Default SetVector to use a DenseSet.

We use to have an odd difference among MapVector and SetVector. The map
used a DenseMop, but the set used a SmallSet, which in turn uses a
std::set.

I have changed SetVector to use a DenseSet. If you were depending on the
old behaviour you can pass an explicit set type or use SmallSetVector.
The common cases for needing to do it are:

* Optimizing for small sets.
* Sets for types not supported by DenseSet.

llvm-svn: 253439
diff --git a/llvm/utils/TableGen/AsmMatcherEmitter.cpp b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
index f1b9ab3..e55bbd3 100644
--- a/llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -1722,7 +1722,7 @@
 }
 
 static unsigned getConverterOperandID(const std::string &Name,
-                                      SetVector<std::string> &Table,
+                                      SmallSetVector<std::string, 16> &Table,
                                       bool &IsNew) {
   IsNew = Table.insert(Name);
 
@@ -1738,8 +1738,8 @@
 static void emitConvertFuncs(CodeGenTarget &Target, StringRef ClassName,
                              std::vector<std::unique_ptr<MatchableInfo>> &Infos,
                              raw_ostream &OS) {
-  SetVector<std::string> OperandConversionKinds;
-  SetVector<std::string> InstructionConversionKinds;
+  SmallSetVector<std::string, 16> OperandConversionKinds;
+  SmallSetVector<std::string, 16> InstructionConversionKinds;
   std::vector<std::vector<uint8_t> > ConversionTable;
   size_t MaxRowLength = 2; // minimum is custom converter plus terminator.
 
diff --git a/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp b/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
index df61511..8ca4a1b 100644
--- a/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
+++ b/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
@@ -65,8 +65,8 @@
 typedef uint32_t DecoderFixup;
 typedef std::vector<DecoderFixup> FixupList;
 typedef std::vector<FixupList> FixupScopeList;
-typedef SetVector<std::string> PredicateSet;
-typedef SetVector<std::string> DecoderSet;
+typedef SmallSetVector<std::string, 16> PredicateSet;
+typedef SmallSetVector<std::string, 16> DecoderSet;
 struct DecoderTableInfo {
   DecoderTable Table;
   FixupScopeList FixupStack;