#15445: SPECIALIZE one of two identical functions does not fire well ---------------------------------+-------------------------------------- Reporter: nobrakal | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by simonpj): Aha. The problem is that we get {{{ RULES: "SPEC plusTwoRec" forall ($dNum :: Num Int). plusTwoRec @ Int $dNum = plusTwoRec_$splusTwoRec }}} but, as you say, Common Subexpression Elimination has decided to replace `plusTwoRec`'s RHS with just `plusTwoRec'`. This is basically a good thing to do (saves code duplication), but if `plusTwoRec` is inlined before the rule has a chance to fire, we'll miss the specialisation. I thought of disabling CSE for functions with RULES; but that seems wrong. Generally, we add a NOINLINE pragma to a function with RULES to ensure that the function does not inline before the rule has a chance to fire. I think we should do the same thing with these auto-generated RULES from specialisations. Patch coming. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15445#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler