Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!snorkelwacker!paperboy!meissner From: meissner@osf.org (Michael Meissner) Newsgroups: comp.sys.m88k Subject: Re: Information wanted on m88000 Risc workstations Message-ID: Date: 11 Jan 90 17:15:13 GMT References: <75406@tut.cis.ohio-state.edu> <10825@encore.Encore.COM> Sender: news@OSF.ORG Organization: Open Software Foundation Lines: 54 In-reply-to: soper@maxzilla.encore.com's message of 8 Jan 90 22:23:07 GMT In article <10825@encore.Encore.COM> soper@maxzilla.encore.com (Pete Soper) writes: | Both GNU C and Green Hills C/C++/F77/Pascal are optimizing compilers that | have 88k code generators available. Surely both have to do instruction | scheduling of some sort to suport the 88k. Perhaps this area needs more | work? Is the 860 so much faster because of raw performance or does it | have the same pipeline issues and a compiler that more effectively supports | them? First of all, to support the 88k, you don't have to do any instruction scheduling, since the hardware will stall if the data is not available. Obviously, there is an advantage to doing scheduling (the numbers I saw were in the 5-10% range). I don't know about extremely recent Greenhills releases, but Greenhills did some limited amount of instruction scheduling, and GNU C did not (unless you count filling the delay slots of branchs/calls as instruction scheduling). Instruction scheduling seems to help floating point the most on the 88k (my gut level reaction is that the compiler does not often times have anything else useful to do to cover the two stalls needed for loads). This tended to show up in integer/system benchmarks, GNU and Greenhills were neck and neck, wheras Greenhills had an advantage in floating point. Bias alert: I spent a year working on the GNU C compiler for the 88k, so I'm not a disinterested observer. | Sort of on this subject, is GNU C the only C compiler shipped with the | DG box, or is it an alternative to Green Hills? Assuming GNU C is "it", | does it play well with Green Hills Fortran, which I'm assuming is still | the official Fortran product? Has DG extended gdb to cover both languages | or is another debugger used with their Fortran product? The only compiler that is included with the DG/UX 88k operating system is GNU C. You can purchase Greenhills C, Fortran, and Pascal if you desire. I believe that Absoft also sells a fortran compiler for DG/UX. All languages on the 88k are expected to meet the 88open Object Compatibility Standard (OCS) with regard to calling sequence, so that you can mix and match (though there is one minor detail that both GNU C and Greenhills fail in the same way). DG does supply it's own debugger to cover all of the languages (mxdb), but you could get by by using gdb (I think there are problems with multidimensioned arrays, and of course describe uses C syntax). Part of the problem, is that COFF is so C specific, but COFF is required by the standards. I believe that the 88k OCS standard makes it impossible for C to call a Fortran function that returns double complex, since C is required to treat it as a function which returns a struct -- which goes in memory, wheras Fortran returns the value in registers. I don't have a copy of the standard anymore, so I can't verify this. -- Michael Meissner email: meissner@osf.org phone: 617-621-8861 Open Software Foundation, 11 Cambridge Center, Cambridge, MA Catproof is an oxymoron, Childproof is nearly so