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 -- Don't apply to expressions that are applied, since that would cause
52 -- us to apply to our own result indefinitely.
53 eta (AppFirst:_) expr = return expr
54 -- Also don't apply to arguments, since this can cause loops with
55 -- funextract. This isn't the proper solution, but due to an
56 -- implementation bug in notappargs, this is how it used to work so far.
57 eta (AppSecond:_) expr = return expr
58 eta c expr | is_fun expr && not (is_lam expr) = do
59 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
60 id <- Trans.lift $ mkInternalVar "param" arg_ty
61 change (Lam id (App expr (Var id)))
62 -- Leave all other expressions unchanged
64 etatop = everywhere ("eta", eta)
66 --------------------------------
68 --------------------------------
69 beta, betatop :: Transform
70 -- Substitute arg for x in expr. For value lambda's, also clone before
72 beta c (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg c expr
73 | otherwise = setChanged >> substitute_clone x arg c expr
74 -- Propagate the application into the let
75 beta c (App (Let binds expr) arg) = change $ Let binds (App expr arg)
76 -- Propagate the application into each of the alternatives
77 beta c (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
79 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
80 ty' = CoreUtils.applyTypeToArg ty arg
81 -- Leave all other expressions unchanged
82 beta c expr = return expr
83 -- Perform this transform everywhere
84 betatop = everywhere ("beta", beta)
86 --------------------------------
88 --------------------------------
89 -- Try to move casts as much downward as possible.
90 castprop, castproptop :: Transform
91 castprop c (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
92 castprop c expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
94 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
95 -- Leave all other expressions unchanged
96 castprop c expr = return expr
97 -- Perform this transform everywhere
98 castproptop = everywhere ("castprop", castprop)
100 --------------------------------
101 -- Cast simplification. Mostly useful for state packing and unpacking, but
102 -- perhaps for others as well.
103 --------------------------------
104 castsimpl, castsimpltop :: Transform
105 castsimpl c expr@(Cast val ty) = do
106 -- Don't extract values that are already simpl
107 local_var <- Trans.lift $ is_local_var val
108 -- Don't extract values that are not representable, to prevent loops with
111 if (not local_var) && repr
113 -- Generate a binder for the expression
114 id <- Trans.lift $ mkBinderFor val "castval"
115 -- Extract the expression
116 change $ Let (NonRec id val) (Cast (Var id) ty)
119 -- Leave all other expressions unchanged
120 castsimpl c expr = return expr
121 -- Perform this transform everywhere
122 castsimpltop = everywhere ("castsimpl", castsimpl)
125 --------------------------------
126 -- Lambda simplication
127 --------------------------------
128 -- Ensure that a lambda always evaluates to a let expressions or a simple
129 -- variable reference.
130 lambdasimpl, lambdasimpltop :: Transform
131 -- Don't simplify a lambda that evaluates to let, since this is already
132 -- normal form (and would cause infinite loops).
133 lambdasimpl c expr@(Lam _ (Let _ _)) = return expr
134 -- Put the of a lambda in its own binding, but not when the expression is
135 -- already a local variable, or not representable (to prevent loops with
137 lambdasimpl c expr@(Lam bndr res) = do
139 local_var <- Trans.lift $ is_local_var res
140 if not local_var && repr
142 id <- Trans.lift $ mkBinderFor res "res"
143 change $ Lam bndr (Let (NonRec id res) (Var id))
145 -- If the result is already a local var or not representable, don't
149 -- Leave all other expressions unchanged
150 lambdasimpl c expr = return expr
151 -- Perform this transform everywhere
152 lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
154 --------------------------------
155 -- let derecursification
156 --------------------------------
157 letderec, letderectop :: Transform
158 letderec c expr@(Let (Rec binds) res) = case liftable of
159 -- Nothing is liftable, just return
161 -- Something can be lifted, generate a new let expression
162 _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
164 -- Make a list of all the binders bound in this recursive let
165 bndrs = map fst binds
166 -- See which bindings are liftable
167 (liftable, nonliftable) = List.partition canlift binds
168 -- Any expression that does not use any of the binders in this recursive let
169 -- can be lifted into a nonrec let. It can't use its own binder either,
170 -- since that would mean the binding is self-recursive and should be in a
171 -- single bind recursive let.
