Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!crdgw1!crdos1!davidsen
From: davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr)
Newsgroups: comp.arch
Subject: Re: Smart I-cache?
Message-ID: <2829@crdos1.crd.ge.COM>
Date: 1 Nov 90 22:34:01 GMT
References: <2823@crdos1.crd.ge.COM> <1157@cameron.egr.duke.edu>
Reply-To: davidsen@crdos1.crd.ge.com (bill davidsen)
Organization: GE Corp R&D Center, Schenectady NY
Lines: 19

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.

  register int (*state)();
  
  /* code */
  if (m < n) (*state)(foo, mumble, barf);

  I agree that this is an infrequent case.
-- 
bill davidsen	(davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen)
      The Twin Peaks Halloween costume: stark naked in a body bag