#15802: Inlining of constant fails when both cross-module and recursive -------------------------------------+------------------------------------- Reporter: j6carey | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mpickering): This is because SpecConstr doesn't work across modules. See https://phabricator.haskell.org/D3566 and #10346 However, your intuition that if you apply a function to a constantly known value then it should reduce is misguided. SpecConstr only works in a narrow set of circumstances and the inliner will never inline recursive functions. If you want to guarantee performance then the only way that I know is to use (typed) template haskell -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15802#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler