[DomTreeUpdater] Move flushing back into the derived classes

Calling a derived method from a base class destructor leaves you in a
half-destroyed state. Sanitizers complain about that.

Author: d0k

llvm/include/llvm/Analysis/DomTreeUpdater.h

@@ -38,6 +38,8 @@ class DomTreeUpdater
       GenericDomTreeUpdater<DomTreeUpdater, DominatorTree, PostDominatorTree>;
   using Base::Base;
 
+  ~DomTreeUpdater() { flush(); }
+
   ///@{
   /// \name Mutation APIs
   ///

llvm/include/llvm/Analysis/GenericDomTreeUpdater.h

@@ -48,7 +48,11 @@ class GenericDomTreeUpdater {
                         UpdateStrategy Strategy_)
       : DT(DT_), PDT(PDT_), Strategy(Strategy_) {}
 
-  ~GenericDomTreeUpdater() { flush(); }
+  ~GenericDomTreeUpdater() {
+    // We cannot call into derived() here as it will already be destroyed.
+    assert(!hasPendingUpdates() &&
+           "Pending updates were not flushed by derived class.");
+  }
 
   /// Returns true if the current strategy is Lazy.
   bool isLazy() const { return Strategy == UpdateStrategy::Lazy; }

llvm/include/llvm/CodeGen/MachineDomTreeUpdater.h

@@ -33,6 +33,8 @@ class MachineDomTreeUpdater
                             MachinePostDominatorTree>;
   using Base::Base;
 
+  ~MachineDomTreeUpdater() { flush(); }
+
   ///@{
   /// \name Mutation APIs
   ///