1 {-# LANGUAGE PackageImports #-}
3 -- This module provides functions for program transformations.
5 module NormalizeTools where
9 import qualified Data.Monoid as Monoid
10 import qualified Control.Arrow as Arrow
11 import qualified Control.Monad as Monad
12 import qualified Control.Monad.Trans.State as State
13 import qualified Control.Monad.Trans.Writer as Writer
14 import qualified "transformers" Control.Monad.Trans as Trans
15 import qualified Data.Map as Map
20 import qualified UniqSupply
21 import qualified Unique
22 import qualified OccName
25 import qualified SrcLoc
27 import qualified IdInfo
28 import qualified CoreUtils
29 import qualified CoreSubst
30 import qualified VarSet
31 import Outputable ( showSDoc, ppr, nest )
36 -- Create a new internal var with the given name and type. A Unique is
37 -- appended to the given name, to ensure uniqueness (not strictly neccesary,
38 -- since the Unique is also stored in the name, but this ensures variable
39 -- names are unique in the output).
40 mkInternalVar :: String -> Type.Type -> TransformMonad Var.Var
41 mkInternalVar str ty = do
43 let occname = OccName.mkVarOcc (str ++ show uniq)
44 let name = Name.mkInternalName uniq occname SrcLoc.noSrcSpan
45 return $ Var.mkLocalIdVar name ty IdInfo.vanillaIdInfo
47 -- Create a new type variable with the given name and kind. A Unique is
48 -- appended to the given name, to ensure uniqueness (not strictly neccesary,
49 -- since the Unique is also stored in the name, but this ensures variable
50 -- names are unique in the output).
51 mkTypeVar :: String -> Type.Kind -> TransformMonad Var.Var
52 mkTypeVar str kind = do
54 let occname = OccName.mkVarOcc (str ++ show uniq)
55 let name = Name.mkInternalName uniq occname SrcLoc.noSrcSpan
56 return $ Var.mkTyVar name kind
58 -- Creates a binder for the given expression with the given name. This
59 -- works for both value and type level expressions, so it can return a Var or
60 -- TyVar (which is just an alias for Var).
61 mkBinderFor :: CoreExpr -> String -> TransformMonad Var.Var
62 mkBinderFor (Type ty) string = mkTypeVar string (Type.typeKind ty)
63 mkBinderFor expr string = mkInternalVar string (CoreUtils.exprType expr)
65 -- Creates a reference to the given variable. This works for both a normal
66 -- variable as well as a type variable
67 mkReferenceTo :: Var.Var -> CoreExpr
68 mkReferenceTo var | Var.isTyVar var = (Type $ Type.mkTyVarTy var)
69 | otherwise = (Var var)
71 cloneVar :: Var.Var -> TransformMonad Var.Var
74 -- Swap out the unique, and reset the IdInfo (I'm not 100% sure what it
75 -- contains, but vannillaIdInfo is always correct, since it means "no info").
76 return $ Var.lazySetVarIdInfo (Var.setVarUnique v uniq) IdInfo.vanillaIdInfo
78 -- Creates a new function with the same name as the given binder (but with a
79 -- new unique) and with the given function body. Returns the new binder for
81 mkFunction :: CoreBndr -> CoreExpr -> TransformMonad CoreBndr
82 mkFunction bndr body = do
83 let ty = CoreUtils.exprType body
85 let newid = Var.setVarType id ty
86 Trans.lift $ addGlobalBind newid body
89 -- Apply the given transformation to all expressions in the given expression,
90 -- including the expression itself.
91 everywhere :: (String, Transform) -> Transform
92 everywhere trans = applyboth (subeverywhere (everywhere trans)) trans
94 -- Apply the first transformation, followed by the second transformation, and
95 -- keep applying both for as long as expression still changes.
96 applyboth :: Transform -> (String, Transform) -> Transform
97 applyboth first (name, second) expr = do
101 (expr'', changed) <- Writer.listen $ second expr'
103 -- trace ("Trying to apply transform " ++ name ++ " to:\n" ++ showSDoc (nest 4 $ ppr expr') ++ "\nType: \n" ++ (showSDoc $ nest 4 $ ppr $ CoreUtils.exprType expr') ++ "\n") $
106 -- trace ("Applying transform " ++ name ++ " to:\n" ++ showSDoc (nest 4 $ ppr expr') ++ "\nType: \n" ++ (showSDoc $ nest 4 $ ppr $ CoreUtils.exprType expr') ++ "\n") $
107 -- trace ("Result of applying " ++ name ++ ":\n" ++ showSDoc (nest 4 $ ppr expr'') ++ "\n" ++ "Type: \n" ++ (showSDoc $ nest 4 $ ppr $ CoreUtils.exprType expr'') ++ "\n" ) $
108 applyboth first (name, second) $
111 -- trace ("No changes") $
114 -- Apply the given transformation to all direct subexpressions (only), not the
115 -- expression itself.
116 subeverywhere :: Transform -> Transform
117 subeverywhere trans (App a b) = do
122 subeverywhere trans (Let (Rec binds) expr) = do
124 binds' <- mapM transbind binds
125 return $ Let (Rec binds') expr'
127 transbind :: (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
128 transbind (b, e) = do
132 subeverywhere trans (Lam x expr) = do
136 subeverywhere trans (Case scrut b t alts) = do
137 scrut' <- trans scrut
138 alts' <- mapM transalt alts
139 return $ Case scrut' b t alts'
141 transalt :: CoreAlt -> TransformMonad CoreAlt
142 transalt (con, binders, expr) = do
144 return (con, binders, expr')
146 subeverywhere trans (Var x) = return $ Var x
147 subeverywhere trans (Lit x) = return $ Lit x
148 subeverywhere trans (Type x) = return $ Type x
150 subeverywhere trans (Cast expr ty) = do
152 return $ Cast expr' ty
154 subeverywhere trans expr = error $ "NormalizeTools.subeverywhere Unsupported expression: " ++ show expr
156 -- Apply the given transformation to all expressions, except for direct
157 -- arguments of an application
158 notappargs :: (String, Transform) -> Transform
159 notappargs trans = applyboth (subnotappargs trans) trans
161 -- Apply the given transformation to all (direct and indirect) subexpressions
162 -- (but not the expression itself), except for direct arguments of an
164 subnotappargs :: (String, Transform) -> Transform
165 subnotappargs trans (App a b) = do
166 a' <- subnotappargs trans a
167 b' <- subnotappargs trans b
170 -- Let subeverywhere handle all other expressions
171 subnotappargs trans expr = subeverywhere (notappargs trans) expr
173 -- Runs each of the transforms repeatedly inside the State monad.
174 dotransforms :: [Transform] -> CoreExpr -> TransformSession CoreExpr
175 dotransforms transs expr = do
176 (expr', changed) <- Writer.runWriterT $ Monad.foldM (flip ($)) expr transs
177 if Monoid.getAny changed then dotransforms transs expr' else return expr'
179 -- Inline all let bindings that satisfy the given condition
180 inlinebind :: ((CoreBndr, CoreExpr) -> Bool) -> Transform
181 inlinebind condition (Let (Rec binds) expr) | not $ null replace =
184 -- Find all simple bindings
185 (replace, others) = List.partition condition binds
186 -- Substitute the to be replaced binders with their expression
187 newexpr = substitute replace (Let (Rec others) expr)
188 -- Leave all other expressions unchanged
189 inlinebind _ expr = return expr
191 -- Sets the changed flag in the TransformMonad, to signify that some
192 -- transform has changed the result
193 setChanged :: TransformMonad ()
194 setChanged = Writer.tell (Monoid.Any True)
196 -- Sets the changed flag and returns the given value.
197 change :: a -> TransformMonad a
202 -- Create a new Unique
203 mkUnique :: TransformMonad Unique.Unique
204 mkUnique = Trans.lift $ do
205 us <- getA tsUniqSupply
206 let (us', us'') = UniqSupply.splitUniqSupply us
207 putA tsUniqSupply us'
208 return $ UniqSupply.uniqFromSupply us''
210 -- Replace each of the binders given with the coresponding expressions in the
212 substitute :: [(CoreBndr, CoreExpr)] -> CoreExpr -> CoreExpr
213 substitute [] expr = expr
214 -- Apply one substitution on the expression, but also on any remaining
215 -- substitutions. This seems to be the only way to handle substitutions like
216 -- [(b, c), (a, b)]. This means we reuse a substitution, which is not allowed
217 -- according to CoreSubst documentation (but it doesn't seem to be a problem).
218 -- TODO: Find out how this works, exactly.
219 substitute ((b, e):subss) expr = substitute subss' expr'
222 subs = (CoreSubst.extendSubst CoreSubst.emptySubst b e)
223 -- Apply this substitution to the main expression
224 expr' = CoreSubst.substExpr subs expr
225 -- Apply this substitution on all the expressions in the remaining
227 subss' = map (Arrow.second (CoreSubst.substExpr subs)) subss
229 -- Run a given TransformSession. Used mostly to setup the right calls and
231 runTransformSession :: UniqSupply.UniqSupply -> TransformSession a -> a
232 runTransformSession uniqSupply session = State.evalState session initState
233 where initState = TransformState uniqSupply Map.empty VarSet.emptyVarSet