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Path: utzoo!mnetor!seismo!rochester!crowl
From: crowl@rochester.arpa (Lawrence Crowl)
Newsgroups: comp.arch
Subject: Re: Benchmarking ...[really Compiler flames]
Message-ID: <317@sol.ARPA>
Date: Fri, 5-Jun-87 10:36:51 EDT
Article-I.D.: sol.317
Posted: Fri Jun  5 10:36:51 1987
Date-Received: Tue, 9-Jun-87 06:59:01 EDT
References: <410@winchester.UUCP> <3490003@wdl1.UUCP> <7261@amdahl.amdahl.com> <787@ttidca.TTI.COM>
Reply-To: crowl@rochester.UUCP (Lawrence Crowl)
Organization: U of Rochester, CS Dept, Rochester, NY
Lines: 31
Keywords: compiler design, compiler designers

In article <787@ttidca.TTI.COM> sorgatz@ttidcb.UUCP
(Erik Sorgatz - Avatar) writes:
>This is the central point: most compilers are dumb. They appear to have been
>written by someone scarcely familar with the hardware environment.

No.  Compilers are written by people who generally do not have the time to
integrate all the details of the hardware into the compiler.  There are two
major requirements on a compiler. One, it MUST generate code which semantically
matches the source.  Two, it SHOULD generate code which is competitive in
efficiency with other compilers.  If the compiler does not meet requirement
one, it does not matter if it meets requirement two.  Now, judging when
requirement two is satisfied is a management decision.  Most managers do not
want to double their investment in a compiler to get 25% faster code.

>Consider this to be my contribution: Wakeup compiler experts! Read the !@#$%^&
>chip spec! Don't assume that your 'meta-pass-intermediate code generators are
>going to produce efficient code; they dont!

My first task is to get correct code.  "Meta-pass-intermediate code generators"
achieve this goal with minimal development effort.  Now, if you want me to
handle the case when instruction A is faster than instruction B, unless B
follows C, except in kernel mode, etc. then you must justify to managment
the SUBSTANTIAL additional cost.

If you want a cheap, efficient compiler, you must give me a simple, orthogonal
architecture.

-- 
  Lawrence Crowl		716-275-5766	University of Rochester
			crowl@rochester.arpa	Computer Science Department
 ...!{allegra,decvax,seismo}!rochester!crowl	Rochester, New York,  14627