#14161: Performance Problems on AST Dump -------------------------------------+------------------------------------- Reporter: h4ck3rm1k3 | Owner: dfeuer Type: bug | Status: patch Priority: low | Milestone: 8.2.2 Component: Compiler | Version: 8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3894 Wiki Page: | -------------------------------------+------------------------------------- Comment (by David Feuer <David.Feuer@…>): In [changeset:"29da01e0a023eea4bbbfd69dd5d854db721233e6/ghc" 29da01e0/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="29da01e0a023eea4bbbfd69dd5d854db721233e6" Make parsed AST dump output lazily Previously, `showAstData` produced a `String`. That `String` would then be converted to a `Doc` using `text` to implement `-ddump-parsed-ast`. But rendering `text` calculates the length of the `String` before doing anything else. Since the AST can be very large, this was bad: the whole dump string (potentially hundreds of millions of `Char`s) was accumulated in memory. Now, `showAstData` produces a `Doc` directly, which seems to work a lot better. As an extra bonus, the code is simpler and cleaner. The formatting has changed a bit, as the previous ad hoc approach didn't really match the pretty printer too well. If someone cares enough to request adjustments, we can surely make them. Reviewers: austin, bgamari, mpickering, alanz Reviewed By: bgamari Subscribers: mpickering, rwbarton, thomie GHC Trac Issues: #14161 Differential Revision: https://phabricator.haskell.org/D3894 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14161#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler