    {-# LANGUAGE BangPatterns #-}

    module GHC.Cmm.Pipeline (
      -- | Converts C-- with an implicit stack and native C-- calls into
      -- optimized, CPS converted and native-call-less C--.  The latter
      -- C-- can be used to generate assembly.
      cmmPipeline
    ) where

    import GHC.Prelude

    import GHC.Cmm
    import GHC.Cmm.Lint
    import GHC.Cmm.Info.Build
    import GHC.Cmm.CommonBlockElim
    import GHC.Cmm.Switch.Implement
    import GHC.Cmm.ProcPoint
    import GHC.Cmm.ContFlowOpt
    import GHC.Cmm.LayoutStack
    import GHC.Cmm.Sink
    import GHC.Cmm.Dataflow.Collections

    import GHC.Types.Unique.Supply
    import GHC.Driver.Session
    import GHC.Driver.Backend
    import GHC.Utils.Error
    import GHC.Utils.Logger
    import GHC.Driver.Env
    import Control.Monad
    import GHC.Utils.Outputable
    import GHC.Platform
    import Data.Either (partitionEithers)

    -----------------------------------------------------------------------------
    -- | Top level driver for C-- pipeline
    -----------------------------------------------------------------------------

    cmmPipeline
     :: HscEnv -- Compilation env including
               -- dynamic flags: -dcmm-lint -ddump-cmm-cps
     -> ModuleSRTInfo        -- Info about SRTs generated so far
     -> CmmGroup             -- Input C-- with Procedures
     -> IO (ModuleSRTInfo, CmmGroupSRTs) -- Output CPS transformed C--

    cmmPipeline :: HscEnv
    -> ModuleSRTInfo -> CmmGroup -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    cmmPipeline HscEnv
    hsc_env ModuleSRTInfo
    srtInfo CmmGroup
    prog = do
      let logger :: Logger
    logger = HscEnv -> Logger
    hsc_logger HscEnv
    hsc_env
      let dflags :: DynFlags
    dflags = HscEnv -> DynFlags
    hsc_dflags HscEnv
    hsc_env
      let forceRes :: (a, t a) -> ()
    forceRes (a
    info, t a
    group) = a
    info a -> () -> ()
    `seq` (a -> () -> ()) -> () -> t a -> ()
    forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr (\a
    decl ()
    r -> a
    decl a -> () -> ()
    `seq` ()
    r) () t a
    group
      Logger
    -> DynFlags
    -> SDoc
    -> ((ModuleSRTInfo, [CmmDeclSRTs]) -> ())
    -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    forall (m :: * -> *) a.
    MonadIO m =>
    Logger -> DynFlags -> SDoc -> (a -> ()) -> m a -> m a
    withTimingSilent Logger
    logger DynFlags
    dflags (String -> SDoc
    text String
    "Cmm pipeline") (ModuleSRTInfo, [CmmDeclSRTs]) -> ()
    forall {t :: * -> *} {a} {a}. Foldable t => (a, t a) -> ()
    forceRes (IO (ModuleSRTInfo, [CmmDeclSRTs])
     -> IO (ModuleSRTInfo, [CmmDeclSRTs]))
    -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    forall a b. (a -> b) -> a -> b
    $ do
         [Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)]
    tops <- {-# SCC "tops" #-} (CmmDecl -> IO (Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)))
    -> CmmGroup
    -> IO [Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)]
    forall (t :: * -> *) (m :: * -> *) a b.
    (Traversable t, Monad m) =>
    (a -> m b) -> t a -> m (t b)
    mapM (Logger
    -> DynFlags
    -> CmmDecl
    -> IO (Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl))
    cpsTop Logger
    logger DynFlags
    dflags) CmmGroup
    prog

