    {-# LANGUAGE GADTs #-}
    {-# LANGUAGE BangPatterns #-}
    {-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
    {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
    module GHC.Cmm.ContFlowOpt
        ( cmmCfgOpts
        , cmmCfgOptsProc
        , removeUnreachableBlocksProc
        , replaceLabels
        )
    where

    import GHC.Prelude hiding (succ, unzip, zip)

    import GHC.Cmm.Dataflow.Block
    import GHC.Cmm.Dataflow.Collections
    import GHC.Cmm.Dataflow.Graph
    import GHC.Cmm.Dataflow.Label
    import GHC.Cmm.BlockId
    import GHC.Cmm
    import GHC.Cmm.Utils
    import GHC.Cmm.Switch (mapSwitchTargets, switchTargetsToList)
    import GHC.Data.Maybe
    import GHC.Utils.Panic
    import GHC.Utils.Misc

    import Control.Monad

    -- Note [What is shortcutting]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- Consider this Cmm code:
    --
    -- L1: ...
    --     goto L2;
    -- L2: goto L3;
    -- L3: ...
    --
    -- Here L2 is an empty block and contains only an unconditional branch
    -- to L3. In this situation any block that jumps to L2 can jump
    -- directly to L3:
    --
    -- L1: ...
    --     goto L3;
    -- L2: goto L3;
    -- L3: ...
    --
    -- In this situation we say that we shortcut L2 to L3. One of
    -- consequences of shortcutting is that some blocks of code may become
    -- unreachable (in the example above this is true for L2).

    -- Note [Control-flow optimisations]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- This optimisation does three things:
    --
    --   - If a block finishes in an unconditional branch to another block
    --     and that is the only jump to that block we concatenate the
    --     destination block at the end of the current one.
    --
    --   - If a block finishes in a call whose continuation block is a
    --     goto, then we can shortcut the destination, making the
    --     continuation block the destination of the goto - but see Note
    --     [Shortcut call returns].
    --
    --   - For any block that is not a call we try to shortcut the
    --     destination(s). Additionally, if a block ends with a
    --     conditional branch we try to invert the condition.
    --
    -- Blocks are processed using postorder DFS traversal. A side effect
    -- of determining traversal order with a graph search is elimination
    -- of any blocks that are unreachable.
    --
    -- Transformations are improved by working from the end of the graph
    -- towards the beginning, because we may be able to perform many
    -- shortcuts in one go.

    -- Note [Shortcut call returns]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- We are going to maintain the "current" graph (LabelMap CmmBlock) as
    -- we go, and also a mapping from BlockId to BlockId, representing
    -- continuation labels that we have renamed.  This latter mapping is
    -- important because we might shortcut a CmmCall continuation.  For
    -- example:
    --
    --    Sp[0] = L
    --    call g returns to L
    --    L: goto M
    --    M: ...
    --
    -- So when we shortcut the L block, we need to replace not only
    -- the continuation of the call, but also references to L in the
    -- code (e.g. the assignment Sp[0] = L):
    --
    --    Sp[0] = M
    --    call g returns to M
    --    M: ...
    --
    -- So we keep track of which labels we have renamed and apply the mapping
    -- at the end with replaceLabels.

    -- Note [Shortcut call returns and proc-points]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- Consider this code that you might get from a recursive
    -- let-no-escape:
    --
    --       goto L1
    --      L1:
    --       if (Hp > HpLim) then L2 else L3
    --      L2:
    --       call stg_gc_noregs returns to L4
    --      L4:
    --       goto L1
    --      L3:
    --       ...
    --       goto L1
    --
    -- Then the control-flow optimiser shortcuts L4.  But that turns L1
    -- into the call-return proc point, and every iteration of the loop
    -- has to shuffle variables to and from the stack.  So we must *not*
    -- shortcut L4.
    --
    -- Moreover not shortcutting call returns is probably fine.  If L4 can
    -- concat with its branch target then it will still do so.  And we
    -- save some compile time because we don't have to traverse all the
    -- code in replaceLabels.
    --
    -- However, we probably do want to do this if we are splitting proc
    -- points, because L1 will be a proc-point anyway, so merging it with
    -- L4 reduces the number of proc points.  Unfortunately recursive
    -- let-no-escapes won't generate very good code with proc-point
    -- splitting on - we should probably compile them to explicitly use
    -- the native calling convention instead.

    cmmCfgOpts :: Bool -> CmmGraph -> CmmGraph
    cmmCfgOpts :: Bool -> CmmGraph -> CmmGraph
    cmmCfgOpts Bool
    split CmmGraph
    g = forall a b. (a, b) -> a
    fst (Bool -> CmmGraph -> (CmmGraph, LabelMap Label)
    blockConcat Bool
    split CmmGraph
    g)

    cmmCfgOptsProc :: Bool -> CmmDecl -> CmmDecl
    cmmCfgOptsProc :: Bool -> CmmDecl -> CmmDecl
    cmmCfgOptsProc Bool
    split (CmmProc CmmTopInfo
    info CLabel
    lbl [GlobalReg]
    live CmmGraph
    g) = forall d h g. h -> CLabel -> [GlobalReg] -> g -> GenCmmDecl d h g
    CmmProc CmmTopInfo
    info' CLabel
    lbl [GlobalReg]
    live CmmGraph
    g'
        where (CmmGraph
    g', LabelMap Label
    env) = Bool -> CmmGraph -> (CmmGraph, LabelMap Label)
    blockConcat Bool
    split CmmGraph
    g
              info' :: CmmTopInfo
    info' = CmmTopInfo
    info{ info_tbls :: LabelMap CmmInfoTable
    info_tbls = LabelMap CmmInfoTable
    new_info_tbls }
              new_info_tbls :: LabelMap CmmInfoTable
    new_info_tbls = forall (map :: * -> *) a. IsMap map => [(KeyOf map, a)] -> map a
    mapFromList (forall a b. (a -> b) -> [a] -> [b]
    map (Label, CmmInfoTable) -> (Label, CmmInfoTable)
    upd_info (forall (map :: * -> *) a. IsMap map => map a -> [(KeyOf map, a)]
    mapToList (CmmTopInfo -> LabelMap CmmInfoTable
    info_tbls CmmTopInfo
    info)))

              -- If we changed any labels, then we have to update the info tables
              -- too, except for the top-level info table because that might be
              -- referred to by other procs.
              upd_info :: (Label, CmmInfoTable) -> (Label, CmmInfoTable)
    upd_info (Label
    k,CmmInfoTable
    info)
                 | Just Label
    k' <- forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    k LabelMap Label
    env
                 = (Label
    k', if Label
    k' forall a. Eq a => a -> a -> Bool
    == forall (n :: Extensibility -> Extensibility -> *).
    GenCmmGraph n -> Label
    g_entry CmmGraph
    g'
                           then CmmInfoTable
    info
                           else CmmInfoTable
    info{ cit_lbl :: CLabel
    cit_lbl = Label -> CLabel
    infoTblLbl Label
    k' })
                 | Bool
    otherwise
                 = (Label
    k,CmmInfoTable
    info)
    cmmCfgOptsProc Bool
    _ CmmDecl
    top = CmmDecl
    top

    blockConcat :: Bool -> CmmGraph -> (CmmGraph, LabelMap BlockId)
    blockConcat :: Bool -> CmmGraph -> (CmmGraph, LabelMap Label)
    blockConcat Bool
    splitting_procs g :: CmmGraph
    g@CmmGraph { g_entry :: forall (n :: Extensibility -> Extensibility -> *).
    GenCmmGraph n -> Label
    g_entry = Label
    entry_id }
      = (LabelMap Label -> CmmGraph -> CmmGraph
    replaceLabels LabelMap Label
    shortcut_map forall a b. (a -> b) -> a -> b
    $ Label -> LabelMap CmmBlock -> CmmGraph
    ofBlockMap Label
    new_entry LabelMap CmmBlock
    new_blocks, LabelMap Label
    shortcut_map')
      where
         -- We might be able to shortcut the entry BlockId itself.
         -- Remember to update the shortcut_map, since we also have to
         -- update the info_tbls mapping now.
         (Label
    new_entry, LabelMap Label
    shortcut_map')
           | Just CmmBlock
    entry_blk <- forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    entry_id LabelMap CmmBlock
    new_blocks
           , Just Label
    dest      <- CmmBlock -> Maybe Label
    canShortcut CmmBlock
    entry_blk
           = (Label
    dest, forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    entry_id Label
    dest LabelMap Label
    shortcut_map)
           | Bool
    otherwise
           = (Label
    entry_id, LabelMap Label
    shortcut_map)

         -- blocks are sorted in reverse postorder, but we want to go from the exit
         -- towards beginning, so we use foldr below.
         blocks :: [CmmBlock]
    blocks = CmmGraph -> [CmmBlock]
    revPostorder CmmGraph
    g
         blockmap :: LabelMap CmmBlock
    blockmap = forall (t :: * -> *) b a.
    Foldable t =>
    (b -> a -> b) -> b -> t a -> b
    foldl' (forall a b c. (a -> b -> c) -> b -> a -> c
    flip forall (block :: Extensibility -> Extensibility -> *).
    (NonLocal block, HasDebugCallStack) =>
    block C C -> LabelMap (block C C) -> LabelMap (block C C)
    addBlock) forall (block :: (Extensibility -> Extensibility -> *)
                     -> Extensibility -> Extensibility -> *)
           (n :: Extensibility -> Extensibility -> *).
    Body' block n
    emptyBody [CmmBlock]
    blocks

         -- Accumulator contains three components:
         --  * map of blocks in a graph
         --  * map of shortcut labels. See Note [Shortcut call returns]
         --  * map containing number of predecessors for each block. We discard
         --    it after we process all blocks.
         (LabelMap CmmBlock
    new_blocks, LabelMap Label
    shortcut_map, LabelMap Int
    _) =
               forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr CmmBlock
    -> (LabelMap CmmBlock, LabelMap Label, LabelMap Int)
    -> (LabelMap CmmBlock, LabelMap Label, LabelMap Int)
    maybe_concat (LabelMap CmmBlock
    blockmap, forall (map :: * -> *) a. IsMap map => map a
    mapEmpty, LabelMap Int
    initialBackEdges) [CmmBlock]
    blocks

         -- Map of predecessors for initial graph. We increase number of
         -- predecessors for entry block by one to denote that it is
         -- target of a jump, even if no block in the current graph jumps
         -- to it.
         initialBackEdges :: LabelMap Int
    initialBackEdges = Label -> LabelMap Int -> LabelMap Int
    incPreds Label
    entry_id ([CmmBlock] -> LabelMap Int
    predMap [CmmBlock]
    blocks)

         maybe_concat :: CmmBlock
                      -> (LabelMap CmmBlock, LabelMap BlockId, LabelMap Int)
                      -> (LabelMap CmmBlock, LabelMap BlockId, LabelMap Int)
         maybe_concat :: CmmBlock
    -> (LabelMap CmmBlock, LabelMap Label, LabelMap Int)
    -> (LabelMap CmmBlock, LabelMap Label, LabelMap Int)
    maybe_concat CmmBlock
    block (!LabelMap CmmBlock
    blocks, !LabelMap Label
    shortcut_map, !LabelMap Int
    backEdges)
            -- If:
            --   (1) current block ends with unconditional branch to b' and
            --   (2) it has exactly one predecessor (namely, current block)
            --
            -- Then:
            --   (1) append b' block at the end of current block
            --   (2) remove b' from the map of blocks
            --   (3) remove information about b' from predecessors map
            --
            -- Since we know that the block has only one predecessor we call
            -- mapDelete directly instead of calling decPreds.
            --
            -- Note that we always maintain an up-to-date list of predecessors, so
            -- we can ignore the contents of shortcut_map
            | CmmBranch Label
    b' <- CmmNode O C
    last
            , Label -> Bool
    hasOnePredecessor Label
    b'
            , Just CmmBlock
    blk' <- forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    b' LabelMap CmmBlock
    blocks
            = let bid' :: Label
    bid' = forall (thing :: Extensibility -> Extensibility -> *)
           (x :: Extensibility).
    NonLocal thing =>
    thing C x -> Label
    entryLabel CmmBlock
    blk'
              in ( forall (map :: * -> *) a. IsMap map => KeyOf map -> map a -> map a
    mapDelete Label
    bid' forall a b. (a -> b) -> a -> b
    $ forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    bid (Block CmmNode C O -> CmmBlock -> CmmBlock
    splice Block CmmNode C O
    head CmmBlock
    blk') LabelMap CmmBlock
    blocks
                 , LabelMap Label
    shortcut_map
                 , forall (map :: * -> *) a. IsMap map => KeyOf map -> map a -> map a
    mapDelete Label
    b' LabelMap Int
    backEdges )

            -- If:
            --   (1) we are splitting proc points (see Note
            --       [Shortcut call returns and proc-points]) and
            --   (2) current block is a CmmCall or CmmForeignCall with
            --       continuation b' and
            --   (3) we can shortcut that continuation to dest
            -- Then:
            --   (1) we change continuation to point to b'
            --   (2) create mapping from b' to dest
            --   (3) increase number of predecessors of dest by 1
            --   (4) decrease number of predecessors of b' by 1
            --
            -- Later we will use replaceLabels to substitute all occurrences of b'
            -- with dest.
            | Bool
    splitting_procs
            , Just Label
    b'   <- CmmNode O C -> Maybe Label
    callContinuation_maybe CmmNode O C
    last
            , Just CmmBlock
    blk' <- forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    b' LabelMap CmmBlock
    blocks
            , Just Label
    dest <- CmmBlock -> Maybe Label
    canShortcut CmmBlock
    blk'
            = ( forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    bid (forall (n :: Extensibility -> Extensibility -> *)
           (e :: Extensibility).
    Block n e O -> n O C -> Block n e C
    blockJoinTail Block CmmNode C O
    head (Label -> CmmNode O C
    update_cont Label
    dest)) LabelMap CmmBlock
    blocks
              , forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    b' Label
    dest LabelMap Label
    shortcut_map
              , Label -> LabelMap Int -> LabelMap Int
    decPreds Label
    b' forall a b. (a -> b) -> a -> b
    $ Label -> LabelMap Int -> LabelMap Int
    incPreds Label
    dest LabelMap Int
    backEdges )

