From 87321fddaeb8706a91293dc244408697a0a24ece Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Fri, 6 May 2016 13:35:03 +0100 Subject: [PATCH] MIPS: Implement __arch_bitrev* using bitswap for MIPSr6 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 Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/13204/ Signed-off-by: Ralf Baechle --- arch/mips/Kconfig | 1 + arch/mips/include/asm/bitrev.h | 30 ++++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) create mode 100644 arch/mips/include/asm/bitrev.h diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 2b7af9014cce..95f05826a16f 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -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 diff --git a/arch/mips/include/asm/bitrev.h b/arch/mips/include/asm/bitrev.h new file mode 100644 index 000000000000..bc739a404ae3 --- /dev/null +++ b/arch/mips/include/asm/bitrev.h @@ -0,0 +1,30 @@ +#ifndef __MIPS_ASM_BITREV_H__ +#define __MIPS_ASM_BITREV_H__ + +#include + +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__ */