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.Monoid as Monoid
20 import qualified CoreUtils
24 import qualified VarSet
25 import qualified CoreFVs
26 import qualified MkCore
27 import Outputable ( showSDoc, ppr, nest )
30 import CLasH.Normalize.NormalizeTypes
31 import CLasH.Translator.TranslatorTypes
32 import CLasH.Normalize.NormalizeTools
33 import qualified CLasH.Utils as Utils
34 import CLasH.Utils.Core.CoreTools
35 import CLasH.Utils.Core.BinderTools
36 import CLasH.Utils.Pretty
38 --------------------------------
39 -- Start of transformations
40 --------------------------------
42 --------------------------------
44 --------------------------------
45 eta, etatop :: Transform
46 eta expr | is_fun expr && not (is_lam expr) = do
47 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
48 id <- Trans.lift $ mkInternalVar "param" arg_ty
49 change (Lam id (App expr (Var id)))
50 -- Leave all other expressions unchanged
52 etatop = notappargs ("eta", eta)
54 --------------------------------
56 --------------------------------
57 beta, betatop :: Transform
58 -- Substitute arg for x in expr. For value lambda's, also clone before
60 beta (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg expr
61 | otherwise = setChanged >> substitute_clone x arg expr
62 -- Propagate the application into the let
63 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
64 -- Propagate the application into each of the alternatives
65 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
67 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
68 ty' = CoreUtils.applyTypeToArg ty arg
69 -- Leave all other expressions unchanged
70 beta expr = return expr
71 -- Perform this transform everywhere
72 betatop = everywhere ("beta", beta)
74 --------------------------------
76 --------------------------------
77 -- Try to move casts as much downward as possible.
78 castprop, castproptop :: Transform
79 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
80 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
82 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
83 -- Leave all other expressions unchanged
84 castprop expr = return expr
85 -- Perform this transform everywhere
86 castproptop = everywhere ("castprop", castprop)
88 --------------------------------
89 -- Cast simplification. Mostly useful for state packing and unpacking, but
90 -- perhaps for others as well.
91 --------------------------------
92 castsimpl, castsimpltop :: Transform
93 castsimpl expr@(Cast val ty) = do
94 -- Don't extract values that are already simpl
95 local_var <- Trans.lift $ is_local_var val
96 -- Don't extract values that are not representable, to prevent loops with
99 if (not local_var) && repr
101 -- Generate a binder for the expression
102 id <- Trans.lift $ mkBinderFor val "castval"
103 -- Extract the expression
104 change $ Let (NonRec id val) (Cast (Var id) ty)
107 -- Leave all other expressions unchanged
108 castsimpl expr = return expr
109 -- Perform this transform everywhere
110 castsimpltop = everywhere ("castsimpl", castsimpl)
113 --------------------------------
114 -- Lambda simplication
115 --------------------------------
116 -- Ensure that a lambda always evaluates to a let expressions or a simple
117 -- variable reference.
118 lambdasimpl, lambdasimpltop :: Transform
119 -- Don't simplify a lambda that evaluates to let, since this is already
120 -- normal form (and would cause infinite loops).
121 lambdasimpl expr@(Lam _ (Let _ _)) = return expr
122 -- Put the of a lambda in its own binding, but not when the expression is
123 -- already a local variable, or not representable (to prevent loops with
125 lambdasimpl expr@(Lam bndr res) = do
127 local_var <- Trans.lift $ is_local_var res
128 if not local_var && repr
130 id <- Trans.lift $ mkBinderFor res "res"
131 change $ Lam bndr (Let (NonRec id res) (Var id))
133 -- If the result is already a local var or not representable, don't
137 -- Leave all other expressions unchanged
138 lambdasimpl expr = return expr
139 -- Perform this transform everywhere
140 lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
142 --------------------------------
143 -- let derecursification
144 --------------------------------
145 letderec, letderectop :: Transform
146 letderec expr@(Let (Rec binds) res) = case liftable of
147 -- Nothing is liftable, just return
149 -- Something can be lifted, generate a new let expression
150 _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
152 -- Make a list of all the binders bound in this recursive let
153 bndrs = map fst binds
154 -- See which bindings are liftable
155 (liftable, nonliftable) = List.partition canlift binds
156 -- Any expression that does not use any of the binders in this recursive let
157 -- can be lifted into a nonrec let. It can't use its own binder either,
158 -- since that would mean the binding is self-recursive and should be in a
159 -- single bind recursive let.
160 canlift (bndr, e) = not $ expr_uses_binders bndrs e
161 -- Leave all other expressions unchanged
162 letderec expr = return expr
163 -- Perform this transform everywhere
164 letderectop = everywhere ("letderec", letderec)
166 --------------------------------
167 -- let simplification
168 --------------------------------
169 letsimpl, letsimpltop :: Transform
170 -- Don't simplify a let that evaluates to another let, since this is already
171 -- normal form (and would cause infinite loops with letflat below).
172 letsimpl expr@(Let _ (Let _ _)) = return expr
173 -- Put the "in ..." value of a let in its own binding, but not when the
174 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
175 letsimpl expr@(Let binds res) = do
177 local_var <- Trans.lift $ is_local_var res
178 if not local_var && repr
180 -- If the result is not a local var already (to prevent loops with
181 -- ourselves), extract it.
182 id <- Trans.lift $ mkBinderFor res "foo"
183 change $ Let binds (Let (NonRec id res) (Var id))
185 -- If the result is already a local var, don't extract it.
188 -- Leave all other expressions unchanged
189 letsimpl expr = return expr
190 -- Perform this transform everywhere
191 letsimpltop = everywhere ("letsimpl", letsimpl)
193 --------------------------------
195 --------------------------------
196 -- Takes a let that binds another let, and turns that into two nested lets.
198 -- let b = (let b' = expr' in res') in res
200 -- let b' = expr' in (let b = res' in res)
201 letflat, letflattop :: Transform
202 -- Turn a nonrec let that binds a let into two nested lets.
203 letflat (Let (NonRec b (Let binds res')) res) =
204 change $ Let binds (Let (NonRec b res') res)
205 letflat (Let (Rec binds) expr) = do
206 -- Flatten each binding.
207 binds' <- Utils.concatM $ Monad.mapM flatbind binds
208 -- Return the new let. We don't use change here, since possibly nothing has
209 -- changed. If anything has changed, flatbind has already flagged that
211 return $ Let (Rec binds') expr
213 -- Turns a binding of a let into a multiple bindings, or any other binding
214 -- into a list with just that binding
215 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
216 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
217 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
218 flatbind (b, expr) = return [(b, expr)]
219 -- Leave all other expressions unchanged
220 letflat expr = return expr
221 -- Perform this transform everywhere
222 letflattop = everywhere ("letflat", letflat)
224 --------------------------------
226 --------------------------------
227 -- Remove empty (recursive) lets
228 letremove, letremovetop :: Transform
229 letremove (Let (Rec []) res) = change res
230 -- Leave all other expressions unchanged
231 letremove expr = return expr
232 -- Perform this transform everywhere
233 letremovetop = everywhere ("letremove", letremove)
235 --------------------------------
236 -- Simple let binding removal
237 --------------------------------
238 -- Remove a = b bindings from let expressions everywhere
239 letremovesimpletop :: Transform
240 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
242 --------------------------------
243 -- Unused let binding removal
244 --------------------------------
245 letremoveunused, letremoveunusedtop :: Transform
246 letremoveunused expr@(Let (NonRec b bound) res) = do
247 let used = expr_uses_binders [b] res
251 letremoveunused expr@(Let (Rec binds) res) = do
252 -- Filter out all unused binds.
253 let binds' = filter dobind binds
254 -- Only set the changed flag if binds got removed
255 changeif (length binds' /= length binds) (Let (Rec binds') res)
257 bound_exprs = map snd binds
258 -- For each bind check if the bind is used by res or any of the bound
260 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
261 -- Leave all other expressions unchanged
262 letremoveunused expr = return expr
263 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
266 --------------------------------
267 -- Identical let binding merging
268 --------------------------------
269 -- Merge two bindings in a let if they are identical
270 -- TODO: We would very much like to use GHC's CSE module for this, but that
271 -- doesn't track if something changed or not, so we can't use it properly.
272 letmerge, letmergetop :: Transform
273 letmerge expr@(Let _ _) = do
274 let (binds, res) = flattenLets expr
275 binds' <- domerge binds
276 return $ mkNonRecLets binds' res
278 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
279 domerge [] = return []
281 es' <- mapM (mergebinds e) es
285 -- Uses the second bind to simplify the second bind, if applicable.
