Add RAPIDJSON_LIKELY/UNLIKELY and apply them in stack

include/rapidjson/internal/stack.h

@@ -98,7 +98,7 @@ public:
     template<typename T>
     RAPIDJSON_FORCEINLINE T* Push(size_t count = 1) {
          // Expand the stack if needed
-        if (stackTop_ + sizeof(T) * count >= stackEnd_)
+        if (RAPIDJSON_UNLIKELY(stackTop_ + sizeof(T) * count >= stackEnd_))
             Expand<T>(count);
 
         T* ret = reinterpret_cast<T*>(stackTop_);

include/rapidjson/rapidjson.h

@@ -343,6 +343,35 @@ RAPIDJSON_NAMESPACE_END
     RAPIDJSON_JOIN(StaticAssertTypedef, __LINE__) RAPIDJSON_STATIC_ASSERT_UNUSED_ATTRIBUTE
 #endif
 
+///////////////////////////////////////////////////////////////////////////////
+// RAPIDJSON_LIKELY, RAPIDJSON_UNLIKELY
+
+//! Compiler branching hint for expression with high probability to be true.
+/*!
+    \ingroup RAPIDJSON_CONFIG
+    \param x Boolean expression likely to be true.
+*/
+#ifndef RAPIDJSON_LIKELY
+#if defined(__GNUC__) || defined(__clang__)
+#define RAPIDJSON_LIKELY(x) __builtin_expect(!!(x), 1)
+#else
+#define RAPIDJSON_LIKELY(x) x
+#endif
+#endif
+
+//! Compiler branching hint for expression with low probability to be true.
+/*!
+    \ingroup RAPIDJSON_CONFIG
+    \param x Boolean expression unlikely to be true.
+*/
+#ifndef RAPIDJSON_UNLIKELY
+#if defined(__GNUC__) || defined(__clang__)
+#define RAPIDJSON_UNLIKELY(x) __builtin_expect(!!(x), 0)
+#else
+#define RAPIDJSON_UNLIKELY(x) x
+#endif
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 // Helpers
 

test/perftest/rapidjsontest.cpp

@@ -346,4 +346,10 @@ TEST_F(RapidJson, SIMD_SUFFIX(ReaderParse_DummyHandler_FileReadStream)) {
     }
 }
 
+TEST_F(RapidJson, StringBuffer) {
+    StringBuffer sb;
+    for (int i = 0; i < 32 * 1024 * 1024; i++)
+        sb.Put(i & 0x7f);
+}
+
 #endif // TEST_RAPIDJSON