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Date: Fri, 16 Dec 2016 15:17:50 -0800 From: Joshua Clayton <stillcompiling@...il.com> To: Alan Tull <atull@...nsource.altera.com>, Moritz Fischer <moritz.fischer@...us.com>, Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <kernel@...gutronix.de>, Fabio Estevam <fabio.estevam@....com> Cc: Mark Rutland <mark.rutland@....com>, Rob Herring <robh+dt@...nel.org>, Anatolij Gustschin <agust@...x.de>, Joshua Clayton <stillcompiling@...il.com>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-fpga@...r.kernel.org Subject: [PATCH v6 1/5] lib: add bitrev8x4() Add a function to reverse bytes within a 32 bit word. Operate on a u32 rather than individual bytes. ARCH specific versions require substantially fewer instructions than working a byte at a time. Signed-off-by: Joshua Clayton <stillcompiling@...il.com> --- include/linux/bitrev.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h index fb790b8..868dcb6 100644 --- a/include/linux/bitrev.h +++ b/include/linux/bitrev.h @@ -27,6 +27,14 @@ static inline u32 __bitrev32(u32 x) return (__bitrev16(x & 0xffff) << 16) | __bitrev16(x >> 16); } +static inline u32 __bitrev8x4(u32 x) +{ + return(__bitrev8(x & 0xff) | + (__bitrev8((x >> 8) & 0xff) << 8) | + (__bitrev8((x >> 16) & 0xff) << 16) | + (__bitrev8((x >> 24) & 0xff) << 24)); +} + #endif /* CONFIG_HAVE_ARCH_BITREVERSE */ #define __constant_bitrev32(x) \ @@ -50,6 +58,15 @@ static inline u32 __bitrev32(u32 x) __x; \ }) +#define __constant_bitrev8x4(x) \ +({ \ + u32 __x = x; \ + __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4); \ + __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2); \ + __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1); \ + __x; \ +}) + #define __constant_bitrev8(x) \ ({ \ u8 __x = x; \ @@ -75,6 +92,14 @@ static inline u32 __bitrev32(u32 x) __bitrev16(__x); \ }) +#define bitrev8x4(x) \ +({ \ + u32 __x = x; \ + __builtin_constant_p(__x) ? \ + __constant_bitrev8x4(__x) : \ + __bitrev8x4(__x); \ +}) + #define bitrev8(x) \ ({ \ u8 __x = x; \ -- 2.9.3
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