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Idris-dev/src/IRTS/Compiler.hs
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1{-|
2Module : IRTS.Compiler
3Description : Coordinates the compilation process.
5License : BSD3
6Maintainer : The Idris Community.
7-}
8{-# LANGUAGE CPP, FlexibleContexts, PatternGuards, TypeSynonymInstances, NamedFieldPuns, MultiWayIf #-}
10module IRTS.Compiler(compile, generate) where
12import Idris.AbsSyntax
13import Idris.ASTUtils
14import Idris.Core.CaseTree
15import Idris.Core.Evaluate
16import Idris.Core.TT
17import Idris.Erasure
18import Idris.Error
19import Idris.Options
20import Idris.Output
21import IRTS.CodegenC
22import IRTS.CodegenCommon
23import IRTS.Defunctionalise
24import IRTS.DumpBC
25import IRTS.Exports
26import IRTS.Inliner
27import IRTS.LangOpts
28import IRTS.Portable
29import IRTS.Simplified
31import Prelude hiding (id, (.))
33import Control.Category
34import Control.Monad.State
35import Data.List
36import Data.Maybe (maybe)
37import qualified Data.Map as M
38import Data.Ord
39import qualified Data.Set as S
40import System.Directory
41import System.Exit
42import System.IO
43import System.Process
45-- | Compile to simplified forms and return CodegenInfo
46compile :: Codegen -> FilePath -> Maybe Term -> Idris CodegenInfo
47compile codegen f mtm = do
48 logCodeGen 1 "Compiling Output."
49 iReport 2 "Compiling Output."
50 checkMVs -- check for undefined metavariables
51 checkTotality -- refuse to compile if there are totality problems
52 exports <- findExports
53 let rootNames = case mtm of
54 Nothing -> []
55 Just t -> freeNames t
57 logCodeGen 1 "Running Erasure Analysis"
58 iReport 3 "Running Erasure Analysis"
59 reachableNames <- performUsageAnalysis
60 (rootNames ++ getExpNames exports)
61 maindef <- case mtm of
62 Nothing -> return []
63 Just tm -> do md <- irMain tm
64 logCodeGen 1 $ "MAIN: " ++ show md
65 return [(sMN 0 "runMain", md)]
66 objs <- getObjectFiles codegen
67 libs <- getLibs codegen
68 flags <- getFlags codegen
69 hdrs <- getHdrs codegen
70 impdirs <- rankedImportDirs f
71 ttDeclarations <- getDeclarations reachableNames
72 defsIn <- mkDecls reachableNames
73 -- if no 'main term' given, generate interface files
74 let iface = case mtm of
75 Nothing -> True
76 Just _ -> False
78 let defs = defsIn ++ maindef
80 -- Inlined top level LDecl made here
81 let defsInlined = inlineAll defs
82 let defsUniq = map (allocUnique (addAlist defsInlined emptyContext))
83 defsInlined
85 logCodeGen 1 "Inlining"
87 dumpCases <- getDumpCases
88 case dumpCases of
89 Nothing -> return ()
90 Just f -> runIO $ writeFile f (showCaseTrees defsUniq)
92 let (nexttag, tagged) = addTags 65536 (liftAll defsInlined)
93 let ctxtIn = addAlist tagged emptyContext
95 logCodeGen 1 "Defunctionalising"
96 iReport 3 "Defunctionalising"
97 let defuns_in = defunctionalise nexttag ctxtIn
98 logCodeGen 5 $ show defuns_in
99 logCodeGen 1 "Inlining"
100 iReport 3 "Inlining"
101 let defuns = inline defuns_in
102 logCodeGen 5 $ show defuns
103 logCodeGen 1 "Resolving variables for CG"
105 let checked = simplifyDefs defuns (toAlist defuns)
106 outty <- outputTy
107 dumpDefun <- getDumpDefun
108 case dumpDefun of
109 Nothing -> return ()
110 Just f -> runIO $ writeFile f (dumpDefuns defuns)
111 triple <- Idris.AbsSyntax.targetTriple
112 cpu <- Idris.AbsSyntax.targetCPU
113 logCodeGen 1 "Generating Code."
114 iReport 2 "Generating Code."
115 case checked of
116 OK c -> do return $ CodegenInfo f outty triple cpu
117 hdrs impdirs objs libs flags
118 NONE c (toAlist defuns)
119 tagged iface exports
120 ttDeclarations
121 Error e -> ierror e
122 where checkMVs = do i <- getIState
123 case map fst (idris_metavars i) \\ primDefs of
124 [] -> return ()
125 ms -> do iputStrLn $ "WARNING: There are incomplete holes:\n " ++ show ms
126 iputStrLn "\nEvaluation of any of these will crash at run time."
127 return ()
128 checkTotality = do i <- getIState
129 case idris_totcheckfail i of
130 [] -> return ()
131 ((fc, msg):fs) -> ierror . At fc . Msg $ "Cannot compile:\n " ++ msg
133generate :: Codegen -> FilePath -> CodegenInfo -> IO ()
134generate codegen mainmod ir
135 = case codegen of
136 -- Built-in code generators (FIXME: lift these out!)
137 Via _ "c" -> codegenC ir
138 -- Any external code generator
139 Via fm cg -> do input <- case fm of
140 IBCFormat -> return mainmod
141 JSONFormat -> do
142 tempdir <- getTemporaryDirectory
143 (fn, h) <- openTempFile tempdir "idris-cg.json"
144 writePortable h ir
145 hClose h
146 return fn
147 let cmd = "idris-codegen-" ++ cg
148 args = [input, "-o", outputFile ir] ++ compilerFlags ir
149 exit <- rawSystem cmd (if interfaces ir then "--interface" : args else args)
150 when (exit /= ExitSuccess) $
151 putStrLn ("FAILURE: " ++ show cmd ++ " " ++ show args)
152 Bytecode -> dumpBC (simpleDecls ir) (outputFile ir)
154irMain :: TT Name -> Idris LDecl
155irMain tm = do
156 i <- irTerm (sMN 0 "runMain") M.empty [] tm
157 return $ LFun [] (sMN 0 "runMain") [] (LForce i)
159mkDecls :: [Name] -> Idris [(Name, LDecl)]
160mkDecls used
161 = do i <- getIState
162 let ds = filter (\(n, d) -> n `elem` used || isCon d) $ ctxtAlist (tt_ctxt i)
163 decls <- mapM build ds
164 return decls
166getDeclarations :: [Name] -> Idris ([(Name, TTDecl)])
167getDeclarations used
168 = do i <- getIState
169 let ds = filter (\(n, (d,_,_,_,_,_)) -> n `elem` used || isCon d) $ ((toAlist . definitions . tt_ctxt) i)
170 return ds
172showCaseTrees :: [(Name, LDecl)] -> String
173showCaseTrees = showSep "\n\n" . map showCT . sortBy (comparing defnRank)
174 where
175 showCT (n, LFun opts f args lexp)
176 = showOpts ++
177 show n ++ " " ++ showSep " " (map show args) ++ " =\n\t"
178 ++ show lexp
179 where
180 showOpts | Inline `elem` opts = "%inline "
181 | otherwise = ""
182 showCT (n, LConstructor c t a) = "data " ++ show n ++ " " ++ show a
184 defnRank :: (Name, LDecl) -> String
185 defnRank (n, LFun _ _ _ _) = "1" ++ nameRank n
186 defnRank (n, LConstructor _ _ _) = "2" ++ nameRank n
188 nameRank :: Name -> String
189 nameRank (UN s) = "1" ++ show s
190 nameRank (MN i s) = "2" ++ show s ++ show i
191 nameRank (NS n ns) = "3" ++ concatMap show (reverse ns) ++ nameRank n
192 nameRank (SN sn) = "4" ++ snRank sn
193 nameRank n = "5" ++ show n
195 snRank :: SpecialName -> String
196 snRank (WhereN i n n') = "1" ++ nameRank n' ++ nameRank n ++ show i
197 snRank (ImplementationN n args) = "2" ++ nameRank n ++ concatMap show args
198 snRank (ParentN n s) = "3" ++ nameRank n ++ show s
199 snRank (MethodN n) = "4" ++ nameRank n
200 snRank (CaseN _ n) = "5" ++ nameRank n
201 snRank (ImplementationCtorN n) = "7" ++ nameRank n
202 snRank (WithN i n) = "8" ++ nameRank n ++ show i
204isCon (TyDecl _ _) = True
205isCon _ = False
207build :: (Name, Def) -> Idris (Name, LDecl)
208build (n, d)
209 = do i <- getIState
210 case getPrim n i of
211 Just (ar, op) ->
212 let args = map (\x -> sMN x "op") [0..] in
213 return (n, (LFun [] n (take ar args)
214 (LOp op (map LV (take ar args)))))
215 _ -> do def <- mkLDecl n d
216 logCodeGen 3 $ "Compiled " ++ show n ++ " =\n\t" ++ show def
217 return (n, def)
218 where getPrim n i
219 | Just (ar, op) <- lookup n (idris_scprims i)
220 = Just (ar, op)
221 | Just ar <- lookup n (S.toList (idris_externs i))
222 = Just (ar, LExternal n)
223 getPrim n i = Nothing
225declArgs args inl n (LLam xs x) = declArgs (args ++ xs) inl n x
226declArgs args inl n x = LFun (if inl then [Inline] else []) n args x
228mkLDecl n (Function tm _)
229 = declArgs [] True n <$> irTerm n M.empty [] tm
231mkLDecl n (CaseOp ci _ _ _ pats cd)
232 = declArgs [] (case_inlinable ci || caseName n) n <$> irTree n args sc
233 where
234 (args, sc) = cases_runtime cd
236 -- Always attempt to inline functions arising from 'case' expressions
237 caseName (SN (CaseN _ _)) = True
238 caseName (SN (WithN _ _)) = True
239 caseName (NS n _) = caseName n
240 caseName _ = False
242mkLDecl n (TyDecl (DCon tag arity _) _) =
243 LConstructor n tag . length <$> fgetState (cg_usedpos . ist_callgraph n)
245mkLDecl n (TyDecl (TCon t a) _) = return $ LConstructor n (-1) a
246mkLDecl n _ = return $ (declArgs [] True n LNothing) -- postulate, never run
248data VarInfo = VI
249 { viMethod :: Maybe Name
250 }
251 deriving Show
253type Vars = M.Map Name VarInfo
255irTerm :: Name -> Vars -> [Name] -> Term -> Idris LExp
256irTerm top vs env tm@(App _ f a) = do
257 ist <- getIState
258 case unApply tm of
259 (P _ n _, args)
260 | n `elem` map fst (idris_metavars ist) \\ primDefs
261 -> return $ LError $ "ABORT: Attempt to evaluate hole " ++ show n
262 (P _ (UN m) _, args)
263 | m == txt "mkForeignPrim"
264 -> doForeign vs env (reverse (drop 4 args)) -- drop implicits
266 (P _ (UN u) _, [_, arg])
267 | u == txt "unsafePerformPrimIO"
268 -> irTerm top vs env arg
270 (P _ (UN u) _, _)
271 | u == txt "assert_unreachable"
272 -> return $ LError $ "ABORT: Reached an unreachable case in " ++ show top
274 (P _ (UN u) _, [_, msg])
275 | u == txt "idris_crash"
276 -> do msg' <- irTerm top vs env msg
277 return $ LOp LCrash [msg']
279 -- TMP HACK - until we get inlining.
280 (P _ (UN r) _, [_, _, _, _, _, arg])
281 | r == txt "replace"
282 -> irTerm top vs env arg
284 -- 'void' doesn't have any pattern clauses and only gets called on
285 -- erased things in higher order contexts (also a TMP HACK...)
