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Add new __unreachable() builtin

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This is one of the few post gcc4.2 builtins that has been implemented by
clang:

__builtin_unreachable is used to indicate that a specific point in the
program cannot be reached, even if the compiler might otherwise think it
can. This is useful to improve optimization and eliminates certain
warnings.

Hinted by:	NetBSD
Differential Revision:	https://reviews.freebsd.org/D2536
This commit is contained in:
Pedro F. Giffuni 2015-05-14 15:49:48 +00:00
parent 60aa2c85fa
commit 732b31de5d
1 changed files with 6 additions and 0 deletions
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6
sys/sys/cdefs.h
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@ -388,6 +388,12 @@
#define __alloc_size(x)
#endif
#if __has_builtin(__builtin_unreachable) || __GNUC_PREREQ__(4, 6)
#define __unreachable() __builtin_unreachable()
#else
#define __unreachable() do {} while (/*CONSTCOND*/0)
#endif
#if __has_attribute(alloc_align) || __GNUC_PREREQ__(4, 9)
#define __alloc_align(x) __attribute__((__alloc_align__(x)))
#else