#15519: Minor code refactoring leads to drastic performance degradation -------------------------------------+------------------------------------- Reporter: danilo2 | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.8.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: SpecConstr Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): To summarise: once we have done #15578, we'll get good perf for {{{ testGrammar1 = <blah> {-# INLINE testGrammar1 #-} test3 = oneShot (runTokenParser testGrammar1) }}} * The `INLINE` ensures that `testGrammar1` is inlined even if it is used in many places. * The `oneShot` is, I'm afraid, still necessary. (You can import it from `GHC.Exts`.) It says that GHC doesn't need to worry about sharing the work of `testGrammar1` between, say, two calls `(test3 src1)` and `(test3 src2)`. You should get reliably good perf with these changes. OK? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15519#comment:24 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler