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>
ARMv6 introduced the REV and REV16 instructions that reverse bytes in
words and halfwords. Use them for the arch-specific implementation of
the byte swapping helpers on ARMv6+.
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
fix the following 'make headers_check' warnings:
usr/include/asm-arm/swab.h:19: include of <linux/types.h> is preferred over <asm/types.h>
usr/include/asm-arm/swab.h:25: found __[us]{8,16,32,64} type without #include <linux/types.h>
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
