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authorDavid Woodhouse <David.Woodhouse@intel.com>2012-12-03 16:25:40 +0000
committerDavid Woodhouse <David.Woodhouse@intel.com>2012-12-06 01:22:31 +0000
commitcf66bb93e0f75e0a4ba1ec070692618fa028e994 (patch)
tree0ae48658adb29f50bdd85a94cbb84670a234f441 /include/linux/compiler-intel.h
parent27d7c2a006a81c04fab00b8cd81b99af3b32738d (diff)
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.h7
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
+