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authorDave Martin <dave.martin@linaro.org>2011-11-24 12:23:18 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-12-06 11:15:26 +0000
commitdf0e74da6df1568e3722466f85f2f08324bc767e (patch)
treeb32cad089d75d0d40d6ef96a0d610d668dc33580 /arch/arm/include/asm/swab.h
parent7dbaa466780a754154531b44c2086f6618cee3a8 (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>
Diffstat (limited to 'arch/arm/include/asm/swab.h')
-rw-r--r--arch/arm/include/asm/swab.h5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h
index 9997ad20eff1..32ee164a2f6b 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)
{