Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!lll-crg!ames!ucbcad!faustus From: faustus@ucbcad.BERKELEY.EDU (Wayne A. Christopher) Newsgroups: comp.lang.c Subject: Re: bit-field pointers / arrays Message-ID: <1170@ucbcad.BERKELEY.EDU> Date: Tue, 16-Dec-86 14:55:27 EST Article-I.D.: ucbcad.1170 Posted: Tue Dec 16 14:55:27 1986 Date-Received: Wed, 17-Dec-86 19:08:36 EST References: <2937@bu-cs.BU.EDU> <321@bms-at.UUCP> Organization: CAD Group, U.C. Berkeley Lines: 28 In article <321@bms-at.UUCP>, stuart@bms-at.UUCP (Stuart D. Gathman) writes: > Unfortunately, a set of macros cannot use hardware bit-field > instructions. Yes they can: you can always write asm("..."). > Here is a list of processors which I know to have > bit-field instructions that I can't get at from 'C': > > NEC V20, V30 > M68000 & family > PDP-11 (From previous posting) > DEC-10, 20 > VAX > > Here are processors which do not: > > 8088 & kin > other 8-bits: 6502 8080 etc You should also include a lot of newer RISC machines in the second category. These machines don't support unaligned word access or in some cases access to individual bytes (you have to load the word and extract it). These machines certainly aren't going to have "set bit" instructions. Also, they're probably going to run faster than the machines with bit instructions, even for code that uses bitfields. Wayne