Use address-taken to disambiguate global variable and indirect memops.

Major steps include:
 1). introduces a not-addr-taken bit-field in GlobalVariable
 2). GlobalOpt pass sets "not-address-taken" if it proves a global varirable 
    dosen't have its address taken.
 3). AA use this info for disambiguation. 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193251 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/GlobalVariable.h

@@ -48,6 +48,7 @@ class GlobalVariable : public GlobalValue, public ilist_node<GlobalVariable> {
                                                // can change from its initial
                                                // value before global
                                                // initializers are run?
+  bool notAddrTaken : 1;                       // Dose not have address taken.
 
 public:
   // allocate space for exactly one operand
@@ -174,6 +175,9 @@ public:
     isExternallyInitializedConstant = Val;
   }
 
+  void setAddressMaybeTaken(bool Val) { notAddrTaken = !Val; }
+  bool AddressMaybeTaken(void) const { return !notAddrTaken; }
+
   /// copyAttributesFrom - copy all additional attributes (those not needed to
   /// create a GlobalVariable) from the GlobalVariable Src to this one.
   void copyAttributesFrom(const GlobalValue *Src);