Path: utzoo!attcan!uunet!mcvax!hp4nl!philapd!ssp1!roelof
From: roelof@idca.tds.PHILIPS.nl (R. Vuurboom)
Newsgroups: comp.arch
Subject: Re: Compiling - RISC vs. CISC
Message-ID: <151@ssp1.idca.tds.philips.nl>
Date: 11 Jul 89 07:33:25 GMT
References: <13976@lanl.gov> <25547@shemp.CS.UCLA.EDU> <26247@amdcad.AMD.COM> <25562@shemp.CS.UCLA.EDU> <26257@amdcad.AMD.COM>
Organization: Philips Telecommunication and Data Systems, The Netherlands
Lines: 51

In article <26257@amdcad.AMD.COM> tim@amd.com (Tim Olson) writes:
>In article <25562@shemp.CS.UCLA.EDU> frazier@cs.ucla.edu (Greg Frazier) writes:
>| In article <26247@amdcad.AMD.COM> tim@amd.com (Tim Olson) writes:
>| >No, RISCs don't *require* very good optimizers; they just make it easier
>| >to perform some optimizations.  Very simple compilers can be used with
>| >fairly good results.
    ^^^^^^^^^^^
>
>I don't agree with this.  Our experience with the early (PCC-based)
>internal compiler for the Am29000 showed pretty good performance with
					  ^^^^^^^^^^^
>little or no standard optimizations (no load scheduling,
>common-subexpression elimination, dead-code elimination, live/dead
>analysis for register allocation, etc.) The only things it performed
>were those required by the architecture, i.e.  delayed branches.  Of

Anybody care to quantify this? Just what sort of performance improvement can I
expect from no-holds-barred optimization over only-what-I-have-to optimization.?

>
>If by "exposed pipeline" you mean that performance will be
>enhanced by instruction scheduling, then I agree.  However, I don't

This term has been confusing me (too?). Is this the (an?) "accepted"
definition of exposed pipeline?

>agree that most RISCs will expose the pipeline to software like the i860
>-- most will provide hardware interlocks.
>
Well...who will and who won't?

>	-- Tim Olson
>	Advanced Micro Devices
>	(tim@amd.com)

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-- 
Roelof Vuurboom  SSP/V3   Philips TDS Apeldoorn, The Netherlands   +31 55 432226
domain: roelof@idca.tds.philips.nl             uucp:  ...!mcvax!philapd!roelof