diff options
| author | Dave Martin <dave.martin@linaro.org> | 2011-11-24 12:23:18 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-12-06 11:15:26 +0000 |
| commit | df0e74da6df1568e3722466f85f2f08324bc767e (patch) | |
| tree | b32cad089d75d0d40d6ef96a0d610d668dc33580 | |
| parent | 7dbaa466780a754154531b44c2086f6618cee3a8 (diff) | |
ARM: 7173/1: Add optimised swahb32() byteswap helper for v6 and above
ARMv6 and later processors have the REV16 instruction, which swaps
the bytes within each halfword of a register value.
This is already used to implement swab16(), but since the native
operation performaed by REV16 is actually swahb32(), this patch
renames the existing swab16() helper accordingly and defines
__arch_swab16() in terms of it. This allows calls to both swab16()
and swahb32() to be optimised.
The compiler's generated code might improve someday, but as of
4.5.2 the code generated for pure C implementing these 16-bit
bytesswaps remains pessimal.
swahb32() is useful for converting 32-bit Thumb instructions
between integer and memory representation on BE8 platforms (among
other uses).
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
| -rw-r--r-- | arch/arm/include/asm/swab.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h index 9997ad20eff..32ee164a2f6 100644 --- a/arch/arm/include/asm/swab.h +++ b/arch/arm/include/asm/swab.h @@ -24,12 +24,13 @@ #if defined(__KERNEL__) && __LINUX_ARM_ARCH__ >= 6 -static inline __attribute_const__ __u16 __arch_swab16(__u16 x) +static inline __attribute_const__ __u32 __arch_swahb32(__u32 x) { __asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x)); return x; } -#define __arch_swab16 __arch_swab16 +#define __arch_swahb32 __arch_swahb32 +#define __arch_swab16(x) ((__u16)__arch_swahb32(x)) static inline __attribute_const__ __u32 __arch_swab32(__u32 x) { |