[PATCH v6 2/5] lib: implement __arch_bitrev8x4()

From	Joshua Clayton <stillcompiling@gmail.com>
Newsgroups	linux.kernel
Subject	[PATCH v6 2/5] lib: implement __arch_bitrev8x4()
Date	2016-12-17 00:20 +0100
Message-ID	<sP9Xb-1Cb-5@gated-at.bofh.it> (permalink)
References	<sP9Xb-1Cb-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Implement faster bitrev8x4() for arm, arm64 and mips, all the platforms
with CONFIG_HAVE_ARCH_BITREVERSE.
ARM platforms just need a byteswap added to the existing __arch_bitrev32()
Amusingly, the mips implementation is exactly the opposite, requiring
removal of the byteswap from its __arch_bitrev32()

Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
---
 arch/arm/include/asm/bitrev.h   | 6 ++++++
 arch/arm64/include/asm/bitrev.h | 6 ++++++
 arch/mips/include/asm/bitrev.h  | 6 ++++++
 include/linux/bitrev.h          | 1 +
 4 files changed, 19 insertions(+)

diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h
index ec291c3..9482f78 100644
--- a/arch/arm/include/asm/bitrev.h
+++ b/arch/arm/include/asm/bitrev.h
@@ -17,4 +17,10 @@ static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x)
 	return __arch_bitrev32((u32)x) >> 24;
 }
 
+static __always_inline __attribute_const__ u32 __arch_bitrev8x4(u32 x)
+{
+	__asm__ ("rbit %0, %1; rev %0, %0" : "=r" (x) : "r" (x));
+	return x;
+}
+
 #endif
diff --git a/arch/arm64/include/asm/bitrev.h b/arch/arm64/include/asm/bitrev.h
index a5a0c36..1801078 100644
--- a/arch/arm64/include/asm/bitrev.h
+++ b/arch/arm64/include/asm/bitrev.h
@@ -16,4 +16,10 @@ static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x)
 	return __arch_bitrev32((u32)x) >> 24;
 }
 
+static __always_inline __attribute_const__ u32 __arch_bitrev8x4(u32 x)
+{
+	__asm__ ("rbit %0, %1; rev %0, %0" : "=r" (x) : "r" (x));
+	return x;
+}
+
 #endif
diff --git a/arch/mips/include/asm/bitrev.h b/arch/mips/include/asm/bitrev.h
index bc739a4..9ac6439 100644
--- a/arch/mips/include/asm/bitrev.h
+++ b/arch/mips/include/asm/bitrev.h
@@ -27,4 +27,10 @@ static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x)
 	return ret;
 }
 
+static __always_inline __attribute_const__ u32 __arch_bitrev8x4(u32 x)
+{
+	u32 ret;
+	asm("bitswap    %0, %1" : "=r"(ret) : "r"(x));
+	return ret;
+}
 #endif /* __MIPS_ASM_BITREV_H__ */
diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index 868dcb6..b1cfa1a 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -9,6 +9,7 @@
 #define __bitrev32 __arch_bitrev32
 #define __bitrev16 __arch_bitrev16
 #define __bitrev8 __arch_bitrev8
+#define __bitrev8x4 __arch_bitrev8x4
 
 #else
 extern u8 const byte_rev_table[256];
-- 
2.9.3

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[PATCH v6 2/5] lib: implement __arch_bitrev8x4() Joshua Clayton <stillcompiling@gmail.com> - 2016-12-17 00:20 +0100
  Re: [PATCH v6 2/5] lib: implement __arch_bitrev8x4() Will Deacon <will.deacon@arm.com> - 2016-12-19 11:10 +0100
    Re: [PATCH v6 2/5] lib: implement __arch_bitrev8x4() Joshua Clayton <stillcompiling@gmail.com> - 2016-12-20 18:30 +0100

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