172 canlift (bndr, e) = not $ expr_uses_binders bndrs e
173 -- Leave all other expressions unchanged
174 letderec c expr = return expr
175 -- Perform this transform everywhere
176 letderectop = everywhere ("letderec", letderec)
178 --------------------------------
179 -- let simplification
180 --------------------------------
181 letsimpl, letsimpltop :: Transform
182 -- Don't simplify a let that evaluates to another let, since this is already
183 -- normal form (and would cause infinite loops with letflat below).
184 letsimpl c expr@(Let _ (Let _ _)) = return expr
185 -- Put the "in ..." value of a let in its own binding, but not when the
186 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
187 letsimpl c expr@(Let binds res) = do
189 local_var <- Trans.lift $ is_local_var res
190 if not local_var && repr
192 -- If the result is not a local var already (to prevent loops with
193 -- ourselves), extract it.
194 id <- Trans.lift $ mkBinderFor res "foo"
195 change $ Let binds (Let (NonRec id res) (Var id))
197 -- If the result is already a local var, don't extract it.
200 -- Leave all other expressions unchanged
201 letsimpl c expr = return expr
202 -- Perform this transform everywhere
203 letsimpltop = everywhere ("letsimpl", letsimpl)
205 --------------------------------
207 --------------------------------
208 -- Takes a let that binds another let, and turns that into two nested lets.
210 -- let b = (let b' = expr' in res') in res
212 -- let b' = expr' in (let b = res' in res)
213 letflat, letflattop :: Transform
214 -- Turn a nonrec let that binds a let into two nested lets.
215 letflat c (Let (NonRec b (Let binds res')) res) =
216 change $ Let binds (Let (NonRec b res') res)
217 letflat c (Let (Rec binds) expr) = do
218 -- Flatten each binding.
219 binds' <- Utils.concatM $ Monad.mapM flatbind binds
220 -- Return the new let. We don't use change here, since possibly nothing has
221 -- changed. If anything has changed, flatbind has already flagged that
223 return $ Let (Rec binds') expr
225 -- Turns a binding of a let into a multiple bindings, or any other binding
226 -- into a list with just that binding
227 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
228 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
229 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
230 flatbind (b, expr) = return [(b, expr)]
231 -- Leave all other expressions unchanged
232 letflat c expr = return expr
233 -- Perform this transform everywhere
234 letflattop = everywhere ("letflat", letflat)
236 --------------------------------
238 --------------------------------
239 -- Remove empty (recursive) lets
240 letremove, letremovetop :: Transform
241 letremove c (Let (Rec []) res) = change res
242 -- Leave all other expressions unchanged
243 letremove c expr = return expr
244 -- Perform this transform everywhere
245 letremovetop = everywhere ("letremove", letremove)
247 --------------------------------
248 -- Simple let binding removal
249 --------------------------------
250 -- Remove a = b bindings from let expressions everywhere
251 letremovesimpletop :: Transform
252 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
254 --------------------------------
255 -- Unused let binding removal
256 --------------------------------
257 letremoveunused, letremoveunusedtop :: Transform
258 letremoveunused c expr@(Let (NonRec b bound) res) = do
259 let used = expr_uses_binders [b] res
263 letremoveunused c expr@(Let (Rec binds) res) = do
264 -- Filter out all unused binds.
265 let binds' = filter dobind binds
266 -- Only set the changed flag if binds got removed
267 changeif (length binds' /= length binds) (Let (Rec binds') res)
269 bound_exprs = map snd binds
270 -- For each bind check if the bind is used by res or any of the bound
272 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
273 -- Leave all other expressions unchanged
274 letremoveunused c expr = return expr
275 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
278 --------------------------------
279 -- Identical let binding merging
280 --------------------------------
281 -- Merge two bindings in a let if they are identical
282 -- TODO: We would very much like to use GHC's CSE module for this, but that
283 -- doesn't track if something changed or not, so we can't use it properly.
284 letmerge, letmergetop :: Transform
285 letmerge c expr@(Let _ _) = do
286 let (binds, res) = flattenLets expr
287 binds' <- domerge binds
288 return $ mkNonRecLets binds' res
290 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
291 domerge [] = return []
293 es' <- mapM (mergebinds e) es
297 -- Uses the second bind to simplify the second bind, if applicable.
298 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
299 mergebinds (b1, e1) (b2, e2)
300 -- Identical expressions? Replace the second binding with a reference to
302 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
303 -- Different expressions? Don't change
304 | otherwise = return (b2, e2)
305 -- Leave all other expressions unchanged
306 letmerge c expr = return expr
307 letmergetop = everywhere ("letmerge", letmerge)
310 --------------------------------
311 -- Non-representable binding inlining
312 --------------------------------
313 -- Remove a = B bindings, with B of a non-representable type, from let
314 -- expressions everywhere. This means that any value that we can't generate a
315 -- signal for, will be inlined and hopefully turned into something we can
318 -- This is a tricky function, which is prone to create loops in the
319 -- transformations. To fix this, we make sure that no transformation will
320 -- create a new let binding with a non-representable type. These other
321 -- transformations will just not work on those function-typed values at first,
322 -- but the other transformations (in particular β-reduction) should make sure
323 -- that the type of those values eventually becomes representable.
324 inlinenonreptop :: Transform
325 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
327 --------------------------------
328 -- Top level function inlining
329 --------------------------------
330 -- This transformation inlines top level bindings that have been generated by
331 -- the compiler and are really simple. Really simple currently means that the
332 -- normalized form only contains a single binding, which catches most of the
333 -- cases where a top level function is created that simply calls a type class
334 -- method with a type and dictionary argument, e.g.
335 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
336 -- which is later called using simply
337 -- fromInteger (smallInteger 10)
338 -- By inlining such calls to simple, compiler generated functions, we prevent
339 -- huge amounts of trivial components in the VHDL output, which the user never
340 -- wanted. We never inline user-defined functions, since we want to preserve
341 -- all structure defined by the user. Currently this includes all functions
342 -- that were created by funextract, since we would get loops otherwise.
344 -- Only functions that are actually completely applied and bound by a
345 -- variable in a let expression are inlined. These are the expressions
346 -- that will eventually generate instantiations of trivial components.
347 -- By not inlining any other reference, we also prevent looping problems
348 -- with funextract and inlinedict.
350 -- Note that "defined by the compiler" isn't completely watertight, since GHC
351 -- doesn't seem to set all those names as "system names", we apply some
353 inlinetoplevel, inlinetopleveltop :: Transform
354 inlinetoplevel (LetBinding:_) expr =
355 case collectArgs expr of
356 -- Any system name is candidate for inlining. Never inline
357 -- user-defined functions, to preserve structure.
358 (Var f, args) | not $ isUserDefined f -> do
359 body_maybe <- needsInline f
362 -- Regenerate all uniques in the to-be-inlined expression
363 body_uniqued <- Trans.lift $ genUniques body
364 -- And replace the variable reference with the unique'd body.
365 change (mkApps body_uniqued args)
367 Nothing -> return expr
368 -- This is not an application of a binder, leave it unchanged.
371 -- Leave all other expressions unchanged
372 inlinetoplevel c expr = return expr
373 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
375 -- | Does the given binder need to be inlined? If so, return the body to
376 -- be used for inlining.
