MIPS: Implement __arch_bitrev* using bitswap for MIPSr6 (87321fdd) · Commits · 戴 / test

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>

arch/mips/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -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

arch/mips/include/asm/bitrev.h

0 → 100644

+30 −0

Original line number	Diff line number	Diff line
		#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__ */

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