Author: Gerd Isenberg
Date: 11:31:42 02/14/03
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On February 14, 2003 at 03:40:53, Matt Taylor wrote: >AFAIK all suggestions are now incorporated: >ftp://24.73.126.6/lsb.h >ftp://24.73.126.6/lsb.c > >Somebody (I no longer remember who) asked me to create a version that does not >use cmovcc so it will run on older chips. I may get around to this, but it is >not high priority. Staying sane is high priority. > >Popcount was also requested; this may make its way into that file very soon -- I >just need to copy code from the K7 optimization manual. > >All versions (inline C and all 3 asm routines) tested in GCC and VC against a >pure-C routine and seem to work for me. > >Once again, suggestions are always welcome. Bug reports are even more welcome. > >Happy bit fiddling! > >-Matt Hi Matt, good work - Thanks again. It's really a reference source on this bitscan topic and a good lession in using preprocessor directives. For me it's even really helpfull to see ms/intel and gcc assembler syntax. With the latter i am not familar with. I tried two of your routines so far, the cmov/single-bsf one and the LSB_32_table lookup one. It's a mess, both without any branches, but IsiChess is stil 2-4% slower with these. I guess some chaotic code size dependent side effects (Athlon Xp 2000+, 512MB SDRAM). Regards, Gerd
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