Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!mentor.cc.purdue.edu!pur-ee!hankd
From: hankd@pur-ee.UUCP (Hank Dietz)
Newsgroups: comp.arch
Subject: Re: VLIW Architecture
Summary: Read about VLIW -- it is good stuff.
Keywords: VLIW
Message-ID: <13050@pur-ee.UUCP>
Date: 3 Oct 89 23:06:57 GMT
References: <251FCB3F.12366@maccs.dcss.mcmaster.ca> <1050@m3.mfci.UUCP> <13038@pur-ee.UUCP> <1629@l.cc.purdue.edu>
Reply-To: hankd@pur-ee.UUCP (Hank Dietz)
Organization: Purdue University Engineering Computer Network
Lines: 30

In article <1629@l.cc.purdue.edu> cik@l.cc.purdue.edu (Herman Rubin) writes:
...[numerous "why don't HLLs let me say..." flames omitted]...
>What does your HLL have to say about these?

What HLL?  What does this have to do with VLIW techniques?  Dr.  Rubin is
complaining about languages -- but we are talking about VLIW compiler
analysis and program transformation technology, not language design.

I hope that this confusion is not common.  Perhaps a lot of compilers do
blindly spit-out the "obvious" code for badly-designed language constructs,
but that certainly isn't the state of the art.  I would think that a person
who has spent some time counting T-states would really appreciate the VLIW
work that Ellis presents in his award-winning PhD thesis...  I know I do.

>... Are you so dead sure that
>I cannot manage such structures better than the compiler?  The most complicated
>instruction set I have seen is MUCH simpler than HLLs.  ...

VLIW technology is complex because of its use of parallelism -- it has very
little to do with instruction set complexity issues.  Generating good code
for a VLIW is most like microcode scheduling/compaction for a huge,
asymmetric, microcoded machine.  You really don't even want to try it by
hand...  well, I know I don't.  And why bother?  VLIW compiler techniques
come very close to optimal schedules every time.  I can't match it, let
alone beat it.

						-hankd@ecn.purdue.edu

"A good workman is known by his tools."
Intro to Chapter 12, F. Brooks, "The Mythical Man-Month," p. 127.