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.Map as Map
17 import qualified Data.Monoid as Monoid
22 import qualified UniqSupply
23 import qualified CoreUtils
25 import qualified TcType
29 import qualified VarSet
30 import qualified NameSet
31 import qualified CoreFVs
32 import qualified CoreUtils
33 import qualified MkCore
34 import qualified HscTypes
35 import Outputable ( showSDoc, ppr, nest )
38 import CLasH.Normalize.NormalizeTypes
39 import CLasH.Translator.TranslatorTypes
40 import CLasH.Normalize.NormalizeTools
41 import CLasH.VHDL.VHDLTypes
42 import qualified CLasH.Utils as Utils
43 import CLasH.Utils.Core.CoreTools
44 import CLasH.Utils.Core.BinderTools
45 import CLasH.Utils.Pretty
47 --------------------------------
48 -- Start of transformations
49 --------------------------------
51 --------------------------------
53 --------------------------------
54 eta, etatop :: Transform
55 eta expr | is_fun expr && not (is_lam expr) = do
56 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
57 id <- Trans.lift $ mkInternalVar "param" arg_ty
58 change (Lam id (App expr (Var id)))
59 -- Leave all other expressions unchanged
61 etatop = notappargs ("eta", eta)
63 --------------------------------
65 --------------------------------
66 beta, betatop :: Transform
67 -- Substitute arg for x in expr. For value lambda's, also clone before
69 beta (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg expr
70 | otherwise = setChanged >> substitute_clone x arg expr
71 -- Propagate the application into the let
72 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
73 -- Propagate the application into each of the alternatives
74 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
76 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
77 ty' = CoreUtils.applyTypeToArg ty arg
78 -- Leave all other expressions unchanged
79 beta expr = return expr
80 -- Perform this transform everywhere
81 betatop = everywhere ("beta", beta)
83 --------------------------------
85 --------------------------------
86 -- Try to move casts as much downward as possible.
87 castprop, castproptop :: Transform
88 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
89 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
91 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
92 -- Leave all other expressions unchanged
93 castprop expr = return expr
94 -- Perform this transform everywhere
95 castproptop = everywhere ("castprop", castprop)
97 --------------------------------
98 -- Cast simplification. Mostly useful for state packing and unpacking, but
99 -- perhaps for others as well.
100 --------------------------------
101 castsimpl, castsimpltop :: Transform
102 castsimpl expr@(Cast val ty) = do
103 -- Don't extract values that are already simpl
104 local_var <- Trans.lift $ is_local_var val
105 -- Don't extract values that are not representable, to prevent loops with
108 if (not local_var) && repr
110 -- Generate a binder for the expression
111 id <- Trans.lift $ mkBinderFor val "castval"
112 -- Extract the expression
113 change $ Let (NonRec id val) (Cast (Var id) ty)
116 -- Leave all other expressions unchanged
117 castsimpl expr = return expr
118 -- Perform this transform everywhere
119 castsimpltop = everywhere ("castsimpl", castsimpl)
122 --------------------------------
123 -- Lambda simplication
124 --------------------------------
125 -- Ensure that a lambda always evaluates to a let expressions or a simple
126 -- variable reference.
127 lambdasimpl, lambdasimpltop :: Transform
128 -- Don't simplify a lambda that evaluates to let, since this is already
129 -- normal form (and would cause infinite loops).
130 lambdasimpl expr@(Lam _ (Let _ _)) = return expr
131 -- Put the of a lambda in its own binding, but not when the expression is
132 -- already a local variable, or not representable (to prevent loops with
134 lambdasimpl expr@(Lam bndr res) = do
136 local_var <- Trans.lift $ is_local_var res
137 if not local_var && repr
139 id <- Trans.lift $ mkBinderFor res "res"
140 change $ Lam bndr (Let (NonRec id res) (Var id))
142 -- If the result is already a local var or not representable, don't
146 -- Leave all other expressions unchanged
147 lambdasimpl expr = return expr
148 -- Perform this transform everywhere
149 lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
151 --------------------------------
152 -- let derecursification
153 --------------------------------
154 letderec, letderectop :: Transform
155 letderec expr@(Let (Rec binds) res) = case liftable of
156 -- Nothing is liftable, just return
158 -- Something can be lifted, generate a new let expression
159 _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
161 -- Make a list of all the binders bound in this recursive let
162 bndrs = map fst binds
163 -- See which bindings are liftable
164 (liftable, nonliftable) = List.partition canlift binds
165 -- Any expression that does not use any of the binders in this recursive let
166 -- can be lifted into a nonrec let. It can't use its own binder either,
167 -- since that would mean the binding is self-recursive and should be in a
168 -- single bind recursive let.
169 canlift (bndr, e) = not $ expr_uses_binders bndrs e
170 -- Leave all other expressions unchanged
171 letderec expr = return expr
172 -- Perform this transform everywhere
173 letderectop = everywhere ("letderec", letderec)
175 --------------------------------
176 -- let simplification
177 --------------------------------
178 letsimpl, letsimpltop :: Transform
179 -- Don't simplify a let that evaluates to another let, since this is already
180 -- normal form (and would cause infinite loops with letflat below).
181 letsimpl expr@(Let _ (Let _ _)) = return expr
182 -- Put the "in ..." value of a let in its own binding, but not when the
183 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
184 letsimpl expr@(Let binds res) = do
186 local_var <- Trans.lift $ is_local_var res
187 if not local_var && repr
189 -- If the result is not a local var already (to prevent loops with
190 -- ourselves), extract it.
191 id <- Trans.lift $ mkBinderFor res "foo"
192 change $ Let binds (Let (NonRec id res) (Var id))
194 -- If the result is already a local var, don't extract it.
197 -- Leave all other expressions unchanged
198 letsimpl expr = return expr
199 -- Perform this transform everywhere
200 letsimpltop = everywhere ("letsimpl", letsimpl)
202 --------------------------------
204 --------------------------------
205 -- Takes a let that binds another let, and turns that into two nested lets.
207 -- let b = (let b' = expr' in res') in res
209 -- let b' = expr' in (let b = res' in res)
210 letflat, letflattop :: Transform
211 -- Turn a nonrec let that binds a let into two nested lets.
212 letflat (Let (NonRec b (Let binds res')) res) =
213 change $ Let binds (Let (NonRec b res') res)
214 letflat (Let (Rec binds) expr) = do
215 -- Flatten each binding.
216 binds' <- Utils.concatM $ Monad.mapM flatbind binds
217 -- Return the new let. We don't use change here, since possibly nothing has
218 -- changed. If anything has changed, flatbind has already flagged that
220 return $ Let (Rec binds') expr
222 -- Turns a binding of a let into a multiple bindings, or any other binding
223 -- into a list with just that binding
224 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
225 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
226 flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
227 flatbind (b, expr) = return [(b, expr)]
228 -- Leave all other expressions unchanged
229 letflat expr = return expr
230 -- Perform this transform everywhere
231 letflattop = everywhere ("letflat", letflat)
233 --------------------------------
235 --------------------------------
236 -- Remove empty (recursive) lets
237 letremove, letremovetop :: Transform
238 letremove (Let (Rec []) res) = change $ res
239 -- Leave all other expressions unchanged
240 letremove expr = return expr
241 -- Perform this transform everywhere
242 letremovetop = everywhere ("letremove", letremove)
244 --------------------------------
245 -- Simple let binding removal
246 --------------------------------
247 -- Remove a = b bindings from let expressions everywhere
248 letremovesimpletop :: Transform
249 letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
251 --------------------------------
252 -- Unused let binding removal
253 --------------------------------
254 letremoveunused, letremoveunusedtop :: Transform
255 letremoveunused expr@(Let (NonRec b bound) res) = do
256 let used = expr_uses_binders [b] res
260 letremoveunused expr@(Let (Rec binds) res) = do
261 -- Filter out all unused binds.
262 let binds' = filter dobind binds
263 -- Only set the changed flag if binds got removed
264 changeif (length binds' /= length binds) (Let (Rec binds') res)
266 bound_exprs = map snd binds
267 -- For each bind check if the bind is used by res or any of the bound
269 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
270 -- Leave all other expressions unchanged
271 letremoveunused expr = return expr
272 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
275 --------------------------------
276 -- Identical let binding merging
277 --------------------------------
278 -- Merge two bindings in a let if they are identical
279 -- TODO: We would very much like to use GHC's CSE module for this, but that
280 -- doesn't track if something changed or not, so we can't use it properly.
281 letmerge, letmergetop :: Transform
282 letmerge expr@(Let _ _) = do
283 let (binds, res) = flattenLets expr
284 binds' <- domerge binds
285 return $ mkNonRecLets binds' res
287 domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
288 domerge [] = return []
290 es' <- mapM (mergebinds e) es
294 -- Uses the second bind to simplify the second bind, if applicable.
295 mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
296 mergebinds (b1, e1) (b2, e2)
297 -- Identical expressions? Replace the second binding with a reference to
299 | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
300 -- Different expressions? Don't change
301 | otherwise = return (b2, e2)
302 -- Leave all other expressions unchanged
303 letmerge expr = return expr
304 letmergetop = everywhere ("letmerge", letmerge)
307 --------------------------------
308 -- Non-representable binding inlining
309 --------------------------------
310 -- Remove a = B bindings, with B of a non-representable type, from let
311 -- expressions everywhere. This means that any value that we can't generate a
312 -- signal for, will be inlined and hopefully turned into something we can
315 -- This is a tricky function, which is prone to create loops in the
316 -- transformations. To fix this, we make sure that no transformation will
317 -- create a new let binding with a non-representable type. These other
318 -- transformations will just not work on those function-typed values at first,
319 -- but the other transformations (in particular β-reduction) should make sure
320 -- that the type of those values eventually becomes representable.
321 inlinenonreptop :: Transform
322 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
324 --------------------------------
325 -- Top level function inlining
326 --------------------------------
327 -- This transformation inlines top level bindings that have been generated by
328 -- the compiler and are really simple. Really simple currently means that the
329 -- normalized form only contains a single binding, which catches most of the
330 -- cases where a top level function is created that simply calls a type class
331 -- method with a type and dictionary argument, e.g.
332 -- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
333 -- which is later called using simply
334 -- fromInteger (smallInteger 10)
335 -- By inlining such calls to simple, compiler generated functions, we prevent
336 -- huge amounts of trivial components in the VHDL output, which the user never
337 -- wanted. We never inline user-defined functions, since we want to preserve
338 -- all structure defined by the user. Currently this includes all functions
339 -- that were created by funextract, since we would get loops otherwise.
341 -- Note that "defined by the compiler" isn't completely watertight, since GHC
342 -- doesn't seem to set all those names as "system names", we apply some
344 inlinetoplevel, inlinetopleveltop :: Transform
345 -- Any system name is candidate for inlining. Never inline user-defined
346 -- functions, to preserve structure.
347 inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
348 norm <- isNormalizeable f
349 -- See if this is a top level binding for which we have a body
350 body_maybe <- Trans.lift $ getGlobalBind f
351 if norm && Maybe.isJust body_maybe
353 -- Get the normalized version
354 norm <- Trans.lift $ getNormalized f
357 -- Regenerate all uniques in the to-be-inlined expression
358 norm_uniqued <- Trans.lift $ genUniques norm
363 -- No body or not normalizeable.
365 -- Leave all other expressions unchanged
366 inlinetoplevel expr = return expr
367 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
369 needsInline :: CoreExpr -> Bool
370 needsInline expr = case splitNormalized expr of
371 -- Inline any function that only has a single definition, it is probably
372 -- simple enough. This might inline some stuff that it shouldn't though it
373 -- will never inline user-defined functions (inlinetoplevel only tries
374 -- system names) and inlining should never break things.
375 (args, [bind], res) -> True
378 --------------------------------
379 -- Scrutinee simplification
380 --------------------------------
381 scrutsimpl,scrutsimpltop :: Transform
382 -- Don't touch scrutinees that are already simple
383 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
384 -- Replace all other cases with a let that binds the scrutinee and a new
385 -- simple scrutinee, but only when the scrutinee is representable (to prevent
386 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
387 -- will be supported anyway...)
388 scrutsimpl expr@(Case scrut b ty alts) = do
392 id <- Trans.lift $ mkBinderFor scrut "scrut"
393 change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
396 -- Leave all other expressions unchanged
397 scrutsimpl expr = return expr
398 -- Perform this transform everywhere
399 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
401 --------------------------------
402 -- Scrutinee binder removal
403 --------------------------------
404 -- A case expression can have an extra binder, to which the scrutinee is bound
405 -- after bringing it to WHNF. This is used for forcing evaluation of strict
406 -- arguments. Since strictness does not matter for us (rather, everything is
407 -- sort of strict), this binder is ignored when generating VHDL, and must thus
408 -- be wild in the normal form.
409 scrutbndrremove, scrutbndrremovetop :: Transform
410 -- If the scrutinee is already simple, and the bndr is not wild yet, replace
411 -- all occurences of the binder with the scrutinee variable.
412 scrutbndrremove (Case (Var scrut) bndr ty alts) | bndr_used = do
413 alts' <- mapM subs_bndr alts
414 return $ Case (Var scrut) wild ty alts'
416 is_used (_, _, expr) = expr_uses_binders [bndr] expr
417 bndr_used = or $ map is_used alts
418 subs_bndr (con, bndrs, expr) = do
419 expr' <- substitute bndr (Var scrut) expr
420 return (con, bndrs, expr')
421 wild = MkCore.mkWildBinder (Id.idType bndr)
422 -- Leave all other expressions unchanged
423 scrutbndrremove expr = return expr
424 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
426 --------------------------------
427 -- Case binder wildening
428 --------------------------------
429 casesimpl, casesimpltop :: Transform
430 -- This is already a selector case (or, if x does not appear in bndrs, a very
431 -- simple case statement that will be removed by caseremove below). Just leave
433 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
434 -- Make sure that all case alternatives have only wild binders and simple
436 -- This is done by creating a new let binding for each non-wild binder, which
437 -- is bound to a new simple selector case statement and for each complex
438 -- expression. We do this only for representable types, to prevent loops with
440 casesimpl expr@(Case scrut b ty alts) = do
441 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
442 let bindings = concat bindingss
443 -- Replace the case with a let with bindings and a case
444 let newlet = mkNonRecLets bindings (Case scrut b ty alts')
445 -- If there are no non-wild binders, or this case is already a simple
446 -- selector (i.e., a single alt with exactly one binding), already a simple
447 -- selector altan no bindings (i.e., no wild binders in the original case),
448 -- don't change anything, otherwise, replace the case.
449 if null bindings then return expr else change newlet
451 -- Generate a single wild binder, since they are all the same
452 wild = MkCore.mkWildBinder
453 -- Wilden the binders of one alt, producing a list of bindings as a
455 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
456 doalt (con, bndrs, expr) = do
457 -- Make each binder wild, if possible
458 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
459 let (newbndrs, bindings_maybe) = unzip bndrs_res
460 -- Extract a complex expression, if possible. For this we check if any of
461 -- the new list of bndrs are used by expr. We can't use free_vars here,
462 -- since that looks at the old bndrs.
463 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) $ expr
464 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
465 -- Create a new alternative
466 let newalt = (con, newbndrs, expr')
467 let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
468 return (bindings, newalt)
470 -- Make wild alternatives for each binder
471 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
472 -- A set of all the binders that are used by the expression
473 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
474 -- Look at the ith binder in the case alternative. Return a new binder
475 -- for it (either the same one, or a wild one) and optionally a let
476 -- binding containing a case expression.
477 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
480 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
481 -- in expr, this means that b is unused if expr does not use it.)
482 let wild = not (VarSet.elemVarSet b free_vars)
483 -- Create a new binding for any representable binder that is not
484 -- already wild and is representable (to prevent loops with
486 if (not wild) && repr
488 -- Create on new binder that will actually capture a value in this
489 -- case statement, and return it.
490 let bty = (Id.idType b)
491 id <- Trans.lift $ mkInternalVar "sel" bty
492 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
493 let caseexpr = Case scrut b bty [(con, binders, Var id)]
494 return (wildbndrs!!i, Just (b, caseexpr))
496 -- Just leave the original binder in place, and don't generate an
497 -- extra selector case.
499 -- Process the expression of a case alternative. Accepts an expression
500 -- and whether this expression uses any of the binders in the
501 -- alternative. Returns an optional new binding and a new expression.
502 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
503 doexpr expr uses_bndrs = do
504 local_var <- Trans.lift $ is_local_var expr
506 -- Extract any expressions that do not use any binders from this
507 -- alternative, is not a local var already and is representable (to
508 -- prevent loops with inlinenonrep).
509 if (not uses_bndrs) && (not local_var) && repr
511 id <- Trans.lift $ mkBinderFor expr "caseval"
512 -- We don't flag a change here, since casevalsimpl will do that above
513 -- based on Just we return here.
514 return $ (Just (id, expr), Var id)
516 -- Don't simplify anything else
517 return (Nothing, expr)
518 -- Leave all other expressions unchanged
519 casesimpl expr = return expr
520 -- Perform this transform everywhere
521 casesimpltop = everywhere ("casesimpl", casesimpl)
523 --------------------------------
525 --------------------------------
526 -- Remove case statements that have only a single alternative and only wild
528 caseremove, caseremovetop :: Transform
529 -- Replace a useless case by the value of its single alternative
530 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
531 -- Find if any of the binders are used by expr
532 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
533 -- Leave all other expressions unchanged
534 caseremove expr = return expr
535 -- Perform this transform everywhere
536 caseremovetop = everywhere ("caseremove", caseremove)
538 --------------------------------
539 -- Argument extraction
540 --------------------------------
541 -- Make sure that all arguments of a representable type are simple variables.
