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From: jqj@cornell.UUCP (J Q Johnson)
Newsgroups: net.arch
Subject: Re: Orthogonal addressing doesn't help multis.
Message-ID: <2693@cornell.UUCP>
Date: Tue, 25-Jun-85 07:05:49 EDT
Article-I.D.: cornell.2693
Posted: Tue Jun 25 07:05:49 1985
Date-Received: Wed, 26-Jun-85 06:38:56 EDT
References: <419@oakhill.UUCP> <6415@boring.UUCP>
Reply-To: jqj@gvax.UUCP (J Q Johnson)
Organization: Cornell Univ. CS Dept.
Lines: 13
Summary: 

In article <482@cmcl2.UUCP> edler@cmcl2.UUCP (Jan Edler) writes:
>Even if you have a uniprocessor with instructions like add-to-memory,
>and those instructions are atomic with respect to interrupts,
>it is probably not possible to take advantage of this property when
>writing in a language other than assembly.  The programmer would not generally
>know when the "atomic" instructions would be used, and when the compiler
>might optomize them away, so he/she wouldn't be able to depend on them.

I don't understand.  Presumably such instructions would be generated by
corresponding high-level constructs in your favorite concurrent programming
language (e.g. all operations on variables declared as semaphores use
the atomic instructions).  If the parser can figure out when you intend
to take advantage of such a feature, it can certainly tell the optimizer!