            -- If:
            --   (1) a block does not end with a call
            -- Then:
            --   (1) if it ends with a conditional attempt to invert the
            --       conditional
            --   (2) attempt to shortcut all destination blocks
            --   (3) if new successors of a block are different from the old ones
            --       update the of predecessors accordingly
            --
            -- A special case of this is a situation when a block ends with an
            -- unconditional jump to a block that can be shortcut.
            | Maybe Label
    Nothing <- CmmNode O C -> Maybe Label
    callContinuation_maybe CmmNode O C
    last
            = let oldSuccs :: [Label]
    oldSuccs = forall (thing :: Extensibility -> Extensibility -> *)
           (e :: Extensibility).
    NonLocal thing =>
    thing e C -> [Label]
    successors CmmNode O C
    last
                  newSuccs :: [Label]
    newSuccs = forall (thing :: Extensibility -> Extensibility -> *)
           (e :: Extensibility).
    NonLocal thing =>
    thing e C -> [Label]
    successors CmmNode O C
    rewrite_last
              in ( forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    bid (forall (n :: Extensibility -> Extensibility -> *)
           (e :: Extensibility).
    Block n e O -> n O C -> Block n e C
    blockJoinTail Block CmmNode C O
    head CmmNode O C
    rewrite_last) LabelMap CmmBlock
    blocks
                 , LabelMap Label
    shortcut_map
                 , if [Label]
    oldSuccs forall a. Eq a => a -> a -> Bool
    == [Label]
    newSuccs
                   then LabelMap Int
    backEdges
                   else forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr Label -> LabelMap Int -> LabelMap Int
    incPreds (forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr Label -> LabelMap Int -> LabelMap Int
    decPreds LabelMap Int
    backEdges [Label]
    oldSuccs) [Label]
    newSuccs )

            -- Otherwise don't do anything
            | Bool
    otherwise
            = ( LabelMap CmmBlock
    blocks, LabelMap Label
    shortcut_map, LabelMap Int
    backEdges )
            where
              (Block CmmNode C O
    head, CmmNode O C
    last) = forall (n :: Extensibility -> Extensibility -> *)
           (e :: Extensibility).
    Block n e C -> (Block n e O, n O C)
    blockSplitTail CmmBlock
    block
              bid :: Label
    bid = forall (thing :: Extensibility -> Extensibility -> *)
           (x :: Extensibility).
    NonLocal thing =>
    thing C x -> Label
    entryLabel CmmBlock
    block

              -- Changes continuation of a call to a specified label
              update_cont :: Label -> CmmNode O C
    update_cont Label
    dest =
                  case CmmNode O C
    last of
                    CmmCall{}        -> CmmNode O C
    last { cml_cont :: Maybe Label
    cml_cont = forall a. a -> Maybe a
    Just Label
    dest }
                    CmmForeignCall{} -> CmmNode O C
    last { succ :: Label
    succ = Label
    dest }
                    CmmNode O C
    _                -> forall a. String -> a
    panic String
    "Can't shortcut continuation."

              -- Attempts to shortcut successors of last node
              shortcut_last :: CmmNode O C
    shortcut_last = (Label -> Label) -> CmmNode O C -> CmmNode O C
    mapSuccessors Label -> Label
    shortcut CmmNode O C
    last
                where
                  shortcut :: Label -> Label
    shortcut Label
    l =
                     case forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    l LabelMap CmmBlock
    blocks of
                       Just CmmBlock
    b | Just Label
    dest <- CmmBlock -> Maybe Label
    canShortcut CmmBlock
    b -> Label
    dest
                       Maybe CmmBlock
    _otherwise -> Label
    l

              rewrite_last :: CmmNode O C
    rewrite_last
                -- Sometimes we can get rid of the conditional completely.
                | CmmCondBranch CmmExpr
    _cond Label
    t Label
    f Maybe Bool
    _l <- CmmNode O C
    shortcut_last
                , Label
    t forall a. Eq a => a -> a -> Bool
    == Label
    f
                = Label -> CmmNode O C
    CmmBranch Label
    t

                -- See Note [Invert Cmm conditionals]
                | CmmCondBranch CmmExpr
    cond Label
    t Label
    f Maybe Bool
    l <- CmmNode O C
    shortcut_last
                , Label -> Bool
    hasOnePredecessor Label
    t -- inverting will make t a fallthrough
                , Maybe Bool -> Bool
    likelyTrue Maybe Bool
    l Bool -> Bool -> Bool
    || (Label -> Int
    numPreds Label
    f forall a. Ord a => a -> a -> Bool
    > Int
    1)
                , Just CmmExpr
    cond' <- CmmExpr -> Maybe CmmExpr
    maybeInvertCmmExpr CmmExpr
    cond
                = CmmExpr -> Label -> Label -> Maybe Bool -> CmmNode O C
    CmmCondBranch CmmExpr
    cond' Label
    f Label
    t (Maybe Bool -> Maybe Bool
    invertLikeliness Maybe Bool
    l)

                -- If all jump destinations of a switch go to the
                -- same target eliminate the switch.
                | CmmSwitch CmmExpr
    _expr SwitchTargets
    targets <- CmmNode O C
    shortcut_last
                , (Label
    t:[Label]
    ts) <- SwitchTargets -> [Label]
    switchTargetsToList SwitchTargets
    targets
                , forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    all (forall a. Eq a => a -> a -> Bool
    == Label
    t) [Label]
    ts
                = Label -> CmmNode O C
    CmmBranch Label
    t

                | Bool
    otherwise
                = CmmNode O C
    shortcut_last

              likelyTrue :: Maybe Bool -> Bool
    likelyTrue (Just Bool
    True)   = Bool
    True
              likelyTrue Maybe Bool
    _             = Bool
    False

              invertLikeliness :: Maybe Bool -> Maybe Bool
              invertLikeliness :: Maybe Bool -> Maybe Bool
    invertLikeliness         = forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    fmap Bool -> Bool
    not

              -- Number of predecessors for a block
              numPreds :: Label -> Int
    numPreds Label
    bid = forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    bid LabelMap Int
    backEdges forall a. Maybe a -> a -> a
    `orElse` Int
    0

              hasOnePredecessor :: Label -> Bool
    hasOnePredecessor Label
    b = Label -> Int
    numPreds Label
    b forall a. Eq a => a -> a -> Bool
    == Int
    1

    {-
      Note [Invert Cmm conditionals]
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      The native code generator always produces jumps to the true branch.
      Falling through to the false branch is however faster. So we try to
      arrange for that to happen.
      This means we invert the condition if:
      * The likely path will become a fallthrough.
      * We can't guarantee a fallthrough for the false branch but for the
        true branch.

      In some cases it's faster to avoid inverting when the false branch is likely.
      However determining when that is the case is neither easy nor cheap so for
      now we always invert as this produces smaller binaries and code that is
      equally fast on average. (On an i7-6700K)

      TODO:
      There is also the edge case when both branches have multiple predecessors.
      In this case we could assume that we will end up with a jump for BOTH
      branches. In this case it might be best to put the likely path in the true
      branch especially if there are large numbers of predecessors as this saves
      us the jump thats not taken. However I haven't tested this and as of early
      2018 we almost never generate cmm where this would apply.
    -}

    -- Functions for incrementing and decrementing number of predecessors. If
    -- decrementing would set the predecessor count to 0, we remove entry from the
    -- map.
    -- Invariant: if a block has no predecessors it should be dropped from the
    -- graph because it is unreachable. maybe_concat is constructed to maintain
    -- that invariant, but calling replaceLabels may introduce unreachable blocks.
    -- We rely on subsequent passes in the Cmm pipeline to remove unreachable
    -- blocks.
    incPreds, decPreds :: BlockId -> LabelMap Int -> LabelMap Int
    incPreds :: Label -> LabelMap Int -> LabelMap Int
    incPreds Label
    bid LabelMap Int
    edges = forall (map :: * -> *) a.
    IsMap map =>
    (a -> a -> a) -> KeyOf map -> a -> map a -> map a
    mapInsertWith forall a. Num a => a -> a -> a
    (+) Label
    bid Int
    1 LabelMap Int
    edges
    decPreds :: Label -> LabelMap Int -> LabelMap Int
    decPreds Label
    bid LabelMap Int
    edges = case forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    bid LabelMap Int
    edges of
                           Just Int
    preds | Int
    preds forall a. Ord a => a -> a -> Bool
    > Int
    1 -> forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    bid (Int
    preds forall a. Num a => a -> a -> a
    - Int
    1) LabelMap Int
    edges
                           Just Int
    _                 -> forall (map :: * -> *) a. IsMap map => KeyOf map -> map a -> map a
    mapDelete Label
    bid LabelMap Int
    edges
                           Maybe Int
    _                      -> LabelMap Int
    edges

