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>
This commit is contained in:
parent
fda901241f
commit
a744fd17b5
|
@ -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:
|
||||
*
|
||||
|
|
|
@ -417,6 +417,14 @@ 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))
|
||||
|
|
Loading…
Reference in a new issue