Date: Sun, 15 Oct 2000 16:46:25 -0700 From: Marcel Moolenaar <marcel@cup.hp.com> To: Doug Rabson <dfr@nlsystems.com> Cc: freebsd-ia64@FreeBSD.ORG Subject: Re: RAW dependency violation Message-ID: <39EA41D1.28D5BDC1@cup.hp.com> References: <Pine.BSF.4.21.0010160018280.22441-100000@salmon.nlsystems.com>
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Doug Rabson wrote: > > > I fixed two RAW dependency violations. I didn't want to step on your > > toes, but I know that hazards are painful, so I'm particularly paying > > attention to that. > > > > BTW: it's a RAW dependency violation, because only branch instructions > > are allowed to use predicate registers defined in the same instruction > > group. Branches are special-cased to allow for low-latency compar-branch > > sequences. > > Great, thanks. I have been relying on gas to detect the violations - I > can't keep all the rules and exceptions in my head. They are hairy; I know. Intel has developed DVLoc for that. Their assembler uses it to detect and prevent hazards. Unfortunately gas doesn't use it. Maybe I can arrange for a standalone hazard checker. In the early stages we might even want consider running such a tool as a separate compiler pass after the assembly pass. Ski isn't that picky, but the hardware is and I don't expect gcc/gas to be bug-free in that respect. It's very comforting to know when code doesn't have hazards - you know it's your fault when things aren't working as expected :-) > Did you intend to attach a patch or have you already committed something? Already committed. > > PS: I have the SKI documentation finished, I only need to put it on my > > homepage. This means I have to figure out how to get it through the > > firewall first :-/ > > Cool! I just discovered today that a bleeding edge -current machine will > run SKI just fine which is very nice. Excellent! It's time I start playing a well... -- Marcel Moolenaar mail: marcel@cup.hp.com / marcel@FreeBSD.org tel: (408) 447-4222 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-ia64" in the body of the message
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