#9441: CSE should deal with letrec -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.2 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): The common subexpression elimination pass (CSE.lhs) doesn't deal with letrec at all, at the moment. We'd like this transformation: {{{ Rec { x = ...x... } ... Rec { y = ...y... } ===> rec { x = ...x... } ... NonRec { y = x } }}} Extending CSE to do this would be a good goal. It would make a good little project. Need to think about how to deal with mutual recursion too! (Or maybe dealing with a singleton `Rec` would do as a start.) The current CSE transform is quite compact and elegeant; I would regret some very hairy new code, and I hope there is a nice elegant way. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9441#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler