@@ -275,23 +275,11 @@ static inline unsigned long fns(unsigned long word, unsigned int n)
* @addr: the address to start counting from
* @value: the value to assign
*/
-static __always_inline void assign_bit(long nr, volatile unsigned long *addr,
- bool value)
-{
- if (value)
- set_bit(nr, addr);
- else
- clear_bit(nr, addr);
-}
+#define assign_bit(nr, addr, value) \
+ ((value) ? set_bit((nr), (addr)) : clear_bit((nr), (addr)))
-static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
- bool value)
-{
- if (value)
- __set_bit(nr, addr);
- else
- __clear_bit(nr, addr);
-}
+#define __assign_bit(nr, addr, value) \
+ ((value) ? __set_bit((nr), (addr)) : __clear_bit((nr), (addr)))
/**
* __ptr_set_bit - Set bit in a pointer's value
Since commit b03fc1173c0c ("bitops: let optimize out non-atomic bitops on compile-time constants"), the compilers are able to expand inline bitmap operations to compile-time initializers when possible. However, during the round of replacement if-__set-else-__clear with __assign_bit() as per Andy's advice, bloat-o-meter showed +1024 bytes difference in object code size for one module (even one function), where the pattern: DECLARE_BITMAP(foo) = { }; // on the stack, zeroed if (a) __set_bit(const_bit_num, foo); if (b) __set_bit(another_const_bit_num, foo); ... is heavily used, although there should be no difference: the bitmap is zeroed, so the second half of __assign_bit() should be compiled-out as a no-op. I either missed the fact that __assign_bit() has bitmap pointer marked as `volatile` (as we usually do for bitops) or was hoping that the compilers would at least try to look past the `volatile` for __always_inline functions. Anyhow, due to that attribute, the compilers were always compiling the whole expression and no mentioned compile-time optimizations were working. Convert __assign_bit() to a macro since it's a very simple if-else and all of the checks are performed inside __set_bit() and __clear_bit(), thus that wrapper has to be as transparent as possible. After that change, despite it showing only -20 bytes change for vmlinux (due to that it's still relatively unpopular), no drastic code size changes happen when replacing if-set-else-clear for onstack bitmaps with __assign_bit(), meaning the compiler now expands them to the actual operations will all the expected optimizations. Atomic assign_bit() is less affected due to its nature, but let's convert it to a macro as well to keep the code consistent and not leave a place for possible suboptimal codegen. Moreover, with certain kernel configuration it actually gives some saves (x86): do_ip_setsockopt 4154 4099 -55 Suggested-by: Yury Norov <yury.norov@gmail.com> # assign_bit() too Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> --- include/linux/bitops.h | 20 ++++---------------- 1 file changed, 4 insertions(+), 16 deletions(-)