IR: Remove MDNodeFwdDecl

Remove `MDNodeFwdDecl` (as promised in r226481).  Aside from API
changes, there's no real functionality change here.
`MDNode::getTemporary()` now forwards to `MDTuple::getTemporary()`,
which returns a tuple with `isTemporary()` equal to true.

The main point is that we can now add temporaries of other `MDNode`
subclasses, needed for PR22235 (I introduced `MDNodeFwdDecl` in the
first place because I didn't recognize this need, and thought they were
only needed to handle forward references).

A few things left out of (or highlighted by) this commit:

  - I've had to remove the (few) uses of `std::unique_ptr<>` to deal
    with temporaries, since the destructor is no longer public.
    `getTemporary()` should probably return the equivalent of
    `std::unique_ptr<T, MDNode::deleteTemporary>`.
  - `MDLocation::getTemporary()` doesn't exist yet (worse, it actually
    does exist, but does the wrong thing: `MDNode::getTemporary()` is
    inherited and returns an `MDTuple`).
  - `MDNode` now only has one subclass, `UniquableMDNode`, and the
    distinction between them is actually somewhat confusing.

I'll fix those up next.

llvm-svn: 226501

3 files changed, 17 insertions, 15 deletions

diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index 290dbe29c70..c5c11157971 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -337,7 +337,8 @@ void DIDescriptor::replaceAllUsesWith(LLVMContext &VMContext, DIDescriptor D) {
     DN = MDNode::get(VMContext, Ops);
   }
 
-  auto *Node = cast<MDNodeFwdDecl>(const_cast<MDNode *>(DbgNode));
+  assert(DbgNode->isTemporary() && "Expected temporary node");
+  auto *Node = const_cast<MDNode *>(DbgNode);
   Node->replaceAllUsesWith(const_cast<MDNode *>(DN));
   MDNode::deleteTemporary(Node);
   DbgNode = DN;
@@ -346,7 +347,8 @@ void DIDescriptor::replaceAllUsesWith(LLVMContext &VMContext, DIDescriptor D) {
 void DIDescriptor::replaceAllUsesWith(MDNode *D) {
   assert(DbgNode && "Trying to replace an unverified type!");
   assert(DbgNode != D && "This replacement should always happen");
-  auto *Node = cast<MDNodeFwdDecl>(const_cast<MDNode *>(DbgNode));
+  assert(DbgNode->isTemporary() && "Expected temporary node");
+  auto *Node = const_cast<MDNode *>(DbgNode);
   Node->replaceAllUsesWith(D);
   MDNode::deleteTemporary(Node);
 }
diff --git a/llvm/lib/IR/Metadata.cpp b/llvm/lib/IR/Metadata.cpp
index 8d83e1652cd..01394137e8e 100644
--- a/llvm/lib/IR/Metadata.cpp
+++ b/llvm/lib/IR/Metadata.cpp
@@ -155,7 +155,8 @@ void ReplaceableMetadataImpl::moveRef(void *Ref, void *New,
 }
 
 void ReplaceableMetadataImpl::replaceAllUsesWith(Metadata *MD) {
-  assert(!(MD && isa<MDNodeFwdDecl>(MD)) && "Expected non-temp node");
+  assert(!(MD && isa<MDNode>(MD) && cast<MDNode>(MD)->isTemporary()) &&
+         "Expected non-temp node");
 
   if (UseMap.empty())
     return;
@@ -471,13 +472,14 @@ void UniquableMDNode::resolveCycles() {
 
   // Resolve all operands.
   for (const auto &Op : operands()) {
-    if (!Op)
+    auto *N = dyn_cast_or_null<UniquableMDNode>(Op);
+    if (!N)
       continue;
-    assert(!isa<MDNodeFwdDecl>(Op) &&
+
+    assert(!N->isTemporary() &&
            "Expected all forward declarations to be resolved");
-    if (auto *N = dyn_cast<UniquableMDNode>(Op))
-      if (!N->isResolved())
-        N->resolveCycles();
+    if (!N->isResolved())
+      N->resolveCycles();
   }
 }
 
@@ -621,7 +623,7 @@ T *UniquableMDNode::storeImpl(T *N, StorageType Storage, StoreT &Store) {
     N->storeDistinctInContext();
     break;
   case Temporary:
-    llvm_unreachable("Unexpected temporary node");
+    break;
   }
   return N;
 }
@@ -723,13 +725,11 @@ void MDLocation::eraseFromStoreImpl() {
   getContext().pImpl->MDLocations.erase(this);
 }
 
-MDNodeFwdDecl *MDNode::getTemporary(LLVMContext &Context,
-                                    ArrayRef<Metadata *> MDs) {
-  return MDNodeFwdDecl::get(Context, MDs);
+void MDNode::deleteTemporary(MDNode *N) {
+  assert(N->isTemporary() && "Expected temporary node");
+  cast<UniquableMDNode>(N)->deleteAsSubclass();
 }
 
-void MDNode::deleteTemporary(MDNode *N) { delete cast<MDNodeFwdDecl>(N); }
-
 void UniquableMDNode::storeDistinctInContext() {
   assert(isResolved() && "Expected resolved nodes");
   Storage = Distinct;
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 4bf2d1a6dc6..f0a149354ae 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -617,7 +617,7 @@ void Verifier::visitMDNode(MDNode &MD) {
   }
 
   // Check these last, so we diagnose problems in operands first.
-  Assert1(!isa<MDNodeFwdDecl>(MD), "Expected no forward declarations!", &MD);
+  Assert1(!MD.isTemporary(), "Expected no forward declarations!", &MD);
   Assert1(MD.isResolved(), "All nodes should be resolved!", &MD);
 }