#10012: Cheap-to-compute values aren't pushed into case branches inducing unnecessary register pressure -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Resolution: | Keywords: 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 nomeata): In comment:4 simon (or ben?) says “duplicating work”, but it seems that the question at hand is not about loss of sharing, but rather code size, right? Floating a let binding into the branches of a case does not duplicate any work, only code. A `{-# INLINE_THROUGH #-}` pragma seems to be a bit unspecific. Do we really want the compiler to inline through everything, no matter how large? Or should this just shift the heuristics a bit? But what is so special about this `case` that makes this a worthwhile thing here, and not in other cases (sic)? Maybe the heuristics can be improved in general? It seems to be more a general question of whether the user wants more speed or smaller code. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10012#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler