)
-      return;
-
-    SmallVector<Metadata *, 4> Variables;
-
-    auto PV = PreservedVariables.find(SP);
-    if (PV != PreservedVariables.end())
-      Variables.append(PV->second.begin(), PV->second.end());
-
-    DINodeArray AV = getOrCreateArray(Variables);
-    TempMDTuple(Temp)->replaceAllUsesWith(AV.get());
-  };
   for (auto *SP : SPs)
-    resolveVariables(SP);
+    finalizeSubprogram(SP);
   for (auto *N : RetainValues)
     if (auto *SP = dyn_cast<DISubprogram>(N))
-      resolveVariables(SP);
+      finalizeSubprogram(SP);
 
   if (!AllGVs.empty())
     CUNode->replaceGlobalVariables(MDTuple::get(VMContext, AllGVs));