{-# LANGUAGE BangPatterns #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} module GHC.Cmm.Dataflow.Graph ( Body , Graph , Graph'(..) , NonLocal(..) , addBlock , bodyList , emptyBody , labelsDefined , mapGraph , mapGraphBlocks , revPostorderFrom ) where import GHC.Prelude import GHC.Utils.Misc import GHC.Cmm.Dataflow.Label import GHC.Cmm.Dataflow.Block import GHC.Cmm.Dataflow.Collections import Data.Kind -- | A (possibly empty) collection of closed/closed blocks type Body n = LabelMap (Block n C C) -- | @Body@ abstracted over @block@ type Body' block (n :: Extensibility -> Extensibility -> Type) = LabelMap (block n C C) ------------------------------- -- | Gives access to the anchor points for -- nonlocal edges as well as the edges themselves class NonLocal thing where entryLabel :: thing C x -> Label -- ^ The label of a first node or block successors :: thing e C -> [Label] -- ^ Gives control-flow successors instance NonLocal n => NonLocal (Block n) where entryLabel :: forall (x :: Extensibility). Block n C x -> Label entryLabel (BlockCO n C 'Open f Block n 'Open 'Open _) = forall (thing :: Extensibility -> Extensibility -> *) (x :: Extensibility). NonLocal thing => thing C x -> Label entryLabel n C 'Open f entryLabel (BlockCC n C 'Open f Block n 'Open 'Open _ n 'Open C _) = forall (thing :: Extensibility -> Extensibility -> *) (x :: Extensibility). NonLocal thing => thing C x -> Label entryLabel n C 'Open f successors :: forall (e :: Extensibility). Block n e C -> [Label] successors (BlockOC Block n 'Open 'Open _ n 'Open C n) = forall (thing :: Extensibility -> Extensibility -> *) (e :: Extensibility). NonLocal thing => thing e C -> [Label] successors n 'Open C n successors (BlockCC n C 'Open _ Block n 'Open 'Open _ n 'Open C n) = forall (thing :: Extensibility -> Extensibility -> *) (e :: Extensibility). NonLocal thing => thing e C -> [Label] successors n 'Open C n emptyBody :: Body' block n emptyBody :: forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *). Body' block n emptyBody = forall (map :: * -> *) a. IsMap map => map a mapEmpty bodyList :: Body' block n -> [(Label,block n C C)] bodyList :: forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *). Body' block n -> [(Label, block n C C)] bodyList Body' block n body = forall (map :: * -> *) a. IsMap map => map a -> [(KeyOf map, a)] mapToList Body' block n body addBlock :: (NonLocal block, HasDebugCallStack) => block C C -> LabelMap (block C C) -> LabelMap (block C C) addBlock :: forall (block :: Extensibility -> Extensibility -> *). (NonLocal block, HasDebugCallStack) => block C C -> LabelMap (block C C) -> LabelMap (block C C) addBlock block C C block LabelMap (block C C) body = forall (map :: * -> *) a. IsMap map => (Maybe a -> Maybe a) -> KeyOf map -> map a -> map a mapAlter Maybe (block C C) -> Maybe (block C C) add Label lbl LabelMap (block C C) body where lbl :: Label lbl = forall (thing :: Extensibility -> Extensibility -> *) (x :: Extensibility). NonLocal thing => thing C x -> Label entryLabel block C C block add :: Maybe (block C C) -> Maybe (block C C) add Maybe (block C C) Nothing = forall a. a -> Maybe a Just block C C block add Maybe (block C C) _ = forall a. HasCallStack => [Char] -> a error forall a b. (a -> b) -> a -> b $ [Char] "duplicate label " forall a. [a] -> [a] -> [a] ++ forall a. Show a => a -> [Char] show Label lbl forall a. [a] -> [a] -> [a] ++ [Char] " in graph" -- --------------------------------------------------------------------------- -- Graph -- | A control-flow graph, which may take any of four shapes (O/O, -- O/C, C/O, C/C). A graph open at the entry has a single, -- distinguished, anonymous entry point; if a graph is closed at the -- entry, its entry point(s) are supplied by a context. type Graph = Graph' Block -- | @Graph'@ is abstracted over the block type, so that we can build -- graphs of annotated blocks for example (Compiler.Hoopl.Dataflow -- needs this). data Graph' block (n :: Extensibility -> Extensibility -> Type) e x where GNil :: Graph' block n O O GUnit :: block n O O -> Graph' block n O O GMany :: MaybeO e (block n O C) -> Body' block n -> MaybeO x (block n C O) -> Graph' block n e x -- ----------------------------------------------------------------------------- -- Mapping over graphs -- | Maps over all nodes in a graph. mapGraph :: (forall e x. n e x -> n' e x) -> Graph n e x -> Graph n' e x mapGraph :: forall (n :: Extensibility -> Extensibility -> *) (n' :: Extensibility -> Extensibility -> *) (e :: Extensibility) (x :: Extensibility). (forall (e :: Extensibility) (x :: Extensibility). n e x -> n' e x) -> Graph n e x -> Graph n' e x mapGraph forall (e :: Extensibility) (x :: Extensibility). n e x -> n' e x f = forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *) (block' :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n' :: Extensibility -> Extensibility -> *) (e :: Extensibility) (x :: Extensibility). (forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x) -> Graph' block n e x -> Graph' block' n' e x mapGraphBlocks (forall (n :: Extensibility -> Extensibility -> *) (n' :: Extensibility -> Extensibility -> *) (e :: Extensibility) (x :: Extensibility). (forall (e1 :: Extensibility) (x1 :: Extensibility). n e1 x1 -> n' e1 x1) -> Block n e x -> Block n' e x mapBlock forall (e :: Extensibility) (x :: Extensibility). n e x -> n' e x f) -- | Function 'mapGraphBlocks' enables a change of representation of blocks, -- nodes, or both. It lifts a polymorphic block transform into a polymorphic -- graph transform. When the block representation stabilizes, a similar -- function should be provided for blocks. mapGraphBlocks :: forall block n block' n' e x . (forall e x . block n e x -> block' n' e x) -> (Graph' block n e x -> Graph' block' n' e x) mapGraphBlocks :: forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *) (block' :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n' :: Extensibility -> Extensibility -> *) (e :: Extensibility) (x :: Extensibility). (forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x) -> Graph' block n e x -> Graph' block' n' e x mapGraphBlocks forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x f = Graph' block n e x -> Graph' block' n' e x map where map :: Graph' block n e x -> Graph' block' n' e x map :: Graph' block n e x -> Graph' block' n' e x map Graph' block n e x GNil = forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *). Graph' block n 'Open 'Open GNil map (GUnit block n 'Open 'Open b) = forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *). block n 'Open 'Open -> Graph' block n 'Open 'Open GUnit (forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x f block n 'Open 'Open b) map (GMany MaybeO e (block n 'Open C) e Body' block n b MaybeO x (block n C 'Open) x) = forall (e :: Extensibility) (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *) (x :: Extensibility). MaybeO e (block n 'Open C) -> Body' block n -> MaybeO x (block n C 'Open) -> Graph' block n e x GMany (forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b fmap forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x f MaybeO e (block n 'Open C) e) (forall (map :: * -> *) a b. IsMap map => (a -> b) -> map a -> map b mapMap forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x f Body' block n b) (forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b fmap forall (e :: Extensibility) (x :: Extensibility). block n e x -> block' n' e x f MaybeO x (block n C 'Open) x) -- ----------------------------------------------------------------------------- -- Extracting Labels from graphs labelsDefined :: forall block n e x . NonLocal (block n) => Graph' block n e x -> LabelSet labelsDefined :: forall (block :: (Extensibility -> Extensibility -> *) -> Extensibility -> Extensibility -> *) (n :: Extensibility -> Extensibility -> *) (e :: Extensibility) (x :: Extensibility). NonLocal (block n) => Graph' block n e x -> LabelSet labelsDefined Graph' block n e x GNil = forall set. IsSet set => set setEmpty labelsDefined (GUnit{}) = forall set. IsSet set => set setEmpty labelsDefined (GMany MaybeO e (block n 'Open C) _ Body' block n body MaybeO x (block n C 'Open) x) = forall (map :: * -> *) b a. IsMap map => (b -> KeyOf map -> a -> b) -> b -> map a -> b mapFoldlWithKey forall a. LabelSet -> ElemOf LabelSet -> a -> LabelSet addEntry (MaybeO x (block n C 'Open) -> LabelSet exitLabel MaybeO x (block n C 'Open) x) Body' block n body where addEntry :: forall a. LabelSet -> ElemOf LabelSet -> a -> LabelSet addEntry :: forall a. LabelSet -> ElemOf LabelSet -> a -> LabelSet addEntry LabelSet labels ElemOf LabelSet label a _ = forall set. IsSet set => ElemOf set -> set -> set setInsert ElemOf LabelSet label LabelSet labels exitLabel :: MaybeO x (block n C O) -> LabelSet exitLabel :: MaybeO x (block n C 'Open) -> LabelSet exitLabel MaybeO x (block n C 'Open) NothingO = forall set. IsSet set => set setEmpty exitLabel (JustO block n C 'Open b) = forall set. IsSet set => ElemOf set -> set setSingleton (forall (thing :: Extensibility -> Extensibility -> *) (x :: Extensibility). NonLocal thing => thing C x -> Label entryLabel block n C 'Open b) ---------------------------------------------------------------- -- | Returns a list of blocks reachable from the provided Labels in the reverse -- postorder. -- -- This is the most important traversal over this data structure. It drops -- unreachable code and puts blocks in an order that is good for solving forward -- dataflow problems quickly. The reverse order is good for solving backward -- dataflow problems quickly. The forward order is also reasonably good for -- emitting instructions, except that it will not usually exploit Forrest -- Baskett's trick of eliminating the unconditional branch from a loop. For -- that you would need a more serious analysis, probably based on dominators, to -- identify loop headers. -- -- For forward analyses we want reverse postorder visitation, consider: -- @ -- A -> [B,C] -- B -> D -- C -> D -- @ -- Postorder: [D, C, B, A] (or [D, B, C, A]) -- Reverse postorder: [A, B, C, D] (or [A, C, B, D]) -- This matters for, e.g., forward analysis, because we want to analyze *both* -- B and C before we analyze D. revPostorderFrom :: forall block. (NonLocal block) => LabelMap (block C C) -> Label -> [block C C] revPostorderFrom :: forall (block :: Extensibility -> Extensibility -> *). NonLocal block => LabelMap (block C C) -> Label -> [block C C] revPostorderFrom LabelMap (block C C) graph Label start = DfsStack (block C C) -> LabelSet -> [block C C] -> [block C C] go DfsStack (block C C) start_worklist forall set. IsSet set => set setEmpty [] where start_worklist :: DfsStack (block C C) start_worklist = Label -> DfsStack (block C C) -> DfsStack (block C C) lookup_for_descend Label start forall a. DfsStack a Nil -- To compute the postorder we need to "visit" a block (mark as done) -- *after* visiting all its successors. So we need to know whether we -- already processed all successors of each block (and @NonLocal@ allows -- arbitrary many successors). So we use an explicit stack with an extra bit -- of information: -- * @ConsTodo@ means to explore the block if it wasn't visited before -- * @ConsMark@ means that all successors were already done and we can add -- the block to the result. -- -- NOTE: We add blocks to the result list in postorder, but we *prepend* -- them (i.e., we use @(:)@), which means that the final list is in reverse -- postorder. go :: DfsStack (block C C) -> LabelSet -> [block C C] -> [block C C] go :: DfsStack (block C C) -> LabelSet -> [block C C] -> [block C C] go DfsStack (block C C) Nil !LabelSet _ ![block C C] result = [block C C] result go (ConsMark block C C block DfsStack (block C C) rest) !LabelSet wip_or_done ![block C C] result = DfsStack (block C C) -> LabelSet -> [block C C] -> [block C C] go DfsStack (block C C) rest LabelSet wip_or_done (block C C block forall a. a -> [a] -> [a] : [block C C] result) go (ConsTodo block C C block DfsStack (block C C) rest) !LabelSet wip_or_done ![block C C] result | forall (thing :: Extensibility -> Extensibility -> *) (x :: Extensibility). NonLocal thing => thing C x -> Label entryLabel block C C block forall set. IsSet set => ElemOf set -> set -> Bool `setMember` LabelSet wip_or_done = DfsStack (block C C) -> LabelSet -> [block C C] -> [block C C] go DfsStack (block C C) rest LabelSet wip_or_done [block C C] result | Bool otherwise = let new_worklist :: DfsStack (block C C) new_worklist = forall (t :: * -> *) a b. Foldable t => (a -> b -> b) -> b -> t a -> b foldr Label -> DfsStack (block C C) -> DfsStack (block C C) lookup_for_descend (forall a. a -> DfsStack a -> DfsStack a ConsMark block C C block DfsStack (block C C) rest) (forall (thing :: Extensibility -> Extensibility -> *) (e :: Extensibility). NonLocal thing => thing e C -> [Label] successors block C C block) in DfsStack (block C C) -> LabelSet -> [block C C] -> [block C C] go DfsStack (block C C) new_worklist (forall set. IsSet set => ElemOf set -> set -> set setInsert (forall (thing :: Extensibility -> Extensibility -> *) (x :: Extensibility). NonLocal thing => thing C x -> Label entryLabel block C C block) LabelSet wip_or_done) [block C C] result lookup_for_descend :: Label -> DfsStack (block C C) -> DfsStack (block C C) lookup_for_descend :: Label -> DfsStack (block C C) -> DfsStack (block C C) lookup_for_descend Label label DfsStack (block C C) wl | Just block C C b <- forall (map :: * -> *) a. IsMap map => KeyOf map -> map a -> Maybe a mapLookup Label label LabelMap (block C C) graph = forall a. a -> DfsStack a -> DfsStack a ConsTodo block C C b DfsStack (block C C) wl | Bool otherwise = forall a. HasCallStack => [Char] -> a error forall a b. (a -> b) -> a -> b $ [Char] "Label that doesn't have a block?! " forall a. [a] -> [a] -> [a] ++ forall a. Show a => a -> [Char] show Label label data DfsStack a = ConsTodo a (DfsStack a) | ConsMark a (DfsStack a) | Nil