Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!leah!itsgw!steinmetz!davidsen
From: davidsen@steinmetz.ge.com (Wm. E. Davidsen Jr)
Newsgroups: comp.arch
Subject: Re: undoing autoincrement
Message-ID: <13414@steinmetz.ge.com>
Date: 24 Mar 89 13:34:01 GMT
References: <21971@agate.BERKELEY.EDU>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Organization: General Electric CRD, Schenectady, NY
Lines: 19

In article <21971@agate.BERKELEY.EDU> matloff@iris.ucdavis.edu (Norm Matloff) writes:

| Suppose there is an instruction containing autoincrement immediately following
| a conditional branch instruction.  If the pipe is such that the autoinc is
| done during or before the branch decision, the autoinc will have to be undone.

  I assume that there are a LOT of instructions which shouldn't follow a
conditional branch. The compiler should be able to handle that. While
I'm not a chip designer, I would assume that the hard part is
exceptions. I would assume that the operation would have to be "atomic"
in the sense that the IC increment and auto increment would never be
separated.

  Would some of the chip designers like to indicate if that's a bigger
problem for RISC than CISC?
-- 
	bill davidsen		(wedu@crd.GE.COM)
  {uunet | philabs}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me