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 (dictdc, (ty':selectors)) | tyargs_neq ty ty' -> error $ "Applying class selector to dictionary without matching type?\n" ++ pprString expr
421 let selector_ids = Class.classSelIds cls in
422 -- Find the selector used in the class' list of selectors
423 case List.elemIndex sel selector_ids of
424 Nothing -> error $ "Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
425 -- Get the corresponding argument from the dictionary
426 Just n -> change (selectors!!n)
428 -- Compare two type arguments, returning True if they are _not_
430 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
431 tyargs_neq _ _ = True
433 -- Leave all other expressions unchanged
434 classopresolution expr = return expr
435 -- Perform this transform everywhere
436 classopresolutiontop = everywhere ("classopresolution", classopresolution)
438 --------------------------------
439 -- Scrutinee simplification
440 --------------------------------
441 scrutsimpl,scrutsimpltop :: Transform
442 -- Don't touch scrutinees that are already simple
443 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
444 -- Replace all other cases with a let that binds the scrutinee and a new
445 -- simple scrutinee, but only when the scrutinee is representable (to prevent
446 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
447 -- will be supported anyway...)
448 scrutsimpl expr@(Case scrut b ty alts) = do
452 id <- Trans.lift $ mkBinderFor scrut "scrut"
453 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
456 -- Leave all other expressions unchanged
457 scrutsimpl expr = return expr
458 -- Perform this transform everywhere
459 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
461 --------------------------------
462 -- Scrutinee binder removal
463 --------------------------------
464 -- A case expression can have an extra binder, to which the scrutinee is bound
465 -- after bringing it to WHNF. This is used for forcing evaluation of strict
466 -- arguments. Since strictness does not matter for us (rather, everything is
467 -- sort of strict), this binder is ignored when generating VHDL, and must thus
468 -- be wild in the normal form.
469 scrutbndrremove, scrutbndrremovetop :: Transform
470 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
471 -- all occurences of the binder with the scrutinee variable.
472 scrutbndrremove (Case (Var scrut) bndr ty alts) | bndr_used = do
473 alts' <- mapM subs_bndr alts
474 change $ Case (Var scrut) wild ty alts'
476 is_used (_, _, expr) = expr_uses_binders [bndr] expr
477 bndr_used = or $ map is_used alts
478 subs_bndr (con, bndrs, expr) = do
479 expr' <- substitute bndr (Var scrut) expr
480 return (con, bndrs, expr')
481 wild = MkCore.mkWildBinder (Id.idType bndr)
482 -- Leave all other expressions unchanged
483 scrutbndrremove expr = return expr
484 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
486 --------------------------------
487 -- Case binder wildening
488 --------------------------------
489 casesimpl, casesimpltop :: Transform
490 -- This is already a selector case (or, if x does not appear in bndrs, a very
491 -- simple case statement that will be removed by caseremove below). Just leave
493 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
494 -- Make sure that all case alternatives have only wild binders and simple
496 -- This is done by creating a new let binding for each non-wild binder, which
497 -- is bound to a new simple selector case statement and for each complex
498 -- expression. We do this only for representable types, to prevent loops with
500 casesimpl expr@(Case scrut b ty alts) = do
501 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
502 let bindings = concat bindingss
503 -- Replace the case with a let with bindings and a case
504 let newlet = mkNonRecLets bindings (Case scrut b ty alts')
505 -- If there are no non-wild binders, or this case is already a simple
506 -- selector (i.e., a single alt with exactly one binding), already a simple
507 -- selector altan no bindings (i.e., no wild binders in the original case),
508 -- don't change anything, otherwise, replace the case.
509 if null bindings then return expr else change newlet
511 -- Generate a single wild binder, since they are all the same
512 wild = MkCore.mkWildBinder
513 -- Wilden the binders of one alt, producing a list of bindings as a
515 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
516 doalt (con, bndrs, expr) = do
517 -- Make each binder wild, if possible
518 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
519 let (newbndrs, bindings_maybe) = unzip bndrs_res
520 -- Extract a complex expression, if possible. For this we check if any of
521 -- the new list of bndrs are used by expr. We can't use free_vars here,
522 -- since that looks at the old bndrs.
523 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
524 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
525 -- Create a new alternative
526 let newalt = (con, newbndrs, expr')
527 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
528 return (bindings, newalt)
530 -- Make wild alternatives for each binder
531 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
532 -- A set of all the binders that are used by the expression
533 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
534 -- Look at the ith binder in the case alternative. Return a new binder
535 -- for it (either the same one, or a wild one) and optionally a let
536 -- binding containing a case expression.
537 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
540 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
541 -- in expr, this means that b is unused if expr does not use it.)
542 let wild = not (VarSet.elemVarSet b free_vars)
543 -- Create a new binding for any representable binder that is not
544 -- already wild and is representable (to prevent loops with
546 if (not wild) && repr
548 -- Create on new binder that will actually capture a value in this
549 -- case statement, and return it.
550 let bty = (Id.idType b)
551 id <- Trans.lift $ mkInternalVar "sel" bty
552 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
553 let caseexpr = Case scrut b bty [(con, binders, Var id)]
554 return (wildbndrs!!i, Just (b, caseexpr))
556 -- Just leave the original binder in place, and don't generate an
557 -- extra selector case.
559 -- Process the expression of a case alternative. Accepts an expression
560 -- and whether this expression uses any of the binders in the
561 -- alternative. Returns an optional new binding and a new expression.
562 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
563 doexpr expr uses_bndrs = do
564 local_var <- Trans.lift $ is_local_var expr
566 -- Extract any expressions that do not use any binders from this
567 -- alternative, is not a local var already and is representable (to
568 -- prevent loops with inlinenonrep).
569 if (not uses_bndrs) && (not local_var) && repr
571 id <- Trans.lift $ mkBinderFor expr "caseval"
572 -- We don't flag a change here, since casevalsimpl will do that above
573 -- based on Just we return here.
574 return (Just (id, expr), Var id)
576 -- Don't simplify anything else
577 return (Nothing, expr)
578 -- Leave all other expressions unchanged
579 casesimpl expr = return expr
580 -- Perform this transform everywhere
581 casesimpltop = everywhere ("casesimpl", casesimpl)
583 --------------------------------
585 --------------------------------
586 -- Remove case statements that have only a single alternative and only wild
588 caseremove, caseremovetop :: Transform
589 -- Replace a useless case by the value of its single alternative
590 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
591 -- Find if any of the binders are used by expr
592 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
593 -- Leave all other expressions unchanged
594 caseremove expr = return expr
595 -- Perform this transform everywhere
596 caseremovetop = everywhere ("caseremove", caseremove)
598 --------------------------------
599 -- Argument extraction
600 --------------------------------
601 -- Make sure that all arguments of a representable type are simple variables.
602 appsimpl, appsimpltop :: Transform
603 -- Simplify all representable arguments. Do this by introducing a new Let
604 -- that binds the argument and passing the new binder in the application.
605 appsimpl expr@(App f arg) = do
606 -- Check runtime representability
608 local_var <- Trans.lift $ is_local_var arg
609 if repr && not local_var
610 then do -- Extract representable arguments
611 id <- Trans.lift $ mkBinderFor arg "arg"
612 change $ Let (NonRec id arg) (App f (Var id))
613 else -- Leave non-representable arguments unchanged
615 -- Leave all other expressions unchanged
616 appsimpl expr = return expr
617 -- Perform this transform everywhere
618 appsimpltop = everywhere ("appsimpl", appsimpl)
620 --------------------------------
621 -- Function-typed argument propagation
622 --------------------------------
623 -- Remove all applications to function-typed arguments, by duplication the
624 -- function called with the function-typed parameter replaced by the free
625 -- variables of the argument passed in.
626 argprop, argproptop :: Transform
627 -- Transform any application of a named function (i.e., skip applications of
628 -- lambda's). Also skip applications that have arguments with free type
629 -- variables, since we can't inline those.
630 argprop expr@(App _ _) | is_var fexpr = do
631 -- Find the body of the function called
632 body_maybe <- Trans.lift $ getGlobalBind f
635 -- Process each of the arguments in turn
636 (args', changed) <- Writer.listen $ mapM doarg args
637 -- See if any of the arguments changed
638 case Monoid.getAny changed of
640 let (newargs', newparams', oldargs) = unzip3 args'
641 let newargs = concat newargs'
642 let newparams = concat newparams'
643 -- Create a new body that consists of a lambda for all new arguments and
644 -- the old body applied to some arguments.
645 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
646 -- Create a new function with the same name but a new body
647 newf <- Trans.lift $ mkFunction f newbody
649 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
650 let init_state_maybe = Map.lookup f ismap in
651 case init_state_maybe of
653 Just init_state -> Map.insert newf init_state ismap)
654 -- Replace the original application with one of the new function to the
656 change $ MkCore.mkCoreApps (Var newf) newargs
658 -- Don't change the expression if none of the arguments changed
661 -- If we don't have a body for the function called, leave it unchanged (it
662 -- should be a primitive function then).
663 Nothing -> return expr
665 -- Find the function called and the arguments
666 (fexpr, args) = collectArgs expr
669 -- Process a single argument and return (args, bndrs, arg), where args are
670 -- the arguments to replace the given argument in the original
671 -- application, bndrs are the binders to include in the top-level lambda
672 -- in the new function body, and arg is the argument to apply to the old
674 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
677 bndrs <- Trans.lift getGlobalBinders
678 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
679 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
681 -- Propagate all complex arguments that are not representable, but not
682 -- arguments with free type variables (since those would require types
683 -- not known yet, which will always be known eventually).
684 -- Find interesting free variables, each of which should be passed to
685 -- the new function instead of the original function argument.
687 -- Interesting vars are those that are local, but not available from the
688 -- top level scope (functions from this module are defined as local, but
689 -- they're not local to this function, so we can freely move references
690 -- to them into another function).
691 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
692 -- Mark the current expression as changed
694 -- TODO: Clone the free_vars (and update references in arg), since
695 -- this might cause conflicts if two arguments that are propagated
696 -- share a free variable. Also, we are now introducing new variables
697 -- into a function that are not fresh, which violates the binder
698 -- uniqueness invariant.
699 return (map Var free_vars, free_vars, arg)
701 -- Representable types will not be propagated, and arguments with free
702 -- type variables will be propagated later.
703 -- Note that we implicitly remove any type variables in the type of
704 -- the original argument by using the type of the actual argument
705 -- for the new formal parameter.
706 -- TODO: preserve original naming?
707 id <- Trans.lift $ mkBinderFor arg "param"
708 -- Just pass the original argument to the new function, which binds it
709 -- to a new id and just pass that new id to the old function body.
710 return ([arg], [id], mkReferenceTo id)
711 -- Leave all other expressions unchanged
712 argprop expr = return expr
713 -- Perform this transform everywhere
714 argproptop = everywhere ("argprop", argprop)
716 --------------------------------
717 -- Function-typed argument extraction
718 --------------------------------
719 -- This transform takes any function-typed argument that cannot be propagated
720 -- (because the function that is applied to it is a builtin function), and
721 -- puts it in a brand new top level binder. This allows us to for example
722 -- apply map to a lambda expression This will not conflict with inlinenonrep,
723 -- since that only inlines local let bindings, not top level bindings.
724 funextract, funextracttop :: Transform
725 funextract expr@(App _ _) | is_var fexpr = do
726 body_maybe <- Trans.lift $ getGlobalBind f
728 -- We don't have a function body for f, so we can perform this transform.
730 -- Find the new arguments
731 args' <- mapM doarg args
732 -- And update the arguments. We use return instead of changed, so the
733 -- changed flag doesn't get set if none of the args got changed.
734 return $ MkCore.mkCoreApps fexpr args'
735 -- We have a function body for f, leave this application to funprop
736 Just _ -> return expr
738 -- Find the function called and the arguments
739 (fexpr, args) = collectArgs expr
741 -- Change any arguments that have a function type, but are not simple yet
742 -- (ie, a variable or application). This means to create a new function
743 -- for map (\f -> ...) b, but not for map (foo a) b.
745 -- We could use is_applicable here instead of is_fun, but I think
746 -- arguments to functions could only have forall typing when existential
747 -- typing is enabled. Not sure, though.
748 doarg arg | not (is_simple arg) && is_fun arg = do
749 -- Create a new top level binding that binds the argument. Its body will
750 -- be extended with lambda expressions, to take any free variables used
751 -- by the argument expression.
752 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
753 let body = MkCore.mkCoreLams free_vars arg
754 id <- Trans.lift $ mkBinderFor body "fun"
755 Trans.lift $ addGlobalBind id body
756 -- Replace the argument with a reference to the new function, applied to
758 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
759 -- Leave all other arguments untouched
760 doarg arg = return arg
762 -- Leave all other expressions unchanged
763 funextract expr = return expr
764 -- Perform this transform everywhere
765 funextracttop = everywhere ("funextract", funextract)
767 --------------------------------
768 -- Ensure that a function that just returns another function (or rather,
769 -- another top-level binder) is still properly normalized. This is a temporary
770 -- solution, we should probably integrate this pass with lambdasimpl and
772 --------------------------------
773 simplrestop expr@(Lam _ _) = return expr
774 simplrestop expr@(Let _ _) = return expr
775 simplrestop expr = do
776 local_var <- Trans.lift $ is_local_var expr
777 -- Don't extract values that are not representable, to prevent loops with
780 if local_var || not repr
784 id <- Trans.lift $ mkBinderFor expr "res"
785 change $ Let (NonRec id expr) (Var id)
786 --------------------------------
787 -- End of transformations
788 --------------------------------
793 -- What transforms to run?
794 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
796 -- | Returns the normalized version of the given function, or an error
797 -- if it is not a known global binder.
799 CoreBndr -- ^ The function to get
800 -> TranslatorSession CoreExpr -- The normalized function body
801 getNormalized bndr = do
802 norm <- getNormalized_maybe bndr
803 return $ Maybe.fromMaybe
804 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
807 -- | Returns the normalized version of the given function, or Nothing
808 -- when the binder is not a known global binder or is not normalizeable.
809 getNormalized_maybe ::
810 CoreBndr -- ^ The function to get
811 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
813 getNormalized_maybe bndr = do
814 expr_maybe <- getGlobalBind bndr
815 normalizeable <- isNormalizeable' bndr
816 if not normalizeable || Maybe.isNothing expr_maybe
818 -- Binder not normalizeable or not found
820 else if is_poly (Var bndr)
822 -- This should really only happen at the top level... TODO: Give
823 -- a different error if this happens down in the recursion.
824 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
826 -- Binder found and is monomorphic. Normalize the expression
827 -- and cache the result.
828 normalized <- Utils.makeCached bndr tsNormalized $
829 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
830 return (Just normalized)
832 -- | Normalize an expression
834 String -- ^ What are we normalizing? For debug output only.
835 -> CoreSyn.CoreExpr -- ^ The expression to normalize
836 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
838 normalizeExpr what expr = do
839 expr_uniqued <- genUniques expr
840 -- Normalize this expression
841 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
842 expr' <- dotransforms transforms expr_uniqued
843 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
846 -- | Split a normalized expression into the argument binders, top level
847 -- bindings and the result binder.
849 CoreExpr -- ^ The normalized expression
850 -> ([CoreBndr], [Binding], CoreBndr)
851 splitNormalized expr = (args, binds, res)
853 (args, letexpr) = CoreSyn.collectBinders expr
854 (binds, resexpr) = flattenLets letexpr
855 res = case resexpr of
857 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"