[PATCH] When CONFIG_CC_OPTIMIZE_FOR_SIZE, allow gcc4 to control inlining

If optimizing for size (CONFIG_CC_OPTIMIZE_FOR_SIZE), allow gcc4 compilers
to decide what to inline and what not - instead of the kernel forcing gcc
to inline all the time.  This requires several places that require to be
inlined to be marked as such, previous patches in this series do that.

Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Arjan van de Ven <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Documentation/feature-removal-schedule.txt

@@ -123,6 +123,15 @@ Who:	Christoph Hellwig <[email protected]>
 
 ---------------------------
 
+What:	CONFIG_FORCED_INLINING
+When:	June 2006
+Why:	Config option is there to see if gcc is good enough. (in january
+        2006). If it is, the behavior should just be the default. If it's not,
+	the option should just go away entirely.
+Who:    Arjan van de Ven
+
+---------------------------
+
 What:	START_ARRAY ioctl for md
 When:	July 2006
 Files:	drivers/md/md.c

include/linux/compiler-gcc4.h

@@ -3,6 +3,15 @@
 /* These definitions are for GCC v4.x.  */
 #include <linux/compiler-gcc.h>
 
+#ifdef CONFIG_FORCED_INLINING
+# undef inline
+# undef __inline__
+# undef __inline
+# define inline			inline		__attribute__((always_inline))
+# define __inline__		__inline__	__attribute__((always_inline))
+# define __inline		__inline	__attribute__((always_inline))
+#endif
+
 #define __attribute_used__	__attribute__((__used__))
 #define __must_check 		__attribute__((warn_unused_result))
 #define __compiler_offsetof(a,b) __builtin_offsetof(a,b)

lib/Kconfig.debug

@@ -195,6 +195,20 @@ config FRAME_POINTER
 	  some architectures or if you use external debuggers.
 	  If you don't debug the kernel, you can say N.
 
+config FORCED_INLINING
+	bool "Force gcc to inline functions marked 'inline'"
+	depends on DEBUG_KERNEL
+	default y
+	help
+	  This option determines if the kernel forces gcc to inline the functions
+	  developers have marked 'inline'. Doing so takes away freedom from gcc to
+	  do what it thinks is best, which is desirable for the gcc 3.x series of
+	  compilers. The gcc 4.x series have a rewritten inlining algorithm and
+	  disabling this option will generate a smaller kernel there. Hopefully
+	  this algorithm is so good that allowing gcc4 to make the decision can
+	  become the default in the future, until then this option is there to
+	  test gcc for this.
+
 config RCU_TORTURE_TEST
 	tristate "torture tests for RCU"
 	depends on DEBUG_KERNEL