Discourage inlining the resize case, as that should happen rather rar…

…ely.

If you additionally reuse buffers, this will increase the performance
further.

The metrics based on some internal benchmarks show a speedup of about 1%:

bitsery <dont inline bad cases>
  BigString: 222092ns
  ComplexLittleObjects: 34115ns
  ComplexLittleObjectsBig: 6222801ns

bitsery <original>
  BigString: 242853ns
  ComplexLittleObjects: 35738ns
  ComplexLittleObjectsBig: 6334747ns

The assembly has been checked to be correct: https://godbolt.org/z/Wr7qvfGrK

Additionally, when allocating code, we can tell the compiler that we are
not resizing to a lower size, this saves on gcc 14 a few instructions.
The improvement should be negligible.

include/bitsery/adapter/buffer.h

@@ -269,12 +269,11 @@ class OutputBufferAdapter
 
   void maybeResize(size_t newOffset, std::true_type)
   {
-    if (newOffset > _bufferSize) {
-      traits::BufferAdapterTraits<Buffer>::increaseBufferSize(
-        *_buffer, _currOffset, newOffset);
-      _beginIt = std::begin(*_buffer);
-      _bufferSize = traits::ContainerTraits<Buffer>::size(*_buffer);
-    }
+    if (newOffset > _bufferSize)
+      BITSERY_UNLIKELY
+      {
+        doResize(newOffset);
+      }
   }
 
   void maybeResize(BITSERY_MAYBE_UNUSED size_t newOffset, std::false_type)
@@ -289,6 +288,14 @@ class OutputBufferAdapter
     std::copy_n(data, size, _beginIt + static_cast<diff_t>(_currOffset));
     _currOffset = newOffset;
   }
+
+  BITSERY_NOINLINE void doResize(size_t newOffset)
+  {
+    traits::BufferAdapterTraits<Buffer>::increaseBufferSize(
+      *_buffer, _currOffset, newOffset);
+    _beginIt = std::begin(*_buffer);
+    _bufferSize = traits::ContainerTraits<Buffer>::size(*_buffer);
+  }
 };
 
 }

include/bitsery/bitsery.h

@@ -36,12 +36,73 @@
   BITSERY_BUILD_VERSION_STR(                                                   \
     BITSERY_MAJOR_VERSION, BITSERY_MINOR_VERSION, BITSERY_PATCH_VERSION)
 
-#if __cplusplus > 201402L
-#define BITSERY_MAYBE_UNUSED [[maybe_unused]]
+#define BITSERY_DO_PRAGMA(x) _Pragma(#x)
+#ifdef __GNUC__
+#define BITSERY_DISABLE_WARNINGS(...)                                          \
+  BITSERY_DO_PRAGMA(GCC diagnostic push)                                       \
+  BITSERY_DO_PRAGMA(GCC diagnostic ignored __VA_ARGS__)
+#define BITSERY_ENABLE_WARNINGS() BITSERY_DO_PRAGMA(GCC diagnostic pop)
+#elif defined(_MSC_VER)
+#define BITSERY_DISABLE_WARNINGS(...)                                          \
+  BITSERY_DO_PRAGMA(GCC diagnostic push)                                       \
+  BITSERY_DO_PRAGMA(GCC diagnostic ignored __VA_ARGS__)                        \
+  BITSERY_DO_PRAGMA(GCC diagnostic pop)
+#define BITSERY_ENABLE_WARNINGS() BITSERY_DO_PRAGMA(GCC diagnostic pop)
+#else
+#define BITSERY_DISABLE_WARNINGS(...)
+#define BITSERY_ENABLE_WARNINGS()
+#endif
+
+#ifdef __clang__
+#define BITSERY_ATTRIBUTE(...)                                                 \
+  BITSERY_DISABLE_WARNINGS("-Wfuture-attribute-extensions")                    \
+  [[__VA_ARGS__]] BITSERY_ENABLE_WARNINGS()
+#elif defined(__GNUC__)
+#define BITSERY_ATTRIBUTE(...) [[__VA_ARGS__]]
+#elif defined(_MSC_VER)
+#define BITSERY_ATTRIBUTE(...) [[__VA_ARGS__]]
+#else
+#define BITSERY_ATTRIBUTE(...) [[__VA_ARGS__]]
+#endif
+
+#if __has_cpp_attribute(likely)
+#define BITSERY_LIKELY BITSERY_ATTRIBUTE(likey)
+#else
+#define BITSERY_LIKELY
+#endif
+
+#if __has_cpp_attribute(unlikely)
+#define BITSERY_UNLIKELY BITSERY_ATTRIBUTE(unlikely)
+#else
+#define BITSERY_UNLIKELY
+#endif
+
+#if __has_cpp_attribute(maybe_unused)
+#define BITSERY_MAYBE_UNUSED BITSERY_ATTRIBUTE(maybe_unused)
 #else
 #define BITSERY_MAYBE_UNUSED
 #endif
 
+#if __GNUC__
+#define BITSERY_NOINLINE __attribute__((noinline))
+#elif defined(_MSC_VER)
+#define BITSERY_NOINLINE __declspec(noinline)
+#else
+#define BITSERY_NOINLINE
+#endif
+
+#if __GNUC__
+#define BITSERY_ASSUME(cond)                                                   \
+  do {                                                                         \
+    if (!(cond))                                                               \
+      __builtin_unreachable();                                                 \
+  } while (0)
+#elif defined(_MSC_VER)
+#define BITSERY_ASSUME(cond) __assume(cond)
+#else
+#define BITSERY_ASSUME(cond)
+#endif
+
 #include "deserializer.h"
 #include "serializer.h"
 

include/bitsery/traits/core/std_defaults.h

@@ -23,6 +23,7 @@
 #ifndef BITSERY_TRAITS_CORE_STD_DEFAULTS_H
 #define BITSERY_TRAITS_CORE_STD_DEFAULTS_H
 
+#include "../../bitsery.h"
 #include "../../details/serialization_common.h"
 #include "traits.h"
 
@@ -103,8 +104,11 @@ struct StdContainerForBufferAdapter<T, true>
       static_cast<size_t>(static_cast<double>(container.size()) * 1.5) + 128;
     // make data cache friendly
     newSize -= newSize % 64; // 64 is cache line size
-    container.resize(
-      (std::max)(newSize > minSize ? newSize : minSize, container.capacity()));
+    auto resize =
+      (std::max)(newSize > minSize ? newSize : minSize, container.capacity());
+    BITSERY_ASSUME(resize >= container.size());
+    BITSERY_ASSUME(resize >= container.capacity());
+    container.resize(resize);
   }
 };