Article View: comp.arch
Article #11511Re: Compilers and efficiency
From: Gideon YUVAL
Date: Thu, 09 May 1991 18:57
Date: Thu, 09 May 1991 18:57
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In article <STEPHEN.91May8001742@pesto.uchicago.edu> stephen@pesto.uchicago.edu (Stephen P Spackman) writes: >Are we talking about "find first one" here? > >Find first one was a pretty useful instruction in our lisp compiler. If you start from the low-order bit, you can find the first "one" bit by: table[ (x XOR (x-1)) MOD 37] On a 386, this is 4X as fast (worst-case) as the "hardware" BSF. -- Gideon Yuval, gideony@microsof.UUCP, 206-882-8080 (fax:206-883-8101;TWX:160520)
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!microsoft!gideony From: gideony@microsoft.UUCP (Gideon YUVAL) Newsgroups: comp.arch Subject: Re: Compilers and efficiency Message-ID: <72252@microsoft.UUCP> Date: 9 May 91 18:57:41 GMT References: <27fa3350.6bc2@petunia.CalPoly.EDU> <9782@mentor.cc.purdue.edu> <11411@mentor.cc.purdue.edu> <653@ctycal.UUCP> <STEPHEN.91May8001742@pesto.uchicago.edu> Reply-To: gideony@microsoft.UUCP (Gideon YUVAL) Organization: Microsoft Corp., Redmond WA Lines: 13