377 needsInline :: CoreBndr -> TransformMonad (Maybe CoreExpr)
379 body_maybe <- Trans.lift $ getGlobalBind f
381 -- No body available?
382 Nothing -> return Nothing
383 Just body -> case CoreSyn.collectArgs body of
384 -- The body is some (top level) binder applied to 0 or more
385 -- arguments. That should be simple enough to inline.
386 (Var f, args) -> return $ Just body
387 -- Body is more complicated, try normalizing it
389 norm_maybe <- Trans.lift $ getNormalized_maybe f
391 -- Noth normalizeable
392 Nothing -> return Nothing
393 Just norm -> case splitNormalized norm of
394 -- The function has just a single binding, so that's simple
396 (args, [bind], res) -> return $ Just norm
397 -- More complicated function, don't inline
400 --------------------------------
401 -- Dictionary inlining
402 --------------------------------
403 -- Inline all top level dictionaries, so we can use them to resolve
404 -- class methods based on the dictionary passed.
405 inlinedict c expr@(Var f) | Id.isDictId f = do
406 body_maybe <- Trans.lift $ getGlobalBind f
408 Nothing -> return expr
409 Just body -> change body
411 -- Leave all other expressions unchanged
412 inlinedict c expr = return expr
413 inlinedicttop = everywhere ("inlinedict", inlinedict)
415 --------------------------------
416 -- ClassOp resolution
417 --------------------------------
418 -- Resolves any class operation to the actual operation whenever
419 -- possible. Class methods (as well as parent dictionary selectors) are
420 -- special "functions" that take a type and a dictionary and evaluate to
421 -- the corresponding method. A dictionary is nothing more than a
422 -- special dataconstructor applied to the type the dictionary is for,
423 -- each of the superclasses and all of the class method definitions for
424 -- that particular type. Since dictionaries all always inlined (top
425 -- levels dictionaries are inlined by inlinedict, local dictionaries are
426 -- inlined by inlinenonrep), we will eventually have something like:
429 -- @ CLasH.HardwareTypes.Bit
430 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
432 -- Here, baz is the method selector for the baz method, while
433 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
434 -- method defined in the Baz Bit instance declaration.
436 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
437 -- which contains the Class it is defined for. From the Class, we can
438 -- get a list of all selectors (both parent class selectors as well as
439 -- method selectors). Since the arguments to D:Baz (after the type
440 -- argument) correspond exactly to this list, we then look up baz in
441 -- that list and replace the entire expression by the corresponding
442 -- argument to D:Baz.
444 -- We don't resolve methods that have a builtin translation (such as
445 -- ==), since the actual implementation is not always (easily)
446 -- translateable. For example, when deriving ==, GHC generates code
447 -- using $con2tag functions to translate a datacon to an int and compare
448 -- that with GHC.Prim.==# . Better to avoid that for now.
449 classopresolution, classopresolutiontop :: Transform
450 classopresolution c expr@(App (App (Var sel) ty) dict) | not is_builtin =
451 case Id.isClassOpId_maybe sel of
452 -- Not a class op selector
453 Nothing -> return expr
454 Just cls -> case collectArgs dict of
455 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
456 (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)
457 | tyargs_neq ty ty' -> error $ "Normalize.classopresolution: Applying class selector to dictionary without matching type?\n" ++ pprString expr
459 let selector_ids = Class.classSelIds cls in
460 -- Find the selector used in the class' list of selectors
461 case List.elemIndex sel selector_ids of
462 Nothing -> error $ "Normalize.classopresolution: Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
463 -- Get the corresponding argument from the dictionary
464 Just n -> change (selectors!!n)
465 (_, _) -> return expr -- Not applying a variable? Don't touch
467 -- Compare two type arguments, returning True if they are _not_
469 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
470 tyargs_neq _ _ = True
471 -- Is this a builtin function / method?
472 is_builtin = elem (Name.getOccString sel) builtinIds
474 -- Leave all other expressions unchanged
475 classopresolution c expr = return expr
476 -- Perform this transform everywhere
477 classopresolutiontop = everywhere ("classopresolution", classopresolution)
479 --------------------------------
480 -- Scrutinee simplification
481 --------------------------------
482 scrutsimpl,scrutsimpltop :: Transform
483 -- Don't touch scrutinees that are already simple
484 scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
485 -- Replace all other cases with a let that binds the scrutinee and a new
486 -- simple scrutinee, but only when the scrutinee is representable (to prevent
487 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
488 -- will be supported anyway...)
489 scrutsimpl c expr@(Case scrut b ty alts) = do
493 id <- Trans.lift $ mkBinderFor scrut "scrut"
494 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
497 -- Leave all other expressions unchanged
498 scrutsimpl c expr = return expr
499 -- Perform this transform everywhere
500 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
502 --------------------------------
503 -- Scrutinee binder removal
504 --------------------------------
505 -- A case expression can have an extra binder, to which the scrutinee is bound
506 -- after bringing it to WHNF. This is used for forcing evaluation of strict
507 -- arguments. Since strictness does not matter for us (rather, everything is
508 -- sort of strict), this binder is ignored when generating VHDL, and must thus
509 -- be wild in the normal form.
510 scrutbndrremove, scrutbndrremovetop :: Transform
511 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
512 -- all occurences of the binder with the scrutinee variable.
513 scrutbndrremove c (Case (Var scrut) bndr ty alts) | bndr_used = do
514 alts' <- mapM subs_bndr alts
515 change $ Case (Var scrut) wild ty alts'
517 is_used (_, _, expr) = expr_uses_binders [bndr] expr
518 bndr_used = or $ map is_used alts
519 subs_bndr (con, bndrs, expr) = do
520 expr' <- substitute bndr (Var scrut) c expr
521 return (con, bndrs, expr')
522 wild = MkCore.mkWildBinder (Id.idType bndr)
523 -- Leave all other expressions unchanged
524 scrutbndrremove c expr = return expr
525 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
527 --------------------------------
528 -- Case binder wildening
529 --------------------------------
530 casesimpl, casesimpltop :: Transform
531 -- This is already a selector case (or, if x does not appear in bndrs, a very
532 -- simple case statement that will be removed by caseremove below). Just leave
534 casesimpl c expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
535 -- Make sure that all case alternatives have only wild binders and simple
537 -- This is done by creating a new let binding for each non-wild binder, which
538 -- is bound to a new simple selector case statement and for each complex
539 -- expression. We do this only for representable types, to prevent loops with
541 casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
542 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
543 let bindings = concat bindingss
544 -- Replace the case with a let with bindings and a case
545 let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
546 -- If there are no non-wild binders, or this case is already a simple
547 -- selector (i.e., a single alt with exactly one binding), already a simple
548 -- selector altan no bindings (i.e., no wild binders in the original case),
549 -- don't change anything, otherwise, replace the case.
550 if null bindings then return expr else change newlet
552 -- Check if the scrutinee binder is used
553 is_used (_, _, expr) = expr_uses_binders [bndr] expr
554 bndr_used = or $ map is_used alts
555 -- Generate a single wild binder, since they are all the same
556 wild = MkCore.mkWildBinder
557 -- Wilden the binders of one alt, producing a list of bindings as a
559 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
560 doalt (con, bndrs, expr) = do
561 -- Make each binder wild, if possible
562 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
563 let (newbndrs, bindings_maybe) = unzip bndrs_res
564 -- Extract a complex expression, if possible. For this we check if any of
565 -- the new list of bndrs are used by expr. We can't use free_vars here,
566 -- since that looks at the old bndrs.
567 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
568 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
569 -- Create a new alternative
570 let newalt = (con, newbndrs, expr')
571 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
572 return (bindings, newalt)
574 -- Make wild alternatives for each binder
575 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
576 -- A set of all the binders that are used by the expression
577 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
578 -- Look at the ith binder in the case alternative. Return a new binder
579 -- for it (either the same one, or a wild one) and optionally a let
580 -- binding containing a case expression.
581 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
584 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
585 -- in expr, this means that b is unused if expr does not use it.)
586 let wild = not (VarSet.elemVarSet b free_vars)
587 -- Create a new binding for any representable binder that is not
588 -- already wild and is representable (to prevent loops with
590 if (not wild) && repr
592 -- Create on new binder that will actually capture a value in this
593 -- case statement, and return it.
594 let bty = (Id.idType b)
595 id <- Trans.lift $ mkInternalVar "sel" bty
596 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
597 let caseexpr = Case scrut b bty [(con, binders, Var id)]
598 return (wildbndrs!!i, Just (b, caseexpr))
600 -- Just leave the original binder in place, and don't generate an
601 -- extra selector case.
603 -- Process the expression of a case alternative. Accepts an expression
604 -- and whether this expression uses any of the binders in the
605 -- alternative. Returns an optional new binding and a new expression.
606 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
607 doexpr expr uses_bndrs = do
608 local_var <- Trans.lift $ is_local_var expr
610 -- Extract any expressions that do not use any binders from this
611 -- alternative, is not a local var already and is representable (to
612 -- prevent loops with inlinenonrep).
613 if (not uses_bndrs) && (not local_var) && repr
615 id <- Trans.lift $ mkBinderFor expr "caseval"
616 -- We don't flag a change here, since casevalsimpl will do that above
617 -- based on Just we return here.
618 return (Just (id, expr), Var id)
620 -- Don't simplify anything else
621 return (Nothing, expr)
622 -- Leave all other expressions unchanged
623 casesimpl c expr = return expr
624 -- Perform this transform everywhere
625 casesimpltop = everywhere ("casesimpl", casesimpl)
627 --------------------------------
629 --------------------------------
630 -- Remove case statements that have only a single alternative and only wild
632 caseremove, caseremovetop :: Transform
633 -- Replace a useless case by the value of its single alternative
634 caseremove c (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
635 -- Find if any of the binders are used by expr
636 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
637 -- Leave all other expressions unchanged
638 caseremove c expr = return expr
639 -- Perform this transform everywhere
640 caseremovetop = everywhere ("caseremove", caseremove)
642 --------------------------------
643 -- Argument extraction
644 --------------------------------
645 -- Make sure that all arguments of a representable type are simple variables.
646 appsimpl, appsimpltop :: Transform
647 -- Simplify all representable arguments. Do this by introducing a new Let
648 -- that binds the argument and passing the new binder in the application.
649 appsimpl c expr@(App f arg) = do
650 -- Check runtime representability
652 local_var <- Trans.lift $ is_local_var arg
653 if repr && not local_var
654 then do -- Extract representable arguments
655 id <- Trans.lift $ mkBinderFor arg "arg"
656 change $ Let (NonRec id arg) (App f (Var id))
657 else -- Leave non-representable arguments unchanged
659 -- Leave all other expressions unchanged
660 appsimpl c expr = return expr
661 -- Perform this transform everywhere
662 appsimpltop = everywhere ("appsimpl", appsimpl)
664 --------------------------------
665 -- Function-typed argument propagation
666 --------------------------------
667 -- Remove all applications to function-typed arguments, by duplication the
668 -- function called with the function-typed parameter replaced by the free
669 -- variables of the argument passed in.
670 argprop, argproptop :: Transform
671 -- Transform any application of a named function (i.e., skip applications of
672 -- lambda's). Also skip applications that have arguments with free type
673 -- variables, since we can't inline those.
674 argprop c expr@(App _ _) | is_var fexpr = do
675 -- Find the body of the function called
676 body_maybe <- Trans.lift $ getGlobalBind f
679 -- Process each of the arguments in turn
680 (args', changed) <- Writer.listen $ mapM doarg args
681 -- See if any of the arguments changed
682 case Monoid.getAny changed of
684 let (newargs', newparams', oldargs) = unzip3 args'
685 let newargs = concat newargs'
686 let newparams = concat newparams'
687 -- Create a new body that consists of a lambda for all new arguments and
688 -- the old body applied to some arguments.
689 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
690 -- Create a new function with the same name but a new body
691 newf <- Trans.lift $ mkFunction f newbody
693 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
694 let init_state_maybe = Map.lookup f ismap in
695 case init_state_maybe of
697 Just init_state -> Map.insert newf init_state ismap)
698 -- Replace the original application with one of the new function to the
700 change $ MkCore.mkCoreApps (Var newf) newargs
702 -- Don't change the expression if none of the arguments changed
705 -- If we don't have a body for the function called, leave it unchanged (it
706 -- should be a primitive function then).
707 Nothing -> return expr
709 -- Find the function called and the arguments
710 (fexpr, args) = collectArgs expr
713 -- Process a single argument and return (args, bndrs, arg), where args are
714 -- the arguments to replace the given argument in the original
715 -- application, bndrs are the binders to include in the top-level lambda
716 -- in the new function body, and arg is the argument to apply to the old
718 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
721 bndrs <- Trans.lift getGlobalBinders
722 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
723 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
725 -- Propagate all complex arguments that are not representable, but not
726 -- arguments with free type variables (since those would require types
727 -- not known yet, which will always be known eventually).
728 -- Find interesting free variables, each of which should be passed to
729 -- the new function instead of the original function argument.
731 -- Interesting vars are those that are local, but not available from the
732 -- top level scope (functions from this module are defined as local, but
733 -- they're not local to this function, so we can freely move references
734 -- to them into another function).
735 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
736 -- Mark the current expression as changed
738 -- TODO: Clone the free_vars (and update references in arg), since
739 -- this might cause conflicts if two arguments that are propagated
740 -- share a free variable. Also, we are now introducing new variables
741 -- into a function that are not fresh, which violates the binder
742 -- uniqueness invariant.
743 return (map Var free_vars, free_vars, arg)
745 -- Representable types will not be propagated, and arguments with free
746 -- type variables will be propagated later.
747 -- Note that we implicitly remove any type variables in the type of
748 -- the original argument by using the type of the actual argument
749 -- for the new formal parameter.
750 -- TODO: preserve original naming?
751 id <- Trans.lift $ mkBinderFor arg "param"
752 -- Just pass the original argument to the new function, which binds it
753 -- to a new id and just pass that new id to the old function body.
754 return ([arg], [id], mkReferenceTo id)
755 -- Leave all other expressions unchanged
756 argprop c expr = return expr
757 -- Perform this transform everywhere
758 argproptop = everywhere ("argprop", argprop)
760 --------------------------------
761 -- Function-typed argument extraction
762 --------------------------------
763 -- This transform takes any function-typed argument that cannot be propagated
764 -- (because the function that is applied to it is a builtin function), and
765 -- puts it in a brand new top level binder. This allows us to for example
766 -- apply map to a lambda expression This will not conflict with inlinenonrep,
767 -- since that only inlines local let bindings, not top level bindings.
768 funextract, funextracttop :: Transform
769 funextract c expr@(App _ _) | is_var fexpr = do
770 body_maybe <- Trans.lift $ getGlobalBind f
772 -- We don't have a function body for f, so we can perform this transform.
774 -- Find the new arguments
775 args' <- mapM doarg args
776 -- And update the arguments. We use return instead of changed, so the
777 -- changed flag doesn't get set if none of the args got changed.
