Didn't we just recently start using some pointer tagging for types with more than 7 constructors? I'm thinking something could be a drop off in
#15696: Derived Ord instance for enumerations with more than 8 elements seems to be incorrect -------------------------------------+------------------------------------- Reporter: mrkkrp | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.2 Component: Compiler | Version: 8.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by heisenbug): Replying to [comment:11 dfeuer]: that code. Nope. That code is not ripe yet. This summer was very busy for me. Another thing: With Peter I discovered last Haskell eXchange (Oct. 2017) that enumerated types with derived `Ord` instances could use `getTag` to derive a constant-time `compare` (and `(==)` too). We were not aware of this optimization already being in the codebase. We'll surely revisit this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15696#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler