Space vs. speed

A good way to get speed at the expense of size is in-line substitution.
While this optimization is not used by many compilers now, I think it
will become very popular as programs tend towards consisting of a large
number of very small procedures. My optimizing compiler for Smalltalk
uses in-line substitution agressively, often substituting half a dozen
levels deep. Sometimes this makes the program smaller, such as when a
closure (block) is eliminated. (The current code for creating a closure
is pretty large.) However, it usually makes the program larger, and
always makes it faster.


Ralph Johnson -- uiucdcs!johnson, johnson@cs.uiuc.edu
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