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 -- Note that "defined by the compiler" isn't completely watertight, since GHC
345 -- doesn't seem to set all those names as "system names", we apply some
347 inlinetoplevel, inlinetopleveltop :: Transform
348 -- HACK: Don't inline == and /=. The default (derived) implementation
349 -- for /= uses the polymorphic version of ==, which gets a dictionary
350 -- for Eq passed in, which contains a reference to itself, resulting in
351 -- an infinite loop in transformation. Not inlining == is really a hack,
352 -- but for now it keeps things working with the most common symptom of
354 inlinetoplevel c expr@(Var f) | Name.getOccString f `elem` ["==", "/="] = return expr
355 -- Any system name is candidate for inlining. Never inline user-defined
356 -- functions, to preserve structure.
357 inlinetoplevel c expr@(Var f) | not $ isUserDefined f = do
358 body_maybe <- needsInline f
361 -- Regenerate all uniques in the to-be-inlined expression
362 body_uniqued <- Trans.lift $ genUniques body
363 -- And replace the variable reference with the unique'd body.
366 Nothing -> return expr
369 -- Leave all other expressions unchanged
370 inlinetoplevel c expr = return expr
371 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
373 -- | Does the given binder need to be inlined? If so, return the body to
374 -- be used for inlining.
375 needsInline :: CoreBndr -> TransformMonad (Maybe CoreExpr)
377 body_maybe <- Trans.lift $ getGlobalBind f
379 -- No body available?
380 Nothing -> return Nothing
381 Just body -> case CoreSyn.collectArgs body of
382 -- The body is some (top level) binder applied to 0 or more
383 -- arguments. That should be simple enough to inline.
384 (Var f, args) -> return $ Just body
385 -- Body is more complicated, try normalizing it
387 norm_maybe <- Trans.lift $ getNormalized_maybe f
389 -- Noth normalizeable
390 Nothing -> return Nothing
391 Just norm -> case splitNormalized norm of
392 -- The function has just a single binding, so that's simple
394 (args, [bind], res) -> return $ Just norm
395 -- More complicated function, don't inline
398 --------------------------------
399 -- Dictionary inlining
400 --------------------------------
401 -- Inline all top level dictionaries, so we can use them to resolve
402 -- class methods based on the dictionary passed.
403 inlinedict c expr@(Var f) | Id.isDictId f = do
404 body_maybe <- Trans.lift $ getGlobalBind f
406 Nothing -> return expr
407 Just body -> change body
409 -- Leave all other expressions unchanged
410 inlinedict c expr = return expr
411 inlinedicttop = everywhere ("inlinedict", inlinedict)
413 --------------------------------
414 -- ClassOp resolution
415 --------------------------------
416 -- Resolves any class operation to the actual operation whenever
417 -- possible. Class methods (as well as parent dictionary selectors) are
418 -- special "functions" that take a type and a dictionary and evaluate to
419 -- the corresponding method. A dictionary is nothing more than a
420 -- special dataconstructor applied to the type the dictionary is for,
421 -- each of the superclasses and all of the class method definitions for
422 -- that particular type. Since dictionaries all always inlined (top
423 -- levels dictionaries are inlined by inlinedict, local dictionaries are
424 -- inlined by inlinenonrep), we will eventually have something like:
427 -- @ CLasH.HardwareTypes.Bit
428 -- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
430 -- Here, baz is the method selector for the baz method, while
431 -- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
432 -- method defined in the Baz Bit instance declaration.
434 -- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
435 -- which contains the Class it is defined for. From the Class, we can
436 -- get a list of all selectors (both parent class selectors as well as
437 -- method selectors). Since the arguments to D:Baz (after the type
438 -- argument) correspond exactly to this list, we then look up baz in
439 -- that list and replace the entire expression by the corresponding
440 -- argument to D:Baz.
442 -- We don't resolve methods that have a builtin translation (such as
443 -- ==), since the actual implementation is not always (easily)
444 -- translateable. For example, when deriving ==, GHC generates code
445 -- using $con2tag functions to translate a datacon to an int and compare
446 -- that with GHC.Prim.==# . Better to avoid that for now.
447 classopresolution, classopresolutiontop :: Transform
448 classopresolution c expr@(App (App (Var sel) ty) dict) | not is_builtin =
449 case Id.isClassOpId_maybe sel of
450 -- Not a class op selector
451 Nothing -> return expr
452 Just cls -> case collectArgs dict of
453 (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
454 (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)
455 | tyargs_neq ty ty' -> error $ "Normalize.classopresolution: Applying class selector to dictionary without matching type?\n" ++ pprString expr
457 let selector_ids = Class.classSelIds cls in
458 -- Find the selector used in the class' list of selectors
459 case List.elemIndex sel selector_ids of
460 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
461 -- Get the corresponding argument from the dictionary
462 Just n -> change (selectors!!n)
463 (_, _) -> return expr -- Not applying a variable? Don't touch
465 -- Compare two type arguments, returning True if they are _not_
467 tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
468 tyargs_neq _ _ = True
469 -- Is this a builtin function / method?
470 is_builtin = elem (Name.getOccString sel) builtinIds
472 -- Leave all other expressions unchanged
473 classopresolution c expr = return expr
474 -- Perform this transform everywhere
475 classopresolutiontop = everywhere ("classopresolution", classopresolution)
477 --------------------------------
478 -- Scrutinee simplification
479 --------------------------------
480 scrutsimpl,scrutsimpltop :: Transform
481 -- Don't touch scrutinees that are already simple
482 scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
483 -- Replace all other cases with a let that binds the scrutinee and a new
484 -- simple scrutinee, but only when the scrutinee is representable (to prevent
485 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
486 -- will be supported anyway...)
487 scrutsimpl c expr@(Case scrut b ty alts) = do
491 id <- Trans.lift $ mkBinderFor scrut "scrut"
492 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
495 -- Leave all other expressions unchanged
496 scrutsimpl c expr = return expr
497 -- Perform this transform everywhere
498 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
500 --------------------------------
501 -- Scrutinee binder removal
502 --------------------------------
503 -- A case expression can have an extra binder, to which the scrutinee is bound
504 -- after bringing it to WHNF. This is used for forcing evaluation of strict
505 -- arguments. Since strictness does not matter for us (rather, everything is
506 -- sort of strict), this binder is ignored when generating VHDL, and must thus
507 -- be wild in the normal form.
508 scrutbndrremove, scrutbndrremovetop :: Transform
509 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
510 -- all occurences of the binder with the scrutinee variable.
511 scrutbndrremove c (Case (Var scrut) bndr ty alts) | bndr_used = do
512 alts' <- mapM subs_bndr alts
513 change $ Case (Var scrut) wild ty alts'
515 is_used (_, _, expr) = expr_uses_binders [bndr] expr
516 bndr_used = or $ map is_used alts
517 subs_bndr (con, bndrs, expr) = do
518 expr' <- substitute bndr (Var scrut) c expr
519 return (con, bndrs, expr')
520 wild = MkCore.mkWildBinder (Id.idType bndr)
521 -- Leave all other expressions unchanged
522 scrutbndrremove c expr = return expr
523 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
525 --------------------------------
526 -- Case binder wildening
527 --------------------------------
528 casesimpl, casesimpltop :: Transform
529 -- This is already a selector case (or, if x does not appear in bndrs, a very
530 -- simple case statement that will be removed by caseremove below). Just leave
532 casesimpl c expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
533 -- Make sure that all case alternatives have only wild binders and simple
535 -- This is done by creating a new let binding for each non-wild binder, which
536 -- is bound to a new simple selector case statement and for each complex
537 -- expression. We do this only for representable types, to prevent loops with
539 casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
540 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
541 let bindings = concat bindingss
542 -- Replace the case with a let with bindings and a case
543 let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
544 -- If there are no non-wild binders, or this case is already a simple
545 -- selector (i.e., a single alt with exactly one binding), already a simple
546 -- selector altan no bindings (i.e., no wild binders in the original case),
547 -- don't change anything, otherwise, replace the case.
