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@xxxxxxxxx>
---
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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