#13623: join points produce bad code for stream fusion -------------------------------------+------------------------------------- Reporter: choenerzs | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.2.1 Component: Compiler | Version: 8.2.1-rc1 Resolution: | Keywords: JoinPoints Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"9e47dc451788cce20acb6a8208c56a7e4dbe246b/ghc" 9e47dc45/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="9e47dc451788cce20acb6a8208c56a7e4dbe246b" Fix loss-of-SpecConstr bug This bug, reported in Trac #13623 has been present since commit b8b3e30a6eedf9f213b8a718573c4827cfa230ba Author: Edward Z. Yang <ezyang@cs.stanford.edu> Date: Fri Jun 24 11:03:47 2016 -0700 Axe RecFlag on TyCons. SpecConstr tries not to specialise indefinitely, and had a limit (see Note [Limit recursive specialisation]) that made use of info about whether or not a data constructor was "recursive". This info vanished in the above commit, making the limit fire much more often -- and indeed it fired in this test case, in a situation where specialisation is /highly/ desirable. I refactored the test, to look instead at the number of iterations of the loop of "and now specialise calls that arise from the specialisation". Actually less code, and more robust. I also added record field names to a couple of constructors, and renamed RuleInfo to SpecInfo. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13623#comment:10> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler