Add BIT_FLS() analogous to BIT_FFS().
The benefit of BIT_FLS() is that ffsl() can be implemented with a count leading zeros instruction which is more widespread available. Submitted by: Sebastian Huber <sebastian.huber@embedded-brains.de> MFC after: 1 week
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=320755
@ -24,7 +24,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd May 24, 2017
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.Dd July 6, 2017
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.Dt BITSET 9
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.Os
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.Sh NAME
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@ -43,6 +43,7 @@
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.Nm BIT_EMPTY ,
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.Nm BIT_ISFULLSET ,
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.Nm BIT_FFS ,
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.Nm BIT_FLS ,
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.Nm BIT_COUNT ,
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.Nm BIT_SUBSET ,
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.Nm BIT_OVERLAP ,
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@ -85,6 +86,8 @@
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.Ft int
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.Fn BIT_FFS "const SETSIZE" "struct STRUCTNAME *bitset"
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.Ft int
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.Fn BIT_FLS "const SETSIZE" "struct STRUCTNAME *bitset"
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.Ft int
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.Fn BIT_COUNT "const SETSIZE" "struct STRUCTNAME *bitset"
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.\"
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.Ft bool
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@ -282,6 +285,23 @@ index parameter to any other
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macro, you must subtract one from the result.
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.Pp
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The
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.Fn BIT_FLS
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macro returns the 1-index of the last (highest) set bit in
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.Fa bitset ,
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or zero if
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.Fa bitset
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is empty.
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Like with
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.Xr fls 3 ,
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to use the non-zero result of
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.Fn BIT_FLS
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as a
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.Fa bit
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index parameter to any other
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.Nm
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macro, you must subtract one from the result.
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.Pp
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The
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.Fn BIT_COUNT
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macro returns the total number of set bits in
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.Fa bitset .
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@ -213,6 +213,21 @@
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__bit; \
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})
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#define BIT_FLS(_s, p) __extension__ ({ \
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__size_t __i; \
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int __bit; \
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\
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__bit = 0; \
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for (__i = __bitset_words((_s)) - 1; __i >= 0; __i--) { \
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if ((p)->__bits[__i] != 0) { \
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__bit = flsl((p)->__bits[__i]); \
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__bit += __i * _BITSET_BITS; \
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break; \
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} \
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} \
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__bit; \
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})
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#define BIT_COUNT(_s, p) __extension__ ({ \
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__size_t __i; \
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int __count; \
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