Re: [9fans] compilers - was GUI toolkit for Plan 9

Re: [9fans] compilers - was GUI toolkit for Plan 9

[Bengt Kleberg]

> Delivered-To: 9fans@cse.psu.edu
> From: Mike Haertel <mike@ducky.net>


> Intel will live to regret this.

Last time (yesterday, but I am unable to find the link) I read about
'new' chips (ie 64-bit chips for general purpose computing) the
conclusion was:
Alpha: very good, but but dead since the new owner Intel will not
develop it.
Mips: good, but but dead since it has been re-targeted for
embedded/games.
PowerPC: good, but dead since it is already too complex
Sparc: middeling, but dead since Sun does not have the money to develop
next generation
Itanium: the only game in town (apart from what AMD will/might do, if
they can afford)

So, basically, Intel might regret it, but they will be the only one alive.


> The idea that "hardware/software co-design" is Good has to rank
> among the great fallacies of computer science and the computing
> industry in the last two decades.  It may allow elegant solutions
> to isolated problems, but problems are never isolated.  Eventually
> either the hardware or the software will need to be replaced, and
> the more cross-dependencies there are the harder this will be.
> Economically it's also really stupid: you are limiting your customers
> to the *intersection* of those who like your hardware and those who
> like your software.

Lets assume that Intel limits its customers to 1. This one beeing
Microsoft. Do you still think that all other customers will continue to
stay away?


bengt

Re: [9fans] compilers - was GUI toolkit for Plan 9

[Thomas Bushnell, BSG]

"AMSRL-CI-CN" <gwyn@arl.army.mil> writes:

> Unfortunately, performance expectations for new processors require
> rather complex architectures involving multiple concurrent pipelines,
> etc. making efficient use of the architectures difficult; therefore more
> responsibility is placed on the code generators.  This seems inevitable.

GCC has a generic mechanism for describing pipelined architectures
that is pretty good.  

Thomas

Re: [9fans] compilers - was GUI toolkit for Plan 9

[AMSRL-CI-CN]

"Mike Haertel" <mike@ducky.net> wrote in message
news:200202270021.g1R0L0s43681@ducky.net...
> The idea that "hardware/software co-design" is Good has to rank
> among the great fallacies of computer science and the computing
> industry in the last two decades.

Unfortunately, performance expectations for new processors require
rather complex architectures involving multiple concurrent pipelines,
etc. making efficient use of the architectures difficult; therefore more
responsibility is placed on the code generators.  This seems inevitable.
There are C compilers whose "code" is actually gate configurations
for FPGAs, etc. which is of course this idea taken to an extreme.

In earlier days of computing, little attention was usually paid to the
requirements of HLLs when designing ISAs, and sometimes what
the IS architects guessed would be helpful really wasn't (e.g. PDP-11
MARK instruction).  (There were a few notable exceptions, e.g.
Burroughs [56][57]00 models.)  The result was that major parts of
processors were not used at all by HLLs, which was bad economics.
This lack of input from compiler developers was widely recognized,
and by the early 1980s several processor manufacturers had changed
their procedures so that the hardware guys and compiler guys talked
to each other early enough to influence the design (of both).

These days, it is generally assumed that most programming is going
to be in C, so attention is focussed on supporting C to the possible
detriment of other languages..

> However they might curse the oddities of the x86 ISA, I am sure the
> Plan 9 developers are grateful for the fact that all x86 implementations
> are designed with a goal of getting at least adeqaute performance
> without recompiling.

?  Intel's x86 architecture was designed to be used from assembly
language, not HLL, and it is pretty bad when judged by its support
for HLLs.  Even the more recent MMX etc. extensions aren't well
suited for use from HLLs except via machine-specific asm hooks.

Re: [9fans] compilers - was GUI toolkit for Plan 9

[Russ Cox]

> Intel will live to regret this. 

Too bad the other processor makers will be dead.

Re: [9fans] compilers - was GUI toolkit for Plan 9

[Mike Haertel]

>Okay, I'm no compiler writer or even very proficient C coder but all this
>talk of turning optimizations off concerns me. Not because of the threat
>of "badly" generated code but because the chip makers (well Intel is the
>only one I really read about) are pushing the responsibility for
>optimization out of the silicon and into the compiler. (providing I
>understand what I read!)

Intel will live to regret this.  It's one thing to design a processor
that provides support for numerous compiler optimizations; it's quite
another to design a processor that *requires* them *all* to get even
adequate performance on a broad spectrum of code.

Anybody want to port 8c and Plan 9 to the Itanium?

(Ok, you can all stop laughing...)

The idea that "hardware/software co-design" is Good has to rank
among the great fallacies of computer science and the computing
industry in the last two decades.  It may allow elegant solutions
to isolated problems, but problems are never isolated.  Eventually
either the hardware or the software will need to be replaced, and
the more cross-dependencies there are the harder this will be.
Economically it's also really stupid: you are limiting your customers
to the *intersection* of those who like your hardware and those who
like your software.

However they might curse the oddities of the x86 ISA, I am sure the
Plan 9 developers are grateful for the fact that all x86 implementations
are designed with a goal of getting at least adeqaute performance
without recompiling.

Re: [9fans] compilers - was GUI toolkit for Plan 9

[jmk]

On Tue Feb 26 16:36:18 EST 2002, matt@proweb.co.uk wrote:
> Has anyone even tried to run plan9 on a Crusoe?

Not personally, but I know people who have done it.

Re: [9fans] compilers - was GUI toolkit for Plan 9

[Theo Honohan]

Matt H wrote:
> 
> Does anybody know how runtime optimizations such as those in the Crusoe
> chip fair at this? If optimization is tricky at compile time sounds like
> doing it at runtime must be hairy. Has anyone even tried to run plan9 on a
> Crusoe?

This is quite an interesting issue.  It's actually a lot easier to
write a clever interpreter (like the Crusoe chip + software) that
optimizes code at runtime than it is to write an offline "binary
translator".  The most obvious examples are the case of runtime code
generation, or self-modifying code; your static analysis of the
code you're translating has to be smart enough to see that coming.
An interpreter that recognizes and optimizes chunks of code
that get called repeatedly is much easier to write.


Incidentally, if your job involves having to explain these issues to
your boss, it's time to go...  :-(

Re: [9fans] compilers - was GUI toolkit for Plan 9

[Matt H]

Okay, I'm no compiler writer or even very proficient C coder but all this
talk of turning optimizations off concerns me. Not because of the threat
of "badly" generated code but because the chip makers (well Intel is the
only one I really read about) are pushing the responsibility for
optimization out of the silicon and into the compiler. (providing I
understand what I read!)

In my minimal contact with C I've regarded optimizations with scorn,
because like disk compression schemes a lá DoubleSpace, my first
encounters were tainted by failure. All optimizations did then (MS C ver 3
on win3.1 i think) was crash quickly.

Does anybody know how runtime optimizations such as those in the Crusoe
chip fair at this? If optimization is tricky at compile time sounds like
doing it at runtime must be hairy. Has anyone even tried to run plan9 on a
Crusoe?

M