Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!versatc!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.arch
Subject: Re: Criteria for comparing RISC processors
Message-ID: <18120@winchester.mips.COM>
Date: 25 Apr 89 21:39:25 GMT
References: <2368@ogccse.ogc.edu> <1464@cfa.cfa.harvard.EDU> <141@dg.dg.com>
Reply-To: mash@mips.COM (John Mashey)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 49

In article <141@dg.dg.com> rec@dg.UUCP (Robert Cousins) writes:
....
>>	Mature code generators.
...
>>
>....can take a long time to develop.  The best example I know of is with 
>compilers.  Some RISC processors (such as MIPS) have extensively tuned 
>compilers behind them.  These compilers are extremely complex and designed 
>to squeeze every bit of speed from them.

>However, other RISC processors (such as the 88000) with less complex
>compilers still beat the pants off of them.  Therefore, it isn't the
---------------------------------------^^^^
>maturity of the code generator, it is the delivered bang/$.
The "them" was a little ambiguous: I assume it meant "CISC chips", not R3000s
(as 3000s were the last "them" mentioned.)

Note that "maturity" of code generators (and compiler technology) in
general, is unfortunately even less well-defined than mips&mflops,
and it's a lot more than generating good code.
I once took a stab at a few verifiable metrics for compiler system
"maturity".  Here are a few quick samples:
- can you mix and match different languages, like C, FORTRAN, Pascal?
	- can you source-debug them, too?
	- can you do the same with COBOL, PL/1, or ADA and the others?
		(much harder; here's where linkage conventions and/or
		symbol tables break)
- compilation speeds
- robust in face of huge programs?
	- can you compile and link (for example) a 1-2-million-line program
	that generates a single executable of 32MB of CODE?
	- can you debug it? 
	- can you compile/link/debug a program that has a 1000 different
	include files?
Hmmm.  here's an interesting question for the net: how about offering examples
of LARGE programs, either in:
	# of files
	# of lines of source
	# of bytes of code generated

	what machine & OS & language does this run on?
	what does it do?
We've seen some real monsters land on our machines; maybe other people
have good examples also.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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