         let ([(CAFEnv, CmmGroup)]
    procs, [(Set CAFLabel, CmmDecl)]
    data_) = [Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)]
    -> ([(CAFEnv, CmmGroup)], [(Set CAFLabel, CmmDecl)])
    forall a b. [Either a b] -> ([a], [b])
    partitionEithers [Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)]
    tops
         (ModuleSRTInfo
    srtInfo, [CmmDeclSRTs]
    cmms) <- {-# SCC "doSRTs" #-} DynFlags
    -> ModuleSRTInfo
    -> [(CAFEnv, CmmGroup)]
    -> [(Set CAFLabel, CmmDecl)]
    -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    doSRTs DynFlags
    dflags ModuleSRTInfo
    srtInfo [(CAFEnv, CmmGroup)]
    procs [(Set CAFLabel, CmmDecl)]
    data_
         let platform :: Platform
    platform = DynFlags -> Platform
    targetPlatform DynFlags
    dflags
         Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    Opt_D_dump_cmm_cps String
    "Post CPS Cmm" DumpFormat
    FormatCMM (Platform -> [CmmDeclSRTs] -> SDoc
    forall env a. OutputableP env a => env -> a -> SDoc
    pdoc Platform
    platform [CmmDeclSRTs]
    cmms)

         (ModuleSRTInfo, [CmmDeclSRTs]) -> IO (ModuleSRTInfo, [CmmDeclSRTs])
    forall (m :: * -> *) a. Monad m => a -> m a
    return (ModuleSRTInfo
    srtInfo, [CmmDeclSRTs]
    cmms)

    cpsTop :: Logger -> DynFlags -> CmmDecl -> IO (Either (CAFEnv, [CmmDecl]) (CAFSet, CmmDecl))
    cpsTop :: Logger
    -> DynFlags
    -> CmmDecl
    -> IO (Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl))
    cpsTop Logger
    _logger DynFlags
    dflags p :: CmmDecl
    p@(CmmData Section
    _ GenCmmStatics 'False
    statics) = Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)
    -> IO (Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl))
    forall (m :: * -> *) a. Monad m => a -> m a
    return ((Set CAFLabel, CmmDecl)
    -> Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)
    forall a b. b -> Either a b
    Right (Platform -> GenCmmStatics 'False -> Set CAFLabel
    cafAnalData (DynFlags -> Platform
    targetPlatform DynFlags
    dflags) GenCmmStatics 'False
    statics, CmmDecl
    p))
    cpsTop Logger
    logger DynFlags
    dflags CmmDecl
    proc =
        do
          ----------- Control-flow optimisations ----------------------------------

          -- The first round of control-flow optimisation speeds up the
          -- later passes by removing lots of empty blocks, so we do it
          -- even when optimisation isn't turned on.
          --
          CmmProc CmmTopInfo
    h CLabel
    l [GlobalReg]
    v CmmGraph
    g <- {-# SCC "cmmCfgOpts(1)" #-}
               CmmDecl -> IO CmmDecl
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CmmDecl -> IO CmmDecl) -> CmmDecl -> IO CmmDecl
    forall a b. (a -> b) -> a -> b
    $ Bool -> CmmDecl -> CmmDecl
    cmmCfgOptsProc Bool
    splitting_proc_points CmmDecl
    proc
          DumpFlag -> String -> CmmGraph -> IO ()
    dump DumpFlag
    Opt_D_dump_cmm_cfg String
    "Post control-flow optimisations" CmmGraph
    g

          let !TopInfo {stack_info :: CmmTopInfo -> CmmStackInfo
    stack_info=StackInfo { arg_space :: CmmStackInfo -> Int
    arg_space = Int
    entry_off
                                             , do_layout :: CmmStackInfo -> Bool
    do_layout = Bool
    do_layout }} = CmmTopInfo
    h

          ----------- Eliminate common blocks -------------------------------------
          CmmGraph
    g <- {-# SCC "elimCommonBlocks" #-}
               GeneralFlag
    -> (CmmGraph -> CmmGraph)
    -> CmmGraph
    -> DumpFlag
    -> String
    -> IO CmmGraph
    condPass GeneralFlag
    Opt_CmmElimCommonBlocks CmmGraph -> CmmGraph
    elimCommonBlocks CmmGraph
    g
                             DumpFlag
    Opt_D_dump_cmm_cbe String
    "Post common block elimination"

          -- Any work storing block Labels must be performed _after_
          -- elimCommonBlocks

          ----------- Implement switches ------------------------------------------
          CmmGraph
    g <- {-# SCC "createSwitchPlans" #-}
               UniqSM CmmGraph -> IO CmmGraph
    forall a. UniqSM a -> IO a
    runUniqSM (UniqSM CmmGraph -> IO CmmGraph) -> UniqSM CmmGraph -> IO CmmGraph
    forall a b. (a -> b) -> a -> b
    $ Backend -> Platform -> CmmGraph -> UniqSM CmmGraph
    cmmImplementSwitchPlans (DynFlags -> Backend
    backend DynFlags
    dflags) Platform
    platform CmmGraph
    g
          DumpFlag -> String -> CmmGraph -> IO ()
    dump DumpFlag
    Opt_D_dump_cmm_switch String
    "Post switch plan" CmmGraph
    g

          ----------- Proc points -------------------------------------------------
          let
            call_pps :: ProcPointSet -- LabelMap
            call_pps :: ProcPointSet
    call_pps = {-# SCC "callProcPoints" #-} CmmGraph -> ProcPointSet
    callProcPoints CmmGraph
    g
          ProcPointSet
    proc_points <-
             if Bool
    splitting_proc_points
                then do
                  ProcPointSet
    pp <- {-# SCC "minimalProcPointSet" #-} UniqSM ProcPointSet -> IO ProcPointSet
    forall a. UniqSM a -> IO a
    runUniqSM (UniqSM ProcPointSet -> IO ProcPointSet)
    -> UniqSM ProcPointSet -> IO ProcPointSet
    forall a b. (a -> b) -> a -> b
    $
                     Platform -> ProcPointSet -> CmmGraph -> UniqSM ProcPointSet
    minimalProcPointSet Platform
    platform ProcPointSet
    call_pps CmmGraph
    g
                  Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    Opt_D_dump_cmm_proc String
    "Proc points"
                        DumpFormat
    FormatCMM (Platform -> CLabel -> SDoc
    forall env a. OutputableP env a => env -> a -> SDoc
    pdoc Platform
    platform CLabel
    l SDoc -> SDoc -> SDoc
    $$ ProcPointSet -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr ProcPointSet
    pp SDoc -> SDoc -> SDoc
    $$ Platform -> CmmGraph -> SDoc
    forall env a. OutputableP env a => env -> a -> SDoc
    pdoc Platform
    platform CmmGraph
    g)
                  ProcPointSet -> IO ProcPointSet
    forall (m :: * -> *) a. Monad m => a -> m a
    return ProcPointSet
    pp
                else
                  ProcPointSet -> IO ProcPointSet
    forall (m :: * -> *) a. Monad m => a -> m a
    return ProcPointSet
    call_pps

          ----------- Layout the stack and manifest Sp ----------------------------
          (CmmGraph
    g, LabelMap StackMap
    stackmaps) <-
               {-# SCC "layoutStack" #-}
               if Bool
    do_layout
                  then UniqSM (CmmGraph, LabelMap StackMap)
    -> IO (CmmGraph, LabelMap StackMap)
    forall a. UniqSM a -> IO a
    runUniqSM (UniqSM (CmmGraph, LabelMap StackMap)
     -> IO (CmmGraph, LabelMap StackMap))
    -> UniqSM (CmmGraph, LabelMap StackMap)
    -> IO (CmmGraph, LabelMap StackMap)
    forall a b. (a -> b) -> a -> b
    $ DynFlags
    -> ProcPointSet
    -> Int
    -> CmmGraph
    -> UniqSM (CmmGraph, LabelMap StackMap)
    cmmLayoutStack DynFlags
    dflags ProcPointSet
    proc_points Int
    entry_off CmmGraph
    g
                  else (CmmGraph, LabelMap StackMap) -> IO (CmmGraph, LabelMap StackMap)
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CmmGraph
    g, LabelMap StackMap
    forall (map :: * -> *) a. IsMap map => map a
    mapEmpty)
          DumpFlag -> String -> CmmGraph -> IO ()
    dump DumpFlag
    Opt_D_dump_cmm_sp String
    "Layout Stack" CmmGraph
    g

          ----------- Sink and inline assignments  --------------------------------
          CmmGraph
    g <- {-# SCC "sink" #-} -- See Note [Sinking after stack layout]
               GeneralFlag
    -> (CmmGraph -> CmmGraph)
    -> CmmGraph
    -> DumpFlag
    -> String
    -> IO CmmGraph
    condPass GeneralFlag
    Opt_CmmSink (Platform -> CmmGraph -> CmmGraph
    cmmSink Platform
    platform) CmmGraph
    g
                        DumpFlag
    Opt_D_dump_cmm_sink String
    "Sink assignments"

          ------------- CAF analysis ----------------------------------------------
          let cafEnv :: CAFEnv
    cafEnv = {-# SCC "cafAnal" #-} Platform -> ProcPointSet -> CLabel -> CmmGraph -> CAFEnv
    cafAnal Platform
    platform ProcPointSet
    call_pps CLabel
    l CmmGraph
    g
          Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    Opt_D_dump_cmm_caf String
    "CAFEnv" DumpFormat
    FormatText (Platform -> CAFEnv -> SDoc
    forall env a. OutputableP env a => env -> a -> SDoc
    pdoc Platform
    platform CAFEnv
    cafEnv)

          CmmGroup
    g <- if Bool
    splitting_proc_points
               then do
                 ------------- Split into separate procedures -----------------------
                 let pp_map :: LabelMap Status
    pp_map = {-# SCC "procPointAnalysis" #-}
                              ProcPointSet -> CmmGraph -> LabelMap Status
    procPointAnalysis ProcPointSet
    proc_points CmmGraph
    g
                 Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    Opt_D_dump_cmm_procmap String
    "procpoint map"
                    DumpFormat
    FormatCMM (LabelMap Status -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr LabelMap Status
    pp_map)
                 CmmGroup
    g <- {-# SCC "splitAtProcPoints" #-} UniqSM CmmGroup -> IO CmmGroup
    forall a. UniqSM a -> IO a
    runUniqSM (UniqSM CmmGroup -> IO CmmGroup) -> UniqSM CmmGroup -> IO CmmGroup
    forall a b. (a -> b) -> a -> b
    $
                      Platform
    -> CLabel
    -> ProcPointSet
    -> ProcPointSet
    -> LabelMap Status
    -> CmmDecl
    -> UniqSM CmmGroup
    splitAtProcPoints Platform
    platform CLabel
    l ProcPointSet
    call_pps ProcPointSet
    proc_points LabelMap Status
    pp_map
                                        (CmmTopInfo -> CLabel -> [GlobalReg] -> CmmGraph -> CmmDecl
    forall d h g. h -> CLabel -> [GlobalReg] -> g -> GenCmmDecl d h g
    CmmProc CmmTopInfo
    h CLabel
    l [GlobalReg]
    v CmmGraph
    g)
                 DumpFlag -> String -> CmmGroup -> IO ()
    dumps DumpFlag
    Opt_D_dump_cmm_split String
    "Post splitting" CmmGroup
    g
                 CmmGroup -> IO CmmGroup
    forall (m :: * -> *) a. Monad m => a -> m a
    return CmmGroup
    g
               else
                 -- attach info tables to return points
                 CmmGroup -> IO CmmGroup
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CmmGroup -> IO CmmGroup) -> CmmGroup -> IO CmmGroup
    forall a b. (a -> b) -> a -> b
    $ [ProcPointSet -> CmmDecl -> CmmDecl
    attachContInfoTables ProcPointSet
    call_pps (CmmTopInfo -> CLabel -> [GlobalReg] -> CmmGraph -> CmmDecl
    forall d h g. h -> CLabel -> [GlobalReg] -> g -> GenCmmDecl d h g
    CmmProc CmmTopInfo
    h CLabel
    l [GlobalReg]
    v CmmGraph
    g)]

          ------------- Populate info tables with stack info -----------------
          CmmGroup
    g <- {-# SCC "setInfoTableStackMap" #-}
               CmmGroup -> IO CmmGroup
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CmmGroup -> IO CmmGroup) -> CmmGroup -> IO CmmGroup
    forall a b. (a -> b) -> a -> b
    $ (CmmDecl -> CmmDecl) -> CmmGroup -> CmmGroup
    forall a b. (a -> b) -> [a] -> [b]
    map (Platform -> LabelMap StackMap -> CmmDecl -> CmmDecl
    setInfoTableStackMap Platform
    platform LabelMap StackMap
    stackmaps) CmmGroup
    g
          DumpFlag -> String -> CmmGroup -> IO ()
    dumps DumpFlag
    Opt_D_dump_cmm_info String
    "after setInfoTableStackMap" CmmGroup
    g

          ----------- Control-flow optimisations -----------------------------
          CmmGroup
    g <- {-# SCC "cmmCfgOpts(2)" #-}
               CmmGroup -> IO CmmGroup
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CmmGroup -> IO CmmGroup) -> CmmGroup -> IO CmmGroup
    forall a b. (a -> b) -> a -> b
    $ if DynFlags -> Int
    optLevel DynFlags
    dflags Int -> Int -> Bool
    forall a. Ord a => a -> a -> Bool
    >= Int
    1
                        then (CmmDecl -> CmmDecl) -> CmmGroup -> CmmGroup
    forall a b. (a -> b) -> [a] -> [b]
    map (Bool -> CmmDecl -> CmmDecl
    cmmCfgOptsProc Bool
    splitting_proc_points) CmmGroup
    g
                        else CmmGroup
    g
          CmmGroup
    g <- CmmGroup -> IO CmmGroup
    forall (m :: * -> *) a. Monad m => a -> m a
    return ((CmmDecl -> CmmDecl) -> CmmGroup -> CmmGroup
    forall a b. (a -> b) -> [a] -> [b]
    map CmmDecl -> CmmDecl
    removeUnreachableBlocksProc CmmGroup
    g)
               -- See Note [unreachable blocks]
          DumpFlag -> String -> CmmGroup -> IO ()
    dumps DumpFlag
    Opt_D_dump_cmm_cfg String
    "Post control-flow optimisations" CmmGroup
    g

          Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)
    -> IO (Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl))
    forall (m :: * -> *) a. Monad m => a -> m a
    return ((CAFEnv, CmmGroup)
    -> Either (CAFEnv, CmmGroup) (Set CAFLabel, CmmDecl)
    forall a b. a -> Either a b
    Left (CAFEnv
    cafEnv, CmmGroup
    g))

      where platform :: Platform
    platform = DynFlags -> Platform
    targetPlatform DynFlags
    dflags
            dump :: DumpFlag -> String -> CmmGraph -> IO ()
    dump = Logger -> DynFlags -> DumpFlag -> String -> CmmGraph -> IO ()
    dumpGraph Logger
    logger DynFlags
    dflags

            dumps :: DumpFlag -> String -> CmmGroup -> IO ()
    dumps DumpFlag
    flag String
    name
               = (CmmDecl -> IO ()) -> CmmGroup -> IO ()
    forall (t :: * -> *) (m :: * -> *) a b.
    (Foldable t, Monad m) =>
    (a -> m b) -> t a -> m ()
    mapM_ (Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    flag String
    name DumpFormat
    FormatCMM (SDoc -> IO ()) -> (CmmDecl -> SDoc) -> CmmDecl -> IO ()
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . Platform -> CmmDecl -> SDoc
    forall env a. OutputableP env a => env -> a -> SDoc
    pdoc Platform
    platform)

            condPass :: GeneralFlag
    -> (CmmGraph -> CmmGraph)
    -> CmmGraph
    -> DumpFlag
    -> String
    -> IO CmmGraph
    condPass GeneralFlag
    flag CmmGraph -> CmmGraph
    pass CmmGraph
    g DumpFlag
    dumpflag String
    dumpname =
                if GeneralFlag -> DynFlags -> Bool
    gopt GeneralFlag
    flag DynFlags
    dflags
                   then do
                        CmmGraph
    g <- CmmGraph -> IO CmmGraph
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CmmGraph -> IO CmmGraph) -> CmmGraph -> IO CmmGraph
    forall a b. (a -> b) -> a -> b
    $ CmmGraph -> CmmGraph
    pass CmmGraph
    g
                        DumpFlag -> String -> CmmGraph -> IO ()
    dump DumpFlag
    dumpflag String
    dumpname CmmGraph
    g
                        CmmGraph -> IO CmmGraph
    forall (m :: * -> *) a. Monad m => a -> m a
    return CmmGraph
    g
                   else CmmGraph -> IO CmmGraph
    forall (m :: * -> *) a. Monad m => a -> m a
    return CmmGraph
    g

            -- we don't need to split proc points for the NCG, unless
            -- tablesNextToCode is off.  The latter is because we have no
            -- label to put on info tables for basic blocks that are not
            -- the entry point.
            splitting_proc_points :: Bool
    splitting_proc_points = DynFlags -> Backend
    backend DynFlags
    dflags Backend -> Backend -> Bool
    forall a. Eq a => a -> a -> Bool
    /= Backend
    NCG
                                 Bool -> Bool -> Bool
    || Bool -> Bool
    not (Platform -> Bool
    platformTablesNextToCode Platform
    platform)
                                 Bool -> Bool -> Bool
    || -- Note [inconsistent-pic-reg]
                                    Bool
    usingInconsistentPicReg
            usingInconsistentPicReg :: Bool
    usingInconsistentPicReg
               = case (Platform -> Arch
    platformArch Platform
    platform, Platform -> OS
    platformOS Platform
    platform, DynFlags -> Bool
    positionIndependent DynFlags
    dflags)
                 of   (Arch
    ArchX86, OS
    OSDarwin, Bool
    pic) -> Bool
    pic
                      (Arch, OS, Bool)
    _                        -> Bool
    False

    -- Note [Sinking after stack layout]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- In the past we considered running sinking pass also before stack
    -- layout, but after making some measurements we realized that:
    --
    --   a) running sinking only before stack layout produces slower
    --      code than running sinking only before stack layout
    --
    --   b) running sinking both before and after stack layout produces
    --      code that has the same performance as when running sinking
    --      only after stack layout.
    --
    -- In other words sinking before stack layout doesn't buy as anything.
    --
    -- An interesting question is "why is it better to run sinking after
    -- stack layout"? It seems that the major reason are stores and loads
    -- generated by stack layout. Consider this code before stack layout:
    --
    --  c1E:
    --      _c1C::P64 = R3;
    --      _c1B::P64 = R2;
    --      _c1A::P64 = R1;
    --      I64[(young<c1D> + 8)] = c1D;
    --      call stg_gc_noregs() returns to c1D, args: 8, res: 8, upd: 8;
    --  c1D:
    --      R3 = _c1C::P64;
    --      R2 = _c1B::P64;
    --      R1 = _c1A::P64;
    --      call (P64[(old + 8)])(R3, R2, R1) args: 8, res: 0, upd: 8;
    --
    -- Stack layout pass will save all local variables live across a call
    -- (_c1C, _c1B and _c1A in this example) on the stack just before
    -- making a call and reload them from the stack after returning from a
    -- call:
    --
    --  c1E:
    --      _c1C::P64 = R3;
    --      _c1B::P64 = R2;
    --      _c1A::P64 = R1;
    --      I64[Sp - 32] = c1D;
    --      P64[Sp - 24] = _c1A::P64;
    --      P64[Sp - 16] = _c1B::P64;
    --      P64[Sp - 8] = _c1C::P64;
    --      Sp = Sp - 32;
    --      call stg_gc_noregs() returns to c1D, args: 8, res: 8, upd: 8;
    --  c1D:
    --      _c1A::P64 = P64[Sp + 8];
    --      _c1B::P64 = P64[Sp + 16];
    --      _c1C::P64 = P64[Sp + 24];
    --      R3 = _c1C::P64;
    --      R2 = _c1B::P64;
    --      R1 = _c1A::P64;
    --      Sp = Sp + 32;
    --      call (P64[Sp])(R3, R2, R1) args: 8, res: 0, upd: 8;
    --
    -- If we don't run sinking pass after stack layout we are basically
    -- left with such code. However, running sinking on this code can lead
    -- to significant improvements:
    --
    --  c1E:
    --      I64[Sp - 32] = c1D;
    --      P64[Sp - 24] = R1;
    --      P64[Sp - 16] = R2;
    --      P64[Sp - 8] = R3;
    --      Sp = Sp - 32;
    --      call stg_gc_noregs() returns to c1D, args: 8, res: 8, upd: 8;
    --  c1D:
    --      R3 = P64[Sp + 24];
    --      R2 = P64[Sp + 16];
    --      R1 = P64[Sp + 8];
    --      Sp = Sp + 32;
    --      call (P64[Sp])(R3, R2, R1) args: 8, res: 0, upd: 8;
    --
    -- Now we only have 9 assignments instead of 15.
    --
    -- There is one case when running sinking before stack layout could
    -- be beneficial. Consider this:
    --
    --   L1:
    --      x = y
    --      call f() returns L2
    --   L2: ...x...y...
    --
    -- Since both x and y are live across a call to f, they will be stored
    -- on the stack during stack layout and restored after the call:
    --
    --   L1:
    --      x = y
    --      P64[Sp - 24] = L2
    --      P64[Sp - 16] = x
    --      P64[Sp - 8]  = y
    --      Sp = Sp - 24
    --      call f() returns L2
    --   L2:
    --      y = P64[Sp + 16]
    --      x = P64[Sp + 8]
    --      Sp = Sp + 24
    --      ...x...y...
    --
    -- However, if we run sinking before stack layout we would propagate x
    -- to its usage place (both x and y must be local register for this to
    -- be possible - global registers cannot be floated past a call):
    --
    --   L1:
    --      x = y
    --      call f() returns L2
    --   L2: ...y...y...
    --
    -- Thus making x dead at the call to f(). If we ran stack layout now
    -- we would generate less stores and loads:
    --
    --   L1:
    --      x = y
    --      P64[Sp - 16] = L2
    --      P64[Sp - 8]  = y
    --      Sp = Sp - 16
    --      call f() returns L2
    --   L2:
    --      y = P64[Sp + 8]
    --      Sp = Sp + 16
    --      ...y...y...
    --
    -- But since we don't see any benefits from running sinking before stack
    -- layout, this situation probably doesn't arise too often in practice.
    --

    {- Note [inconsistent-pic-reg]

    On x86/Darwin, PIC is implemented by inserting a sequence like

        call 1f
     1: popl %reg

    at the proc entry point, and then referring to labels as offsets from
    %reg.  If we don't split proc points, then we could have many entry
    points in a proc that would need this sequence, and each entry point
    would then get a different value for %reg.  If there are any join
    points, then at the join point we don't have a consistent value for
    %reg, so we don't know how to refer to labels.

    Hence, on x86/Darwin, we have to split proc points, and then each proc
    point will get its own PIC initialisation sequence.

    This isn't an issue on x86/ELF, where the sequence is

        call 1f
     1: popl %reg
        addl $_GLOBAL_OFFSET_TABLE_+(.-1b), %reg

    so %reg always has a consistent value: the address of
    _GLOBAL_OFFSET_TABLE_, regardless of which entry point we arrived via.

    -}

    {- Note [unreachable blocks]

    The control-flow optimiser sometimes leaves unreachable blocks behind
    containing junk code.  These aren't necessarily a problem, but
    removing them is good because it might save time in the native code
    generator later.

    -}

    runUniqSM :: UniqSM a -> IO a
    runUniqSM :: forall a. UniqSM a -> IO a
    runUniqSM UniqSM a
    m = do
      UniqSupply
    us <- Char -> IO UniqSupply
    mkSplitUniqSupply Char
    'u'
      a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (UniqSupply -> UniqSM a -> a
    forall a. UniqSupply -> UniqSM a -> a
    initUs_ UniqSupply
    us UniqSM a
    m)

    dumpGraph :: Logger -> DynFlags -> DumpFlag -> String -> CmmGraph -> IO ()
    dumpGraph :: Logger -> DynFlags -> DumpFlag -> String -> CmmGraph -> IO ()
    dumpGraph Logger
    logger DynFlags
    dflags DumpFlag
    flag String
    name CmmGraph
    g = do
      Bool -> IO () -> IO ()
    forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
    when (GeneralFlag -> DynFlags -> Bool
    gopt GeneralFlag
    Opt_DoCmmLinting DynFlags
    dflags) (IO () -> IO ()) -> IO () -> IO ()
    forall a b. (a -> b) -> a -> b
    $ CmmGraph -> IO ()
    do_lint CmmGraph
    g
      Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    flag String
    name DumpFormat
    FormatCMM (Platform -> CmmGraph -> SDoc
    forall env a. OutputableP env a => env -> a -> SDoc
    pdoc Platform
    platform CmmGraph
    g)
     where
      platform :: Platform
    platform = DynFlags -> Platform
    targetPlatform DynFlags
    dflags
      do_lint :: CmmGraph -> IO ()
    do_lint CmmGraph
    g = case Platform -> CmmGraph -> Maybe SDoc
    cmmLintGraph Platform
    platform CmmGraph
    g of
                     Just SDoc
    err -> do { Logger -> DynFlags -> SDoc -> IO ()
    fatalErrorMsg Logger
    logger DynFlags
    dflags SDoc
    err
                                    ; Logger -> DynFlags -> Int -> IO ()
    ghcExit Logger
    logger DynFlags
    dflags Int
    1
                                    }
                     Maybe SDoc
    Nothing  -> () -> IO ()
    forall (m :: * -> *) a. Monad m => a -> m a
    return ()

    dumpWith :: Logger -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith :: Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpWith Logger
    logger DynFlags
    dflags DumpFlag
    flag String
    txt DumpFormat
    fmt SDoc
    sdoc = do
      Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpIfSet_dyn Logger
    logger DynFlags
    dflags DumpFlag
    flag String
    txt DumpFormat
    fmt SDoc
    sdoc
      Bool -> IO () -> IO ()
    forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
    when (Bool -> Bool
    not (DumpFlag -> DynFlags -> Bool
    dopt DumpFlag
    flag DynFlags
    dflags)) (IO () -> IO ()) -> IO () -> IO ()
    forall a b. (a -> b) -> a -> b
    $
        -- If `-ddump-cmm-verbose -ddump-to-file` is specified,
        -- dump each Cmm pipeline stage output to a separate file.  #16930
        Bool -> IO () -> IO ()
    forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
    when (DumpFlag -> DynFlags -> Bool
    dopt DumpFlag
    Opt_D_dump_cmm_verbose DynFlags
    dflags)
          (IO () -> IO ()) -> IO () -> IO ()
    forall a b. (a -> b) -> a -> b
    $ Logger -> DumpAction
    putDumpMsg Logger
    logger DynFlags
    dflags (PrintUnqualified -> PprStyle
    mkDumpStyle PrintUnqualified
    alwaysQualify) DumpFlag
    flag String
    txt DumpFormat
    fmt SDoc
    sdoc
      Logger
    -> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
    dumpIfSet_dyn Logger
    logger DynFlags
    dflags DumpFlag
    Opt_D_dump_cmm_verbose_by_proc String
    txt DumpFormat
    fmt SDoc
    sdoc