286 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
287 mergebinds (b1, e1) (b2, e2)
288 -- Identical expressions? Replace the second binding with a reference to
290 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
291 -- Different expressions? Don't change
292 | otherwise = return (b2, e2)
293 -- Leave all other expressions unchanged
294 letmerge expr = return expr
295 letmergetop = everywhere ("letmerge", letmerge)
298 --------------------------------
299 -- Non-representable binding inlining
300 --------------------------------
301 -- Remove a = B bindings, with B of a non-representable type, from let
302 -- expressions everywhere. This means that any value that we can't generate a
303 -- signal for, will be inlined and hopefully turned into something we can
306 -- This is a tricky function, which is prone to create loops in the
307 -- transformations. To fix this, we make sure that no transformation will
308 -- create a new let binding with a non-representable type. These other
309 -- transformations will just not work on those function-typed values at first,
310 -- but the other transformations (in particular β-reduction) should make sure
311 -- that the type of those values eventually becomes representable.
312 inlinenonreptop :: Transform
313 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
315 --------------------------------
316 -- Top level function inlining
317 --------------------------------
318 -- This transformation inlines top level bindings that have been generated by
319 -- the compiler and are really simple. Really simple currently means that the
320 -- normalized form only contains a single binding, which catches most of the
321 -- cases where a top level function is created that simply calls a type class
322 -- method with a type and dictionary argument, e.g.
323 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
324 -- which is later called using simply
325 -- fromInteger (smallInteger 10)
326 -- By inlining such calls to simple, compiler generated functions, we prevent
327 -- huge amounts of trivial components in the VHDL output, which the user never
328 -- wanted. We never inline user-defined functions, since we want to preserve
329 -- all structure defined by the user. Currently this includes all functions
330 -- that were created by funextract, since we would get loops otherwise.
332 -- Note that "defined by the compiler" isn't completely watertight, since GHC
333 -- doesn't seem to set all those names as "system names", we apply some
335 inlinetoplevel, inlinetopleveltop :: Transform
336 -- Any system name is candidate for inlining. Never inline user-defined
337 -- functions, to preserve structure.
338 inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
339 norm <- isNormalizeable f
340 -- See if this is a top level binding for which we have a body
341 body_maybe <- Trans.lift $ getGlobalBind f
342 if norm && Maybe.isJust body_maybe
344 -- Get the normalized version
345 norm <- Trans.lift $ getNormalized f
348 -- Regenerate all uniques in the to-be-inlined expression
349 norm_uniqued <- Trans.lift $ genUniques norm
354 -- No body or not normalizeable.
356 -- Leave all other expressions unchanged
357 inlinetoplevel expr = return expr
358 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
360 needsInline :: CoreExpr -> Bool
361 needsInline expr = case splitNormalized expr of
362 -- Inline any function that only has a single definition, it is probably
363 -- simple enough. This might inline some stuff that it shouldn't though it
364 -- will never inline user-defined functions (inlinetoplevel only tries
365 -- system names) and inlining should never break things.
366 (args, [bind], res) -> True
369 --------------------------------
370 -- Scrutinee simplification
371 --------------------------------
372 scrutsimpl,scrutsimpltop :: Transform
373 -- Don't touch scrutinees that are already simple
374 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
375 -- Replace all other cases with a let that binds the scrutinee and a new
376 -- simple scrutinee, but only when the scrutinee is representable (to prevent
377 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
378 -- will be supported anyway...)
379 scrutsimpl expr@(Case scrut b ty alts) = do
383 id <- Trans.lift $ mkBinderFor scrut "scrut"
384 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
387 -- Leave all other expressions unchanged
388 scrutsimpl expr = return expr
389 -- Perform this transform everywhere
390 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
392 --------------------------------
393 -- Scrutinee binder removal
394 --------------------------------
395 -- A case expression can have an extra binder, to which the scrutinee is bound
396 -- after bringing it to WHNF. This is used for forcing evaluation of strict
397 -- arguments. Since strictness does not matter for us (rather, everything is
398 -- sort of strict), this binder is ignored when generating VHDL, and must thus
399 -- be wild in the normal form.
400 scrutbndrremove, scrutbndrremovetop :: Transform
401 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
402 -- all occurences of the binder with the scrutinee variable.
403 scrutbndrremove (Case (Var scrut) bndr ty alts) | bndr_used = do
404 alts' <- mapM subs_bndr alts
405 change $ Case (Var scrut) wild ty alts'
407 is_used (_, _, expr) = expr_uses_binders [bndr] expr
408 bndr_used = or $ map is_used alts
409 subs_bndr (con, bndrs, expr) = do
410 expr' <- substitute bndr (Var scrut) expr
411 return (con, bndrs, expr')
412 wild = MkCore.mkWildBinder (Id.idType bndr)
413 -- Leave all other expressions unchanged
414 scrutbndrremove expr = return expr
415 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
417 --------------------------------
418 -- Case binder wildening
419 --------------------------------
420 casesimpl, casesimpltop :: Transform
421 -- This is already a selector case (or, if x does not appear in bndrs, a very
422 -- simple case statement that will be removed by caseremove below). Just leave
424 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
425 -- Make sure that all case alternatives have only wild binders and simple
427 -- This is done by creating a new let binding for each non-wild binder, which
428 -- is bound to a new simple selector case statement and for each complex
429 -- expression. We do this only for representable types, to prevent loops with
431 casesimpl expr@(Case scrut b ty alts) = do
432 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
433 let bindings = concat bindingss
434 -- Replace the case with a let with bindings and a case
435 let newlet = mkNonRecLets bindings (Case scrut b ty alts')
436 -- If there are no non-wild binders, or this case is already a simple
437 -- selector (i.e., a single alt with exactly one binding), already a simple
438 -- selector altan no bindings (i.e., no wild binders in the original case),
439 -- don't change anything, otherwise, replace the case.
440 if null bindings then return expr else change newlet
442 -- Generate a single wild binder, since they are all the same
443 wild = MkCore.mkWildBinder
444 -- Wilden the binders of one alt, producing a list of bindings as a
446 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
447 doalt (con, bndrs, expr) = do
448 -- Make each binder wild, if possible
449 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
450 let (newbndrs, bindings_maybe) = unzip bndrs_res
451 -- Extract a complex expression, if possible. For this we check if any of
452 -- the new list of bndrs are used by expr. We can't use free_vars here,
453 -- since that looks at the old bndrs.
454 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
455 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
456 -- Create a new alternative
457 let newalt = (con, newbndrs, expr')
458 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
459 return (bindings, newalt)
461 -- Make wild alternatives for each binder
462 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
463 -- A set of all the binders that are used by the expression
464 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
465 -- Look at the ith binder in the case alternative. Return a new binder
466 -- for it (either the same one, or a wild one) and optionally a let
467 -- binding containing a case expression.
468 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
471 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
472 -- in expr, this means that b is unused if expr does not use it.)
473 let wild = not (VarSet.elemVarSet b free_vars)
474 -- Create a new binding for any representable binder that is not
475 -- already wild and is representable (to prevent loops with
477 if (not wild) && repr
479 -- Create on new binder that will actually capture a value in this
480 -- case statement, and return it.
481 let bty = (Id.idType b)
482 id <- Trans.lift $ mkInternalVar "sel" bty
483 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
484 let caseexpr = Case scrut b bty [(con, binders, Var id)]
485 return (wildbndrs!!i, Just (b, caseexpr))
487 -- Just leave the original binder in place, and don't generate an
488 -- extra selector case.
490 -- Process the expression of a case alternative. Accepts an expression
491 -- and whether this expression uses any of the binders in the
492 -- alternative. Returns an optional new binding and a new expression.
493 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
494 doexpr expr uses_bndrs = do
495 local_var <- Trans.lift $ is_local_var expr
497 -- Extract any expressions that do not use any binders from this
498 -- alternative, is not a local var already and is representable (to
499 -- prevent loops with inlinenonrep).
500 if (not uses_bndrs) && (not local_var) && repr
502 id <- Trans.lift $ mkBinderFor expr "caseval"
503 -- We don't flag a change here, since casevalsimpl will do that above
504 -- based on Just we return here.
505 return (Just (id, expr), Var id)
507 -- Don't simplify anything else
508 return (Nothing, expr)
509 -- Leave all other expressions unchanged
510 casesimpl expr = return expr
511 -- Perform this transform everywhere
512 casesimpltop = everywhere ("casesimpl", casesimpl)
514 --------------------------------
516 --------------------------------
517 -- Remove case statements that have only a single alternative and only wild
519 caseremove, caseremovetop :: Transform
520 -- Replace a useless case by the value of its single alternative
521 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
522 -- Find if any of the binders are used by expr
523 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
524 -- Leave all other expressions unchanged
525 caseremove expr = return expr
526 -- Perform this transform everywhere
527 caseremovetop = everywhere ("caseremove", caseremove)
529 --------------------------------
530 -- Argument extraction
531 --------------------------------
532 -- Make sure that all arguments of a representable type are simple variables.
