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
26 import qualified VarSet
27 import qualified CoreFVs
28 import qualified Class
29 import qualified MkCore
30 import Outputable ( showSDoc, ppr, nest )
33 import CLasH.Normalize.NormalizeTypes
34 import CLasH.Translator.TranslatorTypes
35 import CLasH.Normalize.NormalizeTools
36 import qualified CLasH.Utils as Utils
37 import CLasH.Utils.Core.CoreTools
38 import CLasH.Utils.Core.BinderTools
39 import CLasH.Utils.Pretty
41 --------------------------------
42 -- Start of transformations
43 --------------------------------
45 --------------------------------
47 --------------------------------
48 eta, etatop :: Transform
49 eta expr | is_fun expr && not (is_lam expr) = do
50 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
51 id <- Trans.lift $ mkInternalVar "param" arg_ty
52 change (Lam id (App expr (Var id)))
53 -- Leave all other expressions unchanged
55 etatop = notappargs ("eta", eta)
57 --------------------------------
59 --------------------------------
60 beta, betatop :: Transform
61 -- Substitute arg for x in expr. For value lambda's, also clone before
63 beta (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg expr
64 | otherwise = setChanged >> substitute_clone x arg expr
65 -- Propagate the application into the let
66 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
67 -- Propagate the application into each of the alternatives
68 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
70 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
71 ty' = CoreUtils.applyTypeToArg ty arg
72 -- Leave all other expressions unchanged
73 beta expr = return expr
74 -- Perform this transform everywhere
75 betatop = everywhere ("beta", beta)
77 --------------------------------
79 --------------------------------
80 -- Try to move casts as much downward as possible.
81 castprop, castproptop :: Transform
82 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
83 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
85 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
86 -- Leave all other expressions unchanged
87 castprop expr = return expr
88 -- Perform this transform everywhere
89 castproptop = everywhere ("castprop", castprop)
91 --------------------------------
92 -- Cast simplification. Mostly useful for state packing and unpacking, but
93 -- perhaps for others as well.
94 --------------------------------
95 castsimpl, castsimpltop :: Transform
96 castsimpl expr@(Cast val ty) = do
97 -- Don't extract values that are already simpl
98 local_var <- Trans.lift $ is_local_var val
99 -- Don't extract values that are not representable, to prevent loops with
102 if (not local_var) && repr
104 -- Generate a binder for the expression
105 id <- Trans.lift $ mkBinderFor val "castval"
106 -- Extract the expression
107 change $ Let (NonRec id val) (Cast (Var id) ty)
110 -- Leave all other expressions unchanged
111 castsimpl expr = return expr
112 -- Perform this transform everywhere
113 castsimpltop = everywhere ("castsimpl", castsimpl)
116 --------------------------------
117 -- Lambda simplication
118 --------------------------------
119 -- Ensure that a lambda always evaluates to a let expressions or a simple
120 -- variable reference.
121 lambdasimpl, lambdasimpltop :: Transform
122 -- Don't simplify a lambda that evaluates to let, since this is already
123 -- normal form (and would cause infinite loops).
124 lambdasimpl expr@(Lam _ (Let _ _)) = return expr
125 -- Put the of a lambda in its own binding, but not when the expression is
126 -- already a local variable, or not representable (to prevent loops with
128 lambdasimpl expr@(Lam bndr res) = do
130 local_var <- Trans.lift $ is_local_var res
131 if not local_var && repr
133 id <- Trans.lift $ mkBinderFor res "res"
134 change $ Lam bndr (Let (NonRec id res) (Var id))
136 -- If the result is already a local var or not representable, don't
140 -- Leave all other expressions unchanged
141 lambdasimpl expr = return expr
142 -- Perform this transform everywhere
143 lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
145 --------------------------------
146 -- let derecursification
147 --------------------------------
148 letderec, letderectop :: Transform
149 letderec expr@(Let (Rec binds) res) = case liftable of
150 -- Nothing is liftable, just return
152 -- Something can be lifted, generate a new let expression
153 _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
155 -- Make a list of all the binders bound in this recursive let
156 bndrs = map fst binds
157 -- See which bindings are liftable
158 (liftable, nonliftable) = List.partition canlift binds
159 -- Any expression that does not use any of the binders in this recursive let
160 -- can be lifted into a nonrec let. It can't use its own binder either,
161 -- since that would mean the binding is self-recursive and should be in a
162 -- single bind recursive let.
163 canlift (bndr, e) = not $ expr_uses_binders bndrs e
164 -- Leave all other expressions unchanged
165 letderec expr = return expr
166 -- Perform this transform everywhere
167 letderectop = everywhere ("letderec", letderec)
169 --------------------------------
170 -- let simplification
171 --------------------------------
172 letsimpl, letsimpltop :: Transform
173 -- Don't simplify a let that evaluates to another let, since this is already
174 -- normal form (and would cause infinite loops with letflat below).
175 letsimpl expr@(Let _ (Let _ _)) = return expr
176 -- Put the "in ..." value of a let in its own binding, but not when the
177 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
178 letsimpl expr@(Let binds res) = do
180 local_var <- Trans.lift $ is_local_var res
181 if not local_var && repr
183 -- If the result is not a local var already (to prevent loops with
184 -- ourselves), extract it.
185 id <- Trans.lift $ mkBinderFor res "foo"
186 change $ Let binds (Let (NonRec id res) (Var id))
188 -- If the result is already a local var, don't extract it.
191 -- Leave all other expressions unchanged
192 letsimpl expr = return expr
193 -- Perform this transform everywhere
194 letsimpltop = everywhere ("letsimpl", letsimpl)
196 --------------------------------
198 --------------------------------
199 -- Takes a let that binds another let, and turns that into two nested lets.
201 -- let b = (let b' = expr' in res') in res
203 -- let b' = expr' in (let b = res' in res)
204 letflat, letflattop :: Transform
205 -- Turn a nonrec let that binds a let into two nested lets.
206 letflat (Let (NonRec b (Let binds res')) res) =
207 change $ Let binds (Let (NonRec b res') res)
208 letflat (Let (Rec binds) expr) = do
209 -- Flatten each binding.
210 binds' <- Utils.concatM $ Monad.mapM flatbind binds
211 -- Return the new let. We don't use change here, since possibly nothing has
212 -- changed. If anything has changed, flatbind has already flagged that
214 return $ Let (Rec binds') expr
216 -- Turns a binding of a let into a multiple bindings, or any other binding
217 -- into a list with just that binding
218 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
219 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
220 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
221 flatbind (b, expr) = return [(b, expr)]
222 -- Leave all other expressions unchanged
223 letflat expr = return expr
224 -- Perform this transform everywhere
225 letflattop = everywhere ("letflat", letflat)
227 --------------------------------
229 --------------------------------
230 -- Remove empty (recursive) lets
231 letremove, letremovetop :: Transform
232 letremove (Let (Rec []) res) = change res
233 -- Leave all other expressions unchanged
234 letremove expr = return expr
235 -- Perform this transform everywhere
236 letremovetop = everywhere ("letremove", letremove)
238 --------------------------------
239 -- Simple let binding removal
240 --------------------------------
241 -- Remove a = b bindings from let expressions everywhere
242 letremovesimpletop :: Transform
243 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
245 --------------------------------
246 -- Unused let binding removal
247 --------------------------------
248 letremoveunused, letremoveunusedtop :: Transform
249 letremoveunused expr@(Let (NonRec b bound) res) = do
250 let used = expr_uses_binders [b] res
254 letremoveunused expr@(Let (Rec binds) res) = do
255 -- Filter out all unused binds.
256 let binds' = filter dobind binds
257 -- Only set the changed flag if binds got removed
258 changeif (length binds' /= length binds) (Let (Rec binds') res)
260 bound_exprs = map snd binds
261 -- For each bind check if the bind is used by res or any of the bound
263 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
264 -- Leave all other expressions unchanged
265 letremoveunused expr = return expr
266 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
269 --------------------------------
270 -- Identical let binding merging
271 --------------------------------
272 -- Merge two bindings in a let if they are identical
273 -- TODO: We would very much like to use GHC's CSE module for this, but that
274 -- doesn't track if something changed or not, so we can't use it properly.
275 letmerge, letmergetop :: Transform
276 letmerge expr@(Let _ _) = do
277 let (binds, res) = flattenLets expr
278 binds' <- domerge binds
279 return $ mkNonRecLets binds' res
281 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
282 domerge [] = return []
284 es' <- mapM (mergebinds e) es
288 -- Uses the second bind to simplify the second bind, if applicable.
289 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
290 mergebinds (b1, e1) (b2, e2)
291 -- Identical expressions? Replace the second binding with a reference to
293 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
294 -- Different expressions? Don't change
295 | otherwise = return (b2, e2)
296 -- Leave all other expressions unchanged
297 letmerge expr = return expr
298 letmergetop = everywhere ("letmerge", letmerge)
301 --------------------------------
302 -- Non-representable binding inlining
303 --------------------------------
304 -- Remove a = B bindings, with B of a non-representable type, from let
305 -- expressions everywhere. This means that any value that we can't generate a
306 -- signal for, will be inlined and hopefully turned into something we can
309 -- This is a tricky function, which is prone to create loops in the
310 -- transformations. To fix this, we make sure that no transformation will
311 -- create a new let binding with a non-representable type. These other
312 -- transformations will just not work on those function-typed values at first,
313 -- but the other transformations (in particular β-reduction) should make sure
314 -- that the type of those values eventually becomes representable.
315 inlinenonreptop :: Transform
316 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
318 --------------------------------
319 -- Top level function inlining
320 --------------------------------
321 -- This transformation inlines top level bindings that have been generated by
322 -- the compiler and are really simple. Really simple currently means that the
323 -- normalized form only contains a single binding, which catches most of the
324 -- cases where a top level function is created that simply calls a type class
325 -- method with a type and dictionary argument, e.g.
326 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
327 -- which is later called using simply
328 -- fromInteger (smallInteger 10)
329 -- By inlining such calls to simple, compiler generated functions, we prevent
330 -- huge amounts of trivial components in the VHDL output, which the user never
331 -- wanted. We never inline user-defined functions, since we want to preserve
332 -- all structure defined by the user. Currently this includes all functions
333 -- that were created by funextract, since we would get loops otherwise.
335 -- Note that "defined by the compiler" isn't completely watertight, since GHC
336 -- doesn't seem to set all those names as "system names", we apply some
338 inlinetoplevel, inlinetopleveltop :: Transform
339 -- Any system name is candidate for inlining. Never inline user-defined
340 -- functions, to preserve structure.
341 inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
342 norm_maybe <- Trans.lift $ getNormalized_maybe f
344 -- No body or not normalizeable.
345 Nothing -> return expr
346 Just norm -> if needsInline norm then do
347 -- Regenerate all uniques in the to-be-inlined expression
348 norm_uniqued <- Trans.lift $ genUniques norm
349 -- And replace the variable reference with the unique'd body.
355 -- Leave all other expressions unchanged
356 inlinetoplevel expr = return expr
357 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
359 needsInline :: CoreExpr -> Bool
360 needsInline expr = case splitNormalized expr of
361 -- Inline any function that only has a single definition, it is probably
362 -- simple enough. This might inline some stuff that it shouldn't though it
363 -- will never inline user-defined functions (inlinetoplevel only tries
364 -- system names) and inlining should never break things.
365 (args, [bind], res) -> True
369 --------------------------------
370 -- Dictionary inlining
371 --------------------------------
372 -- Inline all top level dictionaries, so we can use them to resolve
373 -- class methods based on the dictionary passed.
374 inlinedict expr@(Var f) | Id.isDictId f = do
375 body_maybe <- Trans.lift $ getGlobalBind f
377 Nothing -> return expr
378 Just body -> change body
380 -- Leave all other expressions unchanged
381 inlinedict expr = return expr
382 inlinedicttop = everywhere ("inlinedict", inlinedict)
384 --------------------------------
385 -- ClassOp resolution
386 --------------------------------
387 -- Resolves any class operation to the actual operation whenever
388 -- possible. Class methods (as well as parent dictionary selectors) are
389 -- special "functions" that take a type and a dictionary and evaluate to
390 -- the corresponding method. A dictionary is nothing more than a
391 -- special dataconstructor applied to the type the dictionary is for,
392 -- each of the superclasses and all of the class method definitions for
393 -- that particular type. Since dictionaries all always inlined (top
394 -- levels dictionaries are inlined by inlinedict, local dictionaries are
395 -- inlined by inlinenonrep), we will eventually have something like:
398 -- @ CLasH.HardwareTypes.Bit
399 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
401 -- Here, baz is the method selector for the baz method, while
402 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
403 -- method defined in the Baz Bit instance declaration.
405 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
406 -- which contains the Class it is defined for. From the Class, we can
407 -- get a list of all selectors (both parent class selectors as well as
408 -- method selectors). Since the arguments to D:Baz (after the type
409 -- argument) correspond exactly to this list, we then look up baz in
410 -- that list and replace the entire expression by the corresponding
411 -- argument to D:Baz.
412 classopresolution, classopresolutiontop :: Transform
413 classopresolution expr@(App (App (Var sel) ty) dict) =
414 case Id.isClassOpId_maybe sel of
415 -- Not a class op selector
416 Nothing -> return expr
417 Just cls -> case collectArgs dict of
418 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
419 (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)
420 | tyargs_neq ty ty' -> error $ "Applying class selector to dictionary without matching type?\n" ++ pprString expr
422 let selector_ids = Class.classSelIds cls in
423 -- Find the selector used in the class' list of selectors
424 case List.elemIndex sel selector_ids of
425 Nothing -> error $ "Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
426 -- Get the corresponding argument from the dictionary
427 Just n -> change (selectors!!n)
428 (_, _) -> return expr -- Not applying a variable? Don't touch
430 -- Compare two type arguments, returning True if they are _not_
432 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
433 tyargs_neq _ _ = True
435 -- Leave all other expressions unchanged
436 classopresolution expr = return expr
437 -- Perform this transform everywhere
438 classopresolutiontop = everywhere ("classopresolution", classopresolution)
440 --------------------------------
441 -- Scrutinee simplification
442 --------------------------------
443 scrutsimpl,scrutsimpltop :: Transform
444 -- Don't touch scrutinees that are already simple
445 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
446 -- Replace all other cases with a let that binds the scrutinee and a new
447 -- simple scrutinee, but only when the scrutinee is representable (to prevent
448 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
449 -- will be supported anyway...)
450 scrutsimpl expr@(Case scrut b ty alts) = do
454 id <- Trans.lift $ mkBinderFor scrut "scrut"
455 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
458 -- Leave all other expressions unchanged
459 scrutsimpl expr = return expr
460 -- Perform this transform everywhere
461 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
463 --------------------------------
464 -- Scrutinee binder removal
465 --------------------------------
466 -- A case expression can have an extra binder, to which the scrutinee is bound
467 -- after bringing it to WHNF. This is used for forcing evaluation of strict
468 -- arguments. Since strictness does not matter for us (rather, everything is
469 -- sort of strict), this binder is ignored when generating VHDL, and must thus
470 -- be wild in the normal form.
471 scrutbndrremove, scrutbndrremovetop :: Transform
472 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
473 -- all occurences of the binder with the scrutinee variable.
474 scrutbndrremove (Case (Var scrut) bndr ty alts) | bndr_used = do
475 alts' <- mapM subs_bndr alts
476 change $ Case (Var scrut) wild ty alts'
478 is_used (_, _, expr) = expr_uses_binders [bndr] expr
479 bndr_used = or $ map is_used alts
480 subs_bndr (con, bndrs, expr) = do
481 expr' <- substitute bndr (Var scrut) expr
482 return (con, bndrs, expr')
483 wild = MkCore.mkWildBinder (Id.idType bndr)
484 -- Leave all other expressions unchanged
485 scrutbndrremove expr = return expr
486 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
488 --------------------------------
489 -- Case binder wildening
490 --------------------------------
491 casesimpl, casesimpltop :: Transform
492 -- This is already a selector case (or, if x does not appear in bndrs, a very
493 -- simple case statement that will be removed by caseremove below). Just leave
495 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
496 -- Make sure that all case alternatives have only wild binders and simple
498 -- This is done by creating a new let binding for each non-wild binder, which
499 -- is bound to a new simple selector case statement and for each complex
500 -- expression. We do this only for representable types, to prevent loops with
502 casesimpl expr@(Case scrut b ty alts) = do
503 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
504 let bindings = concat bindingss
505 -- Replace the case with a let with bindings and a case
506 let newlet = mkNonRecLets bindings (Case scrut b ty alts')
507 -- If there are no non-wild binders, or this case is already a simple
508 -- selector (i.e., a single alt with exactly one binding), already a simple
509 -- selector altan no bindings (i.e., no wild binders in the original case),
510 -- don't change anything, otherwise, replace the case.
511 if null bindings then return expr else change newlet
513 -- Generate a single wild binder, since they are all the same
514 wild = MkCore.mkWildBinder
515 -- Wilden the binders of one alt, producing a list of bindings as a
517 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
518 doalt (con, bndrs, expr) = do
519 -- Make each binder wild, if possible
520 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
521 let (newbndrs, bindings_maybe) = unzip bndrs_res
522 -- Extract a complex expression, if possible. For this we check if any of
523 -- the new list of bndrs are used by expr. We can't use free_vars here,
524 -- since that looks at the old bndrs.
525 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
526 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
527 -- Create a new alternative
528 let newalt = (con, newbndrs, expr')
529 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
530 return (bindings, newalt)
532 -- Make wild alternatives for each binder
533 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
534 -- A set of all the binders that are used by the expression
535 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
536 -- Look at the ith binder in the case alternative. Return a new binder
537 -- for it (either the same one, or a wild one) and optionally a let
538 -- binding containing a case expression.
539 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
542 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
543 -- in expr, this means that b is unused if expr does not use it.)
544 let wild = not (VarSet.elemVarSet b free_vars)
545 -- Create a new binding for any representable binder that is not
546 -- already wild and is representable (to prevent loops with
548 if (not wild) && repr
550 -- Create on new binder that will actually capture a value in this
551 -- case statement, and return it.
552 let bty = (Id.idType b)
553 id <- Trans.lift $ mkInternalVar "sel" bty
554 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
555 let caseexpr = Case scrut b bty [(con, binders, Var id)]
556 return (wildbndrs!!i, Just (b, caseexpr))
558 -- Just leave the original binder in place, and don't generate an
559 -- extra selector case.
561 -- Process the expression of a case alternative. Accepts an expression
562 -- and whether this expression uses any of the binders in the
563 -- alternative. Returns an optional new binding and a new expression.
564 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
565 doexpr expr uses_bndrs = do
566 local_var <- Trans.lift $ is_local_var expr
568 -- Extract any expressions that do not use any binders from this
569 -- alternative, is not a local var already and is representable (to
570 -- prevent loops with inlinenonrep).
571 if (not uses_bndrs) && (not local_var) && repr
573 id <- Trans.lift $ mkBinderFor expr "caseval"
574 -- We don't flag a change here, since casevalsimpl will do that above
575 -- based on Just we return here.
576 return (Just (id, expr), Var id)
578 -- Don't simplify anything else
579 return (Nothing, expr)
580 -- Leave all other expressions unchanged
581 casesimpl expr = return expr
582 -- Perform this transform everywhere
583 casesimpltop = everywhere ("casesimpl", casesimpl)
585 --------------------------------
587 --------------------------------
588 -- Remove case statements that have only a single alternative and only wild
590 caseremove, caseremovetop :: Transform
591 -- Replace a useless case by the value of its single alternative
592 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
593 -- Find if any of the binders are used by expr
594 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
595 -- Leave all other expressions unchanged
596 caseremove expr = return expr
597 -- Perform this transform everywhere
598 caseremovetop = everywhere ("caseremove", caseremove)
600 --------------------------------
601 -- Argument extraction
602 --------------------------------
603 -- Make sure that all arguments of a representable type are simple variables.
604 appsimpl, appsimpltop :: Transform
605 -- Simplify all representable arguments. Do this by introducing a new Let
606 -- that binds the argument and passing the new binder in the application.
607 appsimpl expr@(App f arg) = do
608 -- Check runtime representability
610 local_var <- Trans.lift $ is_local_var arg
611 if repr && not local_var
612 then do -- Extract representable arguments
613 id <- Trans.lift $ mkBinderFor arg "arg"
614 change $ Let (NonRec id arg) (App f (Var id))
615 else -- Leave non-representable arguments unchanged
617 -- Leave all other expressions unchanged
618 appsimpl expr = return expr
619 -- Perform this transform everywhere
620 appsimpltop = everywhere ("appsimpl", appsimpl)
622 --------------------------------
623 -- Function-typed argument propagation
624 --------------------------------
625 -- Remove all applications to function-typed arguments, by duplication the
626 -- function called with the function-typed parameter replaced by the free
627 -- variables of the argument passed in.
628 argprop, argproptop :: Transform
629 -- Transform any application of a named function (i.e., skip applications of
630 -- lambda's). Also skip applications that have arguments with free type
631 -- variables, since we can't inline those.
632 argprop expr@(App _ _) | is_var fexpr = do
633 -- Find the body of the function called
634 body_maybe <- Trans.lift $ getGlobalBind f
637 -- Process each of the arguments in turn
638 (args', changed) <- Writer.listen $ mapM doarg args
639 -- See if any of the arguments changed
640 case Monoid.getAny changed of
642 let (newargs', newparams', oldargs) = unzip3 args'
643 let newargs = concat newargs'
644 let newparams = concat newparams'
645 -- Create a new body that consists of a lambda for all new arguments and
646 -- the old body applied to some arguments.
647 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
648 -- Create a new function with the same name but a new body
649 newf <- Trans.lift $ mkFunction f newbody
651 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
652 let init_state_maybe = Map.lookup f ismap in
653 case init_state_maybe of
655 Just init_state -> Map.insert newf init_state ismap)
656 -- Replace the original application with one of the new function to the
658 change $ MkCore.mkCoreApps (Var newf) newargs
660 -- Don't change the expression if none of the arguments changed
663 -- If we don't have a body for the function called, leave it unchanged (it
664 -- should be a primitive function then).
665 Nothing -> return expr
667 -- Find the function called and the arguments
668 (fexpr, args) = collectArgs expr
671 -- Process a single argument and return (args, bndrs, arg), where args are
672 -- the arguments to replace the given argument in the original
673 -- application, bndrs are the binders to include in the top-level lambda
674 -- in the new function body, and arg is the argument to apply to the old
676 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
679 bndrs <- Trans.lift getGlobalBinders
680 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
681 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
683 -- Propagate all complex arguments that are not representable, but not
684 -- arguments with free type variables (since those would require types
685 -- not known yet, which will always be known eventually).
686 -- Find interesting free variables, each of which should be passed to
687 -- the new function instead of the original function argument.
689 -- Interesting vars are those that are local, but not available from the
690 -- top level scope (functions from this module are defined as local, but
691 -- they're not local to this function, so we can freely move references
692 -- to them into another function).
693 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
694 -- Mark the current expression as changed
696 -- TODO: Clone the free_vars (and update references in arg), since
697 -- this might cause conflicts if two arguments that are propagated
698 -- share a free variable. Also, we are now introducing new variables
699 -- into a function that are not fresh, which violates the binder
700 -- uniqueness invariant.
701 return (map Var free_vars, free_vars, arg)
703 -- Representable types will not be propagated, and arguments with free
704 -- type variables will be propagated later.
705 -- Note that we implicitly remove any type variables in the type of
706 -- the original argument by using the type of the actual argument
707 -- for the new formal parameter.
708 -- TODO: preserve original naming?
709 id <- Trans.lift $ mkBinderFor arg "param"
710 -- Just pass the original argument to the new function, which binds it
711 -- to a new id and just pass that new id to the old function body.
712 return ([arg], [id], mkReferenceTo id)
713 -- Leave all other expressions unchanged
714 argprop expr = return expr
715 -- Perform this transform everywhere
716 argproptop = everywhere ("argprop", argprop)
718 --------------------------------
719 -- Function-typed argument extraction
720 --------------------------------
721 -- This transform takes any function-typed argument that cannot be propagated
722 -- (because the function that is applied to it is a builtin function), and
723 -- puts it in a brand new top level binder. This allows us to for example
724 -- apply map to a lambda expression This will not conflict with inlinenonrep,
725 -- since that only inlines local let bindings, not top level bindings.
726 funextract, funextracttop :: Transform
727 funextract expr@(App _ _) | is_var fexpr = do
728 body_maybe <- Trans.lift $ getGlobalBind f
730 -- We don't have a function body for f, so we can perform this transform.
732 -- Find the new arguments
733 args' <- mapM doarg args
734 -- And update the arguments. We use return instead of changed, so the
735 -- changed flag doesn't get set if none of the args got changed.
736 return $ MkCore.mkCoreApps fexpr args'
737 -- We have a function body for f, leave this application to funprop
738 Just _ -> return expr
740 -- Find the function called and the arguments
741 (fexpr, args) = collectArgs expr
743 -- Change any arguments that have a function type, but are not simple yet
744 -- (ie, a variable or application). This means to create a new function
745 -- for map (\f -> ...) b, but not for map (foo a) b.
747 -- We could use is_applicable here instead of is_fun, but I think
748 -- arguments to functions could only have forall typing when existential
749 -- typing is enabled. Not sure, though.
750 doarg arg | not (is_simple arg) && is_fun arg = do
751 -- Create a new top level binding that binds the argument. Its body will
752 -- be extended with lambda expressions, to take any free variables used
753 -- by the argument expression.
754 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
755 let body = MkCore.mkCoreLams free_vars arg
756 id <- Trans.lift $ mkBinderFor body "fun"
757 Trans.lift $ addGlobalBind id body
758 -- Replace the argument with a reference to the new function, applied to
760 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
761 -- Leave all other arguments untouched
762 doarg arg = return arg
764 -- Leave all other expressions unchanged
765 funextract expr = return expr
766 -- Perform this transform everywhere
767 funextracttop = everywhere ("funextract", funextract)
769 --------------------------------
770 -- Ensure that a function that just returns another function (or rather,
771 -- another top-level binder) is still properly normalized. This is a temporary
772 -- solution, we should probably integrate this pass with lambdasimpl and
774 --------------------------------
775 simplrestop expr@(Lam _ _) = return expr
776 simplrestop expr@(Let _ _) = return expr
777 simplrestop expr = do
778 local_var <- Trans.lift $ is_local_var expr
779 -- Don't extract values that are not representable, to prevent loops with
782 if local_var || not repr
786 id <- Trans.lift $ mkBinderFor expr "res"
787 change $ Let (NonRec id expr) (Var id)
788 --------------------------------
789 -- End of transformations
790 --------------------------------
795 -- What transforms to run?
796 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
798 -- | Returns the normalized version of the given function, or an error
799 -- if it is not a known global binder.
801 CoreBndr -- ^ The function to get
802 -> TranslatorSession CoreExpr -- The normalized function body
803 getNormalized bndr = do
804 norm <- getNormalized_maybe bndr
805 return $ Maybe.fromMaybe
806 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
809 -- | Returns the normalized version of the given function, or Nothing
810 -- when the binder is not a known global binder or is not normalizeable.
811 getNormalized_maybe ::
812 CoreBndr -- ^ The function to get
813 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
815 getNormalized_maybe bndr = do
816 expr_maybe <- getGlobalBind bndr
817 normalizeable <- isNormalizeable' bndr
818 if not normalizeable || Maybe.isNothing expr_maybe
820 -- Binder not normalizeable or not found
822 else if is_poly (Var bndr)
824 -- This should really only happen at the top level... TODO: Give
825 -- a different error if this happens down in the recursion.
826 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
828 -- Binder found and is monomorphic. Normalize the expression
829 -- and cache the result.
830 normalized <- Utils.makeCached bndr tsNormalized $
831 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
832 return (Just normalized)
834 -- | Normalize an expression
836 String -- ^ What are we normalizing? For debug output only.
837 -> CoreSyn.CoreExpr -- ^ The expression to normalize
838 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
840 normalizeExpr what expr = do
841 expr_uniqued <- genUniques expr
842 -- Normalize this expression
843 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
844 expr' <- dotransforms transforms expr_uniqued
845 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
848 -- | Split a normalized expression into the argument binders, top level
849 -- bindings and the result binder.
851 CoreExpr -- ^ The normalized expression
852 -> ([CoreBndr], [Binding], CoreBndr)
853 splitNormalized expr = (args, binds, res)
855 (args, letexpr) = CoreSyn.collectBinders expr
856 (binds, resexpr) = flattenLets letexpr
857 res = case resexpr of
859 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"