dolf@idca.tds.PHILIPS.nl (Dolf Grunbauer) (02/12/90)
In article <604@bbxsda.UUCP> scott@bbxsda.UUCP (Scott Amspoker) writes: >Well, it doesn't take much to find instructions on a 680x0 that are >not used by a C compiler. However, my code tends to do a lot of Agreed, but I think there is more than C, so for example instructions like ABCD, NBCD and SBCD which are not used by C seem very handy when using COBOL. I guess for some other instructions this holds also (not necessarily COBOL, but for FORTRAN etc). At least I always though that CISC does not mean: C Instruction Set Computer :-) >structure accesses with pointers such as "pointer->field". The >68020 double-indirect-with-offset addressing mode is a real life saver [...] Again agreed. -- Dolf Grunbauer Tel: +31 55 433233 Internet dolf@idca.tds.philips.nl Philips Telecommunication and Data Systems UUCP ....!mcvax!philapd!dolf Dept. SSP, P.O. Box 245, 7300 AE Apeldoorn, The Netherlands n n n It's a pity my .signature is too small to show you my solution of a + b = c
baum@Apple.COM (Allen J. Baum) (02/13/90)
[] >In article <604@bbxsda.UUCP> scott@bbxsda.UUCP (Scott Amspoker) writes: > >>structure accesses with pointers such as "pointer->field". The >>68020 double-indirect-with-offset addressing mode is a real life saver [...] A very waterlogged lifesaver. It is not clear that the fancy addressing modes run faster than a sequence of simpler insts., according to my sources. It is likely to get worse, rather than better, in future implementations -- baum@apple.com (408)974-3385 {decwrl,hplabs}!amdahl!apple!baum
scott@bbxsda.UUCP (Scott Amspoker) (02/13/90)
In article <38554@apple.Apple.COM> baum@apple.UUCP (Allen Baum) writes: >In article <604@bbxsda.UUCP> scott@bbxsda.UUCP (Scott Amspoker) writes: >>structure accesses with pointers such as "pointer->field". The >>68020 double-indirect-with-offset addressing mode is a real life saver [...] > >A very waterlogged lifesaver. It is not clear that the fancy addressing >modes run faster than a sequence of simpler insts., according to my sources. >It is likely to get worse, rather than better, in future implementations Agreed. However, it think the debate was whether or not C compilers actually use those fancy addressing modes. The answer is, yes. -- Scott Amspoker Basis International, Albuquerque, NM (505) 345-5232 unmvax.cs.unm.edu!bbx!bbxsda!scott
henry@utzoo.uucp (Henry Spencer) (02/14/90)
In article <616@bbxsda.UUCP> scott@bbxsda.UUCP (Scott Amspoker) writes: >>>68020 double-indirect-with-offset addressing mode is a real life saver [...] >>A very waterlogged lifesaver. It is not clear that the fancy addressing >>modes run faster than a sequence of simpler insts... >Agreed. However, it think the debate was whether or not C compilers >actually use those fancy addressing modes. The answer is, yes. The debate was about whether the fancy modes are worthwhile. It is not enough to show that compilers can use them; it is necessary that there be some good reason to use them. If performance is worse, there isn't. -- "The N in NFS stands for Not, | Henry Spencer at U of Toronto Zoology or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
peter@ficc.uu.net (Peter da Silva) (02/14/90)
In article <38554@apple.Apple.COM> baum@apple.UUCP (Allen Baum) writes: > It is not clear that the fancy addressing > modes run faster than a sequence of simpler insts.... Not only that, but sometimes you need a diferent set of fancy addressing modes. For example, to efficiently implement threaded interpreted languages on a CISC it helps to have an autoincrement indirect mode, such as the VAX, PDP-11, and 6809 share... but the 68000 does not. -- _--_|\ Peter da Silva. +1 713 274 5180. <peter@ficc.uu.net>. / \ \_.--._/ Xenix Support -- it's not just a job, it's an adventure! v "Have you hugged your wolf today?" `-_-'