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 eta, etatop :: Transform
51 eta expr | is_fun expr && not (is_lam expr) = do
52 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
53 id <- Trans.lift $ mkInternalVar "param" arg_ty
54 change (Lam id (App expr (Var id)))
55 -- Leave all other expressions unchanged
57 etatop = notappargs ("eta", eta)
59 --------------------------------
61 --------------------------------
62 beta, betatop :: Transform
63 -- Substitute arg for x in expr. For value lambda's, also clone before
65 beta (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg expr
66 | otherwise = setChanged >> substitute_clone x arg expr
67 -- Propagate the application into the let
68 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
69 -- Propagate the application into each of the alternatives
70 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
72 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
73 ty' = CoreUtils.applyTypeToArg ty arg
74 -- Leave all other expressions unchanged
75 beta expr = return expr
76 -- Perform this transform everywhere
77 betatop = everywhere ("beta", beta)
79 --------------------------------
81 --------------------------------
82 -- Try to move casts as much downward as possible.
83 castprop, castproptop :: Transform
84 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
85 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
87 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
88 -- Leave all other expressions unchanged
89 castprop expr = return expr
90 -- Perform this transform everywhere
91 castproptop = everywhere ("castprop", castprop)
93 --------------------------------
94 -- Cast simplification. Mostly useful for state packing and unpacking, but
95 -- perhaps for others as well.
96 --------------------------------
97 castsimpl, castsimpltop :: Transform
98 castsimpl expr@(Cast val ty) = do
99 -- Don't extract values that are already simpl
100 local_var <- Trans.lift $ is_local_var val
101 -- Don't extract values that are not representable, to prevent loops with
104 if (not local_var) && repr
106 -- Generate a binder for the expression
107 id <- Trans.lift $ mkBinderFor val "castval"
108 -- Extract the expression
109 change $ Let (NonRec id val) (Cast (Var id) ty)
112 -- Leave all other expressions unchanged
113 castsimpl expr = return expr
114 -- Perform this transform everywhere
115 castsimpltop = everywhere ("castsimpl", castsimpl)
118 --------------------------------
119 -- Lambda simplication
120 --------------------------------
121 -- Ensure that a lambda always evaluates to a let expressions or a simple
122 -- variable reference.
123 lambdasimpl, lambdasimpltop :: Transform
124 -- Don't simplify a lambda that evaluates to let, since this is already
125 -- normal form (and would cause infinite loops).
126 lambdasimpl expr@(Lam _ (Let _ _)) = return expr
127 -- Put the of a lambda in its own binding, but not when the expression is
128 -- already a local variable, or not representable (to prevent loops with
130 lambdasimpl expr@(Lam bndr res) = do
132 local_var <- Trans.lift $ is_local_var res
133 if not local_var && repr
135 id <- Trans.lift $ mkBinderFor res "res"
136 change $ Lam bndr (Let (NonRec id res) (Var id))
138 -- If the result is already a local var or not representable, don't
142 -- Leave all other expressions unchanged
143 lambdasimpl expr = return expr
144 -- Perform this transform everywhere
145 lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
147 --------------------------------
148 -- let derecursification
149 --------------------------------
150 letderec, letderectop :: Transform
151 letderec expr@(Let (Rec binds) res) = case liftable of
152 -- Nothing is liftable, just return
154 -- Something can be lifted, generate a new let expression
155 _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
157 -- Make a list of all the binders bound in this recursive let
158 bndrs = map fst binds
159 -- See which bindings are liftable
160 (liftable, nonliftable) = List.partition canlift binds
161 -- Any expression that does not use any of the binders in this recursive let
162 -- can be lifted into a nonrec let. It can't use its own binder either,
163 -- since that would mean the binding is self-recursive and should be in a
164 -- single bind recursive let.
165 canlift (bndr, e) = not $ expr_uses_binders bndrs e
166 -- Leave all other expressions unchanged
167 letderec expr = return expr
168 -- Perform this transform everywhere
169 letderectop = everywhere ("letderec", letderec)
171 --------------------------------
172 -- let simplification
173 --------------------------------
174 letsimpl, letsimpltop :: Transform
175 -- Don't simplify a let that evaluates to another let, since this is already
176 -- normal form (and would cause infinite loops with letflat below).
177 letsimpl expr@(Let _ (Let _ _)) = return expr
178 -- Put the "in ..." value of a let in its own binding, but not when the
179 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
180 letsimpl expr@(Let binds res) = do
182 local_var <- Trans.lift $ is_local_var res
183 if not local_var && repr
185 -- If the result is not a local var already (to prevent loops with
186 -- ourselves), extract it.
187 id <- Trans.lift $ mkBinderFor res "foo"
188 change $ Let binds (Let (NonRec id res) (Var id))
190 -- If the result is already a local var, don't extract it.
193 -- Leave all other expressions unchanged
194 letsimpl expr = return expr
195 -- Perform this transform everywhere
196 letsimpltop = everywhere ("letsimpl", letsimpl)
198 --------------------------------
200 --------------------------------
201 -- Takes a let that binds another let, and turns that into two nested lets.
203 -- let b = (let b' = expr' in res') in res
205 -- let b' = expr' in (let b = res' in res)
206 letflat, letflattop :: Transform
207 -- Turn a nonrec let that binds a let into two nested lets.
208 letflat (Let (NonRec b (Let binds res')) res) =
209 change $ Let binds (Let (NonRec b res') res)
210 letflat (Let (Rec binds) expr) = do
211 -- Flatten each binding.
212 binds' <- Utils.concatM $ Monad.mapM flatbind binds
213 -- Return the new let. We don't use change here, since possibly nothing has
214 -- changed. If anything has changed, flatbind has already flagged that
216 return $ Let (Rec binds') expr
218 -- Turns a binding of a let into a multiple bindings, or any other binding
219 -- into a list with just that binding
220 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
221 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
222 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
223 flatbind (b, expr) = return [(b, expr)]
224 -- Leave all other expressions unchanged
225 letflat expr = return expr
226 -- Perform this transform everywhere
227 letflattop = everywhere ("letflat", letflat)
229 --------------------------------
231 --------------------------------
232 -- Remove empty (recursive) lets
233 letremove, letremovetop :: Transform
234 letremove (Let (Rec []) res) = change res
235 -- Leave all other expressions unchanged
236 letremove expr = return expr
237 -- Perform this transform everywhere
238 letremovetop = everywhere ("letremove", letremove)
240 --------------------------------
241 -- Simple let binding removal
242 --------------------------------
243 -- Remove a = b bindings from let expressions everywhere
244 letremovesimpletop :: Transform
245 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
247 --------------------------------
248 -- Unused let binding removal
249 --------------------------------
250 letremoveunused, letremoveunusedtop :: Transform
251 letremoveunused expr@(Let (NonRec b bound) res) = do
252 let used = expr_uses_binders [b] res
256 letremoveunused expr@(Let (Rec binds) res) = do
257 -- Filter out all unused binds.
258 let binds' = filter dobind binds
259 -- Only set the changed flag if binds got removed
260 changeif (length binds' /= length binds) (Let (Rec binds') res)
262 bound_exprs = map snd binds
263 -- For each bind check if the bind is used by res or any of the bound
265 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
266 -- Leave all other expressions unchanged
267 letremoveunused expr = return expr
268 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
271 --------------------------------
272 -- Identical let binding merging
273 --------------------------------
274 -- Merge two bindings in a let if they are identical
275 -- TODO: We would very much like to use GHC's CSE module for this, but that
276 -- doesn't track if something changed or not, so we can't use it properly.
277 letmerge, letmergetop :: Transform
278 letmerge expr@(Let _ _) = do
279 let (binds, res) = flattenLets expr
280 binds' <- domerge binds
281 return $ mkNonRecLets binds' res
283 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
284 domerge [] = return []
286 es' <- mapM (mergebinds e) es
290 -- Uses the second bind to simplify the second bind, if applicable.
291 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
292 mergebinds (b1, e1) (b2, e2)
293 -- Identical expressions? Replace the second binding with a reference to
295 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
296 -- Different expressions? Don't change
297 | otherwise = return (b2, e2)
298 -- Leave all other expressions unchanged
299 letmerge expr = return expr
300 letmergetop = everywhere ("letmerge", letmerge)
303 --------------------------------
304 -- Non-representable binding inlining
305 --------------------------------
306 -- Remove a = B bindings, with B of a non-representable type, from let
307 -- expressions everywhere. This means that any value that we can't generate a
308 -- signal for, will be inlined and hopefully turned into something we can
311 -- This is a tricky function, which is prone to create loops in the
312 -- transformations. To fix this, we make sure that no transformation will
313 -- create a new let binding with a non-representable type. These other
314 -- transformations will just not work on those function-typed values at first,
315 -- but the other transformations (in particular β-reduction) should make sure
316 -- that the type of those values eventually becomes representable.
317 inlinenonreptop :: Transform
318 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
320 --------------------------------
321 -- Top level function inlining
322 --------------------------------
323 -- This transformation inlines top level bindings that have been generated by
324 -- the compiler and are really simple. Really simple currently means that the
325 -- normalized form only contains a single binding, which catches most of the
326 -- cases where a top level function is created that simply calls a type class
327 -- method with a type and dictionary argument, e.g.
328 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
329 -- which is later called using simply
330 -- fromInteger (smallInteger 10)
331 -- By inlining such calls to simple, compiler generated functions, we prevent
332 -- huge amounts of trivial components in the VHDL output, which the user never
333 -- wanted. We never inline user-defined functions, since we want to preserve
334 -- all structure defined by the user. Currently this includes all functions
335 -- that were created by funextract, since we would get loops otherwise.
337 -- Note that "defined by the compiler" isn't completely watertight, since GHC
338 -- doesn't seem to set all those names as "system names", we apply some
340 inlinetoplevel, inlinetopleveltop :: Transform
341 -- Any system name is candidate for inlining. Never inline user-defined
342 -- functions, to preserve structure.
343 inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
344 norm_maybe <- Trans.lift $ getNormalized_maybe f
346 -- No body or not normalizeable.
347 Nothing -> return expr
348 Just norm -> if needsInline norm then do
349 -- Regenerate all uniques in the to-be-inlined expression
350 norm_uniqued <- Trans.lift $ genUniques norm
351 -- And replace the variable reference with the unique'd body.
357 -- Leave all other expressions unchanged
358 inlinetoplevel expr = return expr
359 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
361 needsInline :: CoreExpr -> Bool
362 needsInline expr = case splitNormalized expr of
363 -- Inline any function that only has a single definition, it is probably
364 -- simple enough. This might inline some stuff that it shouldn't though it
365 -- will never inline user-defined functions (inlinetoplevel only tries
366 -- system names) and inlining should never break things.
367 (args, [bind], res) -> True
371 --------------------------------
372 -- Dictionary inlining
373 --------------------------------
374 -- Inline all top level dictionaries, so we can use them to resolve
375 -- class methods based on the dictionary passed.
376 inlinedict expr@(Var f) | Id.isDictId f = do
377 body_maybe <- Trans.lift $ getGlobalBind f
379 Nothing -> return expr
380 Just body -> change body
382 -- Leave all other expressions unchanged
383 inlinedict expr = return expr
384 inlinedicttop = everywhere ("inlinedict", inlinedict)
386 --------------------------------
387 -- ClassOp resolution
388 --------------------------------
389 -- Resolves any class operation to the actual operation whenever
390 -- possible. Class methods (as well as parent dictionary selectors) are
391 -- special "functions" that take a type and a dictionary and evaluate to
392 -- the corresponding method. A dictionary is nothing more than a
393 -- special dataconstructor applied to the type the dictionary is for,
394 -- each of the superclasses and all of the class method definitions for
395 -- that particular type. Since dictionaries all always inlined (top
396 -- levels dictionaries are inlined by inlinedict, local dictionaries are
397 -- inlined by inlinenonrep), we will eventually have something like:
400 -- @ CLasH.HardwareTypes.Bit
401 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
403 -- Here, baz is the method selector for the baz method, while
404 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
405 -- method defined in the Baz Bit instance declaration.
407 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
408 -- which contains the Class it is defined for. From the Class, we can
409 -- get a list of all selectors (both parent class selectors as well as
410 -- method selectors). Since the arguments to D:Baz (after the type
411 -- argument) correspond exactly to this list, we then look up baz in
412 -- that list and replace the entire expression by the corresponding
413 -- argument to D:Baz.
415 -- We don't resolve methods that have a builtin translation (such as
416 -- ==), since the actual implementation is not always (easily)
417 -- translateable. For example, when deriving ==, GHC generates code
418 -- using $con2tag functions to translate a datacon to an int and compare
419 -- that with GHC.Prim.==# . Better to avoid that for now.
420 classopresolution, classopresolutiontop :: Transform
421 classopresolution expr@(App (App (Var sel) ty) dict) | not is_builtin =
422 case Id.isClassOpId_maybe sel of
423 -- Not a class op selector
424 Nothing -> return expr
425 Just cls -> case collectArgs dict of
426 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
427 (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)
428 | tyargs_neq ty ty' -> error $ "Applying class selector to dictionary without matching type?\n" ++ pprString expr
430 let selector_ids = Class.classSelIds cls in
431 -- Find the selector used in the class' list of selectors
432 case List.elemIndex sel selector_ids of
433 Nothing -> error $ "Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
434 -- Get the corresponding argument from the dictionary
435 Just n -> change (selectors!!n)
436 (_, _) -> return expr -- Not applying a variable? Don't touch
438 -- Compare two type arguments, returning True if they are _not_
440 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
441 tyargs_neq _ _ = True
442 -- Is this a builtin function / method?
443 is_builtin = elem (Name.getOccString sel) builtinIds
445 -- Leave all other expressions unchanged
446 classopresolution expr = return expr
447 -- Perform this transform everywhere
448 classopresolutiontop = everywhere ("classopresolution", classopresolution)
450 --------------------------------
451 -- Scrutinee simplification
452 --------------------------------
453 scrutsimpl,scrutsimpltop :: Transform
454 -- Don't touch scrutinees that are already simple
455 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
456 -- Replace all other cases with a let that binds the scrutinee and a new
457 -- simple scrutinee, but only when the scrutinee is representable (to prevent
458 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
459 -- will be supported anyway...)
460 scrutsimpl expr@(Case scrut b ty alts) = do
464 id <- Trans.lift $ mkBinderFor scrut "scrut"
465 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
468 -- Leave all other expressions unchanged
469 scrutsimpl expr = return expr
470 -- Perform this transform everywhere
471 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
473 --------------------------------
474 -- Scrutinee binder removal
475 --------------------------------
476 -- A case expression can have an extra binder, to which the scrutinee is bound
477 -- after bringing it to WHNF. This is used for forcing evaluation of strict
478 -- arguments. Since strictness does not matter for us (rather, everything is
479 -- sort of strict), this binder is ignored when generating VHDL, and must thus
480 -- be wild in the normal form.
481 scrutbndrremove, scrutbndrremovetop :: Transform
482 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
483 -- all occurences of the binder with the scrutinee variable.
484 scrutbndrremove (Case (Var scrut) bndr ty alts) | bndr_used = do
485 alts' <- mapM subs_bndr alts
486 change $ Case (Var scrut) wild ty alts'
488 is_used (_, _, expr) = expr_uses_binders [bndr] expr
489 bndr_used = or $ map is_used alts
490 subs_bndr (con, bndrs, expr) = do
491 expr' <- substitute bndr (Var scrut) expr
492 return (con, bndrs, expr')
493 wild = MkCore.mkWildBinder (Id.idType bndr)
494 -- Leave all other expressions unchanged
495 scrutbndrremove expr = return expr
496 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
498 --------------------------------
499 -- Case binder wildening
500 --------------------------------
501 casesimpl, casesimpltop :: Transform
502 -- This is already a selector case (or, if x does not appear in bndrs, a very
503 -- simple case statement that will be removed by caseremove below). Just leave
505 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
506 -- Make sure that all case alternatives have only wild binders and simple
508 -- This is done by creating a new let binding for each non-wild binder, which
509 -- is bound to a new simple selector case statement and for each complex
510 -- expression. We do this only for representable types, to prevent loops with
512 casesimpl expr@(Case scrut bndr ty alts) | not bndr_used = do
513 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
514 let bindings = concat bindingss
515 -- Replace the case with a let with bindings and a case
516 let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
517 -- If there are no non-wild binders, or this case is already a simple
518 -- selector (i.e., a single alt with exactly one binding), already a simple
519 -- selector altan no bindings (i.e., no wild binders in the original case),
520 -- don't change anything, otherwise, replace the case.
521 if null bindings then return expr else change newlet
523 -- Check if the scrutinee binder is used
524 is_used (_, _, expr) = expr_uses_binders [bndr] expr
525 bndr_used = or $ map is_used alts
526 -- Generate a single wild binder, since they are all the same
527 wild = MkCore.mkWildBinder
528 -- Wilden the binders of one alt, producing a list of bindings as a
530 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
531 doalt (con, bndrs, expr) = do
532 -- Make each binder wild, if possible
533 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
534 let (newbndrs, bindings_maybe) = unzip bndrs_res
535 -- Extract a complex expression, if possible. For this we check if any of
536 -- the new list of bndrs are used by expr. We can't use free_vars here,
537 -- since that looks at the old bndrs.
538 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
539 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
540 -- Create a new alternative
541 let newalt = (con, newbndrs, expr')
542 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
543 return (bindings, newalt)
545 -- Make wild alternatives for each binder
546 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
547 -- A set of all the binders that are used by the expression
548 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
549 -- Look at the ith binder in the case alternative. Return a new binder
550 -- for it (either the same one, or a wild one) and optionally a let
551 -- binding containing a case expression.
552 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
555 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
556 -- in expr, this means that b is unused if expr does not use it.)
557 let wild = not (VarSet.elemVarSet b free_vars)
558 -- Create a new binding for any representable binder that is not
559 -- already wild and is representable (to prevent loops with
561 if (not wild) && repr
563 -- Create on new binder that will actually capture a value in this
564 -- case statement, and return it.
565 let bty = (Id.idType b)
566 id <- Trans.lift $ mkInternalVar "sel" bty
567 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
568 let caseexpr = Case scrut b bty [(con, binders, Var id)]
569 return (wildbndrs!!i, Just (b, caseexpr))
571 -- Just leave the original binder in place, and don't generate an
572 -- extra selector case.
574 -- Process the expression of a case alternative. Accepts an expression
575 -- and whether this expression uses any of the binders in the
576 -- alternative. Returns an optional new binding and a new expression.
577 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
578 doexpr expr uses_bndrs = do
579 local_var <- Trans.lift $ is_local_var expr
581 -- Extract any expressions that do not use any binders from this
582 -- alternative, is not a local var already and is representable (to
583 -- prevent loops with inlinenonrep).
584 if (not uses_bndrs) && (not local_var) && repr
586 id <- Trans.lift $ mkBinderFor expr "caseval"
587 -- We don't flag a change here, since casevalsimpl will do that above
588 -- based on Just we return here.
589 return (Just (id, expr), Var id)
591 -- Don't simplify anything else
592 return (Nothing, expr)
593 -- Leave all other expressions unchanged
594 casesimpl expr = return expr
595 -- Perform this transform everywhere
596 casesimpltop = everywhere ("casesimpl", casesimpl)
598 --------------------------------
600 --------------------------------
601 -- Remove case statements that have only a single alternative and only wild
603 caseremove, caseremovetop :: Transform
604 -- Replace a useless case by the value of its single alternative
605 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
606 -- Find if any of the binders are used by expr
607 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
608 -- Leave all other expressions unchanged
609 caseremove expr = return expr
610 -- Perform this transform everywhere
611 caseremovetop = everywhere ("caseremove", caseremove)
613 --------------------------------
614 -- Argument extraction
615 --------------------------------
616 -- Make sure that all arguments of a representable type are simple variables.
617 appsimpl, appsimpltop :: Transform
618 -- Simplify all representable arguments. Do this by introducing a new Let
619 -- that binds the argument and passing the new binder in the application.
620 appsimpl expr@(App f arg) = do
621 -- Check runtime representability
623 local_var <- Trans.lift $ is_local_var arg
624 if repr && not local_var
625 then do -- Extract representable arguments
626 id <- Trans.lift $ mkBinderFor arg "arg"
627 change $ Let (NonRec id arg) (App f (Var id))
628 else -- Leave non-representable arguments unchanged
630 -- Leave all other expressions unchanged
631 appsimpl expr = return expr
632 -- Perform this transform everywhere
633 appsimpltop = everywhere ("appsimpl", appsimpl)
635 --------------------------------
636 -- Function-typed argument propagation
637 --------------------------------
638 -- Remove all applications to function-typed arguments, by duplication the
639 -- function called with the function-typed parameter replaced by the free
640 -- variables of the argument passed in.
641 argprop, argproptop :: Transform
642 -- Transform any application of a named function (i.e., skip applications of
643 -- lambda's). Also skip applications that have arguments with free type
644 -- variables, since we can't inline those.
645 argprop expr@(App _ _) | is_var fexpr = do
646 -- Find the body of the function called
647 body_maybe <- Trans.lift $ getGlobalBind f
650 -- Process each of the arguments in turn
651 (args', changed) <- Writer.listen $ mapM doarg args
652 -- See if any of the arguments changed
653 case Monoid.getAny changed of
655 let (newargs', newparams', oldargs) = unzip3 args'
656 let newargs = concat newargs'
657 let newparams = concat newparams'
658 -- Create a new body that consists of a lambda for all new arguments and
659 -- the old body applied to some arguments.
660 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
661 -- Create a new function with the same name but a new body
662 newf <- Trans.lift $ mkFunction f newbody
664 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
665 let init_state_maybe = Map.lookup f ismap in
666 case init_state_maybe of
668 Just init_state -> Map.insert newf init_state ismap)
669 -- Replace the original application with one of the new function to the
671 change $ MkCore.mkCoreApps (Var newf) newargs
673 -- Don't change the expression if none of the arguments changed
676 -- If we don't have a body for the function called, leave it unchanged (it
677 -- should be a primitive function then).
678 Nothing -> return expr
680 -- Find the function called and the arguments
681 (fexpr, args) = collectArgs expr
684 -- Process a single argument and return (args, bndrs, arg), where args are
685 -- the arguments to replace the given argument in the original
686 -- application, bndrs are the binders to include in the top-level lambda
687 -- in the new function body, and arg is the argument to apply to the old
689 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
692 bndrs <- Trans.lift getGlobalBinders
693 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
694 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
696 -- Propagate all complex arguments that are not representable, but not
697 -- arguments with free type variables (since those would require types
698 -- not known yet, which will always be known eventually).
699 -- Find interesting free variables, each of which should be passed to
700 -- the new function instead of the original function argument.
702 -- Interesting vars are those that are local, but not available from the
703 -- top level scope (functions from this module are defined as local, but
704 -- they're not local to this function, so we can freely move references
705 -- to them into another function).
706 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
707 -- Mark the current expression as changed
709 -- TODO: Clone the free_vars (and update references in arg), since
710 -- this might cause conflicts if two arguments that are propagated
711 -- share a free variable. Also, we are now introducing new variables
712 -- into a function that are not fresh, which violates the binder
713 -- uniqueness invariant.
714 return (map Var free_vars, free_vars, arg)
716 -- Representable types will not be propagated, and arguments with free
717 -- type variables will be propagated later.
718 -- Note that we implicitly remove any type variables in the type of
719 -- the original argument by using the type of the actual argument
720 -- for the new formal parameter.
721 -- TODO: preserve original naming?
722 id <- Trans.lift $ mkBinderFor arg "param"
723 -- Just pass the original argument to the new function, which binds it
724 -- to a new id and just pass that new id to the old function body.
725 return ([arg], [id], mkReferenceTo id)
726 -- Leave all other expressions unchanged
727 argprop expr = return expr
728 -- Perform this transform everywhere
729 argproptop = everywhere ("argprop", argprop)
731 --------------------------------
732 -- Function-typed argument extraction
733 --------------------------------
734 -- This transform takes any function-typed argument that cannot be propagated
735 -- (because the function that is applied to it is a builtin function), and
736 -- puts it in a brand new top level binder. This allows us to for example
737 -- apply map to a lambda expression This will not conflict with inlinenonrep,
738 -- since that only inlines local let bindings, not top level bindings.
739 funextract, funextracttop :: Transform
740 funextract expr@(App _ _) | is_var fexpr = do
741 body_maybe <- Trans.lift $ getGlobalBind f
743 -- We don't have a function body for f, so we can perform this transform.