778 return $ MkCore.mkCoreApps fexpr args'
779 -- We have a function body for f, leave this application to funprop
780 Just _ -> return expr
782 -- Find the function called and the arguments
783 (fexpr, args) = collectArgs expr
785 -- Change any arguments that have a function type, but are not simple yet
786 -- (ie, a variable or application). This means to create a new function
787 -- for map (\f -> ...) b, but not for map (foo a) b.
789 -- We could use is_applicable here instead of is_fun, but I think
790 -- arguments to functions could only have forall typing when existential
791 -- typing is enabled. Not sure, though.
792 doarg arg | not (is_simple arg) && is_fun arg = do
793 -- Create a new top level binding that binds the argument. Its body will
794 -- be extended with lambda expressions, to take any free variables used
795 -- by the argument expression.
796 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
797 let body = MkCore.mkCoreLams free_vars arg
798 id <- Trans.lift $ mkBinderFor body "fun"
799 Trans.lift $ addGlobalBind id body
800 -- Replace the argument with a reference to the new function, applied to
802 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
803 -- Leave all other arguments untouched
804 doarg arg = return arg
806 -- Leave all other expressions unchanged
807 funextract c expr = return expr
808 -- Perform this transform everywhere
809 funextracttop = everywhere ("funextract", funextract)
811 --------------------------------
812 -- Ensure that a function that just returns another function (or rather,
813 -- another top-level binder) is still properly normalized. This is a temporary
814 -- solution, we should probably integrate this pass with lambdasimpl and
816 --------------------------------
817 simplrestop c expr@(Lam _ _) = return expr
818 simplrestop c expr@(Let _ _) = return expr
819 simplrestop c expr = do
820 local_var <- Trans.lift $ is_local_var expr
821 -- Don't extract values that are not representable, to prevent loops with
824 if local_var || not repr
828 id <- Trans.lift $ mkBinderFor expr "res"
829 change $ Let (NonRec id expr) (Var id)
830 --------------------------------
831 -- End of transformations
832 --------------------------------
837 -- What transforms to run?
838 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
840 -- | Returns the normalized version of the given function, or an error
841 -- if it is not a known global binder.
843 CoreBndr -- ^ The function to get
844 -> TranslatorSession CoreExpr -- The normalized function body
845 getNormalized bndr = do
846 norm <- getNormalized_maybe bndr
847 return $ Maybe.fromMaybe
848 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
851 -- | Returns the normalized version of the given function, or Nothing
852 -- when the binder is not a known global binder or is not normalizeable.
853 getNormalized_maybe ::
854 CoreBndr -- ^ The function to get
855 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
857 getNormalized_maybe bndr = do
858 expr_maybe <- getGlobalBind bndr
859 normalizeable <- isNormalizeable' bndr
860 if not normalizeable || Maybe.isNothing expr_maybe
862 -- Binder not normalizeable or not found
864 else if is_poly (Var bndr)
866 -- This should really only happen at the top level... TODO: Give
867 -- a different error if this happens down in the recursion.
868 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
870 -- Binder found and is monomorphic. Normalize the expression
871 -- and cache the result.
872 normalized <- Utils.makeCached bndr tsNormalized $
873 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
874 return (Just normalized)
876 -- | Normalize an expression
878 String -- ^ What are we normalizing? For debug output only.
879 -> CoreSyn.CoreExpr -- ^ The expression to normalize
880 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
882 normalizeExpr what expr = do
883 expr_uniqued <- genUniques expr
884 -- Normalize this expression
885 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
886 expr' <- dotransforms transforms expr_uniqued
887 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
890 -- | Split a normalized expression into the argument binders, top level
891 -- bindings and the result binder.
893 CoreExpr -- ^ The normalized expression
894 -> ([CoreBndr], [Binding], CoreBndr)
895 splitNormalized expr = (args, binds, res)
897 (args, letexpr) = CoreSyn.collectBinders expr
898 (binds, resexpr) = flattenLets letexpr
899 res = case resexpr of
901 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"