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MIPS: Implement __arch_bitrev* using bitswap for MIPSr6

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Release 6 of the MIPS architecture introduced the bitswap instruction,
which reverses the bits within each byte of a word. Make use of this
instruction to implement the __arch_bitrev* functions, which should be
faster for most MIPSr6 CPUs, reduces code size slightly and allows us to
avoid the lookup table used by the generic implementation, saving 256
bytes in the kernel binary by dropping that.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13204/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2016-05-06 13:35:03 +01:00 committed by Ralf Baechle
parent 015aa05f53
commit 87321fddae
2 changed files with 31 additions and 0 deletions
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1
arch/mips/Kconfig
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@ -2000,6 +2000,7 @@ config CPU_MIPSR2
config CPU_MIPSR6
bool
default y if CPU_MIPS32_R6 || CPU_MIPS64_R6
select HAVE_ARCH_BITREVERSE
select MIPS_SPRAM
config EVA

30
arch/mips/include/asm/bitrev.h Normal file
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@ -0,0 +1,30 @@
#ifndef __MIPS_ASM_BITREV_H__
#define __MIPS_ASM_BITREV_H__
#include <linux/swab.h>
static __always_inline __attribute_const__ u32 __arch_bitrev32(u32 x)
{
u32 ret;
asm("bitswap %0, %1" : "=r"(ret) : "r"(__swab32(x)));
return ret;
}
static __always_inline __attribute_const__ u16 __arch_bitrev16(u16 x)
{
u16 ret;
asm("bitswap %0, %1" : "=r"(ret) : "r"(__swab16(x)));
return ret;
}
static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x)
{
u8 ret;
asm("bitswap %0, %1" : "=r"(ret) : "r"(x));
return ret;
}
#endif /* __MIPS_ASM_BITREV_H__ */