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sourcecode:
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{-# OPTIONS_FRONTEND -Wno-incomplete-patterns #-}
module Analysis.RequiredValue
(AType(..), showAType, AFType(..), showAFType, lubAType, reqValueAnalysis)
where
import FlatCurry.Types
import FlatCurry.Goodies
import Data.List
import RW.Base
import System.IO
import Analysis.Types
import Analysis.ProgInfo
import Analysis.TotallyDefined(siblingCons)
------------------------------------------------------------------------------
-- Our abstract (non-standard) type domain.
-- `Any` represents any expression,
-- `AnyC` represents any value (i.e., constructor-rooted term),
-- `Cons c` a value rooted by the constructor `c`, and
-- `Empty` represents no possible value.
data AType = Any | AnyC | Cons QName | Empty
deriving (Eq, Ord, Show, Read)
--- Is some abstract type a constructor?
isConsValue :: AType -> Bool
isConsValue av = case av of Cons _ -> True
_ -> False
--- Least upper bound of abstract values.
lubAType :: AType -> AType -> AType
lubAType Any _ = Any
lubAType AnyC Any = Any
lubAType AnyC AnyC = AnyC
lubAType AnyC (Cons _) = AnyC
lubAType AnyC Empty = AnyC
lubAType (Cons _) Any = Any
lubAType (Cons _) AnyC = AnyC
lubAType (Cons c) (Cons d) = if c==d then Cons c else AnyC
lubAType (Cons c) Empty = Cons c
lubAType Empty av = av
--- Join two abstract values. The result is `Empty` if they are not compatible.
joinAType :: AType -> AType -> AType
joinAType Any av = av
joinAType AnyC Any = AnyC
joinAType AnyC AnyC = AnyC
joinAType AnyC (Cons c) = Cons c
joinAType AnyC Empty = Empty
joinAType (Cons c) Any = Cons c
joinAType (Cons c) AnyC = Cons c
joinAType (Cons c) (Cons d) = if c==d then Cons c else Empty
joinAType (Cons _) Empty = Empty
joinAType Empty _ = Empty
--- Are two abstract types compatible, i.e., describe common values?
compatibleType :: AType -> AType -> Bool
compatibleType t1 t2 = joinAType t1 t2 /= Empty
-- Shows an abstract value.
showAType :: AOutFormat -> AType -> String
showAType _ Any = "any"
showAType _ AnyC = "cons"
showAType _ (Cons (_,n)) = n --q++"."++n
showAType _ Empty = "_|_"
--- The abstract type of a function.
--- It is either `EmptyFunc`, i.e., contains no information about
--- the possible result of the function,
--- or a list of possible argument/result type pairs.
data AFType = EmptyFunc | AFType [([AType],AType)]
deriving (Read, Show, Eq, Ord)
-- Shows an abstract value.
showAFType :: AOutFormat -> AFType -> String
showAFType _ EmptyFunc = "EmptyFunc"
showAFType aof (AFType fts) = intercalate " | " (map showFType fts)
where
showFType (targs,tres) =
"(" ++ intercalate "," (map (showAType aof) targs) ++ " -> " ++
showAType aof tres ++ ")"
showCalledFuncs :: [(QName,AFType)] -> String
showCalledFuncs =
intercalate "|" . map (\ ((_,f),at) -> f ++ "::" ++ showAFType ANote at)
------------------------------------------------------------------------------
--- An abstract environments used in the analysis of a function associates
--- to each variable (index) an abstract type.
type AEnv = [(Int,AType)]
--- Extend an abstract environment with variables of any type:
extendEnv :: AEnv -> [Int] -> AEnv
extendEnv env vars = zip vars (repeat Any) ++ env
--- Update a variable in an abstract environment:
updateVarInEnv :: AEnv -> Int -> AType -> AEnv
updateVarInEnv [] v _ = error ("Variable "++show v++" not found in environment")
updateVarInEnv ((i,ov):env) v nv =
if i==v then (i,nv) : env
else (i,ov) : updateVarInEnv env v nv
--- Drop the first n elements from the environment component
--- of an environment/type pair:
dropEnv :: Int -> ([a],b) -> ([a],b)
dropEnv n (env,rtype) = (drop n env, rtype)
-- Sorts a list of environment/type pairs by the type.
sortEnvTypes :: [(AEnv,AType)] -> [(AEnv,AType)]
sortEnvTypes = sortBy (\ (e1,t1) (e2,t2) -> (t1,e1) <= (t2,e2))
------------------------------------------------------------------------------
--- The maximum number of different constructors considered for the
--- required value analysis. If a type has more constructors than
--- specified here, it will not be analyzed for individual required
--- constructor values.
maxReqValues :: Int
maxReqValues = 3
--- Required value analysis.
reqValueAnalysis :: Analysis AFType
reqValueAnalysis =
combinedDependencyFuncAnalysis "RequiredValue"
siblingCons EmptyFunc analyseReqVal
analyseReqVal :: ProgInfo [(QName,Int)] -> FuncDecl -> [(QName,AFType)]
-> AFType
analyseReqVal consinfo (Func (m,f) arity _ _ rule) calledfuncs
| m==prelude = maybe (anaresult rule) id (lookup f preludeFuncs)
| otherwise = --trace ("Analyze "++f++"\n"++showCalledFuncs calledfuncs++
-- "\nRESULT: "++showAFType _ (anaresult rule)) $
anaresult rule
where
anaresult (External _) = AFType [(take arity (repeat Any),AnyC)]
anaresult (Rule args rhs) = analyseReqValRule consinfo calledfuncs args rhs
-- add special results for prelude functions here:
preludeFuncs = [("failed",AFType [([],Empty)])
,("==",AFType [([AnyC,AnyC],AnyC)])
,("=:=",AFType [([AnyC,AnyC],AnyC)])
,("$",AFType [([AnyC,Any],AnyC)])
,("$!",AFType [([AnyC,AnyC],AnyC)])
,("$!!",AFType [([AnyC,AnyC],AnyC)])
,("$#",AFType [([AnyC,AnyC],AnyC)])
,("$##",AFType [([AnyC,AnyC],AnyC)])
,("compare",AFType [([AnyC,AnyC],AnyC)])
]
analyseReqValRule :: ProgInfo [(QName,Int)] -> [(QName,AFType)] -> [Int] -> Expr
-> AFType
analyseReqValRule consinfo calledfuncs args rhs =
let initenv = extendEnv [] args
envtypes = reqValExp initenv rhs AnyC
rtypes = map snd envtypes
in -- If some result is `AnyC` and another result is a constructor, then
-- analyze again for all constructors as required results
-- in order to get more precise information.
if any (==AnyC) rtypes && any isConsValue rtypes
then
let somecons = maybe (error "Internal error")
(\ (Cons c) -> c)
(find isConsValue rtypes)
othercons = maybe [] (map fst) (lookupProgInfo somecons consinfo)
consenvtypes = foldr lubEnvTypes []
(map (\rt -> reqValExp initenv rhs rt)
(map Cons (somecons:othercons)))
in AFType (map (\ (env,rtype) -> (map snd env, rtype))
(lubAnyEnvTypes (if length othercons >= maxReqValues
then envtypes
else consenvtypes)))
else AFType (map (\ (env,rtype) -> (map snd env, rtype))
(lubAnyEnvTypes envtypes))
where
reqValExp env exp reqtype = case exp of
Var v -> [(updateVarInEnv env v reqtype, reqtype)]
Lit _ -> [(env, AnyC)] -- too many literal constants...
Comb ConsCall c _ -> [(env, Cons c)] -- analysis of arguments superfluous
Comb FuncCall qf funargs ->
if qf==(prelude,"?") && length funargs == 2
then -- use intended definition of Prelude.? for more precise analysis:
reqValExp env (Or (head funargs) (funargs!!1)) reqtype
else
maybe [(env, AnyC)]
(\ftype -> case ftype of
EmptyFunc -> [(env, Empty)] -- no information available
AFType ftypes ->
let matchingtypes = filter (compatibleType reqtype . snd)
ftypes
-- for all matching types analyze arguments
-- where a constructor value is required:
matchingenvs =
map (\ (ts,rt) ->
let argenvs = concatMap (envForConsArg env)
(zip ts funargs)
in (foldr joinEnv env argenvs, rt))
matchingtypes
in if null matchingtypes
then [(env, Empty)]
else matchingenvs )
(lookup qf calledfuncs)
Comb _ _ _ -> [(env, AnyC)] -- no reasonable info for partial applications
Or e1 e2 -> lubEnvTypes (reqValExp env e1 reqtype)
(reqValExp env e2 reqtype)
Case _ e branches ->
let -- filter non-failing branches:
nfbranches = filter (\ (Branch _ be) ->
be /= Comb FuncCall (prelude,"failed") [])
branches
reqenvs = filter (not . null)
(map (envForBranch env reqtype e) nfbranches)
in if null reqenvs
then [(env, Empty)]
else foldr1 lubEnvTypes reqenvs
Free vars e ->
map (dropEnv (length vars))
(reqValExp (extendEnv env vars) e reqtype)
Let bindings e ->
-- bindings are not analyzed since we don't know whether they are used:
map (dropEnv (length bindings))
(reqValExp (extendEnv env (map fst bindings)) e reqtype)
Typed e _ -> reqValExp env e reqtype
-- compute an expression environment for a function argument if this
-- argument is required to be a constructor:
envForConsArg env (reqtype,exp) =
case reqtype of
AnyC -> [foldr1 lubEnv (map fst (reqValExp env exp AnyC))]
Cons qc -> [foldr1 lubEnv (map fst (reqValExp env exp (Cons qc)))]
_ -> []
-- compute an expression environment and required type for an applied branch
envForBranch env reqtype exp (Branch pat bexp) =
filter (\ (_,rt) -> compatibleType rt reqtype) branchtypes
where
branchtypes = case pat of
LPattern _ -> reqValExp env bexp reqtype
Pattern qc pvars ->
let caseenvs = map fst (reqValExp env exp (Cons qc))
branchenvs =
foldr lubEnvTypes []
(map (\caseenv ->
reqValExp (extendEnv caseenv pvars) bexp reqtype)
caseenvs)
in map (dropEnv (length pvars)) branchenvs
--- "lub" two environment lists. All environment lists are ordered
--- by the result type.
lubEnvTypes :: [(AEnv,AType)] -> [(AEnv,AType)] -> [(AEnv,AType)]
lubEnvTypes [] ets2 = ets2
lubEnvTypes ets1@(_:_) [] = ets1
lubEnvTypes ((env1,t1):ets1) ((env2,t2):ets2)
| t1==Empty = lubEnvTypes ets1 ((env2,t2):ets2) -- ignore "empty" infos
| t2==Empty = lubEnvTypes ((env1,t1):ets1) ets2
| t1==t2 = (lubEnv env1 env2, t1) : lubEnvTypes ets1 ets2
| t1<t2 = (env1,t1) : lubEnvTypes ets1 ((env2,t2):ets2)
| otherwise = (env2,t2) : lubEnvTypes ((env1,t1):ets1) ets2
--- "lub" the environments of the more specific types to the AnyC type
--- (if present).
lubAnyEnvTypes :: [(AEnv,AType)] -> [(AEnv,AType)]
lubAnyEnvTypes envtypes =
if null envtypes || snd (head envtypes) /= AnyC
then envtypes
else foldr1 lubEnvType envtypes : tail envtypes
lubEnvType :: (AEnv,AType) -> (AEnv,AType) -> (AEnv,AType)
lubEnvType (env1,t1) (env2,t2) = (lubEnv env1 env2, lubAType t1 t2)
lubEnv :: AEnv -> AEnv -> AEnv
lubEnv [] _ = []
lubEnv (_:_) [] = []
lubEnv ((i1,v1):env1) env2@(_:_) =
maybe (lubEnv env1 env2)
(\v2 -> (i1, lubAType v1 v2) : lubEnv env1 env2)
(lookup i1 env2)
joinEnv :: AEnv -> AEnv -> AEnv
joinEnv [] _ = []
joinEnv (_:_) [] = []
joinEnv ((i1,v1):env1) env2@(_:_) =
maybe (joinEnv env1 env2)
(\v2 -> (i1, joinAType v1 v2) : joinEnv env1 env2)
(lookup i1 env2)
-- Name of the standard prelude:
prelude :: String
prelude = "Prelude"
------------------------------------------------------------------------------
-- ReadWrite instances:
instance ReadWrite AType where
readRW _ ('0' : r0) = (Any,r0)
readRW _ ('1' : r0) = (AnyC,r0)
readRW strs ('2' : r0) = (Cons a',r1)
where
(a',r1) = readRW strs r0
readRW _ ('3' : r0) = (Empty,r0)
showRW _ strs0 Any = (strs0,showChar '0')
showRW _ strs0 AnyC = (strs0,showChar '1')
showRW params strs0 (Cons a') = (strs1,showChar '2' . show1)
where
(strs1,show1) = showRW params strs0 a'
showRW _ strs0 Empty = (strs0,showChar '3')
writeRW _ h Any strs = hPutChar h '0' >> return strs
writeRW _ h AnyC strs = hPutChar h '1' >> return strs
writeRW params h (Cons a') strs = hPutChar h '2' >> writeRW params h a' strs
writeRW _ h Empty strs = hPutChar h '3' >> return strs
typeOf _ = monoRWType "AType"
instance ReadWrite AFType where
readRW _ ('0' : r0) = (EmptyFunc,r0)
readRW strs ('1' : r0) = (AFType a',r1)
where
(a',r1) = readRW strs r0
showRW _ strs0 EmptyFunc = (strs0,showChar '0')
showRW params strs0 (AFType a') = (strs1,showChar '1' . show1)
where
(strs1,show1) = showRW params strs0 a'
writeRW _ h EmptyFunc strs = hPutChar h '0' >> return strs
writeRW params h (AFType a') strs =
hPutChar h '1' >> writeRW params h a' strs
typeOf _ = monoRWType "AFType"
------------------------------------------------------------------------------
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