From b5b56ba9d4df47e618d4e0f9e1e09bf216733ee8 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 30 Jul 2009 20:21:41 +0000
Subject: [PATCH] Use CallbackVH in AliasSetTracker to avoid getting stuck with
 dangling Value*s.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77623 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Analysis/AliasSetTracker.h | 18 ++++++++++++++++--
 lib/Analysis/AliasSetTracker.cpp        | 24 ++++++++++++++++++++----
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/include/llvm/Analysis/AliasSetTracker.h b/include/llvm/Analysis/AliasSetTracker.h
index 0a9e278b4d9..99d7ce80e5d 100644
--- a/include/llvm/Analysis/AliasSetTracker.h
+++ b/include/llvm/Analysis/AliasSetTracker.h
@@ -18,6 +18,7 @@
 #define LLVM_ANALYSIS_ALIASSETTRACKER_H
 
 #include "llvm/Support/CallSite.h"
+#include "llvm/Support/ValueHandle.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/ADT/ilist.h"
@@ -251,11 +252,24 @@ inline std::ostream& operator<<(std::ostream &OS, const AliasSet &AS) {
 
 
 class AliasSetTracker {
+  /// CallbackVH - A CallbackVH to arrange for AliasSetTracker to be
+  /// notified whenever a Value is deleted.
+  class ASTCallbackVH : public CallbackVH {
+    AliasSetTracker *AST;
+    virtual void deleted();
+  public:
+    ASTCallbackVH(Value *V, AliasSetTracker *AST = 0);
+  };
+
   AliasAnalysis &AA;
   ilist<AliasSet> AliasSets;
 
+  typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*, DenseMapInfo<Value*> >
+    PointerMapType;
+
   // Map from pointers to their node
-  DenseMap<Value*, AliasSet::PointerRec*> PointerMap;
+  PointerMapType PointerMap;
+
 public:
   /// AliasSetTracker ctor - Create an empty collection of AliasSets, and use
   /// the specified alias analysis object to disambiguate load and store
@@ -364,7 +378,7 @@ private:
   // getEntryFor - Just like operator[] on the map, except that it creates an
   // entry for the pointer if it doesn't already exist.
   AliasSet::PointerRec &getEntryFor(Value *V) {
-    AliasSet::PointerRec *&Entry = PointerMap[V];
+    AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
     if (Entry == 0)
       Entry = new AliasSet::PointerRec(V);
     return *Entry;
diff --git a/lib/Analysis/AliasSetTracker.cpp b/lib/Analysis/AliasSetTracker.cpp
index 841cd2be3b2..9f201c322df 100644
--- a/lib/Analysis/AliasSetTracker.cpp
+++ b/lib/Analysis/AliasSetTracker.cpp
@@ -187,8 +187,8 @@ bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const {
 
 void AliasSetTracker::clear() {
   // Delete all the PointerRec entries.
-  for (DenseMap<Value*, AliasSet::PointerRec*>::iterator I = PointerMap.begin(),
-       E = PointerMap.end(); I != E; ++I)
+  for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
+       I != E; ++I)
     I->second->eraseFromList();
   
   PointerMap.clear();
@@ -485,7 +485,7 @@ void AliasSetTracker::deleteValue(Value *PtrVal) {
         AS->removeCallSite(CS);
 
   // First, look up the PointerRec for this pointer.
-  DenseMap<Value*, AliasSet::PointerRec*>::iterator I = PointerMap.find(PtrVal);
+  PointerMapType::iterator I = PointerMap.find(PtrVal);
   if (I == PointerMap.end()) return;  // Noop
 
   // If we found one, remove the pointer from the alias set it is in.
@@ -511,7 +511,7 @@ void AliasSetTracker::copyValue(Value *From, Value *To) {
   AA.copyValue(From, To);
 
   // First, look up the PointerRec for this pointer.
-  DenseMap<Value*, AliasSet::PointerRec*>::iterator I = PointerMap.find(From);
+  PointerMapType::iterator I = PointerMap.find(From);
   if (I == PointerMap.end())
     return;  // Noop
   assert(I->second->hasAliasSet() && "Dead entry?");
@@ -575,6 +575,22 @@ void AliasSetTracker::print(std::ostream &OS) const {
 void AliasSet::dump() const { print (cerr); }
 void AliasSetTracker::dump() const { print(cerr); }
 
+//===----------------------------------------------------------------------===//
+//                     ASTCallbackVH Class Implementation
+//===----------------------------------------------------------------------===//
+
+void AliasSetTracker::ASTCallbackVH::deleted() {
+  assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
+  AST->deleteValue(getValPtr());
+  // this now dangles!
+}
+
+AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
+  : CallbackVH(V == DenseMapInfo<Value *>::getEmptyKey() ? 0 :
+               V == DenseMapInfo<Value *>::getTombstoneKey() ? 0 :
+               V),
+    AST(ast) {}
+
 //===----------------------------------------------------------------------===//
 //                            AliasSetPrinter Pass
 //===----------------------------------------------------------------------===//
-- 
2.34.1