Add a new WeakVH value handle; NFC

docs/ProgrammersManual.rst

@@ -1416,9 +1416,9 @@ llvm/IR/ValueMap.h
 ValueMap is a wrapper around a :ref:`DenseMap <dss_densemap>` mapping
 ``Value*``\ s (or subclasses) to another type.  When a Value is deleted or
 RAUW'ed, ValueMap will update itself so the new version of the key is mapped to
-the same value, just as if the key were a WeakVH.  You can configure exactly how
-this happens, and what else happens on these two events, by passing a ``Config``
-parameter to the ValueMap template.
+the same value, just as if the key were a WeakTrackingVH.  You can configure
+exactly how this happens, and what else happens on these two events, by passing
+a ``Config`` parameter to the ValueMap template.
 
 .. _dss_intervalmap:
 

include/llvm/Analysis/AssumptionCache.h

@@ -48,7 +48,7 @@ class AssumptionCache {
 
   /// \brief Vector of weak value handles to calls of the @llvm.assume
   /// intrinsic.
-  SmallVector<WeakVH, 4> AssumeHandles;
+  SmallVector<WeakTrackingVH, 4> AssumeHandles;
 
   /// \brief Flag tracking whether we have scanned the function yet.
   ///
@@ -86,7 +86,7 @@ class AssumptionCache {
   /// FIXME: We should replace this with pointee_iterator<filter_iterator<...>>
   /// when we can write that to filter out the null values. Then caller code
   /// will become simpler.
-  MutableArrayRef<WeakVH> assumptions() {
+  MutableArrayRef<WeakTrackingVH> assumptions() {
     if (!Scanned)
       scanFunction();
     return AssumeHandles;

include/llvm/Analysis/CallGraph.h

@@ -169,7 +169,7 @@ class CallGraphNode {
 public:
   /// \brief A pair of the calling instruction (a call or invoke)
   /// and the call graph node being called.
-  typedef std::pair<WeakVH, CallGraphNode *> CallRecord;
+  typedef std::pair<WeakTrackingVH, CallGraphNode *> CallRecord;
 
 public:
   typedef std::vector<CallRecord> CalledFunctionsVector;

include/llvm/Analysis/DxilValueCache.h

@@ -31,7 +31,7 @@ struct DxilValueCache : public ImmutablePass {
       void allUsesReplacedWith(Value *) override { setValPtr(nullptr); }
     };
     struct ValueEntry {
-      WeakVH Value;
+      WeakTrackingVH Value;
       ValueVH Self;
       ValueEntry() : Value(nullptr), Self(nullptr) {}
       inline void Set(llvm::Value *Key, llvm::Value *V) {

include/llvm/Analysis/IVUsers.h

@@ -79,7 +79,7 @@ class IVStrideUse : public CallbackVH, public ilist_node<IVStrideUse> {
 
   /// OperandValToReplace - The Value of the operand in the user instruction
   /// that this IVStrideUse is representing.
-  WeakVH OperandValToReplace;
+  WeakTrackingVH OperandValToReplace;
 
   /// PostIncLoops - The set of loops for which Expr has been adjusted to
   /// use post-inc mode. This corresponds with SCEVExpander's post-inc concept.

include/llvm/Analysis/MemoryBuiltins.h

@@ -208,7 +208,7 @@ class ObjectSizeOffsetEvaluator
   : public InstVisitor<ObjectSizeOffsetEvaluator, SizeOffsetEvalType> {
 
   typedef IRBuilder<true, TargetFolder> BuilderTy;
-  typedef std::pair<WeakVH, WeakVH> WeakEvalType;
+  typedef std::pair<WeakTrackingVH, WeakTrackingVH> WeakEvalType;
   typedef DenseMap<const Value*, WeakEvalType> CacheMapTy;
   typedef SmallPtrSet<const Value*, 8> PtrSetTy;
 

include/llvm/Analysis/ScalarEvolutionExpander.h

@@ -138,7 +138,7 @@ namespace llvm {
     /// \brief replace congruent phis with their most canonical
     /// representative. Return the number of phis eliminated.
     unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
-                                 SmallVectorImpl<WeakVH> &DeadInsts,
+                                 SmallVectorImpl<WeakTrackingVH> &DeadInsts,
                                  const TargetTransformInfo *TTI = nullptr);
 
     /// \brief Insert code to directly compute the specified SCEV expression

include/llvm/IR/ValueHandle.h

@@ -45,59 +45,62 @@ class ValueHandleBase {
   ///
   /// This is to avoid having a vtable for the light-weight handle pointers. The
   /// fully general Callback version does have a vtable.
-  enum HandleBaseKind {
-    Assert,
-    Callback,
-    Tracking,
-    Weak
-  };
+  enum HandleBaseKind { Assert, Callback, Weak, WeakTracking };
 
 private:
   PointerIntPair<ValueHandleBase**, 2, HandleBaseKind> PrevPair;
   ValueHandleBase *Next;
 
-  Value* V;
+  Value *Val;
+
+  void setValPtr(Value *V) { Val = V; }
 
   ValueHandleBase(const ValueHandleBase&) = delete;
 public:
   explicit ValueHandleBase(HandleBaseKind Kind)
-    : PrevPair(nullptr, Kind), Next(nullptr), V(nullptr) {}
+    : PrevPair(nullptr, Kind), Next(nullptr), Val(nullptr) {}
   ValueHandleBase(HandleBaseKind Kind, Value *V)
-    : PrevPair(nullptr, Kind), Next(nullptr), V(V) {
-    if (isValid(V))
+    : PrevPair(nullptr, Kind), Next(nullptr), Val(V) {
+    if (isValid(getValPtr()))
       AddToUseList();
   }
   ValueHandleBase(HandleBaseKind Kind, const ValueHandleBase &RHS)
-    : PrevPair(nullptr, Kind), Next(nullptr), V(RHS.V) {
-    if (isValid(V))
+      : PrevPair(nullptr, Kind), Next(nullptr), Val(RHS.getValPtr()) {
+    if (isValid(getValPtr()))
       AddToExistingUseList(RHS.getPrevPtr());
   }
   ~ValueHandleBase() {
-    if (isValid(V))
+    if (isValid(getValPtr()))
       RemoveFromUseList();
   }
 
   Value *operator=(Value *RHS) {
-    if (V == RHS) return RHS;
-    if (isValid(V)) RemoveFromUseList();
-    V = RHS;
-    if (isValid(V)) AddToUseList();
+    if (getValPtr() == RHS)
+      return RHS;
+    if (isValid(getValPtr()))
+      RemoveFromUseList();
+    setValPtr(RHS);
+    if (isValid(getValPtr()))
+      AddToUseList();
     return RHS;
   }
 
   Value *operator=(const ValueHandleBase &RHS) {
-    if (V == RHS.V) return RHS.V;
-    if (isValid(V)) RemoveFromUseList();
-    V = RHS.V;
-    if (isValid(V)) AddToExistingUseList(RHS.getPrevPtr());
-    return V;
+    if (getValPtr() == RHS.getValPtr())
+      return RHS.getValPtr();
+    if (isValid(getValPtr()))
+      RemoveFromUseList();
+    setValPtr(RHS.getValPtr());
+    if (isValid(getValPtr()))
+      AddToExistingUseList(RHS.getPrevPtr());
+    return getValPtr();
   }
 
-  Value *operator->() const { return V; }
-  Value &operator*() const { return *V; }
+  Value *operator->() const { return getValPtr(); }
+  Value &operator*() const { return *getValPtr(); }
 
 protected:
-  Value *getValPtr() const { return V; }
+  Value *getValPtr() const { return Val; }
 
   static bool isValid(Value *V) {
     return V &&
@@ -131,21 +134,52 @@ class ValueHandleBase {
   void RemoveFromUseList();
 };
 
+/// \brief A nullable Value handle that is nullable.
+///
+/// This is a value handle that points to a value, and nulls itself
+/// out if that value is deleted.
+class WeakVH : public ValueHandleBase {
+public:
+  WeakVH() : ValueHandleBase(Weak) {}
+  WeakVH(Value *P) : ValueHandleBase(Weak, P) {}
+  WeakVH(const WeakVH &RHS) : ValueHandleBase(Weak, RHS) {}
+
+  WeakVH &operator=(const WeakVH &RHS) = default;
+
+  Value *operator=(Value *RHS) { return ValueHandleBase::operator=(RHS); }
+  Value *operator=(const ValueHandleBase &RHS) {
+    return ValueHandleBase::operator=(RHS);
+  }
+
+  operator Value *() const { return getValPtr(); }
+};
+
+// Specialize simplify_type to allow WeakVH to participate in
+// dyn_cast, isa, etc.
+template <> struct simplify_type<WeakVH> {
+  typedef Value *SimpleType;
+  static SimpleType getSimplifiedValue(WeakVH &WVH) { return WVH; }
+};
+template <> struct simplify_type<const WeakVH> {
+  typedef Value *SimpleType;
+  static SimpleType getSimplifiedValue(const WeakVH &WVH) { return WVH; }
+};
+
 /// \brief Value handle that is nullable, but tries to track the Value.
 ///
 /// This is a value handle that tries hard to point to a Value, even across
 /// RAUW operations, but will null itself out if the value is destroyed.  this
 /// is useful for advisory sorts of information, but should not be used as the
 /// key of a map (since the map would have to rearrange itself when the pointer
 /// changes).
-class WeakVH : public ValueHandleBase {
+class WeakTrackingVH : public ValueHandleBase {
 public:
-  WeakVH() : ValueHandleBase(Weak) {}
-  WeakVH(Value *P) : ValueHandleBase(Weak, P) {}
-  WeakVH(const WeakVH &RHS)
-    : ValueHandleBase(Weak, RHS) {}
+  WeakTrackingVH() : ValueHandleBase(WeakTracking) {}
+  WeakTrackingVH(Value *P) : ValueHandleBase(WeakTracking, P) {}
+  WeakTrackingVH(const WeakTrackingVH &RHS)
+      : ValueHandleBase(WeakTracking, RHS) {}
 
-  WeakVH &operator=(const WeakVH &RHS) = default;
+  WeakTrackingVH &operator=(const WeakTrackingVH &RHS) = default;
 
   Value *operator=(Value *RHS) {
     return ValueHandleBase::operator=(RHS);
@@ -157,17 +191,23 @@ class WeakVH : public ValueHandleBase {
   operator Value*() const {
     return getValPtr();
   }
+
+  bool pointsToAliveValue() const {
+    return ValueHandleBase::isValid(getValPtr());
+  }
 };
 
-// Specialize simplify_type to allow WeakVH to participate in
+// Specialize simplify_type to allow WeakTrackingVH to participate in
 // dyn_cast, isa, etc.
-template <> struct simplify_type<WeakVH> {
+template <> struct simplify_type<WeakTrackingVH> {
   typedef Value *SimpleType;
-  static SimpleType getSimplifiedValue(WeakVH &WVH) { return WVH; }
+  static SimpleType getSimplifiedValue(WeakTrackingVH &WVH) { return WVH; }
 };
-template <> struct simplify_type<const WeakVH> {
+template <> struct simplify_type<const WeakTrackingVH> {
   typedef Value *SimpleType;
-  static SimpleType getSimplifiedValue(const WeakVH &WVH) { return WVH; }
+  static SimpleType getSimplifiedValue(const WeakTrackingVH &WVH) {
+    return WVH;
+  }
 };
 
 /// \brief Value handle that asserts if the Value is deleted.
@@ -274,39 +314,43 @@ struct isPodLike<AssertingVH<T> > {
 /// to a Value (or subclass) across some operations which may move that value,
 /// but should never destroy it or replace it with some unacceptable type.
 ///
-/// It is an error to do anything with a TrackingVH whose value has been
-/// destroyed, except to destruct it.
-///
 /// It is an error to attempt to replace a value with one of a type which is
 /// incompatible with any of its outstanding TrackingVHs.
-template<typename ValueTy>
-class TrackingVH : public ValueHandleBase {
-  void CheckValidity() const {
-    Value *VP = ValueHandleBase::getValPtr();
+///
+/// It is an error to read from a TrackingVH that does not point to a valid
+/// value.  A TrackingVH is said to not point to a valid value if either it
+/// hasn't yet been assigned a value yet or because the value it was tracking
+/// has since been deleted.
+///
+/// Assigning a value to a TrackingVH is always allowed, even if said TrackingVH
+/// no longer points to a valid value.
+template <typename ValueTy> class TrackingVH {
+  WeakTrackingVH InnerHandle;
 
-    // Null is always ok.
-    if (!VP) return;
+public:
+  ValueTy *getValPtr() const {
+    // HLSL Change begin
+    // This is align with what the original TrackingVH does, Null is always ok.
+    if (InnerHandle.operator llvm::Value *() == nullptr)
+      return nullptr;
+    //HLSL Change end.
 
