From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave.martin@linaro.org (Dave Martin) Date: Wed, 23 Nov 2011 14:42:25 +0000 Subject: [PATCH] ARM: Add optimised swahb32() byteswap helper for v6 and above Message-ID: <1322059345-18842-1-git-send-email-dave.martin@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 --- 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 9997ad2..32ee164 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) { -- 1.7.4.1