#15578: Honour INLINE pragmas on 0-arity bindings -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Looking at `CoreUnfold.mkInlineUnfolding`, a function with an INLINE pragma has its unfolding built with `mkInlineUnfoldingWithArity` (the arity being the syntactic arity in the source code). This function gives the unfolding an `UnfoldingGuidance` of {{{ guide = UnfWhen { ug_arity = arity , ug_unsat_ok = needSaturated , ug_boring_ok = boring_ok } boring_ok = inlineBoringOk expr' }}} And in fact, in `callSiteInline`, you can see that if `ug_arity = 0` then `x` will inline if `boring_ok` is True. What is `boring_ok`? It says whether to inline in an utterly boring context. In {{{ \ y x -> Just (f x y) }}} we don't inline `f` ''even if `f` has an INLINE pragma'' because the context of the call us utterly boring: nothing is known about `x` or `y` or the calling context. So there is really no point in inlining. I don't think this applies to 0-ary INLINE pragmas, as Trac #15519 shows. So I think it may be enough to say, in `mkInlineUnfoldingWithArity`, {{{ boring_ok | arity == 0 = True | otherwise = inlineBoringOk expr' }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15578#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler