Re: Why Plan 9 C compilers don't have asm("")

From: H. Peter Anvin (
Date: Fri Jul 06 2001 - 19:16:57 EST

Followup to: <>
By author: "David S. Miller" <>
In newsgroup:
> Rick Hohensee writes:
> > Forth chips aren't modern in the true-multi-user sense, but if an
> > individual were to design such a beast they could get several of them,
> > hundreds maybe, on FPGAs available now. Such things are coming, because a
> > Forth chip IS something an individual can design.
> And I suppose this zero-cost call is also handling things like keeping
> an N stage deep pipeline full during this call right?

Believe it or not, that's actually a fairly simple part of the whole
machinery. All you need for that is to maintain a call/return stack
in the front end of the pipe. That way, a return that is indeed a
return can be speculated properly; obviously, if the speculation
doesn't work out when you get the return address in the execution
stage you suffer a branch mispredict penalty.


<> at work, <> in private!
"Unix gives you enough rope to shoot yourself in the foot."
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This archive was generated by hypermail 2b29 : Sat Jul 07 2001 - 21:00:19 EST