#14951: SpecContsr needs two runs when one should suffice -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: SpecConstr Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #14844 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
So can we, at this point, decide to include t0 ↦ ScrutOcc in scu_occs?
I'm not at all sure. There might be many specialisations of `l`, with many RULES. Which of them would you like to use when gathering occurrence info `foo`'s argument. Sebastian's thought is interesting though. Perhaps we want the fact that `l`'s argument is scrutinesed to flow from `l` to `l`'s call sites, via some kind of !SpecConstr signature. It might be as if we'd inlined one "layer" of `l` at the call site. I wonder about fixpointing such signatures. Consider {{{ f True x y = case x of (p,q) -> ... f False x y = f True y x }}} We'd get a specialisation for `x`, but (I think) not for `y`. But one for `y` would be good! !SpecConstr is jolly compilicated. Splitting it into an analysis followed by exploitation woudl be a good thing. Just like demand analysis. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14951#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler