wiki:Commentary/Compiler/NewCodeGen

Version 2 (modified by simonpj, 6 years ago) (diff)

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Material about the new code generator

This page summarises work that Norman Ramsey, Simon M, and Simon PJ are doing on re-architecting GHC's back end.

The new Cmm data type

There is a new Cmm data type:

  • ZipCfg contains a generic zipper-based control-flow graph data type. It is generic in the sense that it's polymorphic in the type of middle nodes and last nodes of a block. (Middle nodes don't do control transfers; last nodes only do control transfers.) There are extensive notes at the start of the module.

    The key types it defines are:
    • Block identifiers: BlockId, BlockEnv, BlockSet
    • Control-flow blocks: Block
    • Control-flow graphs: Graph

  • ZipCfgCmm instantiates ZipCfg for Cmm, by defining types Middle and Last and using these to instantiate the polymorphic fields of ZipCfg. It also defines a bunch of smart constructor (mkJump, mkAssign, mkCmmIfThenElse` etc) which make it easy to build Cmm.

Todo list:

  • Get rid of CmmFormals on LastJump and LastCall in ZipCfgCmm

The pipeline

  • Code generator converts STG to Cmm.
  • Simple control flow optimisation (implemented in CmmContFlowOpt)