#9159: cmm case, binary search instead of jump table --------------------------------------------+------------------------------ Reporter: wojteknar | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime performance bug | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Changes (by rwbarton): * type: bug => feature request Comment: Presumably the case on an `Int#` uses a binary search because there's no reason the cases need to be consecutive integers: imagine you change the last case to `1000000# -> Chunk08 w#`. Now a jump table is not a good idea. The case on a `Nat` knows that the tag integer identifying the constructor will be in the range from 0 to 8. We would need some heuristic for when to use binary search vs. a jump table (or perhaps both, if the cases to be matched consist of multiple ranges of consecutive integers). Maybe worth looking into what C compilers do. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9159#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler