Sema: Give a typically small DenseMap some inline capacity.

Also reflow code a bit, no change in functionality.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179382 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index f755b8c..7ef04e9 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -2701,11 +2701,10 @@
   llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
   if (Stored.isNull())
     Stored = Inst;
-  else if (Stored.is<Decl *>()) {
+  else if (DeclArgumentPack *Pack = Stored.dyn_cast<DeclArgumentPack *>())
+    Pack->push_back(Inst);
+  else
     assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
-    Stored = Inst;
-  } else
-    LocalDecls[D].get<DeclArgumentPack *>()->push_back(Inst);
 }
 
 void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,