#6087: Join points need strictness analysis ---------------------------------+------------------------------------------ Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.6.2 Component: Compiler | Version: 7.4.1 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: Runtime performance bug Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Comment(by nfrisby): A second demand analysis at the end of the pipeline does help here. {{{ let { $j_sRv [Dmd=<C(C(S)),U>] :: GHC.Types.Int -> GHC.Types.Int -> [KnightHeuristic.Direction] }}} {{{ Entries Allocs Alloc'd Arity Kinds Function -------------------------------------------------------------------------------- 6003 51444 1334 1 L go{v s12q} (main:KnightHeuristic) 5336 24190 0 2 SS $j{v s12J} (main:KnightHeuristic) }}} becomes {{{ 6003 24764 1334 1 L go{v s187} (main:KnightHeuristic) 5336 31464 0 2 iS $w$j{v s18r} (main:KnightHeuristic) }}} This is ~ -7% overall change in allocation. At O2 (and without my more precise ticky numbers), the opportunity for this improvement gets a bit clobbered, but others apparently show up. {{{ 567 20851 1 0 L go{v s1Ba} (main:KnightHeuristic) 400 5200 2 0 ET main:KnightHeuristic.move{v rfN} 110 2274 5 0 SSiSL main:KnightHeuristic.$wdescendents{v r1qa} 168 1002 1 0 S main:KnightHeuristic.descAndNo{v rfU} }}} becomes {{{ 567 18204 1 0 L go{v s1MK} (main:KnightHeuristic) 111 872 5 0 SSiSL main:KnightHeuristic.$wdescendents{v r1Cl} 169 835 4 0 SSTL main:KnightHeuristic.$wdescAndNo{v r1Cp} }}} For -3.8% allocation. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6087#comment:3> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler