[MemorySSA] Ensure address stability of MemorySSA object.

[gberry]

Summary

Ensure that the MemorySSA object never changes address when using the
new pass manager since the walkers contained by MemorySSA cache pointers
to it at construction time. This is achieved by wrapping the
MemorySSAAnalysis result in a unique_ptr. Also add some asserts that
check for this bug.

[george.burgess.iv]

Woohoo! Thanks for the patch. LGTM.

include/llvm/Transforms/Utils/MemorySSA.h

 
 class MemorySSAWalker;
 
 /// \brief Encapsulates MemorySSA, including all data associated with memory
 /// accesses.
 class MemorySSA {
 public:
   MemorySSA(Function &, AliasAnalysis *, DominatorTree *);
-  MemorySSA(MemorySSA &&);
   ~MemorySSA();
 
   MemorySSAWalker *getWalker();
 
   /// \brief Given a memory Mod/Ref'ing instruction, get the MemorySSA
   /// access associated with it. If passed a basic block gets the memory phi
   /// node that exists for that block, if there is one. Otherwise, this will get
   /// a MemoryUseOrDef.

 
 /// An analysis that produces \c MemorySSA for a function.
 ///
 class MemorySSAAnalysis : public AnalysisInfoMixin<MemorySSAAnalysis> {
   friend AnalysisInfoMixin<MemorySSAAnalysis>;
   static char PassID;
 
 public:
-  typedef MemorySSA Result;
+  typedef std::unique_ptr<MemorySSA> Result;
 
-  MemorySSA run(Function &F, AnalysisManager<Function> &AM);
+  Result run(Function &F, AnalysisManager<Function> &AM);
 };
 
 /// \brief Printer pass for \c MemorySSA.
 class MemorySSAPrinterPass : public PassInfoMixin<MemorySSAPrinterPass> {
   raw_ostream &OS;
 
 public:
   explicit MemorySSAPrinterPass(raw_ostream &OS) : OS(OS) {}
public:
 
   /// \brief Given a memory access, invalidate anything this walker knows about
   /// that access.
   /// This API is used by walkers that store information to perform basic cache
   /// invalidation.  This will be called by MemorySSA at appropriate times for
   /// the walker it uses or returns.
   virtual void invalidateInfo(MemoryAccess *) {}
 
+  virtual void verify(const MemorySSA *MSSA) { assert(MSSA == this->MSSA); }
+
 protected:
   friend class MemorySSA; // For updating MSSA pointer in MemorySSA move
                           // constructor.
   MemorySSA *MSSA;
 };
 
 /// \brief A MemorySSAWalker that does no alias queries, or anything else. It
 /// simply returns the links as they were constructed by the builder.

lib/Transforms/Utils/MemorySSA.cpp

if (WalkResult.IsKnownClobber) {
       Result = OptRes.PrimaryClobber.Clobber;
     }
 
 #ifdef EXPENSIVE_CHECKS
     checkClobberSanity(Current, Result, Q.StartingLoc, MSSA, Q, AA);
 #endif
     return Result;
   }
+
+  void verify(const MemorySSA *MSSA) { assert(MSSA == &this->MSSA); }
 };
 
 struct RenamePassData {
   DomTreeNode *DTN;
   DomTreeNode::const_iterator ChildIt;
   MemoryAccess *IncomingVal;
 
   RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
public:
   /// answer a clobber query.
   void setAutoResetWalker(bool AutoReset) { AutoResetWalker = AutoReset; }
 
   /// Drop the walker's persistent data structures. At the moment, this means
   /// "drop the walker's cache of BasicBlocks ->
   /// earliest-MemoryAccess-we-can-optimize-to". This is necessary if we're
   /// going to have DT updates, if we remove MemoryAccesses, etc.
   void resetClobberWalker() { Walker.reset(); }
+
+  void verify(const MemorySSA *MSSA) override {
+    MemorySSAWalker::verify(MSSA);
+    Walker.verify(MSSA);
+  }
 };
 
