#9132: takeWhile&C. still not fusible -------------------------------------+------------------------------------- Reporter: Blaisorblade | Owner: skeuchel Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 7.8.2 Resolution: | Keywords: fusion Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Moderate (less performance bug | than a day) Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------- Comment (by skeuchel): Hi @Blaisorblade @nomeata, I took the changes from your branch and added a test case for this. However, it causes a 3.9% regression in terms of allocation of the rewrite test in nofib. This occurrence of takeWhile [https://github.com/ghc/nofib/blob/master/spectral/rewrite/Main.lhs#L193] is rewritten to takeWhileFB and then later written back without being fused. However, it seems to change the inline cost of string_of which will result that it will be inlined later and ultimately this results in losing sharing in one case. See this diff [http://lpaste.net/105275] of the output of the inliner/rewriter for some more details. You can clearly see the duplicated let bindings in the core output. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9132#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler