#6070: Fun with the demand analyser -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.4.1 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 osa1): Just tried with GHC HEAD, unused arg in join point in `Unboxed.hs` vanishes with late demand analysis. {{{ let-no-escape { $j_s4wc [Occ=Once*!T[2], Dmd=<C(C(S)),1*C1(C1(U(U,U)))>] :: GHC.Prim.Int# -> GHC.Types.Int -> (# Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z), Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z) #) [LclId[JoinId(2)], Arity=2, Str=<S,U><L,A>, Unf=OtherCon []] = ... }}} After: {{{ let-no-escape { $w$j_s4BK [InlPrag=NOUSERINLINE[0], Occ=Once*!T[1], Dmd=<C(S),1*C1(U(U,U))>] :: GHC.Prim.Int# -> (# Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o), Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o) #) [LclId[JoinId(1)], Arity=1, Str=<S,U>, Unf=OtherCon []] = ... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6070#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler