Date: Fri, 7 Mar 2008 09:17:18 GMT From: "Randall R. Stewart" <rrs@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 137066 for review Message-ID: <200803070917.m279HISY020379@repoman.freebsd.org>
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http://perforce.freebsd.org/chv.cgi?CH=137066 Change 137066 by rrs@rrs-mips2-jnpr on 2008/03/07 09:17:12 Changing to a table driven lookup seems to improve performance on interrupts a bit. I also add a fls64() as well. Affected files ... .. //depot/projects/mips2-jnpr/src/sys/libkern/fls.c#2 edit Differences ... ==== //depot/projects/mips2-jnpr/src/sys/libkern/fls.c#2 (text+ko) ==== @@ -35,14 +35,84 @@ /* * Find Last Set bit */ + +uint8_t fls_mask[256] = { + 0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, + 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, + 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, + 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, + 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, + 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, + 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, + 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, + 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08 +}; + int -fls(int mask) +fls(int m) { - int bit; + int val; + register uint32_t mask = m; + if (mask < 0x00000100) { + val = mask & 0x000000ff; + return (fls_mask[val]); + } + if (mask > 0x00ffffff) { + val = (mask >> 24) & 0x000000ff; + return (fls_mask[val] + 24); + } + if (mask > 0x0000ffff) { + val = (mask >> 16) & 0x000000ff; + return (fls_mask[val] + 16); + } + val = (mask >> 8) & 0x000000ff; + return (fls_mask[val] + 8); +} - if (mask == 0) - return (0); - for (bit = 1; mask != 1; bit++) - mask = (unsigned int)mask >> 1; - return (bit); +int +fls64(uint64_t mask) +{ + int val; + if(mask <= 0x00000000ffffffff) { + val = mask & 0x00000000ffffffff; + return(fls(val)); + } + if(mask > 0x00ffffffffffffff) { + val = (mask >> 56) & 0x000000ff; + return (fls_mask[val] + 56); + } + if (mask > 0x0000ffffffffffff) { + val = (mask >> 48) & 0x000000ff; + return (fls_mask[val] + 48); + } + if (mask > 0x000000ffffffffff) { + val = (mask >> 40) & 0x000000ff; + return (fls_mask[val] + 40); + } + val = (mask >> 32) & 0x000000ff; + return (fls_mask[val] + 32); } +
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