As Segher pointed out, inline asm is better than the volatile casting all over
the place. From the PowerPC patch description:
Also use inline functions instead of macros; this actually
improves code generation (some code becomes a little smaller,
probably because of improved alias information -- just a few
hundred bytes total on a default kernel build, nothing shocking).
My config with march=pentium-m and gcc (GCC) 4.1.2 (Gentoo 4.1.2):
text data bss dec hex filename
3434150 249176 176128 3859454 3ae3fe atomic_normal/vmlinux
3435308 249176 176128 3860612 3ae884 atomic_inlineasm/vmlinux
3436201 249176 176128 3861505 3aec01 atomic_inline_volatile/vmlinux
3436203 249176 176128 3861507 3aec03 atomic_volatile/vmlinux
Signed-off-by: Sebastian Siewior <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Chris Snook <[email protected]>
--- a/include/asm-i386/atomic.h
+++ b/include/asm-i386/atomic.h
@@ -25,7 +25,16 @@ typedef struct { int counter; } atomic_t
*
* Atomically reads the value of @v.
*/
-#define atomic_read(v) ((v)->counter)
+static inline int atomic_read(const atomic_t *v)
+{
+ int t;
+
+ asm volatile(
+ "movl %1,%0"
+ : "=r"(t)
+ : "m"(v->counter));
+ return t;
+}
/**
* atomic_set - set atomic variable
@@ -34,7 +43,13 @@ typedef struct { int counter; } atomic_t
*
* Atomically sets the value of @v to @i.
*/
-#define atomic_set(v,i) (((v)->counter) = (i))
+static inline void atomic_set(atomic_t *v, int i)
+{
+ asm volatile(
+ "movl %1,%0"
+ : "=m"(v->counter)
+ : "ir"(i));
+}
/**
* atomic_add - add integer to atomic variable
--
-
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