Investigate Static Argument Transformation
|Reported by:||jstolarek||Owned by:|
|Type of failure:||Runtime performance bug||Test Case:|
|Related Tickets:||Differential Rev(s):|
Description (last modified by )
At the moment the Static Argument Transformation (SAT) optimisation is not run unless explicitly enabled with
-fstatic-argument-transformation. There was a comment by Max Bolingbroke in DynFlags that said this (that comment is now removed and replaced with a reference to this ticket):
Max writes: I think it's probably best not to enable SAT with -O2 for the 6.10 release. The version of SAT in HEAD at the moment doesn't incorporate several improvements to the heuristics, and I'm concerned that without those changes SAT will interfere with some attempts to write "high performance Haskell", as we saw in some posts on Haskell-Cafe earlier this year. In particular, the version in HEAD lacks the tail call criterion, so many things that look like reasonable loops will be turned into functions with extra (unneccesary) thunk creation.
6.10 was a long time ago. Has anything changed since then? Does it make sense to enable that optimisation now? What are the mentioned heuristics and were they finally implemented? Does anyone know what Haskell-cafe posts does Max refer to?