#16233: HIE file generation is inefficient -------------------------------------+------------------------------------- Reporter: harpocrates | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Generating HIE files eats up a lot of memory and takes a long time. There are at least two big parts to this: * Every expression in the AST is desugared via `deSugarExpr` for the purpose of extracting a type. GHC ends up doing the same work multiple times for the same nodes. Ex: in order to desugar `HsApp _ fun arg`, GHC desugars both `fun` and `arg`, yet the HIE code doesn't cache that (so it ends up desugaring `fun` and `arg` at least once more). * There is a lot of stuff being written into these HIE files, making them quite big (even after compressing/deduplicating type information). One data point: the largest HIE file at time of writing is `Parser.hie`, which is 7.2MB, compared to just 58K for `Parser.hi`Q Writing large files is naturally going to take up memory and be slow. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16233 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler