• Ömer Sinan Ağacan's avatar
    Implement unboxed sum primitive type · 714bebff
    Ömer Sinan Ağacan authored
    Summary:
    This patch implements primitive unboxed sum types, as described in
    https://ghc.haskell.org/trac/ghc/wiki/UnpackedSumTypes.
    
    Main changes are:
    
    - Add new syntax for unboxed sums types, terms and patterns. Hidden
      behind `-XUnboxedSums`.
    
    - Add unlifted unboxed sum type constructors and data constructors,
      extend type and pattern checkers and desugarer.
    
    - Add new RuntimeRep for unboxed sums.
    
    - Extend unarise pass to translate unboxed sums to unboxed tuples right
      before code generation.
    
    - Add `StgRubbishArg` to `StgArg`, and a new type `CmmArg` for better
      code generation when sum values are involved.
    
    - Add user manual section for unboxed sums.
    
    Some other changes:
    
    - Generalize `UbxTupleRep` to `MultiRep` and `UbxTupAlt` to
      `MultiValAlt` to be able to use those with both sums and tuples.
    
    - Don't use `tyConPrimRep` in `isVoidTy`: `tyConPrimRep` is really
      wrong, given an `Any` `TyCon`, there's no way to tell what its kind
      is, but `kindPrimRep` and in turn `tyConPrimRep` returns `PtrRep`.
    
    - Fix some bugs on the way: #12375.
    
    Not included in this patch:
    
    - Update Haddock for new the new unboxed sum syntax.
    
    - `TemplateHaskell` support is left as future work.
    
    For reviewers:
    
    - Front-end code is mostly trivial and adapted from unboxed tuple code
      for type checking, pattern checking, renaming, desugaring etc.
    
    - Main translation routines are in `RepType` and `UnariseStg`.
      Documentation in `UnariseStg` should be enough for understanding
      what's going on.
    
    Credits:
    
    - Johan Tibell wrote the initial front-end and interface file
      extensions.
    
    - Simon Peyton Jones reviewed this patch many times, wrote some code,
      and helped with debugging.
    
    Reviewers: bgamari, alanz, goldfire, RyanGlScott, simonpj, austin,
               simonmar, hvr, erikd
    
    Reviewed By: simonpj
    
    Subscribers: Iceland_jack, ggreif, ezyang, RyanGlScott, goldfire,
                 thomie, mpickering
    
    Differential Revision: https://phabricator.haskell.org/D2259
    714bebff
Unique.hs 14.9 KB