[ValueHandle] Allow invalidation of BB arguments.

This commit changes the invalidation handler from SILInstruction to ValueBase,
and also invalidates SILArguments.

Author: nadavrot

include/swift/SIL/Notifications.h

@@ -17,7 +17,7 @@ namespace swift {
 
 class ValueBase;
 
-/// A protocol (or inferface) for handling instruction deletion notifications.
+/// A protocol (or inferface) for handling value deletion notifications.
 ///
 /// This class is used as a base class for any class that need to accept
 /// instruction deletion notification messages. This is used by passes and

include/swift/SILAnalysis/AliasAnalysis.h

@@ -83,8 +83,7 @@ class AliasAnalysis : public SILAnalysis {
   bool typesMayAlias(SILType T1, SILType T2);
 
 
-  virtual void handleDeleteNotification(ValueBase *I) override {
-  }
+  virtual void handleDeleteNotification(ValueBase *I) override { }
 
 public:
   AliasAnalysis(SILModule *M) :

lib/SIL/SILBasicBlock.cpp

@@ -43,6 +43,11 @@ SILBasicBlock::~SILBasicBlock() {
     getModule().notifyDeleteHandlers(&*I);
   }
 
+  // Invalidate all of the basic block arguments.
+  for (auto *Arg : BBArgList) {
+    getModule().notifyDeleteHandlers(Arg);
+  }
+
   // iplist's destructor is going to destroy the InstList.
 }
 
@@ -100,10 +105,18 @@ void SILBasicBlock::removeFromParent() {
 SILArgument *SILBasicBlock::replaceBBArg(unsigned i, SILType Ty,
                                          const ValueDecl *D) {
   SILModule &M = getParent()->getModule();
+
+
   assert(BBArgList[i]->use_empty() && "Expected no uses of the old BB arg!");
 
+  // Notify the delete handlers that this argument is being deleted.
+  M.notifyDeleteHandlers(BBArgList[i]);
+
   auto *NewArg = new (M) SILArgument(Ty, D);
   NewArg->setParent(this);
+
+  // TODO: When we switch to malloc/free allocation we'll be leaking memory
+  // here.
   BBArgList[i] = NewArg;
 
   return NewArg;

lib/SIL/SILModule.cpp

@@ -676,8 +676,8 @@ removeDeleteNotificationHandler(DeleteNotificationHandler* Handler) {
   NotificationHandlers.remove(Handler);
 }
 
-void SILModule::notifyDeleteHandlers(ValueBase *Item) {
+void SILModule::notifyDeleteHandlers(ValueBase *V) {
   for (auto *Handler : NotificationHandlers) {
-    Handler->handleDeleteNotification(Item);
+    Handler->handleDeleteNotification(V);
   }
 }

lib/SILPasses/SILCombiner/SILCombine.cpp

@@ -355,8 +355,7 @@ class SILCombine : public SILFunctionTransform {
     }
   }
 
-  virtual void handleDeleteNotification(ValueBase *I) override {
-  }
+  virtual void handleDeleteNotification(ValueBase *I) override { }
 
   StringRef getName() override { return "SIL Combine"; }
 };