    module PprCmmZ
        ( pprCmmGraphLikeCmm
        )
    where

    import BlockId
    import Cmm
    import PprCmm
    import Outputable
    import qualified ZipCfgCmmRep as G
    import qualified ZipCfg as Z
    import CmmZipUtil

    import Data.Maybe
    import FastString

    ----------------------------------------------------------------
    -- | The purpose of this function is to print a Cmm zipper graph "as if it were"
    -- a Cmm program.  The objective is dodgy, so it's unsurprising parts of the
    -- code are dodgy as well.

    pprCmmGraphLikeCmm :: G.CmmGraph -> SDoc
    pprCmmGraphLikeCmm g = vcat (swallow blocks)
        where blocks = Z.postorder_dfs g
              swallow :: [G.CmmBlock] -> [SDoc]
              swallow [] = []
              swallow (Z.Block id t : rest) = tail id [] Nothing t rest
              tail id prev' out (Z.ZTail m t) rest = tail id (mid m : prev') out t rest
              tail id prev' out (Z.ZLast (Z.LastOther l)) rest = last id prev' out l rest
              tail id prev' _   (Z.ZLast Z.LastExit)      rest = exit id prev' rest
              mid m = ppr m
              block' id prev'
                  | id == Z.lg_entry g, entry_has_no_pred =
                                vcat (text "<entry>" : reverse prev')
                  | otherwise = hang (ppr id <> colon) 4 (vcat (reverse prev'))
              last id prev' out l n =
                  let endblock stmt = block' id (stmt : prev') : swallow n in
                  case l of
                    G.LastBranch tgt ->
                        case n of
                          Z.Block id' t : bs
                              | tgt == id', unique_pred id'
                              -> tail id prev' out t bs  -- optimize out redundant labels
                          _ -> endblock (ppr $ CmmBranch tgt)
                    l@(G.LastCondBranch expr tid fid) ->
                      let ft id = text "// fall through to " <> ppr id in
                      case n of
                        Z.Block id' t : bs
                          | id' == fid, isNothing out ->
                              tail id (ft fid : ppr (CmmCondBranch expr tid) : prev') Nothing t bs
                          | id' == tid, Just e' <- maybeInvertCmmExpr expr, isNothing out->
                              tail id (ft tid : ppr (CmmCondBranch e'   fid) : prev') Nothing t bs
                        _ -> endblock $ with_out out l
                    l@(G.LastSwitch {})      -> endblock $ with_out out l
                    l@(G.LastCall _ _ _ _ _) -> endblock $ with_out out l
              exit id prev' n = -- highly irregular (assertion violation?)
                  let endblock stmt = block' id (stmt : prev') : swallow n in
                  endblock (text "// <exit>")
              preds = zipPreds g
              entry_has_no_pred = case lookupBlockEnv preds (Z.lg_entry g) of
                                    Nothing -> True
                                    Just s -> isEmptyBlockSet s
              single_preds =
                  let add b single =
                        let id = Z.blockId b
                        in  case lookupBlockEnv preds id of
                              Nothing -> single
                              Just s -> if sizeBlockSet s == 1 then
                                            extendBlockSet single id
                                        else single
                  in  Z.fold_blocks add emptyBlockSet g
              unique_pred id = elemBlockSet id single_preds

    with_out :: Maybe (G.Convention, CmmActuals) -> G.Last -> SDoc
    with_out Nothing l = ptext (sLit "??no-arguments??") <+> ppr l
    with_out (Just (conv, args)) l = last l
        where last (G.LastCall e k _ _ _) =
                  hcat [ptext (sLit "... = foreign "),
                        doubleQuotes(ppr conv), space,
                        ppr_target e, parens ( commafy $ map ppr args ),
                        ptext (sLit " \"safe\""),
                        text " returns to " <+> ppr k,
                        semi ]
              last l = ppr l
              ppr_target (CmmLit lit) = pprLit lit
              ppr_target fn'          = parens (ppr fn')
              commafy xs = hsep $ punctuate comma xs