    -- Checks if a block consists only of "goto dest". If it does than we return
    -- "Just dest" label. See Note [What is shortcutting]
    canShortcut :: CmmBlock -> Maybe BlockId
    canShortcut :: CmmBlock -> Maybe Label
    canShortcut CmmBlock
    block
        | (CmmNode C O
    _, Block CmmNode O O
    middle, CmmBranch Label
    dest) <- forall (n :: Extensibility -> Extensibility -> *).
    Block n C C -> (n C O, Block n O O, n O C)
    blockSplit CmmBlock
    block
        , forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    all forall {e :: Extensibility} {x :: Extensibility}.
    CmmNode e x -> Bool
    dont_care forall a b. (a -> b) -> a -> b
    $ forall (n :: Extensibility -> Extensibility -> *).
    Block n O O -> [n O O]
    blockToList Block CmmNode O O
    middle
        = forall a. a -> Maybe a
    Just Label
    dest
        | Bool
    otherwise
        = forall a. Maybe a
    Nothing
        where dont_care :: CmmNode e x -> Bool
    dont_care CmmComment{} = Bool
    True
              dont_care CmmTick{}    = Bool
    True
              dont_care CmmNode e x
    _other       = Bool
    False

    -- Concatenates two blocks. First one is assumed to be open on exit, the second
    -- is assumed to be closed on entry (i.e. it has a label attached to it, which
    -- the splice function removes by calling snd on result of blockSplitHead).
    splice :: Block CmmNode C O -> CmmBlock -> CmmBlock
    splice :: Block CmmNode C O -> CmmBlock -> CmmBlock
    splice Block CmmNode C O
    head CmmBlock
    rest = CmmNode C O
    entry forall (n :: Extensibility -> Extensibility -> *)
           (x :: Extensibility).
    n C O -> Block n O x -> Block n C x
    `blockJoinHead` Block CmmNode O O
    code0 forall (n :: Extensibility -> Extensibility -> *)
           (e :: Extensibility) (x :: Extensibility).
    Block n e O -> Block n O x -> Block n e x
    `blockAppend` Block CmmNode O C
    code1
      where (CmmEntry Label
    lbl CmmTickScope
    sc0, Block CmmNode O O
    code0) = forall (n :: Extensibility -> Extensibility -> *)
           (x :: Extensibility).
    Block n C x -> (n C O, Block n O x)
    blockSplitHead Block CmmNode C O
    head
            (CmmEntry Label
    _   CmmTickScope
    sc1, Block CmmNode O C
    code1) = forall (n :: Extensibility -> Extensibility -> *)
           (x :: Extensibility).
    Block n C x -> (n C O, Block n O x)
    blockSplitHead CmmBlock
    rest
            entry :: CmmNode C O
    entry = Label -> CmmTickScope -> CmmNode C O
    CmmEntry Label
    lbl (CmmTickScope -> CmmTickScope -> CmmTickScope
    combineTickScopes CmmTickScope
    sc0 CmmTickScope
    sc1)

    -- If node is a call with continuation call return Just label of that
    -- continuation. Otherwise return Nothing.
    callContinuation_maybe :: CmmNode O C -> Maybe BlockId
    callContinuation_maybe :: CmmNode O C -> Maybe Label
    callContinuation_maybe (CmmCall { cml_cont :: CmmNode O C -> Maybe Label
    cml_cont = Just Label
    b }) = forall a. a -> Maybe a
    Just Label
    b
    callContinuation_maybe (CmmForeignCall { succ :: CmmNode O C -> Label
    succ = Label
    b })   = forall a. a -> Maybe a
    Just Label
    b
    callContinuation_maybe CmmNode O C
    _ = forall a. Maybe a
    Nothing

    -- Map over the CmmGraph, replacing each label with its mapping in the
    -- supplied LabelMap.
    replaceLabels :: LabelMap BlockId -> CmmGraph -> CmmGraph
    replaceLabels :: LabelMap Label -> CmmGraph -> CmmGraph
    replaceLabels LabelMap Label
    env CmmGraph
    g
      | forall (map :: * -> *) a. IsMap map => map a -> Bool
    mapNull LabelMap Label
    env = CmmGraph
    g
      | Bool
    otherwise   = CmmGraph -> CmmGraph
    replace_eid forall a b. (a -> b) -> a -> b
    $ (forall (e :: Extensibility) (x :: Extensibility).
     CmmNode e x -> CmmNode e x)
    -> CmmGraph -> CmmGraph
    mapGraphNodes1 forall (e :: Extensibility) (x :: Extensibility).
    CmmNode e x -> CmmNode e x
    txnode CmmGraph
    g
       where
         replace_eid :: CmmGraph -> CmmGraph
    replace_eid CmmGraph
    g = CmmGraph
    g {g_entry :: Label
    g_entry = Label -> Label
    lookup (forall (n :: Extensibility -> Extensibility -> *).
    GenCmmGraph n -> Label
    g_entry CmmGraph
    g)}
         lookup :: Label -> Label
    lookup Label
    id = forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> map a -> Maybe a
    mapLookup Label
    id LabelMap Label
    env forall a. Maybe a -> a -> a
    `orElse` Label
    id

         txnode :: CmmNode e x -> CmmNode e x
         txnode :: forall (e :: Extensibility) (x :: Extensibility).
    CmmNode e x -> CmmNode e x
    txnode (CmmBranch Label
    bid) = Label -> CmmNode O C
    CmmBranch (Label -> Label
    lookup Label
    bid)
         txnode (CmmCondBranch CmmExpr
    p Label
    t Label
    f Maybe Bool
    l) =
           CmmExpr -> Label -> Label -> Maybe Bool -> CmmNode O C
    mkCmmCondBranch (CmmExpr -> CmmExpr
    exp CmmExpr
    p) (Label -> Label
    lookup Label
    t) (Label -> Label
    lookup Label
    f) Maybe Bool
    l
         txnode (CmmSwitch CmmExpr
    e SwitchTargets
    ids) =
           CmmExpr -> SwitchTargets -> CmmNode O C
    CmmSwitch (CmmExpr -> CmmExpr
    exp CmmExpr
    e) ((Label -> Label) -> SwitchTargets -> SwitchTargets
    mapSwitchTargets Label -> Label
    lookup SwitchTargets
    ids)
         txnode (CmmCall CmmExpr
    t Maybe Label
    k [GlobalReg]
    rg Int
    a Int
    res Int
    r) =
           CmmExpr
    -> Maybe Label -> [GlobalReg] -> Int -> Int -> Int -> CmmNode O C
    CmmCall (CmmExpr -> CmmExpr
    exp CmmExpr
    t) (forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
    liftM Label -> Label
    lookup Maybe Label
    k) [GlobalReg]
    rg Int
    a Int
    res Int
    r
         txnode fc :: CmmNode e x
    fc@CmmForeignCall{} =
           CmmNode e x
    fc{ args :: [CmmExpr]
    args = forall a b. (a -> b) -> [a] -> [b]
    map CmmExpr -> CmmExpr
    exp (CmmNode O C -> [CmmExpr]
    args CmmNode e x
    fc), succ :: Label
    succ = Label -> Label
    lookup (CmmNode O C -> Label
    succ CmmNode e x
    fc) }
         txnode CmmNode e x
    other = forall (e :: Extensibility) (x :: Extensibility).
    (CmmExpr -> CmmExpr) -> CmmNode e x -> CmmNode e x
    mapExpDeep CmmExpr -> CmmExpr
    exp CmmNode e x
    other

         exp :: CmmExpr -> CmmExpr
         exp :: CmmExpr -> CmmExpr
    exp (CmmLit (CmmBlock Label
    bid))                = CmmLit -> CmmExpr
    CmmLit (Label -> CmmLit
    CmmBlock (Label -> Label
    lookup Label
    bid))
         exp (CmmStackSlot (Young Label
    id) Int
    i) = Area -> Int -> CmmExpr
    CmmStackSlot (Label -> Area
    Young (Label -> Label
    lookup Label
    id)) Int
    i
         exp CmmExpr
    e                                      = CmmExpr
    e

    mkCmmCondBranch :: CmmExpr -> Label -> Label -> Maybe Bool -> CmmNode O C
    mkCmmCondBranch :: CmmExpr -> Label -> Label -> Maybe Bool -> CmmNode O C
    mkCmmCondBranch CmmExpr
    p Label
    t Label
    f Maybe Bool
    l =
      if Label
    t forall a. Eq a => a -> a -> Bool
    == Label
    f then Label -> CmmNode O C
    CmmBranch Label
    t else CmmExpr -> Label -> Label -> Maybe Bool -> CmmNode O C
    CmmCondBranch CmmExpr
    p Label
    t Label
    f Maybe Bool
    l

    -- Build a map from a block to its set of predecessors.
    predMap :: [CmmBlock] -> LabelMap Int
    predMap :: [CmmBlock] -> LabelMap Int
    predMap [CmmBlock]
    blocks = forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr forall {map :: * -> *} {a}
           {thing :: Extensibility -> Extensibility -> *}
           {e :: Extensibility}.
    (KeyOf map ~ Label, IsMap map, Num a, NonLocal thing) =>
    thing e C -> map a -> map a
    add_preds forall (map :: * -> *) a. IsMap map => map a
    mapEmpty [CmmBlock]
    blocks
      where
        add_preds :: thing e C -> map a -> map a
    add_preds thing e C
    block map a
    env = forall (t :: * -> *) a b.
    Foldable t =>
    (a -> b -> b) -> b -> t a -> b
    foldr forall {map :: * -> *} {a}.
    (IsMap map, Num a) =>
    KeyOf map -> map a -> map a
    add map a
    env (forall (thing :: Extensibility -> Extensibility -> *)
           (e :: Extensibility).
    NonLocal thing =>
    thing e C -> [Label]
    successors thing e C
    block)
          where add :: KeyOf map -> map a -> map a
    add KeyOf map
    lbl map a
    env = forall (map :: * -> *) a.
    IsMap map =>
    (a -> a -> a) -> KeyOf map -> a -> map a -> map a
    mapInsertWith forall a. Num a => a -> a -> a
    (+) KeyOf map
    lbl a
    1 map a
    env

    -- Removing unreachable blocks
    removeUnreachableBlocksProc :: CmmDecl -> CmmDecl
    removeUnreachableBlocksProc :: CmmDecl -> CmmDecl
    removeUnreachableBlocksProc proc :: CmmDecl
    proc@(CmmProc CmmTopInfo
    info CLabel
    lbl [GlobalReg]
    live CmmGraph
    g)
       | [CmmBlock]
    used_blocks forall a. [a] -> Int -> Bool
    `lengthLessThan` forall (map :: * -> *) a. IsMap map => map a -> Int
    mapSize (CmmGraph -> LabelMap CmmBlock
    toBlockMap CmmGraph
    g)
       = forall d h g. h -> CLabel -> [GlobalReg] -> g -> GenCmmDecl d h g
    CmmProc CmmTopInfo
    info' CLabel
    lbl [GlobalReg]
    live CmmGraph
    g'
       | Bool
    otherwise
       = CmmDecl
    proc
       where
         g' :: CmmGraph
    g'    = Label -> [CmmBlock] -> CmmGraph
    ofBlockList (forall (n :: Extensibility -> Extensibility -> *).
    GenCmmGraph n -> Label
    g_entry CmmGraph
    g) [CmmBlock]
    used_blocks
         info' :: CmmTopInfo
    info' = CmmTopInfo
    info { info_tbls :: LabelMap CmmInfoTable
    info_tbls = LabelMap CmmInfoTable -> LabelMap CmmInfoTable
    keep_used (CmmTopInfo -> LabelMap CmmInfoTable
    info_tbls CmmTopInfo
    info) }
                 -- Remove any info_tbls for unreachable

         keep_used :: LabelMap CmmInfoTable -> LabelMap CmmInfoTable
         keep_used :: LabelMap CmmInfoTable -> LabelMap CmmInfoTable
    keep_used LabelMap CmmInfoTable
    bs = forall (map :: * -> *) b a.
    IsMap map =>
    (b -> KeyOf map -> a -> b) -> b -> map a -> b
    mapFoldlWithKey LabelMap CmmInfoTable
    -> Label -> CmmInfoTable -> LabelMap CmmInfoTable
    keep forall (map :: * -> *) a. IsMap map => map a
    mapEmpty LabelMap CmmInfoTable
    bs

         keep :: LabelMap CmmInfoTable -> Label -> CmmInfoTable -> LabelMap CmmInfoTable
         keep :: LabelMap CmmInfoTable
    -> Label -> CmmInfoTable -> LabelMap CmmInfoTable
    keep LabelMap CmmInfoTable
    env Label
    l CmmInfoTable
    i | Label
    l forall set. IsSet set => ElemOf set -> set -> Bool
    `setMember` LabelSet
    used_lbls = forall (map :: * -> *) a.
    IsMap map =>
    KeyOf map -> a -> map a -> map a
    mapInsert Label
    l CmmInfoTable
    i LabelMap CmmInfoTable
    env
                      | Bool
    otherwise               = LabelMap CmmInfoTable
    env

         used_blocks :: [CmmBlock]
         used_blocks :: [CmmBlock]
    used_blocks = CmmGraph -> [CmmBlock]
    revPostorder CmmGraph
    g

         used_lbls :: LabelSet
         used_lbls :: LabelSet
    used_lbls = forall set. IsSet set => [ElemOf set] -> set
    setFromList forall a b. (a -> b) -> a -> b
    $ forall a b. (a -> b) -> [a] -> [b]
    map forall (thing :: Extensibility -> Extensibility -> *)
           (x :: Extensibility).
    NonLocal thing =>
    thing C x -> Label
    entryLabel [CmmBlock]
    used_blocks