Superoptimizer – A Look at the Smallest Program
32 points by linggen 5 days ago | 6 comments
gregdaniels421 2 hours ago
Same author did the synthesis kernel with Carl Pu, I think? The Synthesis kernel was genius, but relied on self modifying code, so can't work with modern chips well.
replyconvolvatron 2 hours ago
yes. Calton Pu. is that really such a problem? JITs seem to work pretty well, I'm pretty sure synthesis was more about creating custom paths than being strictly self-modifying, but it's been a long time.
replyupdate: oh, I just remembered why it _is_ an issue for modern processors, Massalin leaned very heavily on the general purpose double compare-and-swap that was present on some generations of the 68k architecture, and x86-64 only has double contiguous compare and swap
petercooper 26 minutes ago
This has long been one of my favorite papers, if only for the opening example. When I walked through it, it was an eye opener to a different level of thinking about code, one that assembly and democoders are probably working in every day.
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It constantly trys to do the most things with the least things. Take all the shortcuts to achieve the same outcome, often misconstrued with laziness, quality deficiency, or hard to understand.
For example, something as simple as timing may superoptimize and minimize instruction sets. Using one resource to do all the things needed at once versus calling the resource multiple times at different times shrinks the overall program a lot.