286 (P _ (UN r) _, _)
287 | r == txt "void"
288 -> return LNothing
290 -- Laziness, the old way
291 (P _ (UN l) _, [_, arg])
292 | l == txt "lazy"
293 -> error "lazy has crept in somehow"
295 (P _ (UN l) _, [_, arg])
296 | l == txt "force"
297 -> LForce <$> irTerm top vs env arg
299 -- Laziness, the new way
300 (P _ (UN l) _, [_, _, arg])
301 | l == txt "Delay"
302 -> LLazyExp <$> irTerm top vs env arg
304 (P _ (UN l) _, [_, _, arg])
305 | l == txt "Force"
306 -> LForce <$> irTerm top vs env arg
308 (P _ (UN a) _, [_, _, _, arg])
309 | a == txt "assert_smaller"
310 -> irTerm top vs env arg
312 (P _ (UN a) _, [_, arg])
313 | a == txt "assert_total"
314 -> irTerm top vs env arg
316 (P _ (UN p) _, [_, arg])
317 | p == txt "par"
318 -> do arg' <- irTerm top vs env arg
319 return $ LOp LPar [LLazyExp arg']
321 (P _ (UN pf) _, [arg])
322 | pf == txt "prim_fork"
323 -> do arg' <- irTerm top vs env arg
324 return $ LOp LFork [LLazyExp arg']
326 (P _ (UN m) _, [_,size,t])
327 | m == txt "malloc"
328 -> irTerm top vs env t
330 (P _ (UN tm) _, [_,t])
331 | tm == txt "trace_malloc"
332 -> irTerm top vs env t -- TODO
334 -- This case is here until we get more general inlining. It's just
335 -- a really common case, and the laziness hurts...
336 (P _ (NS (UN be) [b,p]) _, [_,x,(App _ (App _ (App _ (P _ (UN d) _) _) _) t),
337 (App _ (App _ (App _ (P _ (UN d') _) _) _) e)])
338 | be == txt "ifThenElse"
339 , d == txt "Delay"
340 , d' == txt "Delay"
341 , b == txt "Bool"
342 , p == txt "Prelude"
343 -> do
344 x' <- irTerm top vs env x
345 t' <- irTerm top vs env t
346 e' <- irTerm top vs env e
347 return (LCase Shared x'
348 [LConCase 0 (sNS (sUN "False") ["Bool","Prelude"]) [] e'
349 ,LConCase 1 (sNS (sUN "True" ) ["Bool","Prelude"]) [] t'
350 ])
352 -- data constructor
353 (P (DCon t arity _) n _, args) -> do
354 detag <- fgetState (opt_detaggable . ist_optimisation n)
355 used <- map fst <$> fgetState (cg_usedpos . ist_callgraph n)
357 let isNewtype = length used == 1 && detag
358 let argsPruned = [a | (i,a) <- zip [0..] args, i `elem` used]
360 -- The following code removes fields from data constructors
361 -- and performs the newtype optimisation.
362 --
363 -- The general rule here is:
364 -- Everything we get as input is not touched by erasure,
365 -- so it conforms to the official arities and types
366 -- and we can reason about it like it's plain TT.
367 --
368 -- It's only the data that leaves this point that's erased
369 -- and possibly no longer typed as the original TT version.
370 --
371 -- Especially, underapplied constructors must yield functions
372 -- even if all the remaining arguments are erased
373 -- (the resulting function *will* be applied, to NULLs).
374 --
375 -- This will probably need rethinking when we get erasure from functions.
377 -- "padLams" will wrap our term in LLam-bdas and give us
378 -- the "list of future unerased args" coming from these lambdas.
379 --
380 -- We can do whatever we like with the list of unerased args,
381 -- hence it takes a lambda: \unerased_argname_list -> resulting_LExp.
382 let padLams = padLambdas used (length args) arity
384 case compare (length args) arity of
386 -- overapplied
387 GT -> ifail ("overapplied data constructor: " ++ show tm ++
388 "\nDEBUG INFO:\n" ++
389 "Arity: " ++ show arity ++ "\n" ++
390 "Arguments: " ++ show args ++ "\n" ++
391 "Pruned arguments: " ++ show argsPruned)
393 -- exactly saturated
394 EQ | isNewtype
395 -> irTerm top vs env (head argsPruned)
397 -- compile Nat-likes as bigints
398 | Just LikeZ <- isLikeNat ist n
399 -> irTerm top vs env $ Constant (BI 0)
401 -- compile Nat-likes as bigints
402 | Just LikeS <- isLikeNat ist n
403 -> irTerm top vs env $
404 App Complete (P Ref (sUN "prim__addBigInt") Erased) (Constant $ BI 1)
406 | otherwise -- not newtype, plain data ctor
407 -> buildApp (LV n) argsPruned
409 -- not saturated, underapplied
410 LT | isNewtype -- newtype
411 , length argsPruned == 1 -- and we already have the value
412 -> padLams . (\tm [] -> tm) -- the [] asserts there are no unerased args
413 <$> irTerm top vs env (head argsPruned)
415 | isNewtype -- newtype but the value is not among args yet
416 -> return . padLams $ \[vn] -> LApp False (LV n) [LV vn]
418 -- compile Nat-likes as bigints
419 | Just LikeS <- isLikeNat ist n
420 -> irTerm top vs env $
421 App Complete (P Ref (sUN "prim__addBigInt") Erased) (Constant $ BI 1)
423 -- not a newtype, just apply to a constructor
424 | otherwise
425 -> padLams . applyToNames <$> buildApp (LV n) argsPruned
427 -- type constructor
428 (P (TCon t a) n _, args) -> return LNothing
430 -- an external name applied to arguments
431 (P _ n _, args) | S.member (n, length args) (idris_externs ist) -> do
432 LOp (LExternal n) <$> mapM (irTerm top vs env) args
434 -- a name applied to arguments
435 (P _ n _, args) -> do
436 case lookup n (idris_scprims ist) of
437 -- if it's a primitive that is already saturated,
438 -- compile to the corresponding op here already to save work
439 Just (arity, op) | length args == arity
440 -> LOp op <$> mapM (irTerm top vs env) args
442 -- otherwise, just apply the name
443 _ -> applyName n ist args
445 -- turn de bruijn vars into regular named references and try again
446 (V i, args) -> irTerm top vs env $ mkApp (P Bound (env !! i) Erased) args
448 (f, args)
449 -> LApp False
450 <$> irTerm top vs env f
451 <*> mapM (irTerm top vs env) args
453 where
454 buildApp :: LExp -> [Term] -> Idris LExp
455 buildApp e [] = return e
456 buildApp e xs = LApp False e <$> mapM (irTerm top vs env) xs
458 applyToNames :: LExp -> [Name] -> LExp
459 applyToNames tm [] = tm
460 applyToNames tm ns = LApp False tm $ map LV ns
462 padLambdas :: [Int] -> Int -> Int -> ([Name] -> LExp) -> LExp
463 padLambdas used startIdx endSIdx mkTerm
464 = LLam allNames $ mkTerm nonerasedNames
465 where
466 allNames = [sMN i "sat" | i <- [startIdx .. endSIdx-1]]
467 nonerasedNames = [sMN i "sat" | i <- [startIdx .. endSIdx-1], i `elem` used]
469 applyName :: Name -> IState -> [Term] -> Idris LExp
470 applyName n ist args =
471 LApp False (LV n) <$> mapM (irTerm top vs env . erase) (zip [0..] args)
472 where
473 erase (i, x)
474 | i >= arity || i `elem` used = x
475 | otherwise = Erased
477 arity = case fst4 <$> lookupCtxtExact n (definitions . tt_ctxt $ ist) of
478 Just (CaseOp ci ty tys def tot cdefs) -> length tys
479 Just (TyDecl (DCon tag ar _) _) -> ar
480 Just (TyDecl Ref ty) -> length $ getArgTys ty
481 Just (Operator ty ar op) -> ar
482 Just def -> error $ "unknown arity: " ++ show (n, def)
483 Nothing -> 0 -- no definition, probably local name => can't erase anything
485 -- name for purposes of usage info lookup
486 uName
487 | Just n' <- viMethod =<< M.lookup n vs = n'
488 | otherwise = n
490 used = maybe [] (map fst . usedpos) $ lookupCtxtExact uName (idris_callgraph ist)
491 fst4 (x,_,_,_,_,_) = x
493irTerm top vs env (P _ n _) = return $ LV n
494irTerm top vs env (V i)
495 | i >= 0 && i < length env = return $ LV (env!!i)
496 | otherwise = ifail $ "bad de bruijn index: " ++ show i
498irTerm top vs env (Bind n (Lam _ _) sc) = LLam [n'] <$> irTerm top vs (n':env) sc
499 where
500 n' = uniqueName n env
502irTerm top vs env (Bind n (Let _ _ v) sc)
503 = LLet n <$> irTerm top vs env v <*> irTerm top vs (n : env) sc
505irTerm top vs env (Bind _ _ _) = return $ LNothing
507irTerm top vs env (Proj t (-1)) = do
508 t' <- irTerm top vs env t
509 return $ LOp (LMinus (ATInt ITBig))
510 [t', LConst (BI 1)]
512irTerm top vs env (Proj t i) = LProj <$> irTerm top vs env t <*> pure i
513irTerm top vs env (Constant TheWorld) = return LNothing
514irTerm top vs env (Constant c) = return (LConst c)
515irTerm top vs env (TType _) = return LNothing
516irTerm top vs env Erased = return LNothing
517irTerm top vs env Impossible = return LNothing
519data LikeNat = LikeZ | LikeS
521isLikeNat :: IState -> Name -> Maybe LikeNat
522isLikeNat ist cn
523 | Just cTy <- lookupTyExact cn $ tt_ctxt ist
524 , (P TCon{} tyN _, _) <- unApply $ getRetTy cTy
525 , Just (z, s) <- natLikeCtors tyN cTy
526 = if | cn == z -> Just LikeZ
527 | cn == s -> Just LikeS
528 | otherwise -> Nothing
529 where
530 natLikeCtors :: Name -> Type -> Maybe (Name, Name)
531 natLikeCtors tyN cTy = case lookupCtxtExact tyN $ idris_datatypes ist of
532 Just TI{con_names = [z, s]}
533 | 0 <- getUsedCount z
534 , looksLikeS tyN s cTy
535 -> Just (z, s)
537 Just TI{con_names = [s, z]}
538 | 0 <- getUsedCount z
539 , looksLikeS tyN s cTy
540 -> Just (z, s)
542 _ -> Nothing
544 getUsedCount :: Name -> Int
545 getUsedCount n =
546 maybe 0 (length . usedpos)
547 $ lookupCtxtExact n
548 $ idris_callgraph ist
550 looksLikeS :: Name -> Name -> Type -> Bool
551 looksLikeS tyN cn cTy
552 | Just [(i, _)] <- fmap usedpos $ lookupCtxtExact cn $ idris_callgraph ist
553 , [recTy] <- [recTy | (j, (_n, recTy)) <- zip [0..] (getArgTys cTy), j == i]
554 , (P TCon{} recTyN _, _) <- unApply recTy
555 , recTyN == tyN
556 = True
558 | otherwise = False
560doForeign :: Vars -> [Name] -> [Term] -> Idris LExp
561doForeign vs env (ret : fname : world : args)
562 = do args' <- mapM splitArg args
563 let fname' = toFDesc fname
564 let ret' = toFDesc ret
565 return $ LForeign ret' fname' args'
566 where
567 splitArg tm | (_, [_,_,l,r]) <- unApply tm -- pair, two implicits
568 = do let l' = toFDesc l
569 r' <- irTerm (sMN 0 "__foreignCall") vs env r
570 return (l', r')
571 splitArg _ = ifail $ "Badly formed foreign function call: " ++
572 show (ret : fname : world : args)
575 toFDesc (Constant (Str str)) = FStr str
576 toFDesc tm
577 | (P _ n _, []) <- unApply tm = FCon (deNS n)
578 | (P _ n _, as) <- unApply tm = FApp (deNS n) (map toFDesc as)
579 toFDesc _ = FUnknown
581 deNS (NS n _) = n
582 deNS n = n
583doForeign vs env xs = ifail "Badly formed foreign function call"
585irTree :: Name -> [Name] -> SC -> Idris LExp
586irTree top args tree = do
587 logCodeGen 3 $ "Compiling " ++ show args ++ "\n" ++ show tree
588 LLam args <$> irSC top M.empty tree
590irSC :: Name -> Vars -> SC -> Idris LExp
591irSC top vs (STerm t) = irTerm top vs [] t
592irSC top vs (UnmatchedCase str) = return $ LError str
594irSC top vs (ProjCase tm alts) = do
595 tm' <- irTerm top vs [] tm
596 alts' <- mapM (irAlt top vs tm') alts
597 return $ LCase Shared tm' alts'
599-- Transform matching on Delay to applications of Force.
600irSC top vs (Case up n [ConCase (UN delay) i [_, _, n'] sc])
601 | delay == txt "Delay"
602 = do sc' <- irSC top vs sc -- mkForce n' n sc
603 return $ lsubst n' (LForce (LV n)) sc'
605-- There are two transformations in this case:
606--
607-- 1. Newtype-case elimination:
608-- case {e0} of
609-- wrap({e1}) -> P({e1}) ==> P({e0})
610--
611-- This is important because newtyped constructors are compiled away entirely
612-- and we need to do that everywhere.
613--
614-- 2. Unused-case elimination (only valid for singleton branches):
615-- case {e0} of ==> P
616-- C(x,y) -> P[... x,y not used ...]
617--
618-- This is important for runtime because sometimes we case on irrelevant data:
619--
620-- In the example above, {e0} will most probably have been erased
621-- so this vain projection would make the resulting program segfault
622-- because the code generator still emits a PROJECT(...) G-machine instruction.
623--
624-- Hence, we check whether the variables are used at all
625-- and erase the casesplit if they are not.
626--
627irSC top vs (Case up n [alt]) = do
628 replacement <- case alt of
629 ConCase cn a ns sc -> do
630 detag <- fgetState (opt_detaggable . ist_optimisation cn)
631 used <- map fst <$> fgetState (cg_usedpos . ist_callgraph cn)
632 if detag && length used == 1
633 then return . Just $ substSC (ns !! head used) n sc
634 else return Nothing
635 _ -> return Nothing
637 case replacement of
638 Just sc -> irSC top vs sc
639 _ -> do
640 alt' <- irAlt top vs (LV n) alt
641 return $ case namesBoundIn alt' `usedIn` subexpr alt' of
642 [] -> subexpr alt' -- strip the unused top-most case
643 _ -> LCase up (LV n) [alt']
644 where
645 namesBoundIn :: LAlt -> [Name]
646 namesBoundIn (LConCase cn i ns sc) = ns
647 namesBoundIn (LConstCase c sc) = []
648 namesBoundIn (LDefaultCase sc) = []
650 subexpr :: LAlt -> LExp
651 subexpr (LConCase _ _ _ e) = e
652 subexpr (LConstCase _ e) = e
653 subexpr (LDefaultCase e) = e
655-- FIXME: When we have a non-singleton case-tree of the form
656--
657-- case {e0} of
658-- C(x) => ...
659-- ... => ...
660--
661-- and C is detaggable (the only constructor of the family), we can be sure
662-- that the first branch will be always taken -- so we add special handling
663-- to remove the dead default branch.
664--
665-- If we don't do so and C is newtype-optimisable, we will miss this newtype
666-- transformation and the resulting code will probably segfault.
667--
668-- This work-around is not entirely optimal; the best approach would be
669-- to ensure that such case trees don't arise in the first place.
670--
671irSC top vs (Case up n alts@[ConCase cn a ns sc, DefaultCase sc']) = do
672 detag <- fgetState (opt_detaggable . ist_optimisation cn)
673 if detag
674 then irSC top vs (Case up n [ConCase cn a ns sc])
675 else LCase up (LV n) <$> mapM (irAlt top vs (LV n)) alts
677irSC top vs sc@(Case up n alts) = do
678 -- check that neither alternative needs the newtype optimisation,
679 -- see comment above
680 goneWrong <- or <$> mapM isDetaggable alts
681 when goneWrong
682 $ ifail ("irSC: non-trivial case-match on detaggable data: " ++ show sc)
684 -- everything okay
685 LCase up (LV n) <$> mapM (irAlt top vs (LV n)) alts
686 where
687 isDetaggable (ConCase cn _ _ _) = fgetState $ opt_detaggable . ist_optimisation cn
688 isDetaggable _ = return False
690irSC top vs ImpossibleCase = return LNothing
692irAlt :: Name -> Vars -> LExp -> CaseAlt -> Idris LAlt
694-- this leaves out all unused arguments of the constructor
695irAlt top vs tm (ConCase n t args sc) = do
696 likeNat <- isLikeNat <$> getIState <*> pure n
697 used <- map fst <$> fgetState (cg_usedpos . ist_callgraph n)
698 let usedArgs = [a | (i,a) <- zip [0..] args, i `elem` used]
700 case likeNat of
701 -- like S
702 Just LikeS -> do
703 sc' <- irSC top vs sc
704 case usedArgs of
705 [pv] -> return $ LDefaultCase $ LLet pv
706 ( LOp
707 (LMinus (ATInt ITBig))
708 [ tm
709 , LConst (BI 1)
710 ]
711 )
712 sc'
714 _ -> ifail $ "irAlt/LikeS: multiple used args: " ++ show usedArgs
716 -- like Z
717 Just LikeZ -> LConstCase (BI 0) <$> irSC top vs sc
719 -- not like Nat
720 Nothing -> LConCase (-1) n usedArgs <$> irSC top (methodVars `M.union` vs) sc
721 where
722 methodVars = case n of
723 SN (ImplementationCtorN interfaceName)
724 -> M.fromList [(v, VI
725 { viMethod = Just $ mkFieldName n i
726 }) | (v,i) <- zip args [0..]]
727 _
728 -> M.empty -- not an implementation constructor
730irAlt top vs _ (ConstCase x rhs)
731 | matchable x = LConstCase x <$> irSC top vs rhs
732 | matchableTy x = LDefaultCase <$> irSC top vs rhs
733 where
734 matchable (I _) = True
735 matchable (BI _) = True
736 matchable (Ch _) = True
737 matchable (Str _) = True
738 matchable (B8 _) = True
739 matchable (B16 _) = True
740 matchable (B32 _) = True
741 matchable (B64 _) = True
742 matchable _ = False
744 matchableTy (AType (ATInt ITNative)) = True
745 matchableTy (AType (ATInt ITBig)) = True
746 matchableTy (AType (ATInt ITChar)) = True
747 matchableTy StrType = True
749 matchableTy (AType (ATInt (ITFixed IT8))) = True
750 matchableTy (AType (ATInt (ITFixed IT16))) = True
751 matchableTy (AType (ATInt (ITFixed IT32))) = True
752 matchableTy (AType (ATInt (ITFixed IT64))) = True
754 matchableTy _ = False
756irAlt top vs tm (SucCase n rhs) = do
757 rhs' <- irSC top vs rhs
758 return $ LDefaultCase (LLet n (LOp (LMinus (ATInt ITBig))
759 [tm,
760 LConst (BI 1)]) rhs')
762irAlt top vs _ (ConstCase c rhs)
763 = ifail $ "Can't match on (" ++ show c ++ ")"
765irAlt top vs _ (DefaultCase rhs)
766 = LDefaultCase <$> irSC top vs rhs