Path: utzoo!mnetor!uunet!lll-winken!lll-tis!mordor!sri-spam!sri-unix!garth!walter
From: walter@garth.UUCP (Walter Bays)
Newsgroups: comp.lang.c
Subject: Re: volatile
Message-ID: <595@garth.UUCP>
Date: 10 Apr 88 00:44:20 GMT
References: <12578@brl-adm.ARPA> <1988Mar25.172355.348@utzoo.uucp> <18686@think.UUCP> <4217@ihlpf.ATT.COM> <10914@mimsy.UUCP> <150@ghostwheel.UUCP> <4346@ihlpf.ATT.COM>
Reply-To: walter@garth.UUCP (Walter Bays)
Organization: INTERGRAPH (APD) -- Palo Alto, CA
Lines: 23

In article <4346@ihlpf.ATT.COM> nevin1@ihlpf.UUCP (00704a-Liber,N.J.) writes:
>No, what this means is that in the future, when we have highly optimizing
>compilers and highly efficient hardware (such as caches,etc.), that this code
>may break.  In order to do certain types of optimizations, certain assumptions
>have to be made.  For example, if I know that a certain variable has no
>aliases, then in the implementation I can keep it's value in a cache (which
>is faster) without having to update the actual memory location it is
>suppose to be stored at.  As things stand now, these assumptions are made
>on a compiler-by-compiler basis.

I agree.  Worse, in many cases the future is now.  Usually the
compiler must forgo optimizations that would work for nearly all
programs for fear of breaking a few.  And remember, optimization is
more important for RISC than for CISC.  C wizards will use 'volatile'
and 'noalias'.  Ordinary users may totally ignore them, and will still
get the benefit of faster applications running on faster kernels.
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