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When testing in userspace, UBSAN pointed out that shifting into the sign bit is undefined behaviour. It doesn't really make sense to ask for the highest set bit of a negative value, so just turn the argument type into an unsigned int. Some architectures (eg ppc) already had it declared as an unsigned int, so I don't expect too many problems. Link: http://lkml.kernel.org/r/20181105221117.31828-1-willy@infradead.org Signed-off-by: Matthew Wilcox <willy@infradead.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
49 lines
1.2 KiB
C
49 lines
1.2 KiB
C
/*
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* linux/arch/unicore32/include/asm/bitops.h
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*
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* Code specific to PKUnity SoC and UniCore ISA
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*
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* Copyright (C) 2001-2010 GUAN Xue-tao
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef __UNICORE_BITOPS_H__
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#define __UNICORE_BITOPS_H__
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#define _ASM_GENERIC_BITOPS_FLS_H_
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#define _ASM_GENERIC_BITOPS___FLS_H_
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#define _ASM_GENERIC_BITOPS_FFS_H_
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#define _ASM_GENERIC_BITOPS___FFS_H_
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/*
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* On UNICORE, those functions can be implemented around
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* the cntlz instruction for much better code efficiency.
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*/
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static inline int fls(unsigned int x)
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{
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int ret;
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asm("cntlz\t%0, %1" : "=r" (ret) : "r" (x) : "cc");
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ret = 32 - ret;
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return ret;
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}
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#define __fls(x) (fls(x) - 1)
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#define ffs(x) ({ unsigned long __t = (x); fls(__t & -__t); })
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#define __ffs(x) (ffs(x) - 1)
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#include <asm-generic/bitops.h>
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/* following definitions: to avoid using codes in lib/find_*.c */
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#define find_next_bit find_next_bit
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#define find_next_zero_bit find_next_zero_bit
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#define find_first_bit find_first_bit
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#define find_first_zero_bit find_first_zero_bit
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#include <asm-generic/bitops/find.h>
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#endif /* __UNICORE_BITOPS_H__ */
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