#10918: Float once-used let binding into a recursive function -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by simonpj): Oh, you are right! The inliner is a much better place to do this, specifically, the code in `preInlineUnconditionally`. It deals with the case where we have {{{ let x = <expression> in ....x..... }}} where there is a single syntactic occurrence of x, not inside a lambda (unless it's a one-shot lambda). The occurrence analyser marks `x` with an `OccInfo` of `OneOcc`. So you want to teach the occurrence analyser how to make `x` as "occurs once" even though it occurs inside a lambda which is called more than once (the one for `go`). Or perhaps, when the occurrence analyser is about to mark it it as `OneOcc True ...`, where the `True` is the `InsideLam` info, we can switch the `InsideLam` info to `False` if `x` is marked "demanded once" In haste Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10918#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler