Fix a wrong use of AA in FlattenCFG

Author: Chengjunp

llvm/lib/Transforms/Utils/FlattenCFG.cpp

@@ -357,8 +357,12 @@ bool FlattenCFGOpt::CompareIfRegionBlock(BasicBlock *Block1, BasicBlock *Block2,
       for (BasicBlock::iterator BI(PBI2), BE(PTI2); BI != BE; ++BI) {
         if (BI->mayReadFromMemory() || BI->mayWriteToMemory()) {
           // Check alias with Head2.
-          if (!AA || !AA->isNoAlias(&*iter1, &*BI))
-            return false;
+          if (AA) {
+            MemoryLocation Loc1 = MemoryLocation::get(&*iter1);
+            MemoryLocation Loc2 = MemoryLocation::get(&*BI);
+            if (!AA->isNoAlias(Loc1, Loc2))
+              return false;
+          }
         }
       }
     }