diff options
| author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2015-11-06 05:45:02 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-11-06 06:34:48 +0300 |
| commit | a744fd17b5233360681ce03e43804406745b680b (patch) | |
| tree | 3b7600477b108469dd2e435e32d861100e559dce /include/linux/compiler-gcc.h | |
| parent | fda901241fb89449244537db4fb27b06e491b74f (diff) | |
| download | linux-a744fd17b5233360681ce03e43804406745b680b.tar.xz | |
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>
Diffstat (limited to 'include/linux/compiler-gcc.h')
| -rw-r--r-- | include/linux/compiler-gcc.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 8efb40e61d6e..02fa6176120d 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -210,6 +210,23 @@ #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: * |