[PATCH] i386: use C code for current_thread_info()
Chuck Ebbert [Tue, 27 Jun 2006 09:53:47 +0000 (02:53 -0700)]
Using C code for current_thread_info() lets the compiler optimize it.
With gcc 4.0.2, kernel is smaller:

    text           data     bss     dec     hex filename
 3645212         555556  312024 4512792  44dc18 2.6.17-rc6-nb-post/vmlinux
 3647276         555556  312024 4514856  44e428 2.6.17-rc6-nb/vmlinux
 -------
   -2064

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-i386/thread_info.h

index fdbc7f4..ff1e2b1 100644 (file)
@@ -83,17 +83,15 @@ struct thread_info {
 #define init_stack             (init_thread_union.stack)
 
 
+/* how to get the current stack pointer from C */
+register unsigned long current_stack_pointer asm("esp") __attribute_used__;
+
 /* how to get the thread information struct from C */
 static inline struct thread_info *current_thread_info(void)
 {
-       struct thread_info *ti;
-       __asm__("andl %%esp,%0; ":"=r" (ti) : "0" (~(THREAD_SIZE - 1)));
-       return ti;
+       return (struct thread_info *)(current_stack_pointer & ~(THREAD_SIZE - 1));
 }
 
-/* how to get the current stack pointer from C */
-register unsigned long current_stack_pointer asm("esp") __attribute_used__;
-
 /* thread information allocation */
 #ifdef CONFIG_DEBUG_STACK_USAGE
 #define alloc_thread_info(tsk)                                 \