Use SmallVector for the requirements on an InstAlias.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155034 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/AsmWriterEmitter.cpp b/utils/TableGen/AsmWriterEmitter.cpp
index 0d6d0c8..d079b45 100644
--- a/utils/TableGen/AsmWriterEmitter.cpp
+++ b/utils/TableGen/AsmWriterEmitter.cpp
@@ -590,7 +590,7 @@
   std::map<StringRef, unsigned> OpMap;
   std::string Result;
   std::string AsmString;
-  std::vector<Record*> ReqFeatures;
+  SmallVector<Record*, 4> ReqFeatures;
 public:
   IAPrinter(std::string R, std::string AS)
     : Result(R), AsmString(AS) {}