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[PATCH] FRV: Optimise ffs()
Optimise ffs(x) by using fls(x & x - 1) which we optimise to use the SCAN instruction. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -157,8 +157,6 @@ static inline int __test_bit(int nr, const volatile void * addr)
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__constant_test_bit((nr),(addr)) : \
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__constant_test_bit((nr),(addr)) : \
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__test_bit((nr),(addr)))
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__test_bit((nr),(addr)))
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#include <asm-generic/bitops/ffs.h>
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#include <asm-generic/bitops/__ffs.h>
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#include <asm-generic/bitops/find.h>
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#include <asm-generic/bitops/find.h>
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/**
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/**
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@ -227,6 +225,37 @@ int fls64(u64 n)
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}
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}
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/**
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* ffs - find first bit set
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* @x: the word to search
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*
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* - return 32..1 to indicate bit 31..0 most least significant bit set
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* - return 0 to indicate no bits set
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*/
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static inline __attribute__((const))
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int ffs(int x)
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{
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/* Note: (x & -x) gives us a mask that is the least significant
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* (rightmost) 1-bit of the value in x.
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*/
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return fls(x & -x);
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}
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/**
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* __ffs - find first bit set
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* @x: the word to search
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*
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* - return 31..0 to indicate bit 31..0 most least significant bit set
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* - if no bits are set in x, the result is undefined
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*/
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static inline __attribute__((const))
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int __ffs(unsigned long x)
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{
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int bit;
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asm("scan %1,gr0,%0" : "=r"(bit) : "r"(x & -x));
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return 31 - bit;
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}
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#include <asm-generic/bitops/sched.h>
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#include <asm-generic/bitops/sched.h>
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#include <asm-generic/bitops/hweight.h>
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#include <asm-generic/bitops/hweight.h>
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