-    // Check that this value is valid (i.e., it hasn't been deleted). We
-    // explicitly delay this check until access to avoid requiring clients to be
-    // unnecessarily careful w.r.t. destruction.
-    assert(ValueHandleBase::isValid(VP) && "Tracked Value was deleted!");
+    assert(InnerHandle.pointsToAliveValue() &&
+           "TrackingVH must be non-null and valid on dereference!");
 
     // Check that the value is a member of the correct subclass. We would like
     // to check this property on assignment for better debugging, but we don't
     // want to require a virtual interface on this VH. Instead we allow RAUW to
     // replace this value with a value of an invalid type, and check it here.
-    assert(isa<ValueTy>(VP) &&
+    assert(isa<ValueTy>(InnerHandle) &&
            "Tracked Value was replaced by one with an invalid type!");
+    return cast<ValueTy>(InnerHandle);
   }
 
-  ValueTy *getValPtr() const {
-    CheckValidity();
-    return (ValueTy*)ValueHandleBase::getValPtr();
-  }
   void setValPtr(ValueTy *P) {
-    CheckValidity();
-    ValueHandleBase::operator=(GetAsValue(P));
+    // Assigning to non-valid TrackingVH's are fine so we just unconditionally
+    // assign here.
+    InnerHandle = GetAsValue(P);
   }
 
   // Convert a ValueTy*, which may be const, to the type the base
@@ -315,9 +359,9 @@ class TrackingVH : public ValueHandleBase {
   static Value *GetAsValue(const Value *V) { return const_cast<Value*>(V); }
 
 public:
-  TrackingVH() : ValueHandleBase(Tracking) {}
-  TrackingVH(ValueTy *P) : ValueHandleBase(Tracking, GetAsValue(P)) {}
-  TrackingVH(const TrackingVH &RHS) : ValueHandleBase(Tracking, RHS) {}
+  TrackingVH() {}
+  TrackingVH(ValueTy *P) { setValPtr(P); }
+  TrackingVH(const TrackingVH &RHS) { setValPtr(RHS.getValPtr()); } // HLSL Change
 
   operator ValueTy*() const {
     return getValPtr();
@@ -368,7 +412,8 @@ class CallbackVH : public ValueHandleBase {
   ///
   /// Called when this->getValPtr() is destroyed, inside ~Value(), so you
   /// may call any non-virtual Value method on getValPtr(), but no subclass
-  /// methods.  If WeakVH were implemented as a CallbackVH, it would use this
+  /// methods.  If WeakTrackingVH were implemented as a CallbackVH, it would use
+  /// this
   /// method to call setValPtr(NULL).  AssertingVH would use this method to
   /// cause an assertion failure.
   ///
@@ -379,7 +424,8 @@ class CallbackVH : public ValueHandleBase {
   /// \brief Callback for Value RAUW.
   ///
   /// Called when this->getValPtr()->replaceAllUsesWith(new_value) is called,
-  /// _before_ any of the uses have actually been replaced.  If WeakVH were
+  /// _before_ any of the uses have actually been replaced.  If WeakTrackingVH
+  /// were
   /// implemented as a CallbackVH, it would use this method to call
   /// setValPtr(new_value).  AssertingVH would do nothing in this method.
   virtual void allUsesReplacedWith(Value *) {}

include/llvm/Transforms/Utils/Cloning.h

@@ -209,7 +209,7 @@ class InlineFunctionInfo {
 
   /// InlinedCalls - InlineFunction fills this in with callsites that were
   /// inlined from the callee.  This is only filled in if CG is non-null.
-  SmallVector<WeakVH, 8> InlinedCalls;
+  SmallVector<WeakTrackingVH, 8> InlinedCalls;
 
   void reset() {
     StaticAllocas.clear();

include/llvm/Transforms/Utils/SimplifyIndVar.h

@@ -58,12 +58,13 @@ class IVVisitor {
 /// simplifyUsersOfIV - Simplify instructions that use this induction variable
 /// by using ScalarEvolution to analyze the IV's recurrence.
 bool simplifyUsersOfIV(PHINode *CurrIV, ScalarEvolution *SE, LPPassManager *LPM,
-                       SmallVectorImpl<WeakVH> &Dead, IVVisitor *V = nullptr);
+                       SmallVectorImpl<WeakTrackingVH> &Dead,
+                       IVVisitor *V = nullptr);
 
 /// SimplifyLoopIVs - Simplify users of induction variables within this
 /// loop. This does not actually change or add IVs.
 bool simplifyLoopIVs(Loop *L, ScalarEvolution *SE, LPPassManager *LPM,
-                     SmallVectorImpl<WeakVH> &Dead);
+                     SmallVectorImpl<WeakTrackingVH> &Dead);
 
 } // namespace llvm
 

include/llvm/Transforms/Utils/ValueMapper.h

@@ -20,7 +20,7 @@
 namespace llvm {
   class Value;
   class Instruction;
-  typedef ValueMap<const Value *, WeakVH> ValueToValueMapTy;
+  typedef ValueMap<const Value *, WeakTrackingVH> ValueToValueMapTy;
 
   /// ValueMapTypeRemapper - This is a class that can be implemented by clients
   /// to remap types when cloning constants and instructions.