 /// \brief Rename a single basic block into MemorySSA form.
 /// Uses the standard SSA renaming algorithm.
 /// \returns The new incoming value.
 MemoryAccess *MemorySSA::renameBlock(BasicBlock *BB,
                                      MemoryAccess *IncomingVal) {
   auto It = PerBlockAccesses.find(BB);

 }
 
 MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
     : AA(AA), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
       NextID(0) {
   buildMemorySSA();
 }
 
-MemorySSA::MemorySSA(MemorySSA &&MSSA)
-    : AA(MSSA.AA), DT(MSSA.DT), F(MSSA.F),
-      ValueToMemoryAccess(std::move(MSSA.ValueToMemoryAccess)),
-      PerBlockAccesses(std::move(MSSA.PerBlockAccesses)),
-      LiveOnEntryDef(std::move(MSSA.LiveOnEntryDef)),
-      BlockNumberingValid(std::move(MSSA.BlockNumberingValid)),
-      BlockNumbering(std::move(MSSA.BlockNumbering)),
-      Walker(std::move(MSSA.Walker)), NextID(MSSA.NextID) {
-  // Update the Walker MSSA pointer so it doesn't point to the moved-from MSSA
-  // object any more.
-  Walker->MSSA = this;
-}
-
 MemorySSA::~MemorySSA() {
   // Drop all our references
   for (const auto &Pair : PerBlockAccesses)
     for (MemoryAccess &MA : *Pair.second)
       MA.dropAllReferences();
 }
 
 MemorySSA::AccessList *MemorySSA::getOrCreateAccessList(const BasicBlock *BB) {
void MemorySSA::dump() const {
   MemorySSAAnnotatedWriter Writer(this);
   F.print(dbgs(), &Writer);
 }
 
 void MemorySSA::verifyMemorySSA() const {
   verifyDefUses(F);
   verifyDomination(F);
   verifyOrdering(F);
+  Walker->verify(this);
 }
 
 /// \brief Verify that the order and existence of MemoryAccesses matches the
 /// order and existence of memory affecting instructions.
 void MemorySSA::verifyOrdering(Function &F) const {
   // Walk all the blocks, comparing what the lookups think and what the access
   // lists think, as well as the order in the blocks vs the order in the access
   // lists.
bool MemorySSAPrinterLegacyPass::runOnFunction(Function &F) {
   MSSA.print(dbgs());
   if (VerifyMemorySSA)
     MSSA.verifyMemorySSA();
   return false;
 }
 
 char MemorySSAAnalysis::PassID;
 
-MemorySSA MemorySSAAnalysis::run(Function &F, AnalysisManager<Function> &AM) {
+std::unique_ptr<MemorySSA>
+MemorySSAAnalysis::run(Function &F, AnalysisManager<Function> &AM) {
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &AA = AM.getResult<AAManager>(F);
-  return MemorySSA(F, &AA, &DT);
+  return make_unique<MemorySSA>(F, &AA, &DT);
 }
 
 PreservedAnalyses MemorySSAPrinterPass::run(Function &F,
                                             FunctionAnalysisManager &AM) {
   OS << "MemorySSA for function: " << F.getName() << "\n";
-  AM.getResult<MemorySSAAnalysis>(F).print(OS);
+  AM.getResult<MemorySSAAnalysis>(F)->print(OS);
 
   return PreservedAnalyses::all();
 }
 
 PreservedAnalyses MemorySSAVerifierPass::run(Function &F,
                                              FunctionAnalysisManager &AM) {
-  AM.getResult<MemorySSAAnalysis>(F).verifyMemorySSA();
+  AM.getResult<MemorySSAAnalysis>(F)->verifyMemorySSA();
 
   return PreservedAnalyses::all();
 }
 
 char MemorySSAWrapperPass::ID = 0;
 
 MemorySSAWrapperPass::MemorySSAWrapperPass() : FunctionPass(ID) {
   initializeMemorySSAWrapperPassPass(*PassRegistry::getPassRegistry());