1 {-# LANGUAGE PackageImports #-}
3 -- Functions to bring a Core expression in normal form. This module provides a
4 -- top level function "normalize", and defines the actual transformation passes that
7 module CLasH.Normalize (getNormalized, normalizeExpr, splitNormalized) where
11 import qualified Maybe
13 import qualified "transformers" Control.Monad.Trans as Trans
14 import qualified Control.Monad as Monad
15 import qualified Control.Monad.Trans.Writer as Writer
16 import qualified Data.Accessor.Monad.Trans.State as MonadState
17 import qualified Data.Monoid as Monoid
18 import qualified Data.Map as Map
22 import qualified CoreUtils
27 import qualified DataCon
28 import qualified VarSet
29 import qualified CoreFVs
30 import qualified Class
31 import qualified MkCore
32 import Outputable ( showSDoc, ppr, nest )
35 import CLasH.Normalize.NormalizeTypes
36 import CLasH.Translator.TranslatorTypes
37 import CLasH.Normalize.NormalizeTools
38 import CLasH.VHDL.Constants (builtinIds)
39 import qualified CLasH.Utils as Utils
40 import CLasH.Utils.Core.CoreTools
41 import CLasH.Utils.Core.BinderTools
42 import CLasH.Utils.Pretty
44 --------------------------------
45 -- Start of transformations
46 --------------------------------
48 --------------------------------
50 --------------------------------
51 -- Make sure all parameters to the normalized functions are named by top
52 -- level lambda expressions. For this we apply η expansion to the
53 -- function body (possibly enclosed in some lambda abstractions) while
54 -- it has a function type. Eventually this will result in a function
55 -- body consisting of a bunch of nested lambdas containing a
56 -- non-function value (e.g., a complete application).
57 eta, etatop :: Transform
58 eta c expr | is_fun expr && not (is_lam expr) && all (== LambdaBody) c = do
59 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
60 id <- Trans.lift $ mkInternalVar "param" arg_ty
61 change (Lam id (App expr (Var id)))
62 -- Leave all other expressions unchanged
64 etatop = everywhere ("eta", eta)
66 --------------------------------
68 --------------------------------
69 beta, betatop :: Transform
70 -- Substitute arg for x in expr. For value lambda's, also clone before
72 beta c (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg c expr
73 | otherwise = setChanged >> substitute_clone x arg c expr
74 -- Propagate the application into the let
75 beta c (App (Let binds expr) arg) = change $ Let binds (App expr arg)
76 -- Propagate the application into each of the alternatives
77 beta c (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
79 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
80 ty' = CoreUtils.applyTypeToArg ty arg
81 -- Leave all other expressions unchanged
82 beta c expr = return expr
83 -- Perform this transform everywhere
84 betatop = everywhere ("beta", beta)
86 --------------------------------
87 -- Case of known constructor simplification
88 --------------------------------
89 -- If a case expressions scrutinizes a datacon application, we can
90 -- determine which alternative to use and remove the case alltogether.
91 -- We replace it with a let expression the binds every binder in the
92 -- alternative bound to the corresponding argument of the datacon. We do
93 -- this instead of substituting the binders, to prevent duplication of
94 -- work and preserve sharing wherever appropriate.
95 knowncase, knowncasetop :: Transform
96 knowncase context expr@(Case scrut@(App _ _) bndr ty alts) | not bndr_used = do
97 case collectArgs scrut of
98 (Var f, args) -> case Id.isDataConId_maybe f of
99 -- Not a dataconstructor? Don't change anything (probably a
101 Nothing -> return expr
103 let (altcon, bndrs, res) = case List.find (\(altcon, bndrs, res) -> altcon == (DataAlt dc)) alts of
104 Just alt -> alt -- Return the alternative found
105 Nothing -> head alts -- If the datacon is not present, the first must be the default alternative
106 -- Double check if we have either the correct alternative, or
108 if altcon /= (DataAlt dc) && altcon /= DEFAULT then error ("Normalize.knowncase: Invalid core, datacon not found in alternatives and DEFAULT alternative is not first? " ++ pprString expr) else return ()
109 -- Find out how many arguments to drop (type variables and
110 -- predicates like dictionaries).
111 let (tvs, preds, _, _) = DataCon.dataConSig dc
112 let count = length tvs + length preds
113 -- Create a let expression that binds each of the binders in
114 -- this alternative to the corresponding argument of the data
116 let binds = zip bndrs (drop count args)
117 change $ Let (Rec binds) res
118 _ -> return expr -- Scrutinee is not an application of a var
120 is_used (_, _, expr) = expr_uses_binders [bndr] expr
121 bndr_used = or $ map is_used alts
123 -- Leave all other expressions unchanged
124 knowncase c expr = return expr
125 -- Perform this transform everywhere
126 knowncasetop = everywhere ("knowncase", knowncase)
128 --------------------------------
130 --------------------------------
131 -- Try to move casts as much downward as possible.
132 castprop, castproptop :: Transform
133 castprop c (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
134 castprop c expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
136 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
137 -- Leave all other expressions unchanged
138 castprop c expr = return expr
139 -- Perform this transform everywhere
140 castproptop = everywhere ("castprop", castprop)
142 --------------------------------
143 -- Cast simplification. Mostly useful for state packing and unpacking, but
144 -- perhaps for others as well.
145 --------------------------------
146 castsimpl, castsimpltop :: Transform
147 castsimpl c expr@(Cast val ty) = do
148 -- Don't extract values that are already simpl
149 local_var <- Trans.lift $ is_local_var val
150 -- Don't extract values that are not representable, to prevent loops with
153 if (not local_var) && repr
155 -- Generate a binder for the expression
156 id <- Trans.lift $ mkBinderFor val "castval"
157 -- Extract the expression
158 change $ Let (NonRec id val) (Cast (Var id) ty)
161 -- Leave all other expressions unchanged
162 castsimpl c expr = return expr
163 -- Perform this transform everywhere
164 castsimpltop = everywhere ("castsimpl", castsimpl)
166 --------------------------------
167 -- Return value simplification
168 --------------------------------
169 -- Ensure the return value of a function follows proper normal form. eta
170 -- expansion ensures the body starts with lambda abstractions, this
171 -- transformation ensures that the lambda abstractions always contain a
172 -- recursive let and that, when the return value is representable, the
173 -- let contains a local variable reference in its body.
174 retvalsimpl c expr | all (== LambdaBody) c && not (is_lam expr) && not (is_let expr) = do
175 local_var <- Trans.lift $ is_local_var expr
177 if not local_var && repr
179 id <- Trans.lift $ mkBinderFor expr "res"
180 change $ Let (Rec [(id, expr)]) (Var id)
184 retvalsimpl c expr@(Let (Rec binds) body) | all (== LambdaBody) c = do
185 -- Don't extract values that are already a local variable, to prevent
186 -- loops with ourselves.
187 local_var <- Trans.lift $ is_local_var body
188 -- Don't extract values that are not representable, to prevent loops with
191 if not local_var && repr
193 id <- Trans.lift $ mkBinderFor body "res"
194 change $ Let (Rec ((id, body):binds)) (Var id)
199 -- Leave all other expressions unchanged
200 retvalsimpl c expr = return expr
201 -- Perform this transform everywhere
202 retvalsimpltop = everywhere ("retvalsimpl", retvalsimpl)
204 --------------------------------
205 -- let derecursification
206 --------------------------------
207 letrec, letrectop :: Transform
208 letrec c expr@(Let (NonRec bndr val) res) =
209 change $ Let (Rec [(bndr, val)]) res
211 -- Leave all other expressions unchanged
212 letrec c expr = return expr
213 -- Perform this transform everywhere
214 letrectop = everywhere ("letrec", letrec)
216 --------------------------------
218 --------------------------------
219 -- Takes a let that binds another let, and turns that into two nested lets.
221 -- let b = (let b' = expr' in res') in res
223 -- let b' = expr' in (let b = res' in res)
224 letflat, letflattop :: Transform
225 -- Turn a nonrec let that binds a let into two nested lets.
226 letflat c (Let (NonRec b (Let binds res')) res) =
227 change $ Let binds (Let (NonRec b res') res)
228 letflat c (Let (Rec binds) expr) = do
229 -- Flatten each binding.
230 binds' <- Utils.concatM $ Monad.mapM flatbind binds
231 -- Return the new let. We don't use change here, since possibly nothing has
232 -- changed. If anything has changed, flatbind has already flagged that
234 return $ Let (Rec binds') expr
236 -- Turns a binding of a let into a multiple bindings, or any other binding
237 -- into a list with just that binding
238 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
239 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
240 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
241 flatbind (b, expr) = return [(b, expr)]
242 -- Leave all other expressions unchanged
243 letflat c expr = return expr
244 -- Perform this transform everywhere
245 letflattop = everywhere ("letflat", letflat)
247 --------------------------------
249 --------------------------------
250 -- Remove empty (recursive) lets
251 letremove, letremovetop :: Transform
252 letremove c (Let (Rec []) res) = change res
253 -- Leave all other expressions unchanged
254 letremove c expr = return expr
255 -- Perform this transform everywhere
256 letremovetop = everywhere ("letremove", letremove)
258 --------------------------------
259 -- Simple let binding removal
260 --------------------------------
261 -- Remove a = b bindings from let expressions everywhere
262 letremovesimpletop :: Transform
263 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
265 --------------------------------
266 -- Unused let binding removal
267 --------------------------------
268 letremoveunused, letremoveunusedtop :: Transform
269 letremoveunused c expr@(Let (NonRec b bound) res) = do
270 let used = expr_uses_binders [b] res
274 letremoveunused c expr@(Let (Rec binds) res) = do
275 -- Filter out all unused binds.
276 let binds' = filter dobind binds
277 -- Only set the changed flag if binds got removed
278 changeif (length binds' /= length binds) (Let (Rec binds') res)
280 bound_exprs = map snd binds
281 -- For each bind check if the bind is used by res or any of the bound
283 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
284 -- Leave all other expressions unchanged
285 letremoveunused c expr = return expr
286 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
289 --------------------------------
290 -- Identical let binding merging
291 --------------------------------
292 -- Merge two bindings in a let if they are identical
293 -- TODO: We would very much like to use GHC's CSE module for this, but that
294 -- doesn't track if something changed or not, so we can't use it properly.
295 letmerge, letmergetop :: Transform
296 letmerge c expr@(Let _ _) = do
297 let (binds, res) = flattenLets expr
298 binds' <- domerge binds
299 return $ mkNonRecLets binds' res
301 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
302 domerge [] = return []
304 es' <- mapM (mergebinds e) es
308 -- Uses the second bind to simplify the second bind, if applicable.
309 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
310 mergebinds (b1, e1) (b2, e2)
311 -- Identical expressions? Replace the second binding with a reference to
313 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
314 -- Different expressions? Don't change
315 | otherwise = return (b2, e2)
316 -- Leave all other expressions unchanged
317 letmerge c expr = return expr
318 letmergetop = everywhere ("letmerge", letmerge)
321 --------------------------------
322 -- Non-representable binding inlining
323 --------------------------------
324 -- Remove a = B bindings, with B of a non-representable type, from let
325 -- expressions everywhere. This means that any value that we can't generate a
326 -- signal for, will be inlined and hopefully turned into something we can
329 -- This is a tricky function, which is prone to create loops in the
330 -- transformations. To fix this, we make sure that no transformation will
331 -- create a new let binding with a non-representable type. These other
332 -- transformations will just not work on those function-typed values at first,
333 -- but the other transformations (in particular β-reduction) should make sure
334 -- that the type of those values eventually becomes representable.
335 inlinenonreptop :: Transform
336 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
338 --------------------------------
339 -- Top level function inlining
340 --------------------------------
341 -- This transformation inlines simple top level bindings. Simple
342 -- currently means that the body is only a single application (though
343 -- the complexity of the arguments is not currently checked) or that the
344 -- normalized form only contains a single binding. This should catch most of the
345 -- cases where a top level function is created that simply calls a type class
346 -- method with a type and dictionary argument, e.g.
347 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
348 -- which is later called using simply
349 -- fromInteger (smallInteger 10)
351 -- These useless wrappers are created by GHC automatically. If we don't
352 -- inline them, we get loads of useless components cluttering the
355 -- Note that the inlining could also inline simple functions defined by
356 -- the user, not just GHC generated functions. It turns out to be near
357 -- impossible to reliably determine what functions are generated and
358 -- what functions are user-defined. Instead of guessing (which will
359 -- inline less than we want) we will just inline all simple functions.
361 -- Only functions that are actually completely applied and bound by a
362 -- variable in a let expression are inlined. These are the expressions
363 -- that will eventually generate instantiations of trivial components.
364 -- By not inlining any other reference, we also prevent looping problems
365 -- with funextract and inlinedict.
366 inlinetoplevel, inlinetopleveltop :: Transform
367 inlinetoplevel (LetBinding:_) expr | not (is_fun expr) =
368 case collectArgs expr of
370 body_maybe <- needsInline f
373 -- Regenerate all uniques in the to-be-inlined expression
374 body_uniqued <- Trans.lift $ genUniques body
375 -- And replace the variable reference with the unique'd body.
376 change (mkApps body_uniqued args)
378 Nothing -> return expr
379 -- This is not an application of a binder, leave it unchanged.
382 -- Leave all other expressions unchanged
383 inlinetoplevel c expr = return expr
384 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
386 -- | Does the given binder need to be inlined? If so, return the body to
387 -- be used for inlining.
388 needsInline :: CoreBndr -> TransformMonad (Maybe CoreExpr)
390 body_maybe <- Trans.lift $ getGlobalBind f
392 -- No body available?
393 Nothing -> return Nothing
394 Just body -> case CoreSyn.collectArgs body of
395 -- The body is some (top level) binder applied to 0 or more
396 -- arguments. That should be simple enough to inline.
397 (Var f, args) -> return $ Just body
398 -- Body is more complicated, try normalizing it
400 norm_maybe <- Trans.lift $ getNormalized_maybe False f
402 -- Noth normalizeable
403 Nothing -> return Nothing
404 Just norm -> case splitNormalizedNonRep norm of
405 -- The function has just a single binding, so that's simple
407 (args, [bind], Var res) -> return $ Just norm
408 -- More complicated function, don't inline
411 --------------------------------
412 -- Dictionary inlining
413 --------------------------------
414 -- Inline all top level dictionaries, that are in a position where
415 -- classopresolution can actually resolve them. This makes this
416 -- transformation look similar to classoperesolution below, but we'll
417 -- keep them separated for clarity. By not inlining other dictionaries,
418 -- we prevent expression sizes exploding when huge type level integer
419 -- dictionaries are inlined which can never be expanded (in casts, for
421 inlinedict c expr@(App (App (Var sel) ty) (Var dict)) | not is_builtin && is_classop = do
422 body_maybe <- Trans.lift $ getGlobalBind dict
424 -- No body available (no source available, or a local variable /
426 Nothing -> return expr
427 Just body -> change (App (App (Var sel) ty) body)
429 -- Is this a builtin function / method?
430 is_builtin = elem (Name.getOccString sel) builtinIds
431 -- Are we dealing with a class operation selector?
432 is_classop = Maybe.isJust (Id.isClassOpId_maybe sel)
434 -- Leave all other expressions unchanged
435 inlinedict c expr = return expr
436 inlinedicttop = everywhere ("inlinedict", inlinedict)
438 --------------------------------
439 -- ClassOp resolution
440 --------------------------------
441 -- Resolves any class operation to the actual operation whenever
442 -- possible. Class methods (as well as parent dictionary selectors) are
443 -- special "functions" that take a type and a dictionary and evaluate to
444 -- the corresponding method. A dictionary is nothing more than a
445 -- special dataconstructor applied to the type the dictionary is for,
446 -- each of the superclasses and all of the class method definitions for
447 -- that particular type. Since dictionaries all always inlined (top
448 -- levels dictionaries are inlined by inlinedict, local dictionaries are
449 -- inlined by inlinenonrep), we will eventually have something like:
452 -- @ CLasH.HardwareTypes.Bit
453 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
455 -- Here, baz is the method selector for the baz method, while
456 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
457 -- method defined in the Baz Bit instance declaration.
459 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
460 -- which contains the Class it is defined for. From the Class, we can
461 -- get a list of all selectors (both parent class selectors as well as
462 -- method selectors). Since the arguments to D:Baz (after the type
463 -- argument) correspond exactly to this list, we then look up baz in
464 -- that list and replace the entire expression by the corresponding
465 -- argument to D:Baz.
467 -- We don't resolve methods that have a builtin translation (such as
468 -- ==), since the actual implementation is not always (easily)
469 -- translateable. For example, when deriving ==, GHC generates code
470 -- using $con2tag functions to translate a datacon to an int and compare
471 -- that with GHC.Prim.==# . Better to avoid that for now.
472 classopresolution, classopresolutiontop :: Transform
473 classopresolution c expr@(App (App (Var sel) ty) dict) | not is_builtin =
474 case Id.isClassOpId_maybe sel of
475 -- Not a class op selector
476 Nothing -> return expr
477 Just cls -> case collectArgs dict of
478 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
479 (Var dictdc, (ty':selectors)) | not (Maybe.isJust (Id.isDataConId_maybe dictdc)) -> return expr -- Dictionary is not a datacon yet (but e.g., a top level binder)
480 | tyargs_neq ty ty' -> error $ "Normalize.classopresolution: Applying class selector to dictionary without matching type?\n" ++ pprString expr
482 let selector_ids = Class.classSelIds cls in
483 -- Find the selector used in the class' list of selectors
484 case List.elemIndex sel selector_ids of
485 Nothing -> error $ "Normalize.classopresolution: Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
486 -- Get the corresponding argument from the dictionary
487 Just n -> change (selectors!!n)
488 (_, _) -> return expr -- Not applying a variable? Don't touch
490 -- Compare two type arguments, returning True if they are _not_
492 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
493 tyargs_neq _ _ = True
494 -- Is this a builtin function / method?
495 is_builtin = elem (Name.getOccString sel) builtinIds
497 -- Leave all other expressions unchanged
498 classopresolution c expr = return expr
499 -- Perform this transform everywhere
500 classopresolutiontop = everywhere ("classopresolution", classopresolution)
502 --------------------------------
503 -- Scrutinee simplification
504 --------------------------------
505 scrutsimpl,scrutsimpltop :: Transform
506 -- Don't touch scrutinees that are already simple
507 scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
508 -- Replace all other cases with a let that binds the scrutinee and a new
509 -- simple scrutinee, but only when the scrutinee is representable (to prevent
510 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
511 -- will be supported anyway...)
512 scrutsimpl c expr@(Case scrut b ty alts) = do
516 id <- Trans.lift $ mkBinderFor scrut "scrut"
517 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
520 -- Leave all other expressions unchanged
521 scrutsimpl c expr = return expr
522 -- Perform this transform everywhere
523 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
525 --------------------------------
526 -- Scrutinee binder removal
527 --------------------------------
528 -- A case expression can have an extra binder, to which the scrutinee is bound
529 -- after bringing it to WHNF. This is used for forcing evaluation of strict
530 -- arguments. Since strictness does not matter for us (rather, everything is
531 -- sort of strict), this binder is ignored when generating VHDL, and must thus
532 -- be wild in the normal form.
533 scrutbndrremove, scrutbndrremovetop :: Transform
534 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
535 -- all occurences of the binder with the scrutinee variable.
536 scrutbndrremove c (Case (Var scrut) bndr ty alts) | bndr_used = do
537 alts' <- mapM subs_bndr alts
538 change $ Case (Var scrut) wild ty alts'
540 is_used (_, _, expr) = expr_uses_binders [bndr] expr
541 bndr_used = or $ map is_used alts
542 subs_bndr (con, bndrs, expr) = do
543 expr' <- substitute bndr (Var scrut) c expr
544 return (con, bndrs, expr')
545 wild = MkCore.mkWildBinder (Id.idType bndr)
546 -- Leave all other expressions unchanged
547 scrutbndrremove c expr = return expr
548 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
550 --------------------------------
551 -- Case binder wildening
552 --------------------------------
553 casesimpl, casesimpltop :: Transform
554 -- This is already a selector case (or, if x does not appear in bndrs, a very
555 -- simple case statement that will be removed by caseremove below). Just leave
557 casesimpl c expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
558 -- Make sure that all case alternatives have only wild binders and simple
560 -- This is done by creating a new let binding for each non-wild binder, which
561 -- is bound to a new simple selector case statement and for each complex
562 -- expression. We do this only for representable types, to prevent loops with
564 casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
565 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
566 let bindings = concat bindingss
567 -- Replace the case with a let with bindings and a case
568 let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
569 -- If there are no non-wild binders, or this case is already a simple
570 -- selector (i.e., a single alt with exactly one binding), already a simple
571 -- selector altan no bindings (i.e., no wild binders in the original case),
572 -- don't change anything, otherwise, replace the case.
573 if null bindings then return expr else change newlet
575 -- Check if the scrutinee binder is used
576 is_used (_, _, expr) = expr_uses_binders [bndr] expr
577 bndr_used = or $ map is_used alts
578 -- Generate a single wild binder, since they are all the same
579 wild = MkCore.mkWildBinder
580 -- Wilden the binders of one alt, producing a list of bindings as a
582 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
583 doalt (con, bndrs, expr) = do
584 -- Make each binder wild, if possible
585 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
586 let (newbndrs, bindings_maybe) = unzip bndrs_res
587 -- Extract a complex expression, if possible. For this we check if any of
588 -- the new list of bndrs are used by expr. We can't use free_vars here,
589 -- since that looks at the old bndrs.
590 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
591 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
592 -- Create a new alternative
593 let newalt = (con, newbndrs, expr')
594 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
595 return (bindings, newalt)
597 -- Make wild alternatives for each binder
598 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
599 -- A set of all the binders that are used by the expression
600 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
601 -- Look at the ith binder in the case alternative. Return a new binder
602 -- for it (either the same one, or a wild one) and optionally a let
603 -- binding containing a case expression.
604 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
607 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
608 -- in expr, this means that b is unused if expr does not use it.)
609 let wild = not (VarSet.elemVarSet b free_vars)
610 -- Create a new binding for any representable binder that is not
611 -- already wild and is representable (to prevent loops with
613 if (not wild) && repr
615 caseexpr <- Trans.lift $ mkSelCase scrut i
616 -- Create a new binder that will actually capture a value in this
617 -- case statement, and return it.
618 return (wildbndrs!!i, Just (b, caseexpr))
620 -- Just leave the original binder in place, and don't generate an
621 -- extra selector case.
623 -- Process the expression of a case alternative. Accepts an expression
624 -- and whether this expression uses any of the binders in the
625 -- alternative. Returns an optional new binding and a new expression.
626 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
627 doexpr expr uses_bndrs = do
628 local_var <- Trans.lift $ is_local_var expr
630 -- Extract any expressions that do not use any binders from this
631 -- alternative, is not a local var already and is representable (to
632 -- prevent loops with inlinenonrep).
633 if (not uses_bndrs) && (not local_var) && repr
635 id <- Trans.lift $ mkBinderFor expr "caseval"
636 -- We don't flag a change here, since casevalsimpl will do that above
637 -- based on Just we return here.
638 return (Just (id, expr), Var id)
640 -- Don't simplify anything else
641 return (Nothing, expr)
642 -- Leave all other expressions unchanged
643 casesimpl c expr = return expr
644 -- Perform this transform everywhere
645 casesimpltop = everywhere ("casesimpl", casesimpl)
647 --------------------------------
649 --------------------------------
650 -- Remove case statements that have only a single alternative and only wild
652 caseremove, caseremovetop :: Transform
653 -- Replace a useless case by the value of its single alternative
654 caseremove c (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
655 -- Find if any of the binders are used by expr
656 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
657 -- Leave all other expressions unchanged
658 caseremove c expr = return expr
659 -- Perform this transform everywhere
660 caseremovetop = everywhere ("caseremove", caseremove)
662 --------------------------------
663 -- Argument extraction
664 --------------------------------
665 -- Make sure that all arguments of a representable type are simple variables.
666 appsimpl, appsimpltop :: Transform
667 -- Simplify all representable arguments. Do this by introducing a new Let
668 -- that binds the argument and passing the new binder in the application.
669 appsimpl c expr@(App f arg) = do
670 -- Check runtime representability
672 local_var <- Trans.lift $ is_local_var arg
673 if repr && not local_var
674 then do -- Extract representable arguments
675 id <- Trans.lift $ mkBinderFor arg "arg"
676 change $ Let (NonRec id arg) (App f (Var id))
677 else -- Leave non-representable arguments unchanged
679 -- Leave all other expressions unchanged
680 appsimpl c expr = return expr
681 -- Perform this transform everywhere
682 appsimpltop = everywhere ("appsimpl", appsimpl)
684 --------------------------------
685 -- Function-typed argument propagation
686 --------------------------------
687 -- Remove all applications to function-typed arguments, by duplication the
688 -- function called with the function-typed parameter replaced by the free
689 -- variables of the argument passed in.