745 -- Find the new arguments
746 args' <- mapM doarg args
747 -- And update the arguments. We use return instead of changed, so the
748 -- changed flag doesn't get set if none of the args got changed.
749 return $ MkCore.mkCoreApps fexpr args'
750 -- We have a function body for f, leave this application to funprop
751 Just _ -> return expr
753 -- Find the function called and the arguments
754 (fexpr, args) = collectArgs expr
756 -- Change any arguments that have a function type, but are not simple yet
757 -- (ie, a variable or application). This means to create a new function
758 -- for map (\f -> ...) b, but not for map (foo a) b.
760 -- We could use is_applicable here instead of is_fun, but I think
761 -- arguments to functions could only have forall typing when existential
762 -- typing is enabled. Not sure, though.
763 doarg arg | not (is_simple arg) && is_fun arg = do
764 -- Create a new top level binding that binds the argument. Its body will
765 -- be extended with lambda expressions, to take any free variables used
766 -- by the argument expression.
767 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
768 let body = MkCore.mkCoreLams free_vars arg
769 id <- Trans.lift $ mkBinderFor body "fun"
770 Trans.lift $ addGlobalBind id body
771 -- Replace the argument with a reference to the new function, applied to
773 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
774 -- Leave all other arguments untouched
775 doarg arg = return arg
777 -- Leave all other expressions unchanged
778 funextract expr = return expr
779 -- Perform this transform everywhere
780 funextracttop = everywhere ("funextract", funextract)
782 --------------------------------
783 -- Ensure that a function that just returns another function (or rather,
784 -- another top-level binder) is still properly normalized. This is a temporary
785 -- solution, we should probably integrate this pass with lambdasimpl and
787 --------------------------------
788 simplrestop expr@(Lam _ _) = return expr
789 simplrestop expr@(Let _ _) = return expr
790 simplrestop expr = do
791 local_var <- Trans.lift $ is_local_var expr
792 -- Don't extract values that are not representable, to prevent loops with
795 if local_var || not repr
799 id <- Trans.lift $ mkBinderFor expr "res"
800 change $ Let (NonRec id expr) (Var id)
801 --------------------------------
802 -- End of transformations
803 --------------------------------
808 -- What transforms to run?
809 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
811 -- | Returns the normalized version of the given function, or an error
812 -- if it is not a known global binder.
814 CoreBndr -- ^ The function to get
815 -> TranslatorSession CoreExpr -- The normalized function body
816 getNormalized bndr = do
817 norm <- getNormalized_maybe bndr
818 return $ Maybe.fromMaybe
819 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
822 -- | Returns the normalized version of the given function, or Nothing
823 -- when the binder is not a known global binder or is not normalizeable.
824 getNormalized_maybe ::
825 CoreBndr -- ^ The function to get
826 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
828 getNormalized_maybe bndr = do
829 expr_maybe <- getGlobalBind bndr
830 normalizeable <- isNormalizeable' bndr
831 if not normalizeable || Maybe.isNothing expr_maybe
833 -- Binder not normalizeable or not found
835 else if is_poly (Var bndr)
837 -- This should really only happen at the top level... TODO: Give
838 -- a different error if this happens down in the recursion.
839 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
841 -- Binder found and is monomorphic. Normalize the expression
842 -- and cache the result.
843 normalized <- Utils.makeCached bndr tsNormalized $
844 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
845 return (Just normalized)
847 -- | Normalize an expression
849 String -- ^ What are we normalizing? For debug output only.
850 -> CoreSyn.CoreExpr -- ^ The expression to normalize
851 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
853 normalizeExpr what expr = do
854 expr_uniqued <- genUniques expr
855 -- Normalize this expression
856 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
857 expr' <- dotransforms transforms expr_uniqued
858 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
861 -- | Split a normalized expression into the argument binders, top level
862 -- bindings and the result binder.
864 CoreExpr -- ^ The normalized expression
865 -> ([CoreBndr], [Binding], CoreBndr)
866 splitNormalized expr = (args, binds, res)
868 (args, letexpr) = CoreSyn.collectBinders expr
869 (binds, resexpr) = flattenLets letexpr
870 res = case resexpr of
872 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"