533 appsimpl, appsimpltop :: Transform
534 -- Simplify all representable arguments. Do this by introducing a new Let
535 -- that binds the argument and passing the new binder in the application.
536 appsimpl expr@(App f arg) = do
537 -- Check runtime representability
539 local_var <- Trans.lift $ is_local_var arg
540 if repr && not local_var
541 then do -- Extract representable arguments
542 id <- Trans.lift $ mkBinderFor arg "arg"
543 change $ Let (NonRec id arg) (App f (Var id))
544 else -- Leave non-representable arguments unchanged
546 -- Leave all other expressions unchanged
547 appsimpl expr = return expr
548 -- Perform this transform everywhere
549 appsimpltop = everywhere ("appsimpl", appsimpl)
551 --------------------------------
552 -- Function-typed argument propagation
553 --------------------------------
554 -- Remove all applications to function-typed arguments, by duplication the
555 -- function called with the function-typed parameter replaced by the free
556 -- variables of the argument passed in.
557 argprop, argproptop :: Transform
558 -- Transform any application of a named function (i.e., skip applications of
559 -- lambda's). Also skip applications that have arguments with free type
560 -- variables, since we can't inline those.
561 argprop expr@(App _ _) | is_var fexpr = do
562 -- Find the body of the function called
563 body_maybe <- Trans.lift $ getGlobalBind f
566 -- Process each of the arguments in turn
567 (args', changed) <- Writer.listen $ mapM doarg args
568 -- See if any of the arguments changed
569 case Monoid.getAny changed of
571 let (newargs', newparams', oldargs) = unzip3 args'
572 let newargs = concat newargs'
573 let newparams = concat newparams'
574 -- Create a new body that consists of a lambda for all new arguments and
575 -- the old body applied to some arguments.
576 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
577 -- Create a new function with the same name but a new body
578 newf <- Trans.lift $ mkFunction f newbody
579 -- Replace the original application with one of the new function to the
581 change $ MkCore.mkCoreApps (Var newf) newargs
583 -- Don't change the expression if none of the arguments changed
586 -- If we don't have a body for the function called, leave it unchanged (it
587 -- should be a primitive function then).
588 Nothing -> return expr
590 -- Find the function called and the arguments
591 (fexpr, args) = collectArgs expr
594 -- Process a single argument and return (args, bndrs, arg), where args are
595 -- the arguments to replace the given argument in the original
596 -- application, bndrs are the binders to include in the top-level lambda
597 -- in the new function body, and arg is the argument to apply to the old
599 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
602 bndrs <- Trans.lift getGlobalBinders
603 let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
604 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
606 -- Propagate all complex arguments that are not representable, but not
607 -- arguments with free type variables (since those would require types
608 -- not known yet, which will always be known eventually).
609 -- Find interesting free variables, each of which should be passed to
610 -- the new function instead of the original function argument.
612 -- Interesting vars are those that are local, but not available from the
613 -- top level scope (functions from this module are defined as local, but
614 -- they're not local to this function, so we can freely move references
615 -- to them into another function).
616 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
617 -- Mark the current expression as changed
619 -- TODO: Clone the free_vars (and update references in arg), since
620 -- this might cause conflicts if two arguments that are propagated
621 -- share a free variable. Also, we are now introducing new variables
622 -- into a function that are not fresh, which violates the binder
623 -- uniqueness invariant.
624 return (map Var free_vars, free_vars, arg)
626 -- Representable types will not be propagated, and arguments with free
627 -- type variables will be propagated later.
628 -- Note that we implicitly remove any type variables in the type of
629 -- the original argument by using the type of the actual argument
630 -- for the new formal parameter.
631 -- TODO: preserve original naming?
632 id <- Trans.lift $ mkBinderFor arg "param"
633 -- Just pass the original argument to the new function, which binds it
634 -- to a new id and just pass that new id to the old function body.
635 return ([arg], [id], mkReferenceTo id)
636 -- Leave all other expressions unchanged
637 argprop expr = return expr
638 -- Perform this transform everywhere
639 argproptop = everywhere ("argprop", argprop)
641 --------------------------------
642 -- Function-typed argument extraction
643 --------------------------------
644 -- This transform takes any function-typed argument that cannot be propagated
645 -- (because the function that is applied to it is a builtin function), and
646 -- puts it in a brand new top level binder. This allows us to for example
647 -- apply map to a lambda expression This will not conflict with inlinenonrep,
648 -- since that only inlines local let bindings, not top level bindings.
649 funextract, funextracttop :: Transform
650 funextract expr@(App _ _) | is_var fexpr = do
651 body_maybe <- Trans.lift $ getGlobalBind f
653 -- We don't have a function body for f, so we can perform this transform.
655 -- Find the new arguments
656 args' <- mapM doarg args
657 -- And update the arguments. We use return instead of changed, so the
658 -- changed flag doesn't get set if none of the args got changed.
659 return $ MkCore.mkCoreApps fexpr args'
660 -- We have a function body for f, leave this application to funprop
661 Just _ -> return expr
663 -- Find the function called and the arguments
664 (fexpr, args) = collectArgs expr
666 -- Change any arguments that have a function type, but are not simple yet
667 -- (ie, a variable or application). This means to create a new function
668 -- for map (\f -> ...) b, but not for map (foo a) b.
670 -- We could use is_applicable here instead of is_fun, but I think
671 -- arguments to functions could only have forall typing when existential
672 -- typing is enabled. Not sure, though.
673 doarg arg | not (is_simple arg) && is_fun arg = do
674 -- Create a new top level binding that binds the argument. Its body will
675 -- be extended with lambda expressions, to take any free variables used
676 -- by the argument expression.
677 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
678 let body = MkCore.mkCoreLams free_vars arg
679 id <- Trans.lift $ mkBinderFor body "fun"
680 Trans.lift $ addGlobalBind id body
681 -- Replace the argument with a reference to the new function, applied to
683 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
684 -- Leave all other arguments untouched
685 doarg arg = return arg
687 -- Leave all other expressions unchanged
688 funextract expr = return expr
689 -- Perform this transform everywhere
690 funextracttop = everywhere ("funextract", funextract)
692 --------------------------------
693 -- Ensure that a function that just returns another function (or rather,
694 -- another top-level binder) is still properly normalized. This is a temporary
695 -- solution, we should probably integrate this pass with lambdasimpl and
697 --------------------------------
698 simplrestop expr@(Lam _ _) = return expr
699 simplrestop expr@(Let _ _) = return expr
700 simplrestop expr = do
701 local_var <- Trans.lift $ is_local_var expr
702 -- Don't extract values that are not representable, to prevent loops with
705 if local_var || not repr
709 id <- Trans.lift $ mkBinderFor expr "res"
710 change $ Let (NonRec id expr) (Var id)
711 --------------------------------
712 -- End of transformations
713 --------------------------------
718 -- What transforms to run?
719 transforms = [inlinetopleveltop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
721 -- | Returns the normalized version of the given function.
723 CoreBndr -- ^ The function to get
724 -> TranslatorSession CoreExpr -- The normalized function body
726 getNormalized bndr = Utils.makeCached bndr tsNormalized $
727 if is_poly (Var bndr)
729 -- This should really only happen at the top level... TODO: Give
730 -- a different error if this happens down in the recursion.
731 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
733 expr <- getBinding bndr
734 normalizeExpr (show bndr) expr
736 -- | Normalize an expression
738 String -- ^ What are we normalizing? For debug output only.
739 -> CoreSyn.CoreExpr -- ^ The expression to normalize
740 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
742 normalizeExpr what expr = do
743 expr_uniqued <- genUniques expr
744 -- Normalize this expression
745 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
746 expr' <- dotransforms transforms expr_uniqued
747 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
750 -- | Get the value that is bound to the given binder at top level. Fails when
751 -- there is no such binding.
753 CoreBndr -- ^ The binder to get the expression for
754 -> TranslatorSession CoreExpr -- ^ The value bound to the binder
756 getBinding bndr = Utils.makeCached bndr tsBindings $
757 -- If the binding isn't in the "cache" (bindings map), then we can't create
758 -- it out of thin air, so return an error.
759 error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr
761 -- | Split a normalized expression into the argument binders, top level
762 -- bindings and the result binder.
764 CoreExpr -- ^ The normalized expression
765 -> ([CoreBndr], [Binding], CoreBndr)
766 splitNormalized expr = (args, binds, res)
768 (args, letexpr) = CoreSyn.collectBinders expr
769 (binds, resexpr) = flattenLets letexpr
770 res = case resexpr of
772 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"