Optimization and language level

[D Gary Grady]

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It has been noted that programmers sometimes need a language that does a
lot of optimization, but that sometimes they need one that does a fairly
simple-minded translation.  I wonder if it would be worth it for
language designers and implementors to consider allowing local control
of optimization by means of statement (or even expression-level)
pragmas.  The Burroughs systems programming language on their old medium
systems (2600 and so on) allowed something like this.  As I recall, a
statement could be followed by a colon and some gibberish controlling
its semantics (I believe these were assembly language mnemonics).  I
have seen some Pascal compilers that allowed (or seemed to allow)
control of optimization level at any point in the program, but the
meaning of this was not well-defined.  IBM's PL/I Optimizing compiler
lets you specify down to the external-block level whether you want to
permit the compiler to rearrange statements.

An implementation of C might do this by means of pragmas within
comments.  Would it show up often enough to really be useful?  For
numerical analysts, perhaps....

-- 

D Gary Grady
Duke University Computation Center, Durham, NC  27706
(919) 684-4146
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