• Simon Peyton Jones's avatar
    Add -faggressive-primops plus refactoring in CoreUtils · 601c983d
    Simon Peyton Jones authored
    I'm experimenting with making GHC a bit more aggressive about
      a) dropping case expressions if the result is unused
            Simplify.rebuildCase, CaseElim equation
      b) floating case expressions inwards
            FloatIn.fiExpr, AnnCase
    In both cases the new behaviour is gotten with a static (debug)
    flag -faggressive-primops.  The extra "aggression" is to allow
    discarding and floating in for side-effecting operations.  See
    the new, extensive Note [PrimOp can_fail and has_side_effects]
    in PrimoOp.
    When discarding a case with unused binders, in the lifted-type
    case it's definitely ok if the scrutinee terminates; previously
    we were checking exprOkForSpeculation, which is significantly
    So I wanted a new function CoreUtils.exprCertainlyTerminates.
    In doing this I ended up with a significant refactoring in
    CoreUtils.  The new structure has quite a lot of nice sharing:
        exprIsCheap             = exprIsCheap' isHNFApp
        exprIsExpandable        = exprIsCheap' isConLikeApp
        exprIsHNF               = exprIsHNFlike isHNFApp
        exprIsConLike           = exprIsHNFlike isConLikeApp
        exprCertainlyTerminates = exprIsHNFlike isTerminatingApp
StaticFlags.hs 17.5 KB