Refactor force-inlining macros and use EIGEN_ALWAYS_INLINE to force inlining of the integer overflow helpers, whose non-inlining caused major performance problems, see the mailing list thread 'Significant perf regression probably due to bug #363 patches'

Eigen/src/Core/PlainObjectBase.h

@@ -35,7 +35,7 @@
 namespace internal {
 
 template<typename Index>
-inline void check_rows_cols_for_overflow(Index rows, Index cols)
+EIGEN_ALWAYS_INLINE void check_rows_cols_for_overflow(Index rows, Index cols)
 {
   // http://hg.mozilla.org/mozilla-central/file/6c8a909977d3/xpcom/ds/CheckedInt.h#l242
   // we assume Index is signed

Eigen/src/Core/products/GeneralBlockPanelKernel.h

@@ -118,14 +118,14 @@ inline void computeProductBlockingSizes(std::ptrdiff_t& k, std::ptrdiff_t& m, st
   // FIXME (a bit overkill maybe ?)
 
   template<typename CJ, typename A, typename B, typename C, typename T> struct gebp_madd_selector {
-    EIGEN_STRONG_INLINE EIGEN_ALWAYS_INLINE_ATTRIB static void run(const CJ& cj, A& a, B& b, C& c, T& /*t*/)
+    EIGEN_ALWAYS_INLINE static void run(const CJ& cj, A& a, B& b, C& c, T& /*t*/)
     {
       c = cj.pmadd(a,b,c);
     }
   };
 
   template<typename CJ, typename T> struct gebp_madd_selector<CJ,T,T,T,T> {
-    EIGEN_STRONG_INLINE EIGEN_ALWAYS_INLINE_ATTRIB static void run(const CJ& cj, T& a, T& b, T& c, T& t)
+    EIGEN_ALWAYS_INLINE static void run(const CJ& cj, T& a, T& b, T& c, T& t)
     {
       t = b; t = cj.pmul(a,t); c = padd(c,t);
     }

Eigen/src/Core/util/Macros.h

@@ -130,31 +130,34 @@
 #define EIGEN_MAKESTRING2(a) #a
 #define EIGEN_MAKESTRING(a) EIGEN_MAKESTRING2(a)
 
-// EIGEN_ALWAYS_INLINE_ATTRIB should be use in the declaration of function
-// which should be inlined even in debug mode.
-// FIXME with the always_inline attribute,
-// gcc 3.4.x reports the following compilation error:
-//   Eval.h:91: sorry, unimplemented: inlining failed in call to 'const Eigen::Eval<Derived> Eigen::MatrixBase<Scalar, Derived>::eval() const'
-//    : function body not available
-#if EIGEN_GNUC_AT_LEAST(4,0)
-#define EIGEN_ALWAYS_INLINE_ATTRIB __attribute__((always_inline))
-#else
-#define EIGEN_ALWAYS_INLINE_ATTRIB
-#endif
-
 #if EIGEN_GNUC_AT_LEAST(4,1) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 #define EIGEN_FLATTEN_ATTRIB __attribute__((flatten))
 #else
 #define EIGEN_FLATTEN_ATTRIB
 #endif
 
-// EIGEN_FORCE_INLINE means "inline as much as possible"
+// EIGEN_STRONG_INLINE is a stronger version of the inline, using __forceinline on MSVC,
+// but it still doesn't use GCC's always_inline. This is useful in (common) situations where MSVC needs forceinline
+// but GCC is still doing fine with just inline.
 #if (defined _MSC_VER) || (defined __INTEL_COMPILER)
 #define EIGEN_STRONG_INLINE __forceinline
 #else
 #define EIGEN_STRONG_INLINE inline
 #endif
 
+// EIGEN_ALWAYS_INLINE is the stronget, it has the effect of making the function inline and adding every possible
+// attribute to maximize inlining. This should only be used when really necessary: in particular,
+// it uses __attribute__((always_inline)) on GCC, which most of the time is useless and can severely harm compile times.
+// FIXME with the always_inline attribute,
+// gcc 3.4.x reports the following compilation error:
+//   Eval.h:91: sorry, unimplemented: inlining failed in call to 'const Eigen::Eval<Derived> Eigen::MatrixBase<Scalar, Derived>::eval() const'
+//    : function body not available
+#if EIGEN_GNUC_AT_LEAST(4,0)
+#define EIGEN_ALWAYS_INLINE __attribute__((always_inline)) inline
+#else
+#define EIGEN_ALWAYS_INLINE EIGEN_STRONG_INLINE
+#endif
+
 #if (defined __GNUC__)
 #define EIGEN_DONT_INLINE __attribute__((noinline))
 #elif (defined _MSC_VER)

Eigen/src/Core/util/Memory.h

@@ -354,7 +354,7 @@ template<typename T> inline void destruct_elements_of_array(T *ptr, size_t size)
 *****************************************************************************/
 
 template<typename T>
-inline void check_size_for_overflow(size_t size)
+EIGEN_ALWAYS_INLINE void check_size_for_overflow(size_t size)
 {
   if(size > size_t(-1) / sizeof(T))
     throw_std_bad_alloc();