690 argprop, argproptop :: Transform
691 -- Transform any application of a named function (i.e., skip applications of
692 -- lambda's). Also skip applications that have arguments with free type
693 -- variables, since we can't inline those.
694 argprop c expr@(App _ _) | is_var fexpr = do
695 -- Find the body of the function called
696 body_maybe <- Trans.lift $ getGlobalBind f
699 -- Process each of the arguments in turn
700 (args', changed) <- Writer.listen $ mapM doarg args
701 -- See if any of the arguments changed
702 case Monoid.getAny changed of
704 let (newargs', newparams', oldargs) = unzip3 args'
705 let newargs = concat newargs'
706 let newparams = concat newparams'
707 -- Create a new body that consists of a lambda for all new arguments and
708 -- the old body applied to some arguments.
709 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
710 -- Create a new function with the same name but a new body
711 newf <- Trans.lift $ mkFunction f newbody
713 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
714 let init_state_maybe = Map.lookup f ismap in
715 case init_state_maybe of
717 Just init_state -> Map.insert newf init_state ismap)
718 -- Replace the original application with one of the new function to the
720 change $ MkCore.mkCoreApps (Var newf) newargs
722 -- Don't change the expression if none of the arguments changed
725 -- If we don't have a body for the function called, leave it unchanged (it
726 -- should be a primitive function then).
727 Nothing -> return expr
729 -- Find the function called and the arguments
730 (fexpr, args) = collectArgs expr
733 -- Process a single argument and return (args, bndrs, arg), where args are
734 -- the arguments to replace the given argument in the original
735 -- application, bndrs are the binders to include in the top-level lambda
736 -- in the new function body, and arg is the argument to apply to the old
738 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
741 bndrs <- Trans.lift getGlobalBinders
742 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
743 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
745 -- Propagate all complex arguments that are not representable, but not
746 -- arguments with free type variables (since those would require types
747 -- not known yet, which will always be known eventually).
748 -- Find interesting free variables, each of which should be passed to
749 -- the new function instead of the original function argument.
751 -- Interesting vars are those that are local, but not available from the
752 -- top level scope (functions from this module are defined as local, but
753 -- they're not local to this function, so we can freely move references
754 -- to them into another function).
755 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
756 -- Mark the current expression as changed
758 -- TODO: Clone the free_vars (and update references in arg), since
759 -- this might cause conflicts if two arguments that are propagated
760 -- share a free variable. Also, we are now introducing new variables
761 -- into a function that are not fresh, which violates the binder
762 -- uniqueness invariant.
763 return (map Var free_vars, free_vars, arg)
765 -- Representable types will not be propagated, and arguments with free
766 -- type variables will be propagated later.
767 -- Note that we implicitly remove any type variables in the type of
768 -- the original argument by using the type of the actual argument
769 -- for the new formal parameter.
770 -- TODO: preserve original naming?
771 id <- Trans.lift $ mkBinderFor arg "param"
772 -- Just pass the original argument to the new function, which binds it
773 -- to a new id and just pass that new id to the old function body.
774 return ([arg], [id], mkReferenceTo id)
775 -- Leave all other expressions unchanged
776 argprop c expr = return expr
777 -- Perform this transform everywhere
778 argproptop = everywhere ("argprop", argprop)
780 --------------------------------
781 -- Function-typed argument extraction
782 --------------------------------
783 -- This transform takes any function-typed argument that cannot be propagated
784 -- (because the function that is applied to it is a builtin function), and
785 -- puts it in a brand new top level binder. This allows us to for example
786 -- apply map to a lambda expression This will not conflict with inlinenonrep,
787 -- since that only inlines local let bindings, not top level bindings.
788 funextract, funextracttop :: Transform
789 funextract c expr@(App _ _) | is_var fexpr = do
790 body_maybe <- Trans.lift $ getGlobalBind f
792 -- We don't have a function body for f, so we can perform this transform.
794 -- Find the new arguments
795 args' <- mapM doarg args
796 -- And update the arguments. We use return instead of changed, so the
797 -- changed flag doesn't get set if none of the args got changed.
798 return $ MkCore.mkCoreApps fexpr args'
799 -- We have a function body for f, leave this application to funprop
800 Just _ -> return expr
802 -- Find the function called and the arguments
803 (fexpr, args) = collectArgs expr
805 -- Change any arguments that have a function type, but are not simple yet
806 -- (ie, a variable or application). This means to create a new function
807 -- for map (\f -> ...) b, but not for map (foo a) b.
809 -- We could use is_applicable here instead of is_fun, but I think
810 -- arguments to functions could only have forall typing when existential
811 -- typing is enabled. Not sure, though.
812 doarg arg | not (is_simple arg) && is_fun arg = do
813 -- Create a new top level binding that binds the argument. Its body will
814 -- be extended with lambda expressions, to take any free variables used
815 -- by the argument expression.
816 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
817 let body = MkCore.mkCoreLams free_vars arg
818 id <- Trans.lift $ mkBinderFor body "fun"
819 Trans.lift $ addGlobalBind id body
820 -- Replace the argument with a reference to the new function, applied to
822 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
823 -- Leave all other arguments untouched
824 doarg arg = return arg
826 -- Leave all other expressions unchanged
827 funextract c expr = return expr
828 -- Perform this transform everywhere
829 funextracttop = everywhere ("funextract", funextract)
831 --------------------------------
832 -- End of transformations
833 --------------------------------
838 -- What transforms to run?
839 transforms = [inlinedicttop, inlinetopleveltop, knowncasetop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letrectop, letremovetop, retvalsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop]
841 -- | Returns the normalized version of the given function, or an error
842 -- if it is not a known global binder.
844 Bool -- ^ Allow the result to be unrepresentable?
845 -> CoreBndr -- ^ The function to get
846 -> TranslatorSession CoreExpr -- The normalized function body
847 getNormalized result_nonrep bndr = do
848 norm <- getNormalized_maybe result_nonrep bndr
849 return $ Maybe.fromMaybe
850 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
853 -- | Returns the normalized version of the given function, or Nothing
854 -- when the binder is not a known global binder or is not normalizeable.
855 getNormalized_maybe ::
856 Bool -- ^ Allow the result to be unrepresentable?
857 -> CoreBndr -- ^ The function to get
858 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
860 getNormalized_maybe result_nonrep bndr = do
861 expr_maybe <- getGlobalBind bndr
862 normalizeable <- isNormalizeable result_nonrep bndr
863 if not normalizeable || Maybe.isNothing expr_maybe
865 -- Binder not normalizeable or not found
868 -- Binder found and is monomorphic. Normalize the expression
869 -- and cache the result.
870 normalized <- Utils.makeCached bndr tsNormalized $
871 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
872 return (Just normalized)
874 -- | Normalize an expression
876 String -- ^ What are we normalizing? For debug output only.
877 -> CoreSyn.CoreExpr -- ^ The expression to normalize
878 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
880 normalizeExpr what expr = do
881 startcount <- MonadState.get tsTransformCounter
882 expr_uniqued <- genUniques expr
883 -- Normalize this expression
884 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
885 expr' <- dotransforms transforms expr_uniqued
886 endcount <- MonadState.get tsTransformCounter
887 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')
888 ++ "\nNeeded " ++ show (endcount - startcount) ++ " transformations to normalize " ++ what) $
891 -- | Split a normalized expression into the argument binders, top level
892 -- bindings and the result binder. This function returns an error if
893 -- the type of the expression is not representable.
895 CoreExpr -- ^ The normalized expression
896 -> ([CoreBndr], [Binding], CoreBndr)
897 splitNormalized expr =
898 case splitNormalizedNonRep expr of
899 (args, binds, Var res) -> (args, binds, res)
900 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"
902 -- Split a normalized expression, whose type can be unrepresentable.
903 splitNormalizedNonRep::
904 CoreExpr -- ^ The normalized expression
905 -> ([CoreBndr], [Binding], CoreExpr)
906 splitNormalizedNonRep expr = (args, binds, resexpr)
908 (args, letexpr) = CoreSyn.collectBinders expr
909 (binds, resexpr) = flattenLets letexpr