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compiler.h: add __visible 

gcc 4.6+ has support for a externally_visible attribute that prevents the
optimizer from optimizing unused symbols away.  Add a __visible macro to
use it with that compiler version or later.

This is used (at least) by the "Link Time Optimization" patchset.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andi Kleen 2012-09-17 14:09:15 -07:00 committed by Linus Torvalds
parent 579035dc5d
commit 9a858dc7ce
2 changed files with 11 additions and 0 deletions
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7
include/linux/compiler-gcc4.h
View File

@ -49,6 +49,13 @@
#endif
#endif
#if __GNUC_MINOR__ >= 6
/*
* Tell the optimizer that something else uses this function or variable.
*/
#define __visible __attribute__((externally_visible))
#endif
#if __GNUC_MINOR__ > 0
#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
#endif

4
include/linux/compiler.h
View File

@ -278,6 +278,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
# define __section(S) __attribute__ ((__section__(#S)))
#endif
#ifndef __visible
#define __visible
#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))