When we don't inline, we should still perform a bounds check to avoid
#14295: tagToEnum# leads to some silly closures -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 Resolution: | Keywords: datacon-tags 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 simonpj): the thunk, no? Good point. I suppose so... but * If we did this we'd better give a different name to the primop that can't fail; otherwise the transformation is plain confusing. * I'm uncomfortable with transformations that are not readily expressed in Core. E.g. we could have {{{ case x of 0# -> blah DEFAULT -> ...(noFailQuotInt# y x)... }}} since we know that `x` is non-zero in the default branch. But then we might float the subexpression out, and the claim would no longer hold. We don't have a solid way to prevent this. So yes one could do it as a `CorePrep` tactic, but it's delicate; and we risk not getting the benefits because we don't implement the follow-on transformations. * I doubt it's worth doing in practice. i.e. the same engineering effort spent elsewhere might yield more benefit. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14295#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler