From 1b98b7347248b959a76157a1da16ce70253fb597 Mon Sep 17 00:00:00 2001
From: Benoit Jacob <jacob.benoit.1@gmail.com>
Date: Sun, 6 Nov 2011 16:27:41 -0500
Subject: 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/util/Macros.h | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

(limited to 'Eigen/src/Core/util/Macros.h')

diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index df676fcf4..2b3810bcc 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/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)
-- 
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