Fix some abuse of auto flagged by clang's -Wrange-loop-analysis.

llvm-svn: 261524
diff --git a/llvm/lib/Transforms/Utils/MemorySSA.cpp b/llvm/lib/Transforms/Utils/MemorySSA.cpp
index b162567..5fa5baf 100644
--- a/llvm/lib/Transforms/Utils/MemorySSA.cpp
+++ b/llvm/lib/Transforms/Utils/MemorySSA.cpp
@@ -473,7 +473,7 @@
       if (!MD)
         continue;
 
-      for (const auto &U : MD->users()) {
+      for (User *U : MD->users()) {
         BasicBlock *UseBlock;
         // Things are allowed to flow to phi nodes over their predecessor edge.
         if (auto *P = dyn_cast<MemoryPhi>(U)) {