548 if null bindings then return expr else change newlet
550 -- Check if the scrutinee binder is used
551 is_used (_, _, expr) = expr_uses_binders [bndr] expr
552 bndr_used = or $ map is_used alts
553 -- Generate a single wild binder, since they are all the same
554 wild = MkCore.mkWildBinder
555 -- Wilden the binders of one alt, producing a list of bindings as a
557 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
558 doalt (con, bndrs, expr) = do
559 -- Make each binder wild, if possible
560 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
561 let (newbndrs, bindings_maybe) = unzip bndrs_res
562 -- Extract a complex expression, if possible. For this we check if any of
563 -- the new list of bndrs are used by expr. We can't use free_vars here,
564 -- since that looks at the old bndrs.
565 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
566 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
567 -- Create a new alternative
568 let newalt = (con, newbndrs, expr')
569 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
570 return (bindings, newalt)
572 -- Make wild alternatives for each binder
573 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
574 -- A set of all the binders that are used by the expression
575 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
576 -- Look at the ith binder in the case alternative. Return a new binder
577 -- for it (either the same one, or a wild one) and optionally a let
578 -- binding containing a case expression.
579 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
582 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
583 -- in expr, this means that b is unused if expr does not use it.)
584 let wild = not (VarSet.elemVarSet b free_vars)
585 -- Create a new binding for any representable binder that is not
586 -- already wild and is representable (to prevent loops with
588 if (not wild) && repr
590 -- Create on new binder that will actually capture a value in this
591 -- case statement, and return it.
592 let bty = (Id.idType b)
593 id <- Trans.lift $ mkInternalVar "sel" bty
594 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
595 let caseexpr = Case scrut b bty [(con, binders, Var id)]
596 return (wildbndrs!!i, Just (b, caseexpr))
598 -- Just leave the original binder in place, and don't generate an
599 -- extra selector case.
601 -- Process the expression of a case alternative. Accepts an expression
602 -- and whether this expression uses any of the binders in the
603 -- alternative. Returns an optional new binding and a new expression.
604 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
605 doexpr expr uses_bndrs = do
606 local_var <- Trans.lift $ is_local_var expr
608 -- Extract any expressions that do not use any binders from this
609 -- alternative, is not a local var already and is representable (to
610 -- prevent loops with inlinenonrep).
611 if (not uses_bndrs) && (not local_var) && repr
613 id <- Trans.lift $ mkBinderFor expr "caseval"
614 -- We don't flag a change here, since casevalsimpl will do that above
615 -- based on Just we return here.
616 return (Just (id, expr), Var id)
618 -- Don't simplify anything else
619 return (Nothing, expr)
620 -- Leave all other expressions unchanged
621 casesimpl c expr = return expr
622 -- Perform this transform everywhere
623 casesimpltop = everywhere ("casesimpl", casesimpl)
625 --------------------------------
627 --------------------------------
628 -- Remove case statements that have only a single alternative and only wild
630 caseremove, caseremovetop :: Transform
631 -- Replace a useless case by the value of its single alternative
632 caseremove c (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
633 -- Find if any of the binders are used by expr
634 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
635 -- Leave all other expressions unchanged
636 caseremove c expr = return expr
637 -- Perform this transform everywhere
638 caseremovetop = everywhere ("caseremove", caseremove)
640 --------------------------------
641 -- Argument extraction
642 --------------------------------
643 -- Make sure that all arguments of a representable type are simple variables.
644 appsimpl, appsimpltop :: Transform
645 -- Simplify all representable arguments. Do this by introducing a new Let
646 -- that binds the argument and passing the new binder in the application.
647 appsimpl c expr@(App f arg) = do
648 -- Check runtime representability
650 local_var <- Trans.lift $ is_local_var arg
651 if repr && not local_var
652 then do -- Extract representable arguments
653 id <- Trans.lift $ mkBinderFor arg "arg"
654 change $ Let (NonRec id arg) (App f (Var id))
655 else -- Leave non-representable arguments unchanged
657 -- Leave all other expressions unchanged
658 appsimpl c expr = return expr
659 -- Perform this transform everywhere
660 appsimpltop = everywhere ("appsimpl", appsimpl)
662 --------------------------------
663 -- Function-typed argument propagation
664 --------------------------------
665 -- Remove all applications to function-typed arguments, by duplication the
666 -- function called with the function-typed parameter replaced by the free
667 -- variables of the argument passed in.
668 argprop, argproptop :: Transform
669 -- Transform any application of a named function (i.e., skip applications of
670 -- lambda's). Also skip applications that have arguments with free type
671 -- variables, since we can't inline those.
672 argprop c expr@(App _ _) | is_var fexpr = do
673 -- Find the body of the function called
674 body_maybe <- Trans.lift $ getGlobalBind f
677 -- Process each of the arguments in turn
678 (args', changed) <- Writer.listen $ mapM doarg args
679 -- See if any of the arguments changed
680 case Monoid.getAny changed of
682 let (newargs', newparams', oldargs) = unzip3 args'
683 let newargs = concat newargs'
684 let newparams = concat newparams'
685 -- Create a new body that consists of a lambda for all new arguments and
686 -- the old body applied to some arguments.
687 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
688 -- Create a new function with the same name but a new body
689 newf <- Trans.lift $ mkFunction f newbody
691 Trans.lift $ MonadState.modify tsInitStates (\ismap ->
692 let init_state_maybe = Map.lookup f ismap in
693 case init_state_maybe of
695 Just init_state -> Map.insert newf init_state ismap)
696 -- Replace the original application with one of the new function to the
698 change $ MkCore.mkCoreApps (Var newf) newargs
700 -- Don't change the expression if none of the arguments changed
703 -- If we don't have a body for the function called, leave it unchanged (it
704 -- should be a primitive function then).
705 Nothing -> return expr
707 -- Find the function called and the arguments
708 (fexpr, args) = collectArgs expr
711 -- Process a single argument and return (args, bndrs, arg), where args are
712 -- the arguments to replace the given argument in the original
713 -- application, bndrs are the binders to include in the top-level lambda
714 -- in the new function body, and arg is the argument to apply to the old
716 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
719 bndrs <- Trans.lift getGlobalBinders
720 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
721 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
723 -- Propagate all complex arguments that are not representable, but not
724 -- arguments with free type variables (since those would require types
725 -- not known yet, which will always be known eventually).
726 -- Find interesting free variables, each of which should be passed to
727 -- the new function instead of the original function argument.
729 -- Interesting vars are those that are local, but not available from the
730 -- top level scope (functions from this module are defined as local, but
731 -- they're not local to this function, so we can freely move references
732 -- to them into another function).
733 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
734 -- Mark the current expression as changed
736 -- TODO: Clone the free_vars (and update references in arg), since
737 -- this might cause conflicts if two arguments that are propagated
738 -- share a free variable. Also, we are now introducing new variables
739 -- into a function that are not fresh, which violates the binder
740 -- uniqueness invariant.
741 return (map Var free_vars, free_vars, arg)
743 -- Representable types will not be propagated, and arguments with free
744 -- type variables will be propagated later.
745 -- Note that we implicitly remove any type variables in the type of
746 -- the original argument by using the type of the actual argument
747 -- for the new formal parameter.
748 -- TODO: preserve original naming?
749 id <- Trans.lift $ mkBinderFor arg "param"
750 -- Just pass the original argument to the new function, which binds it
751 -- to a new id and just pass that new id to the old function body.
752 return ([arg], [id], mkReferenceTo id)
753 -- Leave all other expressions unchanged
754 argprop c expr = return expr
755 -- Perform this transform everywhere
756 argproptop = everywhere ("argprop", argprop)
758 --------------------------------
759 -- Function-typed argument extraction
760 --------------------------------
761 -- This transform takes any function-typed argument that cannot be propagated
762 -- (because the function that is applied to it is a builtin function), and
763 -- puts it in a brand new top level binder. This allows us to for example
764 -- apply map to a lambda expression This will not conflict with inlinenonrep,
765 -- since that only inlines local let bindings, not top level bindings.
766 funextract, funextracttop :: Transform
767 funextract c expr@(App _ _) | is_var fexpr = do
768 body_maybe <- Trans.lift $ getGlobalBind f
770 -- We don't have a function body for f, so we can perform this transform.
772 -- Find the new arguments
773 args' <- mapM doarg args
774 -- And update the arguments. We use return instead of changed, so the
775 -- changed flag doesn't get set if none of the args got changed.
776 return $ MkCore.mkCoreApps fexpr args'
777 -- We have a function body for f, leave this application to funprop
778 Just _ -> return expr
780 -- Find the function called and the arguments
781 (fexpr, args) = collectArgs expr
783 -- Change any arguments that have a function type, but are not simple yet
784 -- (ie, a variable or application). This means to create a new function
785 -- for map (\f -> ...) b, but not for map (foo a) b.
787 -- We could use is_applicable here instead of is_fun, but I think
788 -- arguments to functions could only have forall typing when existential
789 -- typing is enabled. Not sure, though.
790 doarg arg | not (is_simple arg) && is_fun arg = do
791 -- Create a new top level binding that binds the argument. Its body will
792 -- be extended with lambda expressions, to take any free variables used
793 -- by the argument expression.
794 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
795 let body = MkCore.mkCoreLams free_vars arg
796 id <- Trans.lift $ mkBinderFor body "fun"
797 Trans.lift $ addGlobalBind id body
798 -- Replace the argument with a reference to the new function, applied to
800 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
801 -- Leave all other arguments untouched
802 doarg arg = return arg
804 -- Leave all other expressions unchanged
805 funextract c expr = return expr
806 -- Perform this transform everywhere
807 funextracttop = everywhere ("funextract", funextract)
809 --------------------------------
810 -- Ensure that a function that just returns another function (or rather,
811 -- another top-level binder) is still properly normalized. This is a temporary
812 -- solution, we should probably integrate this pass with lambdasimpl and
814 --------------------------------
815 simplrestop c expr@(Lam _ _) = return expr
816 simplrestop c expr@(Let _ _) = return expr
817 simplrestop c expr = do
818 local_var <- Trans.lift $ is_local_var expr
819 -- Don't extract values that are not representable, to prevent loops with
822 if local_var || not repr
826 id <- Trans.lift $ mkBinderFor expr "res"
827 change $ Let (NonRec id expr) (Var id)
828 --------------------------------
829 -- End of transformations
830 --------------------------------
835 -- What transforms to run?
836 transforms = [inlinedicttop, inlinetopleveltop, classopresolutiontop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
838 -- | Returns the normalized version of the given function, or an error
839 -- if it is not a known global binder.
841 CoreBndr -- ^ The function to get
842 -> TranslatorSession CoreExpr -- The normalized function body
843 getNormalized bndr = do
844 norm <- getNormalized_maybe bndr
845 return $ Maybe.fromMaybe
846 (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
849 -- | Returns the normalized version of the given function, or Nothing
850 -- when the binder is not a known global binder or is not normalizeable.
851 getNormalized_maybe ::
852 CoreBndr -- ^ The function to get
853 -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
855 getNormalized_maybe bndr = do
856 expr_maybe <- getGlobalBind bndr
857 normalizeable <- isNormalizeable' bndr
858 if not normalizeable || Maybe.isNothing expr_maybe
860 -- Binder not normalizeable or not found
862 else if is_poly (Var bndr)
864 -- This should really only happen at the top level... TODO: Give
865 -- a different error if this happens down in the recursion.
866 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
868 -- Binder found and is monomorphic. Normalize the expression
869 -- and cache the result.
870 normalized <- Utils.makeCached bndr tsNormalized $
871 normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
872 return (Just normalized)
874 -- | Normalize an expression
876 String -- ^ What are we normalizing? For debug output only.
877 -> CoreSyn.CoreExpr -- ^ The expression to normalize
878 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
880 normalizeExpr what expr = do
881 expr_uniqued <- genUniques expr
882 -- Normalize this expression
883 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
884 expr' <- dotransforms transforms expr_uniqued
885 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
888 -- | Split a normalized expression into the argument binders, top level
889 -- bindings and the result binder.
891 CoreExpr -- ^ The normalized expression
892 -> ([CoreBndr], [Binding], CoreBndr)
893 splitNormalized expr = (args, binds, res)
895 (args, letexpr) = CoreSyn.collectBinders expr
896 (binds, resexpr) = flattenLets letexpr
897 res = case resexpr of
899 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"