#12357: Increasing maximum constraint tuple size significantly blows up compiler allocations -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2400 Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): In comment:21 I described the plan. Now I'll describe the reality, which includes a few wrinkles. As it turns out, we actually **do** include almost all of the tuple types in the original name cache. We can see this by noticing that `newHscEnv` initializes the namecache as `(initNameCache us allKnownKeyNames)`, where `allKnownKeyNames` includes, {{{#!hs knownKeyNames = concat [ ... , concatMap tycon_kk_names typeNatTyCons , concatMap (tycon_kk_names . tupleTyCon Boxed) [2..mAX_TUPLE_SIZE] -- Yuk , cTupleTyConNames , ... ] allKnownKeyNames = knownKeyNames ++ ... }}} Consequently, if you remove the `isBuiltInOcc_maybe` checks entirely things //almost// continue to work; almost because you will note that unboxed tuples are missing. This had led me to assume that all tuples were missing from the name cache. However, if you add unboxed tuples to `knownKeyNames` things validate without any trouble. So, the question now is whether we want to change this by removing tuples from the original name cache. To answer this let's consider what this would entail: I believe the only sensible way to implement comment:21 would be to filter out tuples from `allKnownKeyNames` when initializing the name cache. I specifically do not propose to remove tuples from `allKnownKeysNames` since the `TcTypeable` implementation relies on them being present so it knows to generate type representations for them. Is filtering them out worthwhile? I'll try to take some measurements to find out, but I'm not entirely convinced (at least for tuples; unboxed sums may be another story). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12357#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler