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 simple top level bindings. Simple
331 -- currently means that the body is only a single application (though
332 -- the complexity of the arguments is not currently checked) or that the
333 -- normalized form only contains a single binding. This should catch most of the
334 -- cases where a top level function is created that simply calls a type class
335 -- method with a type and dictionary argument, e.g.
336 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
337 -- which is later called using simply
338 -- fromInteger (smallInteger 10)
340 -- These useless wrappers are created by GHC automatically. If we don't
341 -- inline them, we get loads of useless components cluttering the
344 -- Note that the inlining could also inline simple functions defined by
345 -- the user, not just GHC generated functions. It turns out to be near
346 -- impossible to reliably determine what functions are generated and
347 -- what functions are user-defined. Instead of guessing (which will
348 -- inline less than we want) we will just inline all simple functions.
350 -- Only functions that are actually completely applied and bound by a
351 -- variable in a let expression are inlined. These are the expressions
352 -- that will eventually generate instantiations of trivial components.
353 -- By not inlining any other reference, we also prevent looping problems
354 -- with funextract and inlinedict.
355 inlinetoplevel, inlinetopleveltop :: Transform
356 inlinetoplevel (LetBinding:_) expr | not (is_fun expr) =
357 case collectArgs expr of
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, that are in a position where
404 -- classopresolution can actually resolve them. This makes this
405 -- transformation look similar to classoperesolution below, but we'll
406 -- keep them separated for clarity. By not inlining other dictionaries,
407 -- we prevent expression sizes exploding when huge type level integer
408 -- dictionaries are inlined which can never be expanded (in casts, for
410 inlinedict c expr@(App (App (Var sel) ty) (Var dict)) | not is_builtin && is_classop = do
411 body_maybe <- Trans.lift $ getGlobalBind dict
413 -- No body available (no source available, or a local variable /
415 Nothing -> return expr
416 Just body -> change (App (App (Var sel) ty) body)
418 -- Is this a builtin function / method?
419 is_builtin = elem (Name.getOccString sel) builtinIds
420 -- Are we dealing with a class operation selector?
421 is_classop = Maybe.isJust (Id.isClassOpId_maybe sel)
423 -- Leave all other expressions unchanged
424 inlinedict c expr = return expr
425 inlinedicttop = everywhere ("inlinedict", inlinedict)
427 --------------------------------
428 -- ClassOp resolution
429 --------------------------------
430 -- Resolves any class operation to the actual operation whenever
431 -- possible. Class methods (as well as parent dictionary selectors) are
432 -- special "functions" that take a type and a dictionary and evaluate to
433 -- the corresponding method. A dictionary is nothing more than a
434 -- special dataconstructor applied to the type the dictionary is for,
435 -- each of the superclasses and all of the class method definitions for
436 -- that particular type. Since dictionaries all always inlined (top
437 -- levels dictionaries are inlined by inlinedict, local dictionaries are
438 -- inlined by inlinenonrep), we will eventually have something like:
441 -- @ CLasH.HardwareTypes.Bit
442 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
444 -- Here, baz is the method selector for the baz method, while
445 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
446 -- method defined in the Baz Bit instance declaration.
448 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
449 -- which contains the Class it is defined for. From the Class, we can
450 -- get a list of all selectors (both parent class selectors as well as
451 -- method selectors). Since the arguments to D:Baz (after the type
452 -- argument) correspond exactly to this list, we then look up baz in
453 -- that list and replace the entire expression by the corresponding
454 -- argument to D:Baz.
456 -- We don't resolve methods that have a builtin translation (such as
457 -- ==), since the actual implementation is not always (easily)
458 -- translateable. For example, when deriving ==, GHC generates code
459 -- using $con2tag functions to translate a datacon to an int and compare
460 -- that with GHC.Prim.==# . Better to avoid that for now.
461 classopresolution, classopresolutiontop :: Transform
462 classopresolution c expr@(App (App (Var sel) ty) dict) | not is_builtin =
463 case Id.isClassOpId_maybe sel of
464 -- Not a class op selector
465 Nothing -> return expr
466 Just cls -> case collectArgs dict of
467 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
468 (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)
469 | tyargs_neq ty ty' -> error $ "Normalize.classopresolution: Applying class selector to dictionary without matching type?\n" ++ pprString expr
471 let selector_ids = Class.classSelIds cls in
472 -- Find the selector used in the class' list of selectors
473 case List.elemIndex sel selector_ids of
474 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
475 -- Get the corresponding argument from the dictionary
476 Just n -> change (selectors!!n)
477 (_, _) -> return expr -- Not applying a variable? Don't touch
479 -- Compare two type arguments, returning True if they are _not_
481 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
482 tyargs_neq _ _ = True
483 -- Is this a builtin function / method?
484 is_builtin = elem (Name.getOccString sel) builtinIds
486 -- Leave all other expressions unchanged
487 classopresolution c expr = return expr
488 -- Perform this transform everywhere
489 classopresolutiontop = everywhere ("classopresolution", classopresolution)
491 --------------------------------
492 -- Scrutinee simplification
493 --------------------------------
494 scrutsimpl,scrutsimpltop :: Transform
495 -- Don't touch scrutinees that are already simple
496 scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
497 -- Replace all other cases with a let that binds the scrutinee and a new
498 -- simple scrutinee, but only when the scrutinee is representable (to prevent
499 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
500 -- will be supported anyway...)
501 scrutsimpl c expr@(Case scrut b ty alts) = do
505 id <- Trans.lift $ mkBinderFor scrut "scrut"
506 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
509 -- Leave all other expressions unchanged
510 scrutsimpl c expr = return expr
511 -- Perform this transform everywhere
512 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
514 --------------------------------
515 -- Scrutinee binder removal
516 --------------------------------
517 -- A case expression can have an extra binder, to which the scrutinee is bound
518 -- after bringing it to WHNF. This is used for forcing evaluation of strict
519 -- arguments. Since strictness does not matter for us (rather, everything is
520 -- sort of strict), this binder is ignored when generating VHDL, and must thus
521 -- be wild in the normal form.
522 scrutbndrremove, scrutbndrremovetop :: Transform
523 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
524 -- all occurences of the binder with the scrutinee variable.
525 scrutbndrremove c (Case (Var scrut) bndr ty alts) | bndr_used = do
526 alts' <- mapM subs_bndr alts
527 change $ Case (Var scrut) wild ty alts'
529 is_used (_, _, expr) = expr_uses_binders [bndr] expr
530 bndr_used = or $ map is_used alts
531 subs_bndr (con, bndrs, expr) = do
532 expr' <- substitute bndr (Var scrut) c expr
533 return (con, bndrs, expr')
534 wild = MkCore.mkWildBinder (Id.idType bndr)
535 -- Leave all other expressions unchanged
536 scrutbndrremove c expr = return expr
537 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
539 --------------------------------
540 -- Case binder wildening
541 --------------------------------
542 casesimpl, casesimpltop :: Transform
543 -- This is already a selector case (or, if x does not appear in bndrs, a very
544 -- simple case statement that will be removed by caseremove below). Just leave
546 casesimpl c expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
547 -- Make sure that all case alternatives have only wild binders and simple
549 -- This is done by creating a new let binding for each non-wild binder, which
550 -- is bound to a new simple selector case statement and for each complex
551 -- expression. We do this only for representable types, to prevent loops with
553 casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
554 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
555 let bindings = concat bindingss
556 -- Replace the case with a let with bindings and a case
557 let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
558 -- If there are no non-wild binders, or this case is already a simple
559 -- selector (i.e., a single alt with exactly one binding), already a simple
560 -- selector altan no bindings (i.e., no wild binders in the original case),
561 -- don't change anything, otherwise, replace the case.
562 if null bindings then return expr else change newlet
564 -- Check if the scrutinee binder is used
565 is_used (_, _, expr) = expr_uses_binders [bndr] expr
566 bndr_used = or $ map is_used alts
567 -- Generate a single wild binder, since they are all the same
568 wild = MkCore.mkWildBinder
569 -- Wilden the binders of one alt, producing a list of bindings as a
571 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
572 doalt (con, bndrs, expr) = do
573 -- Make each binder wild, if possible
574 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
575 let (newbndrs, bindings_maybe) = unzip bndrs_res
576 -- Extract a complex expression, if possible. For this we check if any of
577 -- the new list of bndrs are used by expr. We can't use free_vars here,
578 -- since that looks at the old bndrs.
579 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
580 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
581 -- Create a new alternative
582 let newalt = (con, newbndrs, expr')
583 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
584 return (bindings, newalt)
586 -- Make wild alternatives for each binder
587 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
588 -- A set of all the binders that are used by the expression
589 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
590 -- Look at the ith binder in the case alternative. Return a new binder
591 -- for it (either the same one, or a wild one) and optionally a let
592 -- binding containing a case expression.
593 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
596 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
597 -- in expr, this means that b is unused if expr does not use it.)
598 let wild = not (VarSet.elemVarSet b free_vars)
599 -- Create a new binding for any representable binder that is not
600 -- already wild and is representable (to prevent loops with
602 if (not wild) && repr
604 -- Create on new binder that will actually capture a value in this
605 -- case statement, and return it.
606 let bty = (Id.idType b)
607 id <- Trans.lift $ mkInternalVar "sel" bty
608 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
609 let caseexpr = Case scrut b bty [(con, binders, Var id)]
610 return (wildbndrs!!i, Just (b, caseexpr))
612 -- Just leave the original binder in place, and don't generate an
613 -- extra selector case.
615 -- Process the expression of a case alternative. Accepts an expression
616 -- and whether this expression uses any of the binders in the
617 -- alternative. Returns an optional new binding and a new expression.
618 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
619 doexpr expr uses_bndrs = do
620 local_var <- Trans.lift $ is_local_var expr
622 -- Extract any expressions that do not use any binders from this
623 -- alternative, is not a local var already and is representable (to
624 -- prevent loops with inlinenonrep).
625 if (not uses_bndrs) && (not local_var) && repr
627 id <- Trans.lift $ mkBinderFor expr "caseval"
628 -- We don't flag a change here, since casevalsimpl will do that above
629 -- based on Just we return here.
630 return (Just (id, expr), Var id)
632 -- Don't simplify anything else
633 return (Nothing, expr)
634 -- Leave all other expressions unchanged
635 casesimpl c expr = return expr
636 -- Perform this transform everywhere
637 casesimpltop = everywhere ("casesimpl", casesimpl)
639 --------------------------------
641 --------------------------------
642 -- Remove case statements that have only a single alternative and only wild
644 caseremove, caseremovetop :: Transform
645 -- Replace a useless case by the value of its single alternative
646 caseremove c (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
647 -- Find if any of the binders are used by expr
648 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
649 -- Leave all other expressions unchanged
650 caseremove c expr = return expr
651 -- Perform this transform everywhere
652 caseremovetop = everywhere ("caseremove", caseremove)
654 --------------------------------
655 -- Argument extraction
656 --------------------------------
657 -- Make sure that all arguments of a representable type are simple variables.
658 appsimpl, appsimpltop :: Transform
659 -- Simplify all representable arguments. Do this by introducing a new Let
660 -- that binds the argument and passing the new binder in the application.
661 appsimpl c expr@(App f arg) = do
662 -- Check runtime representability
664 local_var <- Trans.lift $ is_local_var arg
665 if repr && not local_var
666 then do -- Extract representable arguments
667 id <- Trans.lift $ mkBinderFor arg "arg"
668 change $ Let (NonRec id arg) (App f (Var id))
669 else -- Leave non-representable arguments unchanged
671 -- Leave all other expressions unchanged
672 appsimpl c expr = return expr
673 -- Perform this transform everywhere
674 appsimpltop = everywhere ("appsimpl", appsimpl)
676 --------------------------------
677 -- Function-typed argument propagation
678 --------------------------------
679 -- Remove all applications to function-typed arguments, by duplication the
680 -- function called with the function-typed parameter replaced by the free
681 -- variables of the argument passed in.
682 argprop, argproptop :: Transform
683 -- Transform any application of a named function (i.e., skip applications of
684 -- lambda's). Also skip applications that have arguments with free type
685 -- variables, since we can't inline those.
686 argprop c expr@(App _ _) | is_var fexpr = do
687 -- Find the body of the function called
688 body_maybe <- Trans.lift $ getGlobalBind f
691 -- Process each of the arguments in turn
692 (args', changed) <- Writer.listen $ mapM doarg args
693 -- See if any of the arguments changed
694 case Monoid.getAny changed of
696 let (newargs', newparams', oldargs) = unzip3 args'
697 let newargs = concat newargs'
698 let newparams = concat newparams'
699 -- Create a new body that consists of a lambda for all new arguments and
700 -- the old body applied to some arguments.
701 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
702 -- Create a new function with the same name but a new body
703 newf <- Trans.lift $ mkFunction f newbody
705 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
706 let init_state_maybe = Map.lookup f ismap in
707 case init_state_maybe of
709 Just init_state -> Map.insert newf init_state ismap)
710 -- Replace the original application with one of the new function to the
712 change $ MkCore.mkCoreApps (Var newf) newargs
714 -- Don't change the expression if none of the arguments changed
717 -- If we don't have a body for the function called, leave it unchanged (it
718 -- should be a primitive function then).
719 Nothing -> return expr
721 -- Find the function called and the arguments
722 (fexpr, args) = collectArgs expr
725 -- Process a single argument and return (args, bndrs, arg), where args are
726 -- the arguments to replace the given argument in the original
727 -- application, bndrs are the binders to include in the top-level lambda
728 -- in the new function body, and arg is the argument to apply to the old
730 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
733 bndrs <- Trans.lift getGlobalBinders
734 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
735 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
737 -- Propagate all complex arguments that are not representable, but not
738 -- arguments with free type variables (since those would require types
739 -- not known yet, which will always be known eventually).
740 -- Find interesting free variables, each of which should be passed to
741 -- the new function instead of the original function argument.
743 -- Interesting vars are those that are local, but not available from the
744 -- top level scope (functions from this module are defined as local, but
745 -- they're not local to this function, so we can freely move references
746 -- to them into another function).
747 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
748 -- Mark the current expression as changed
750 -- TODO: Clone the free_vars (and update references in arg), since
751 -- this might cause conflicts if two arguments that are propagated
752 -- share a free variable. Also, we are now introducing new variables
753 -- into a function that are not fresh, which violates the binder
754 -- uniqueness invariant.
755 return (map Var free_vars, free_vars, arg)
757 -- Representable types will not be propagated, and arguments with free
758 -- type variables will be propagated later.
759 -- Note that we implicitly remove any type variables in the type of
760 -- the original argument by using the type of the actual argument
761 -- for the new formal parameter.
762 -- TODO: preserve original naming?
763 id <- Trans.lift $ mkBinderFor arg "param"
764 -- Just pass the original argument to the new function, which binds it
765 -- to a new id and just pass that new id to the old function body.
766 return ([arg], [id], mkReferenceTo id)
767 -- Leave all other expressions unchanged
768 argprop c expr = return expr
769 -- Perform this transform everywhere
770 argproptop = everywhere ("argprop", argprop)
772 --------------------------------
773 -- Function-typed argument extraction
774 --------------------------------
775 -- This transform takes any function-typed argument that cannot be propagated
776 -- (because the function that is applied to it is a builtin function), and
777 -- puts it in a brand new top level binder. This allows us to for example
778 -- apply map to a lambda expression This will not conflict with inlinenonrep,
779 -- since that only inlines local let bindings, not top level bindings.
780 funextract, funextracttop :: Transform
781 funextract c expr@(App _ _) | is_var fexpr = do
782 body_maybe <- Trans.lift $ getGlobalBind f
784 -- We don't have a function body for f, so we can perform this transform.
786 -- Find the new arguments
787 args' <- mapM doarg args
788 -- And update the arguments. We use return instead of changed, so the
789 -- changed flag doesn't get set if none of the args got changed.
790 return $ MkCore.mkCoreApps fexpr args'
791 -- We have a function body for f, leave this application to funprop
792 Just _ -> return expr
794 -- Find the function called and the arguments
795 (fexpr, args) = collectArgs expr
797 -- Change any arguments that have a function type, but are not simple yet
798 -- (ie, a variable or application). This means to create a new function
799 -- for map (\f -> ...) b, but not for map (foo a) b.
801 -- We could use is_applicable here instead of is_fun, but I think
802 -- arguments to functions could only have forall typing when existential
803 -- typing is enabled. Not sure, though.
804 doarg arg | not (is_simple arg) && is_fun arg = do
805 -- Create a new top level binding that binds the argument. Its body will
806 -- be extended with lambda expressions, to take any free variables used
807 -- by the argument expression.
808 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
809 let body = MkCore.mkCoreLams free_vars arg
810 id <- Trans.lift $ mkBinderFor body "fun"
811 Trans.lift $ addGlobalBind id body
812 -- Replace the argument with a reference to the new function, applied to
814 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
815 -- Leave all other arguments untouched
816 doarg arg = return arg
818 -- Leave all other expressions unchanged
819 funextract c expr = return expr
820 -- Perform this transform everywhere
821 funextracttop = everywhere ("funextract", funextract)
823 --------------------------------
824 -- Ensure that a function that just returns another function (or rather,
825 -- another top-level binder) is still properly normalized. This is a temporary
826 -- solution, we should probably integrate this pass with lambdasimpl and
828 --------------------------------
829 simplrestop c expr@(Lam _ _) = return expr
830 simplrestop c expr@(Let _ _) = return expr
831 simplrestop c expr = do
832 local_var <- Trans.lift $ is_local_var expr
833 -- Don't extract values that are not representable, to prevent loops with
836 if local_var || not repr
840 id <- Trans.lift $ mkBinderFor expr "res"
841 change $ Let (NonRec id expr) (Var id)
842 --------------------------------
843 -- End of transformations
844 --------------------------------
849 -- What transforms to run?
850 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
852 -- | Returns the normalized version of the given function, or an error
853 -- if it is not a known global binder.
855 CoreBndr -- ^ The function to get
856 -> TranslatorSession CoreExpr -- The normalized function body
857 getNormalized bndr = do
858 norm <- getNormalized_maybe bndr
859 return $ Maybe.fromMaybe
860 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
863 -- | Returns the normalized version of the given function, or Nothing
864 -- when the binder is not a known global binder or is not normalizeable.
865 getNormalized_maybe ::
866 CoreBndr -- ^ The function to get
867 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
869 getNormalized_maybe bndr = do
870 expr_maybe <- getGlobalBind bndr
871 normalizeable <- isNormalizeable' bndr
872 if not normalizeable || Maybe.isNothing expr_maybe
874 -- Binder not normalizeable or not found
876 else if is_poly (Var bndr)
878 -- This should really only happen at the top level... TODO: Give
879 -- a different error if this happens down in the recursion.
880 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
882 -- Binder found and is monomorphic. Normalize the expression
883 -- and cache the result.
884 normalized <- Utils.makeCached bndr tsNormalized $
885 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
886 return (Just normalized)
888 -- | Normalize an expression
890 String -- ^ What are we normalizing? For debug output only.
891 -> CoreSyn.CoreExpr -- ^ The expression to normalize
892 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
894 normalizeExpr what expr = do
895 expr_uniqued <- genUniques expr
896 -- Normalize this expression
897 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
898 expr' <- dotransforms transforms expr_uniqued
899 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
902 -- | Split a normalized expression into the argument binders, top level
903 -- bindings and the result binder.
905 CoreExpr -- ^ The normalized expression
906 -> ([CoreBndr], [Binding], CoreBndr)
907 splitNormalized expr = (args, binds, res)
909 (args, letexpr) = CoreSyn.collectBinders expr
910 (binds, resexpr) = flattenLets letexpr
911 res = case resexpr of
913 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"