diff options
| author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2015-11-05 18:45:02 -0800 |
|---|---|---|
| committer | Alex Shi <alex.shi@linaro.org> | 2016-04-13 11:12:52 +0800 |
| commit | cf21721d8e5a6c46bb2ad296f80e5bb718a0168e (patch) | |
| tree | 32927e5a54c788eaf8e7f214352c6465ad0c2e81 | |
| parent | cd5cc28de311109b14b04c92b449c747151151e3 (diff) | |
compiler.h: add support for function attribute assume_aligned
gcc 4.9 added the function attribute assume_aligned, indicating to the
caller that the returned pointer may be assumed to have a certain minimal
alignment. This is useful if, for example, the return value is passed to
memset(). Add a shorthand macro for that.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit a744fd17b5233360681ce03e43804406745b680b)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
| -rw-r--r-- | include/linux/compiler-gcc.h | 17 | ||||
| -rw-r--r-- | include/linux/compiler.h | 8 |
2 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 4a5fd6468375..fae719c3572b 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -203,6 +203,23 @@ #define __visible __attribute__((externally_visible)) #endif + +#if GCC_VERSION >= 40900 +/* + * __assume_aligned(n, k): Tell the optimizer that the returned + * pointer can be assumed to be k modulo n. The second argument is + * optional (default 0), so we use a variadic macro to make the + * shorthand. + * + * Beware: Do not apply this to functions which may return + * ERR_PTRs. Also, it is probably unwise to apply it to functions + * returning extra information in the low bits (but in that case the + * compiler should see some alignment anyway, when the return value is + * massaged by 'flags = ptr & 3; ptr &= ~3;'). + */ +#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) +#endif + /* * GCC 'asm goto' miscompiles certain code sequences: * diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 9122f03cef4f..98be9bdb2105 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -410,6 +410,14 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s #define __visible #endif +/* + * Assume alignment of return value. + */ +#ifndef __assume_aligned +#define __assume_aligned(a, ...) +#endif + + /* Are two types/vars the same type (ignoring qualifiers)? */ #ifndef __same_type # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) |