[MemorySSA] Add convenience APIs in updater to avoid needing MSSA.

Summary:
Ideally passes should not need to pass MSSA around and do all updates through the updater.
Add convenience APIs to help with that.

Reviewers: george.burgess.iv

Subscribers: sanjoy, jlebar, llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D48334

llvm-svn: 335179

llvm/include/llvm/Analysis/MemorySSAUpdater.h

@@ -138,6 +138,17 @@ public:
   /// on the MemoryAccess for that store/load.
   void removeMemoryAccess(MemoryAccess *);
 
+  /// Remove MemoryAccess for a given instruction, if a MemoryAccess exists.
+  /// This should be called when an instruction (load/store) is deleted from
+  /// the program.
+  void removeMemoryAccess(const Instruction *I) {
+    if (MemoryAccess *MA = MSSA->getMemoryAccess(I))
+      removeMemoryAccess(MA);
+  }
+
+  /// Get handle on MemorySSA.
+  MemorySSA* getMemorySSA() const { return MSSA; }
+
 private:
   // Move What before Where in the MemorySSA IR.
   template <class WhereType>