Deforestation (tracking issue)

[ychenfo]

TODO

• Lumberhack mk 4 PR

  • Duplication of definitions
  • Check for regressions induced by label-sharing; it any, add a Config flag to tweak createLabelsForDuplicatedBranches in hkmc2/shared/src/main/scala/hkmc2/semantics/ucs/Normalization.scala
  • Transform explicit returns into implicit ones in the top-level blocks
  • Constrain public fields against no-change strategy

• Transform more places

  • Class methods
  • Record field initializers
  • Also, fuse records?

• Apply Lumberhack to compiled files

  • Support customizable list of "see-through" modules such as NofibPrelude: use syntax @seethrough import "..."

• Float out lambda binders

  • Benchmark nofib test suite

• Deal with side effects

• Deal with curried class parameter lists – by internalizing "virtual" $\eta$ expansions that only get realized/reified when needed for rewriting

Missing Implementation

• restParam
• multiple parameter lists
• Deforestation related to functions and values inside classes/modules
• Match blocks with non-Value.Ref scrutinees (like Match(Select(…), …)))
  I put this as a missing implementation here because I am not sure how to handle selections inside branches related to non-Value.Ref scrutinees — but maybe this is not strictly a “missing implementation” because it seems that although the definition of Match says that the scrut can be a Path, the scrut currently always seems to be compiled to a Value.Ref.

More todos

• Merging of duplicated consumers
  • After fusion, some duplicated consumers may have identical bodies, they can be merged
  • Before fusion, duplication of consumers may lead to loss of fusion opportunities
• Reification of recursive strategies

Ad-hoc things to generalize

• Remove the special-casing of the "force" and "lazy" and use annotations instead
• Don't special-case NofibPreluse – instead, allow listing a set of file to optimize with