wiki:Status/SLPJ-Tickets

Version 59 (modified by simonpj, 5 years ago) (diff)

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This page collects tickets that Simon PJ is interested in, so that he remembers them

Performance

Arity

  • #2915: arity too small
  • #2762: arity analysis would fix a space leak
  • #1216: array indexing, inlining/arity bug
  • #2902: an excellent example of the need for arity analysis
  • #2823: another arity expansion bug (related to dictionaries)
  • #2440: bad code with type families; I believe this is also arity-related
  • #2762: Arity analysis
  • #2368: ASSERT fails in CorePrep. Seems to be arity-related.
  • #2831: error expressions and arities

Inlining

  • #3198: check this is still ok after the Big INLINE Patch
  • #3181: check unboxing regression fixed in Big INLINE Patch
  • #3073 and Commentary/Compiler/DesugaringInstances: better desugaring for instances
  • #2422: interaction of inlining and specialisation
  • #2396: default class method not inlined
  • #2354: NOINLINE pragma ignored
  • #2353: GHC inliner doesn't inline
  • #2078: INLINing improvement; ask Christian.Maeder@… to see if it improves CASL
  • #2840: top level unlifted string literals
  • #3123: feature request: recursive inlining and peeling

New code generator

  • #2253: NCG could do better. Look at this when John D’s ncg is working
  • #783: SRTs getting big
  • #2289: cheap check at start of case alternatives
  • #2731: avoiding unnecessary evaluation when unpacking constructors

Other performance

  • #3138: returning a known constructor (Lennart's cmonad package)
  • #2988: better float-in
  • #2940: do CSE after CorePrep
  • #2670: record selectors behaving badly wrt optimisation
  • #1434: Slow conversion Double to Int
  • #2439: Strict dictionaries
  • #2132: Optimise nested comparisons: if you know x>0 then you know x>=1 etc. Maybe a special pass that knows about arithmetic?
  • #149: float-out/CSE
  • #2289, #2387, #1600: nested CPR analysis
  • #2092: Possible quadratic-sized Eq instances. Does it really go quadratic, or does the join-point inlining machinery prevent it? Still to check: delicacy wrt case-of-case
  • #2255, #2643: Improve SpecConstr for free variables, and for join points.
  • #2374: SAT and MutableByteArray Max?
  • #3065: better code in quot/rem

Compiler performance

  • #1969: quadratic behaviour in the specialiser
  • #2346: desugaring let-bindings
  • Use wildcards for dead variables in interface files.

Outright bugs

  • #1148, #2267, #1074, #2436, #1792, (related #3082): “Unused import” warnings should be generated from RdrNames
  • #2182: GHCi session retains instance after removing a module from scope
  • #2152: Bogus inlining of foregn import. Arises from seeing through a NOINLINE in exprIsConApp_maybe
  • #1241: Lifting the Coverage Condition for functional dependencies isn’t the Right Thing Manuel
  • #2256: Incomplete inference due to lack of quantification over implication constraints. Also, see “BUG WARNING” in TcSimplify line 717 or thereabouts. fdPredsOfInsts is returning preds that mention quantified variables, which is quite wrong Manuel
  • #2239: Lack of improvement with type functions Manuel
  • #1954: Incorrect “defined but not used” msg

Types and type inference

  • #1496: Newtype deriving and type families type soundness problem
  • #1897: Ambiguity: don't infer a type that can't be checked if the type is given as a signature (this one is important). See SPJ's mailbox: Haskell type system/Ambiguity.
  • #2859: optimise coercion terms
  • #2641: revise what -XExtendedDefaultRules does
  • #1634: deep skolemisation
  • #3018: be lazier about solving class instances
  • #3108: interaction of fundeps and type class solving
  • #2357: Implement the Haskell Prime proposal for polymorphic pattern bindings

Impredicativity

  • #2846: polymorphism leaking into constraints
  • #2193: Bad error message with impredicative types
  • #1330: another bad error message (Church2)

Better error messages

  • #3169: better occurs-check error message
  • #2648: Report out of date interface files robustly
  • #2599: Better error message for non-rigid types
  • #2588: Better error message about ‘forall’
  • #2360: Better location info in occurs-check message.
  • #1856: Better error message for mutually recursive modules
  • #1928: Confusing type error message (Claus makes suggestions)
  • #2534: Another confusing type error message
  • #2442: Better error message heuristics for “not in scope” Max B’s patch
  • #2340: Better TH error recovery. Easy to do; change to signature of qRecover.
  • #2900: Improve decomposition of function types
  • #3023: Apply fundeps before printing error

Features

  • #3217: better flag handling for GHCi
  • #788: Class aliases
  • #2806: Require bang patterns on unlifted let-bindings
  • #2600: Bind type variables in RULES
  • #1930: Infix type operators: a+b.
  • #960: Generate local info for ‘undefined’. Implicit location parameters in general
  • #1475: Allow TH to generate import declarations
  • #2135: Warn when exporting a function whose type mentions a type constructor defined locally but not itself exported
  • #2526: Add -fwarn-missing-export-signatures
  • #2119: Explicitly importing deprecated symbols should generate deprecation warnings
  • #2116: GHCi should load as much of the module as it can
  • #2207: Load interfaces for GHC.* even without -O
  • #1231: Better deprecations

Not sure what to do about these

  • #2284: the state-hack "optimisation" causes much re-computation