| Message ID | 6c1c052d3c1d0c02a791aaaf8e114360ab1cb4e7.1481918884.git.stillcompiling@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Dec 16, 2016 at 03:17:51PM -0800, Joshua Clayton wrote: > 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)); This is broken -- you're operating on 64-bit registers. I only noticed because if you write: swab32(bitrev32(x)) then GCC generates: rbit w0, w0 rev w0, w0 so perhaps we should just implement the asm-generic version like that and not bother with the arch-specific stuff? Will
Will, On 12/19/2016 02:06 AM, Will Deacon wrote: > On Fri, Dec 16, 2016 at 03:17:51PM -0800, Joshua Clayton wrote: >> 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)); > This is broken -- you're operating on 64-bit registers. I only noticed > because if you write: Ugh. mea culpa. I squinted at the AARCH64 asm and erroneously believed it to be the same as arm. > swab32(bitrev32(x)) > > then GCC generates: > > rbit w0, w0 > rev w0, w0 > > so perhaps we should just implement the asm-generic version like that > and not bother with the arch-specific stuff? > > Will You are so right. That is exactly what I will do. Thanks, Joshua
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];
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(+)