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From: jbuck@galileo.berkeley.edu (Joe Buck)
Newsgroups: comp.arch
Subject: Re: Smart I-cache?
Message-ID: <39324@ucbvax.BERKELEY.EDU>
Date: 1 Nov 90 22:08:37 GMT
References: <2823@crdos1.crd.ge.COM> <1157@cameron.egr.duke.edu>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: jbuck@galileo.berkeley.edu (Joe Buck)
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In article <1157@cameron.egr.duke.edu>, rfk@egr.duke.edu (Robert F. Krick) writes:
|> Since the program flow information is extracted prior to execution, SPA 
|> cannot *improve* the performance for branches which have dynamically 
|> defined targets (i.e. jmp r2).  With the notable exception of subroutine
|> returns which SPA can handle without any loss in performance, the degradation
|> associated with this class of branch instructions is insignificant ( << 1%),
|> because these instructions are sufficiently rare in compiled code from 
|> languages such as FORTRAN and C.

Object-oriented languages are becoming more popular; there are many more
indirect branches (in C++, these are virtual function calls) in such
languages.  However, I have no statistics on what fraction of instructions
in such programs are indirect branches, and this may vary widely from
program to program.  You'd do very poorly on Forth code, but I doubt that
you care all that much. :-)

> We have developed a working `proof of concept' prototype.  In addition, 
> we have applied for patent protection in both the USA and Japan.

Have you gotten it to the point where you can run the SPECmarks on it
(meaning that you've finished Fortran and C compilers that can provide
the scheduling information)?


--
Joe Buck
jbuck@galileo.berkeley.edu	 {uunet,ucbvax}!galileo.berkeley.edu!jbuck