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From: minow@decvax.UUCP (Martin Minow)
Newsgroups: net.lang.c
Subject: Can ANSI Standard C be "Optimized"
Message-ID: <404@decvax.UUCP>
Date: Mon, 12-Mar-84 20:23:49 EST
Article-I.D.: decvax.404
Posted: Mon Mar 12 20:23:49 1984
Date-Received: Tue, 13-Mar-84 20:38:57 EST
References: <6061@decwrl.UUCP>
Organization: DEC UNIX Engineering Group
Lines: 20

In the interesting and well-detailed series of optimization
comparisons between C and Bliss, it was pointed out several
times that Bliss performs many multi-statement optimizations
the C ignores.

If I read the Draft ANSI Standard correctly, it would seem to preclude
any optimizations across statement (;) boundaries.  Thus, simple for
satements cannot take advantage of loop control instructions such
as SOB on the PDP-11.

Therefore, many of the failings of the C optimizers are inherent
in the definition of the language, and not simply due to laziness
on the part of the compiler writers.  (And, no, I don't know
why this restriction was put in the draft standard.)

Martin Minow
decvax!minow