Special case 0 and 1 matcher in makeAllOfComposite().

Summary:
Remove unnecessary wrapping for the 0 and 1 matcher cases of
makeAllOfComposite(). We don't need a variadic wrapper for those cases.
Refactor TrueMatcher to take advandage of the new conversions between
DynTypedMatcher and Matcher<T>. Also, make it a singleton.
This change improves our clang-tidy related benchmarks by ~12%.

Reviewers: klimek

Subscribers: klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D5675

llvm-svn: 219431

1 files changed, 25 insertions, 0 deletions

diff --git a/clang/lib/ASTMatchers/ASTMatchersInternal.cpp b/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
index ec60f0d9498..f6fd5ba2a3f 100644
--- a/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
+++ b/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
@@ -13,6 +13,7 @@
 
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/ASTMatchers/ASTMatchersInternal.h"
+#include "llvm/Support/ManagedStatic.h"
 
 namespace clang {
 namespace ast_matchers {
@@ -64,6 +65,25 @@ class IdDynMatcher : public DynMatcherInterface {
   const IntrusiveRefCntPtr<DynMatcherInterface> InnerMatcher;
 };
 
+/// \brief A matcher that always returns true.
+///
+/// We only ever need one instance of this matcher, so we create a global one
+/// and reuse it to reduce the overhead of the matcher and increase the chance
+/// of cache hits.
+struct TrueMatcherImpl {
+  TrueMatcherImpl() : Instance(new Impl) {}
+  const IntrusiveRefCntPtr<DynMatcherInterface> Instance;
+
+  class Impl : public DynMatcherInterface {
+   public:
+    bool dynMatches(const ast_type_traits::DynTypedNode &, ASTMatchFinder *,
+                    BoundNodesTreeBuilder *) const override {
+      return true;
+    }
+  };
+};
+static llvm::ManagedStatic<TrueMatcherImpl> TrueMatcherInstance;
+
 }  // namespace
 
 DynTypedMatcher DynTypedMatcher::constructVariadic(
@@ -83,6 +103,11 @@ DynTypedMatcher DynTypedMatcher::constructVariadic(
   return Result;
 }
 
+DynTypedMatcher DynTypedMatcher::trueMatcher(
+    ast_type_traits::ASTNodeKind NodeKind) {
+  return DynTypedMatcher(NodeKind, NodeKind, TrueMatcherInstance->Instance);
+}
+
 DynTypedMatcher DynTypedMatcher::dynCastTo(
     const ast_type_traits::ASTNodeKind Kind) const {
   auto Copy = *this;