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| author |   David Woodhouse <David.Woodhouse@intel.com> | 2012-12-03 16:25:40 +0000 |
|---|---|---|
| committer | David Woodhouse <David.Woodhouse@intel.com> | 2012-12-06 01:22:31 +0000 |
| commit | cf66bb93e0f75e0a4ba1ec070692618fa028e994 (patch) | |
| tree | 0ae48658adb29f50bdd85a94cbb84670a234f441 /include/linux/compiler-intel.h | |
| parent | vfs: clear to the end of the buffer on partial buffer reads (diff) | |
| download | linux-dev-cf66bb93e0f75e0a4ba1ec070692618fa028e994.tar.xz linux-dev-cf66bb93e0f75e0a4ba1ec070692618fa028e994.zip | |
byteorder: allow arch to opt to use GCC intrinsics for byteswapping
Since GCC 4.4, there have been __builtin_bswap32() and __builtin_bswap16()
intrinsics. A __builtin_bswap16() came a little later (4.6 for PowerPC,
48 for other platforms).
By using these instead of the inline assembler that most architectures
have in their __arch_swabXX() macros, we let the compiler see what's
actually happening. The resulting code should be at least as good, and
much *better* in the cases where it can be combined with a nearby load
or store, using a load-and-byteswap or store-and-byteswap instruction
(e.g. lwbrx/stwbrx on PowerPC, movbe on Atom).
When GCC is sufficiently recent *and* the architecture opts in to using
the intrinsics by setting CONFIG_ARCH_USE_BUILTIN_BSWAP, they will be
used in preference to the __arch_swabXX() macros. An architecture which
does not set ARCH_USE_BUILTIN_BSWAP will continue to use its own
hand-crafted macros.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'include/linux/compiler-intel.h')
| -rw-r--r-- | include/linux/compiler-intel.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h index d8e636e5607d..973ce10c40b6 100644 --- a/include/linux/compiler-intel.h +++ b/include/linux/compiler-intel.h @@ -29,3 +29,10 @@ #endif #define uninitialized_var(x) x + +#ifndef __HAVE_BUILTIN_BSWAP16__ +/* icc has this, but it's called _bswap16 */ +#define __HAVE_BUILTIN_BSWAP16__ +#define __builtin_bswap16 _bswap16 +#endif + |