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 VarSet
28 import qualified CoreFVs
29 import qualified Class
30 import qualified MkCore
31 import Outputable ( showSDoc, ppr, nest )
34 import CLasH.Normalize.NormalizeTypes
35 import CLasH.Translator.TranslatorTypes
36 import CLasH.Normalize.NormalizeTools
37 import CLasH.VHDL.Constants (builtinIds)
38 import qualified CLasH.Utils as Utils
39 import CLasH.Utils.Core.CoreTools
40 import CLasH.Utils.Core.BinderTools
41 import CLasH.Utils.Pretty
43 --------------------------------
44 -- Start of transformations
45 --------------------------------
47 --------------------------------
49 --------------------------------
50 -- Make sure all parameters to the normalized functions are named by top
51 -- level lambda expressions. For this we apply η expansion to the
52 -- function body (possibly enclosed in some lambda abstractions) while
53 -- it has a function type. Eventually this will result in a function
54 -- body consisting of a bunch of nested lambdas containing a
55 -- non-function value (e.g., a complete application).
56 eta, etatop :: Transform
57 eta c expr | is_fun expr && not (is_lam expr) && all (== LambdaBody) c = do
58 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
59 id <- Trans.lift $ mkInternalVar "param" arg_ty
60 change (Lam id (App expr (Var id)))
61 -- Leave all other expressions unchanged
63 etatop = everywhere ("eta", eta)
65 --------------------------------
67 --------------------------------
68 beta, betatop :: Transform
69 -- Substitute arg for x in expr. For value lambda's, also clone before
71 beta c (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg c expr
72 | otherwise = setChanged >> substitute_clone x arg c expr
73 -- Propagate the application into the let
74 beta c (App (Let binds expr) arg) = change $ Let binds (App expr arg)
75 -- Propagate the application into each of the alternatives
76 beta c (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
78 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
79 ty' = CoreUtils.applyTypeToArg ty arg
80 -- Leave all other expressions unchanged
81 beta c expr = return expr
82 -- Perform this transform everywhere
83 betatop = everywhere ("beta", beta)
85 --------------------------------
87 --------------------------------
88 -- Try to move casts as much downward as possible.
89 castprop, castproptop :: Transform
90 castprop c (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
91 castprop c expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
93 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
94 -- Leave all other expressions unchanged
95 castprop c expr = return expr
96 -- Perform this transform everywhere
97 castproptop = everywhere ("castprop", castprop)
99 --------------------------------
100 -- Cast simplification. Mostly useful for state packing and unpacking, but
101 -- perhaps for others as well.
102 --------------------------------
103 castsimpl, castsimpltop :: Transform
104 castsimpl c expr@(Cast val ty) = do
105 -- Don't extract values that are already simpl
106 local_var <- Trans.lift $ is_local_var val
107 -- Don't extract values that are not representable, to prevent loops with
110 if (not local_var) && repr
112 -- Generate a binder for the expression
113 id <- Trans.lift $ mkBinderFor val "castval"
114 -- Extract the expression
115 change $ Let (NonRec id val) (Cast (Var id) ty)
118 -- Leave all other expressions unchanged
119 castsimpl c expr = return expr
120 -- Perform this transform everywhere
121 castsimpltop = everywhere ("castsimpl", castsimpl)
123 --------------------------------
124 -- Return value simplification
125 --------------------------------
126 -- Ensure the return value of a function follows proper normal form. eta
127 -- expansion ensures the body starts with lambda abstractions, this
128 -- transformation ensures that the lambda abstractions always contain a
129 -- recursive let and that, when the return value is representable, the
130 -- let contains a local variable reference in its body.
131 retvalsimpl c expr | all (== LambdaBody) c && not (is_lam expr) && not (is_let expr) = do
132 local_var <- Trans.lift $ is_local_var expr
134 if not local_var && repr
136 id <- Trans.lift $ mkBinderFor expr "res"
137 change $ Let (Rec [(id, expr)]) (Var id)
141 retvalsimpl c expr@(Let (Rec binds) body) | all (== LambdaBody) c = do
142 -- Don't extract values that are already a local variable, to prevent
143 -- loops with ourselves.
144 local_var <- Trans.lift $ is_local_var body
145 -- Don't extract values that are not representable, to prevent loops with
148 if not local_var && repr
150 id <- Trans.lift $ mkBinderFor body "res"
151 change $ Let (Rec ((id, body):binds)) (Var id)
156 -- Leave all other expressions unchanged
157 retvalsimpl c expr = return expr
158 -- Perform this transform everywhere
159 retvalsimpltop = everywhere ("retvalsimpl", retvalsimpl)
161 --------------------------------
162 -- let derecursification
163 --------------------------------
164 letrec, letrectop :: Transform
165 letrec c expr@(Let (NonRec bndr val) res) =
166 change $ Let (Rec [(bndr, val)]) res
168 -- Leave all other expressions unchanged
169 letrec c expr = return expr
170 -- Perform this transform everywhere
171 letrectop = everywhere ("letrec", letrec)
173 --------------------------------
175 --------------------------------
176 -- Takes a let that binds another let, and turns that into two nested lets.
178 -- let b = (let b' = expr' in res') in res
180 -- let b' = expr' in (let b = res' in res)
181 letflat, letflattop :: Transform
182 -- Turn a nonrec let that binds a let into two nested lets.
183 letflat c (Let (NonRec b (Let binds res')) res) =
184 change $ Let binds (Let (NonRec b res') res)
185 letflat c (Let (Rec binds) expr) = do
186 -- Flatten each binding.
187 binds' <- Utils.concatM $ Monad.mapM flatbind binds
188 -- Return the new let. We don't use change here, since possibly nothing has
189 -- changed. If anything has changed, flatbind has already flagged that
191 return $ Let (Rec binds') expr
193 -- Turns a binding of a let into a multiple bindings, or any other binding
194 -- into a list with just that binding
195 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
196 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
197 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
198 flatbind (b, expr) = return [(b, expr)]
199 -- Leave all other expressions unchanged
200 letflat c expr = return expr
201 -- Perform this transform everywhere
202 letflattop = everywhere ("letflat", letflat)
204 --------------------------------
206 --------------------------------
207 -- Remove empty (recursive) lets
208 letremove, letremovetop :: Transform
209 letremove c (Let (Rec []) res) = change res
210 -- Leave all other expressions unchanged
211 letremove c expr = return expr
212 -- Perform this transform everywhere
213 letremovetop = everywhere ("letremove", letremove)
215 --------------------------------
216 -- Simple let binding removal
217 --------------------------------
218 -- Remove a = b bindings from let expressions everywhere
219 letremovesimpletop :: Transform
220 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
222 --------------------------------
223 -- Unused let binding removal
224 --------------------------------
225 letremoveunused, letremoveunusedtop :: Transform
226 letremoveunused c expr@(Let (NonRec b bound) res) = do
227 let used = expr_uses_binders [b] res
231 letremoveunused c expr@(Let (Rec binds) res) = do
232 -- Filter out all unused binds.
233 let binds' = filter dobind binds
234 -- Only set the changed flag if binds got removed
235 changeif (length binds' /= length binds) (Let (Rec binds') res)
237 bound_exprs = map snd binds
238 -- For each bind check if the bind is used by res or any of the bound
240 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
241 -- Leave all other expressions unchanged
242 letremoveunused c expr = return expr
243 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
246 --------------------------------
247 -- Identical let binding merging
248 --------------------------------
249 -- Merge two bindings in a let if they are identical
250 -- TODO: We would very much like to use GHC's CSE module for this, but that
251 -- doesn't track if something changed or not, so we can't use it properly.
252 letmerge, letmergetop :: Transform
253 letmerge c expr@(Let _ _) = do
254 let (binds, res) = flattenLets expr
255 binds' <- domerge binds
256 return $ mkNonRecLets binds' res
258 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
259 domerge [] = return []
261 es' <- mapM (mergebinds e) es
265 -- Uses the second bind to simplify the second bind, if applicable.
266 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
267 mergebinds (b1, e1) (b2, e2)
268 -- Identical expressions? Replace the second binding with a reference to
270 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
271 -- Different expressions? Don't change
272 | otherwise = return (b2, e2)
273 -- Leave all other expressions unchanged
274 letmerge c expr = return expr
275 letmergetop = everywhere ("letmerge", letmerge)
278 --------------------------------
279 -- Non-representable binding inlining
280 --------------------------------
281 -- Remove a = B bindings, with B of a non-representable type, from let
282 -- expressions everywhere. This means that any value that we can't generate a
283 -- signal for, will be inlined and hopefully turned into something we can
286 -- This is a tricky function, which is prone to create loops in the
287 -- transformations. To fix this, we make sure that no transformation will
288 -- create a new let binding with a non-representable type. These other
289 -- transformations will just not work on those function-typed values at first,
290 -- but the other transformations (in particular β-reduction) should make sure
291 -- that the type of those values eventually becomes representable.
292 inlinenonreptop :: Transform
293 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
295 --------------------------------
296 -- Top level function inlining
297 --------------------------------
298 -- This transformation inlines simple top level bindings. Simple
299 -- currently means that the body is only a single application (though
300 -- the complexity of the arguments is not currently checked) or that the
301 -- normalized form only contains a single binding. This should catch most of the
302 -- cases where a top level function is created that simply calls a type class
303 -- method with a type and dictionary argument, e.g.
304 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
305 -- which is later called using simply
306 -- fromInteger (smallInteger 10)
308 -- These useless wrappers are created by GHC automatically. If we don't
309 -- inline them, we get loads of useless components cluttering the
312 -- Note that the inlining could also inline simple functions defined by
313 -- the user, not just GHC generated functions. It turns out to be near
314 -- impossible to reliably determine what functions are generated and
315 -- what functions are user-defined. Instead of guessing (which will
316 -- inline less than we want) we will just inline all simple functions.
318 -- Only functions that are actually completely applied and bound by a
319 -- variable in a let expression are inlined. These are the expressions
320 -- that will eventually generate instantiations of trivial components.
321 -- By not inlining any other reference, we also prevent looping problems
322 -- with funextract and inlinedict.
323 inlinetoplevel, inlinetopleveltop :: Transform
324 inlinetoplevel (LetBinding:_) expr | not (is_fun expr) =
325 case collectArgs expr of
327 body_maybe <- needsInline f
330 -- Regenerate all uniques in the to-be-inlined expression
331 body_uniqued <- Trans.lift $ genUniques body
332 -- And replace the variable reference with the unique'd body.
333 change (mkApps body_uniqued args)
335 Nothing -> return expr
336 -- This is not an application of a binder, leave it unchanged.
339 -- Leave all other expressions unchanged
340 inlinetoplevel c expr = return expr
341 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
343 -- | Does the given binder need to be inlined? If so, return the body to
344 -- be used for inlining.
345 needsInline :: CoreBndr -> TransformMonad (Maybe CoreExpr)
347 body_maybe <- Trans.lift $ getGlobalBind f
349 -- No body available?
350 Nothing -> return Nothing
351 Just body -> case CoreSyn.collectArgs body of
352 -- The body is some (top level) binder applied to 0 or more
353 -- arguments. That should be simple enough to inline.
354 (Var f, args) -> return $ Just body
355 -- Body is more complicated, try normalizing it
357 norm_maybe <- Trans.lift $ getNormalized_maybe f
359 -- Noth normalizeable
360 Nothing -> return Nothing
361 Just norm -> case splitNormalized norm of
362 -- The function has just a single binding, so that's simple
364 (args, [bind], res) -> return $ Just norm
365 -- More complicated function, don't inline
368 --------------------------------
369 -- Dictionary inlining
370 --------------------------------
371 -- Inline all top level dictionaries, that are in a position where
372 -- classopresolution can actually resolve them. This makes this
373 -- transformation look similar to classoperesolution below, but we'll
374 -- keep them separated for clarity. By not inlining other dictionaries,
375 -- we prevent expression sizes exploding when huge type level integer
376 -- dictionaries are inlined which can never be expanded (in casts, for
378 inlinedict c expr@(App (App (Var sel) ty) (Var dict)) | not is_builtin && is_classop = do
379 body_maybe <- Trans.lift $ getGlobalBind dict
381 -- No body available (no source available, or a local variable /
383 Nothing -> return expr
384 Just body -> change (App (App (Var sel) ty) body)
386 -- Is this a builtin function / method?
387 is_builtin = elem (Name.getOccString sel) builtinIds
388 -- Are we dealing with a class operation selector?
389 is_classop = Maybe.isJust (Id.isClassOpId_maybe sel)
391 -- Leave all other expressions unchanged
392 inlinedict c expr = return expr
393 inlinedicttop = everywhere ("inlinedict", inlinedict)
395 --------------------------------
396 -- ClassOp resolution
397 --------------------------------
398 -- Resolves any class operation to the actual operation whenever
399 -- possible. Class methods (as well as parent dictionary selectors) are
400 -- special "functions" that take a type and a dictionary and evaluate to
401 -- the corresponding method. A dictionary is nothing more than a
402 -- special dataconstructor applied to the type the dictionary is for,
403 -- each of the superclasses and all of the class method definitions for
404 -- that particular type. Since dictionaries all always inlined (top
405 -- levels dictionaries are inlined by inlinedict, local dictionaries are
406 -- inlined by inlinenonrep), we will eventually have something like:
409 -- @ CLasH.HardwareTypes.Bit
410 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
412 -- Here, baz is the method selector for the baz method, while
413 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
414 -- method defined in the Baz Bit instance declaration.
416 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
417 -- which contains the Class it is defined for. From the Class, we can
418 -- get a list of all selectors (both parent class selectors as well as
419 -- method selectors). Since the arguments to D:Baz (after the type
420 -- argument) correspond exactly to this list, we then look up baz in
421 -- that list and replace the entire expression by the corresponding
422 -- argument to D:Baz.
424 -- We don't resolve methods that have a builtin translation (such as
425 -- ==), since the actual implementation is not always (easily)
426 -- translateable. For example, when deriving ==, GHC generates code
427 -- using $con2tag functions to translate a datacon to an int and compare
428 -- that with GHC.Prim.==# . Better to avoid that for now.
429 classopresolution, classopresolutiontop :: Transform
430 classopresolution c expr@(App (App (Var sel) ty) dict) | not is_builtin =
431 case Id.isClassOpId_maybe sel of
432 -- Not a class op selector
433 Nothing -> return expr
434 Just cls -> case collectArgs dict of
435 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
436 (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)
437 | tyargs_neq ty ty' -> error $ "Normalize.classopresolution: Applying class selector to dictionary without matching type?\n" ++ pprString expr
439 let selector_ids = Class.classSelIds cls in
440 -- Find the selector used in the class' list of selectors
441 case List.elemIndex sel selector_ids of
442 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
443 -- Get the corresponding argument from the dictionary
444 Just n -> change (selectors!!n)
445 (_, _) -> return expr -- Not applying a variable? Don't touch
447 -- Compare two type arguments, returning True if they are _not_
449 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
450 tyargs_neq _ _ = True
451 -- Is this a builtin function / method?
452 is_builtin = elem (Name.getOccString sel) builtinIds
454 -- Leave all other expressions unchanged
455 classopresolution c expr = return expr
456 -- Perform this transform everywhere
457 classopresolutiontop = everywhere ("classopresolution", classopresolution)
459 --------------------------------
460 -- Scrutinee simplification
461 --------------------------------
462 scrutsimpl,scrutsimpltop :: Transform
463 -- Don't touch scrutinees that are already simple
464 scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
465 -- Replace all other cases with a let that binds the scrutinee and a new
466 -- simple scrutinee, but only when the scrutinee is representable (to prevent
467 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
468 -- will be supported anyway...)
469 scrutsimpl c expr@(Case scrut b ty alts) = do
473 id <- Trans.lift $ mkBinderFor scrut "scrut"
474 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
477 -- Leave all other expressions unchanged
478 scrutsimpl c expr = return expr
479 -- Perform this transform everywhere
480 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
482 --------------------------------
483 -- Scrutinee binder removal
484 --------------------------------
485 -- A case expression can have an extra binder, to which the scrutinee is bound
486 -- after bringing it to WHNF. This is used for forcing evaluation of strict
487 -- arguments. Since strictness does not matter for us (rather, everything is
488 -- sort of strict), this binder is ignored when generating VHDL, and must thus
489 -- be wild in the normal form.
490 scrutbndrremove, scrutbndrremovetop :: Transform
491 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
492 -- all occurences of the binder with the scrutinee variable.
493 scrutbndrremove c (Case (Var scrut) bndr ty alts) | bndr_used = do
494 alts' <- mapM subs_bndr alts
495 change $ Case (Var scrut) wild ty alts'
497 is_used (_, _, expr) = expr_uses_binders [bndr] expr
498 bndr_used = or $ map is_used alts
499 subs_bndr (con, bndrs, expr) = do
500 expr' <- substitute bndr (Var scrut) c expr
501 return (con, bndrs, expr')
502 wild = MkCore.mkWildBinder (Id.idType bndr)
503 -- Leave all other expressions unchanged
504 scrutbndrremove c expr = return expr
505 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
507 --------------------------------
508 -- Case binder wildening
509 --------------------------------
510 casesimpl, casesimpltop :: Transform
511 -- This is already a selector case (or, if x does not appear in bndrs, a very
512 -- simple case statement that will be removed by caseremove below). Just leave
514 casesimpl c expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
515 -- Make sure that all case alternatives have only wild binders and simple
517 -- This is done by creating a new let binding for each non-wild binder, which
518 -- is bound to a new simple selector case statement and for each complex
519 -- expression. We do this only for representable types, to prevent loops with
521 casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
522 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
523 let bindings = concat bindingss
524 -- Replace the case with a let with bindings and a case
525 let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
526 -- If there are no non-wild binders, or this case is already a simple
527 -- selector (i.e., a single alt with exactly one binding), already a simple
528 -- selector altan no bindings (i.e., no wild binders in the original case),
529 -- don't change anything, otherwise, replace the case.
530 if null bindings then return expr else change newlet
532 -- Check if the scrutinee binder is used
533 is_used (_, _, expr) = expr_uses_binders [bndr] expr
534 bndr_used = or $ map is_used alts
535 -- Generate a single wild binder, since they are all the same
536 wild = MkCore.mkWildBinder
537 -- Wilden the binders of one alt, producing a list of bindings as a
539 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
540 doalt (con, bndrs, expr) = do
541 -- Make each binder wild, if possible
542 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
543 let (newbndrs, bindings_maybe) = unzip bndrs_res
544 -- Extract a complex expression, if possible. For this we check if any of
545 -- the new list of bndrs are used by expr. We can't use free_vars here,
546 -- since that looks at the old bndrs.
547 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
548 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
549 -- Create a new alternative
550 let newalt = (con, newbndrs, expr')
551 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
552 return (bindings, newalt)
554 -- Make wild alternatives for each binder
555 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
556 -- A set of all the binders that are used by the expression
557 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
558 -- Look at the ith binder in the case alternative. Return a new binder
559 -- for it (either the same one, or a wild one) and optionally a let
560 -- binding containing a case expression.
561 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
564 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
565 -- in expr, this means that b is unused if expr does not use it.)
566 let wild = not (VarSet.elemVarSet b free_vars)
567 -- Create a new binding for any representable binder that is not
568 -- already wild and is representable (to prevent loops with
570 if (not wild) && repr
572 -- Create on new binder that will actually capture a value in this
573 -- case statement, and return it.
574 let bty = (Id.idType b)
575 id <- Trans.lift $ mkInternalVar "sel" bty
576 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
577 let caseexpr = Case scrut b bty [(con, binders, Var id)]
578 return (wildbndrs!!i, Just (b, caseexpr))
580 -- Just leave the original binder in place, and don't generate an
581 -- extra selector case.
583 -- Process the expression of a case alternative. Accepts an expression
584 -- and whether this expression uses any of the binders in the
585 -- alternative. Returns an optional new binding and a new expression.
586 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
587 doexpr expr uses_bndrs = do
588 local_var <- Trans.lift $ is_local_var expr
590 -- Extract any expressions that do not use any binders from this
591 -- alternative, is not a local var already and is representable (to
592 -- prevent loops with inlinenonrep).
593 if (not uses_bndrs) && (not local_var) && repr
595 id <- Trans.lift $ mkBinderFor expr "caseval"
596 -- We don't flag a change here, since casevalsimpl will do that above
597 -- based on Just we return here.
598 return (Just (id, expr), Var id)
600 -- Don't simplify anything else
601 return (Nothing, expr)
602 -- Leave all other expressions unchanged
603 casesimpl c expr = return expr
604 -- Perform this transform everywhere
605 casesimpltop = everywhere ("casesimpl", casesimpl)
607 --------------------------------
609 --------------------------------
610 -- Remove case statements that have only a single alternative and only wild
612 caseremove, caseremovetop :: Transform
613 -- Replace a useless case by the value of its single alternative
614 caseremove c (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
615 -- Find if any of the binders are used by expr
616 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
617 -- Leave all other expressions unchanged
618 caseremove c expr = return expr
619 -- Perform this transform everywhere
620 caseremovetop = everywhere ("caseremove", caseremove)
622 --------------------------------
623 -- Argument extraction
624 --------------------------------
625 -- Make sure that all arguments of a representable type are simple variables.
626 appsimpl, appsimpltop :: Transform
627 -- Simplify all representable arguments. Do this by introducing a new Let
628 -- that binds the argument and passing the new binder in the application.
629 appsimpl c expr@(App f arg) = do
630 -- Check runtime representability
632 local_var <- Trans.lift $ is_local_var arg
633 if repr && not local_var
634 then do -- Extract representable arguments
635 id <- Trans.lift $ mkBinderFor arg "arg"
636 change $ Let (NonRec id arg) (App f (Var id))
637 else -- Leave non-representable arguments unchanged
639 -- Leave all other expressions unchanged
640 appsimpl c expr = return expr
641 -- Perform this transform everywhere
642 appsimpltop = everywhere ("appsimpl", appsimpl)
644 --------------------------------
645 -- Function-typed argument propagation
646 --------------------------------
647 -- Remove all applications to function-typed arguments, by duplication the
648 -- function called with the function-typed parameter replaced by the free
649 -- variables of the argument passed in.
650 argprop, argproptop :: Transform
651 -- Transform any application of a named function (i.e., skip applications of
652 -- lambda's). Also skip applications that have arguments with free type
653 -- variables, since we can't inline those.
654 argprop c expr@(App _ _) | is_var fexpr = do
655 -- Find the body of the function called
656 body_maybe <- Trans.lift $ getGlobalBind f
659 -- Process each of the arguments in turn
660 (args', changed) <- Writer.listen $ mapM doarg args
661 -- See if any of the arguments changed
662 case Monoid.getAny changed of
664 let (newargs', newparams', oldargs) = unzip3 args'
665 let newargs = concat newargs'
666 let newparams = concat newparams'
667 -- Create a new body that consists of a lambda for all new arguments and
668 -- the old body applied to some arguments.
669 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
670 -- Create a new function with the same name but a new body
671 newf <- Trans.lift $ mkFunction f newbody
673 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
674 let init_state_maybe = Map.lookup f ismap in
675 case init_state_maybe of
677 Just init_state -> Map.insert newf init_state ismap)
678 -- Replace the original application with one of the new function to the
680 change $ MkCore.mkCoreApps (Var newf) newargs
682 -- Don't change the expression if none of the arguments changed
685 -- If we don't have a body for the function called, leave it unchanged (it
686 -- should be a primitive function then).
687 Nothing -> return expr
689 -- Find the function called and the arguments
690 (fexpr, args) = collectArgs expr
693 -- Process a single argument and return (args, bndrs, arg), where args are
694 -- the arguments to replace the given argument in the original
695 -- application, bndrs are the binders to include in the top-level lambda
696 -- in the new function body, and arg is the argument to apply to the old
698 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
701 bndrs <- Trans.lift getGlobalBinders
702 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
703 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
705 -- Propagate all complex arguments that are not representable, but not
706 -- arguments with free type variables (since those would require types
707 -- not known yet, which will always be known eventually).
708 -- Find interesting free variables, each of which should be passed to
709 -- the new function instead of the original function argument.
711 -- Interesting vars are those that are local, but not available from the
712 -- top level scope (functions from this module are defined as local, but
713 -- they're not local to this function, so we can freely move references
714 -- to them into another function).
715 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
716 -- Mark the current expression as changed
718 -- TODO: Clone the free_vars (and update references in arg), since
719 -- this might cause conflicts if two arguments that are propagated
720 -- share a free variable. Also, we are now introducing new variables
721 -- into a function that are not fresh, which violates the binder
722 -- uniqueness invariant.
723 return (map Var free_vars, free_vars, arg)
725 -- Representable types will not be propagated, and arguments with free
726 -- type variables will be propagated later.
727 -- Note that we implicitly remove any type variables in the type of
728 -- the original argument by using the type of the actual argument
729 -- for the new formal parameter.
730 -- TODO: preserve original naming?
731 id <- Trans.lift $ mkBinderFor arg "param"
732 -- Just pass the original argument to the new function, which binds it
733 -- to a new id and just pass that new id to the old function body.
734 return ([arg], [id], mkReferenceTo id)
735 -- Leave all other expressions unchanged
736 argprop c expr = return expr
737 -- Perform this transform everywhere
738 argproptop = everywhere ("argprop", argprop)
740 --------------------------------
741 -- Function-typed argument extraction
742 --------------------------------
743 -- This transform takes any function-typed argument that cannot be propagated
744 -- (because the function that is applied to it is a builtin function), and
745 -- puts it in a brand new top level binder. This allows us to for example
746 -- apply map to a lambda expression This will not conflict with inlinenonrep,
747 -- since that only inlines local let bindings, not top level bindings.
748 funextract, funextracttop :: Transform
749 funextract c expr@(App _ _) | is_var fexpr = do
750 body_maybe <- Trans.lift $ getGlobalBind f
752 -- We don't have a function body for f, so we can perform this transform.
754 -- Find the new arguments
755 args' <- mapM doarg args
756 -- And update the arguments. We use return instead of changed, so the
757 -- changed flag doesn't get set if none of the args got changed.
758 return $ MkCore.mkCoreApps fexpr args'
759 -- We have a function body for f, leave this application to funprop
760 Just _ -> return expr
762 -- Find the function called and the arguments
763 (fexpr, args) = collectArgs expr
765 -- Change any arguments that have a function type, but are not simple yet
766 -- (ie, a variable or application). This means to create a new function
767 -- for map (\f -> ...) b, but not for map (foo a) b.
769 -- We could use is_applicable here instead of is_fun, but I think
770 -- arguments to functions could only have forall typing when existential
771 -- typing is enabled. Not sure, though.
772 doarg arg | not (is_simple arg) && is_fun arg = do
773 -- Create a new top level binding that binds the argument. Its body will
774 -- be extended with lambda expressions, to take any free variables used
775 -- by the argument expression.
776 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
777 let body = MkCore.mkCoreLams free_vars arg
778 id <- Trans.lift $ mkBinderFor body "fun"
779 Trans.lift $ addGlobalBind id body
780 -- Replace the argument with a reference to the new function, applied to
782 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
783 -- Leave all other arguments untouched
784 doarg arg = return arg
786 -- Leave all other expressions unchanged
787 funextract c expr = return expr
788 -- Perform this transform everywhere
789 funextracttop = everywhere ("funextract", funextract)
791 --------------------------------
792 -- End of transformations
793 --------------------------------
798 -- What transforms to run?
799 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letrectop, letremovetop, retvalsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop]
801 -- | Returns the normalized version of the given function, or an error
802 -- if it is not a known global binder.
804 CoreBndr -- ^ The function to get
805 -> TranslatorSession CoreExpr -- The normalized function body
806 getNormalized bndr = do
807 norm <- getNormalized_maybe bndr
808 return $ Maybe.fromMaybe
809 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
812 -- | Returns the normalized version of the given function, or Nothing
813 -- when the binder is not a known global binder or is not normalizeable.
814 getNormalized_maybe ::
815 CoreBndr -- ^ The function to get
816 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
818 getNormalized_maybe bndr = do
819 expr_maybe <- getGlobalBind bndr
820 normalizeable <- isNormalizeable' bndr
821 if not normalizeable || Maybe.isNothing expr_maybe
823 -- Binder not normalizeable or not found
825 else if is_poly (Var bndr)
827 -- This should really only happen at the top level... TODO: Give
828 -- a different error if this happens down in the recursion.
829 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
831 -- Binder found and is monomorphic. Normalize the expression
832 -- and cache the result.
833 normalized <- Utils.makeCached bndr tsNormalized $
834 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
835 return (Just normalized)
837 -- | Normalize an expression
839 String -- ^ What are we normalizing? For debug output only.
840 -> CoreSyn.CoreExpr -- ^ The expression to normalize
841 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
843 normalizeExpr what expr = do
844 startcount <- MonadState.get tsTransformCounter
845 expr_uniqued <- genUniques expr
846 -- Normalize this expression
847 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
848 expr' <- dotransforms transforms expr_uniqued
849 endcount <- MonadState.get tsTransformCounter
850 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')
851 ++ "\nNeeded " ++ show (endcount - startcount) ++ " transformations to normalize " ++ what) $
854 -- | Split a normalized expression into the argument binders, top level
855 -- bindings and the result binder. This function returns an error if
856 -- the type of the expression is not representable.
858 CoreExpr -- ^ The normalized expression
859 -> ([CoreBndr], [Binding], CoreBndr)
860 splitNormalized expr =
861 case splitNormalizedNonRep expr of
862 (args, binds, Var res) -> (args, binds, res)
863 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"
865 -- Split a normalized expression, whose type can be unrepresentable.
866 splitNormalizedNonRep::
867 CoreExpr -- ^ The normalized expression
868 -> ([CoreBndr], [Binding], CoreExpr)
869 splitNormalizedNonRep expr = (args, binds, resexpr)
871 (args, letexpr) = CoreSyn.collectBinders expr
872 (binds, resexpr) = flattenLets letexpr