542 appsimpl, appsimpltop :: Transform
543 -- Simplify all representable arguments. Do this by introducing a new Let
544 -- that binds the argument and passing the new binder in the application.
545 appsimpl expr@(App f arg) = do
546 -- Check runtime representability
548 local_var <- Trans.lift $ is_local_var arg
549 if repr && not local_var
550 then do -- Extract representable arguments
551 id <- Trans.lift $ mkBinderFor arg "arg"
552 change $ Let (NonRec id arg) (App f (Var id))
553 else -- Leave non-representable arguments unchanged
555 -- Leave all other expressions unchanged
556 appsimpl expr = return expr
557 -- Perform this transform everywhere
558 appsimpltop = everywhere ("appsimpl", appsimpl)
560 --------------------------------
561 -- Function-typed argument propagation
562 --------------------------------
563 -- Remove all applications to function-typed arguments, by duplication the
564 -- function called with the function-typed parameter replaced by the free
565 -- variables of the argument passed in.
566 argprop, argproptop :: Transform
567 -- Transform any application of a named function (i.e., skip applications of
568 -- lambda's). Also skip applications that have arguments with free type
569 -- variables, since we can't inline those.
570 argprop expr@(App _ _) | is_var fexpr = do
571 -- Find the body of the function called
572 body_maybe <- Trans.lift $ getGlobalBind f
575 -- Process each of the arguments in turn
576 (args', changed) <- Writer.listen $ mapM doarg args
577 -- See if any of the arguments changed
578 case Monoid.getAny changed of
580 let (newargs', newparams', oldargs) = unzip3 args'
581 let newargs = concat newargs'
582 let newparams = concat newparams'
583 -- Create a new body that consists of a lambda for all new arguments and
584 -- the old body applied to some arguments.
585 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
586 -- Create a new function with the same name but a new body
587 newf <- Trans.lift $ mkFunction f newbody
588 -- Replace the original application with one of the new function to the
590 change $ MkCore.mkCoreApps (Var newf) newargs
592 -- Don't change the expression if none of the arguments changed
595 -- If we don't have a body for the function called, leave it unchanged (it
596 -- should be a primitive function then).
597 Nothing -> return expr
599 -- Find the function called and the arguments
600 (fexpr, args) = collectArgs expr
603 -- Process a single argument and return (args, bndrs, arg), where args are
604 -- the arguments to replace the given argument in the original
605 -- application, bndrs are the binders to include in the top-level lambda
606 -- in the new function body, and arg is the argument to apply to the old
608 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
611 bndrs <- Trans.lift getGlobalBinders
612 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
613 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
615 -- Propagate all complex arguments that are not representable, but not
616 -- arguments with free type variables (since those would require types
617 -- not known yet, which will always be known eventually).
618 -- Find interesting free variables, each of which should be passed to
619 -- the new function instead of the original function argument.
621 -- Interesting vars are those that are local, but not available from the
622 -- top level scope (functions from this module are defined as local, but
623 -- they're not local to this function, so we can freely move references
624 -- to them into another function).
625 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
626 -- Mark the current expression as changed
628 return (map Var free_vars, free_vars, arg)
630 -- Representable types will not be propagated, and arguments with free
631 -- type variables will be propagated later.
632 -- TODO: preserve original naming?
633 id <- Trans.lift $ mkBinderFor arg "param"
634 -- Just pass the original argument to the new function, which binds it
635 -- to a new id and just pass that new id to the old function body.
636 return ([arg], [id], mkReferenceTo id)
637 -- Leave all other expressions unchanged
638 argprop expr = return expr
639 -- Perform this transform everywhere
640 argproptop = everywhere ("argprop", argprop)
642 --------------------------------
643 -- Function-typed argument extraction
644 --------------------------------
645 -- This transform takes any function-typed argument that cannot be propagated
646 -- (because the function that is applied to it is a builtin function), and
647 -- puts it in a brand new top level binder. This allows us to for example
648 -- apply map to a lambda expression This will not conflict with inlinenonrep,
649 -- since that only inlines local let bindings, not top level bindings.
650 funextract, funextracttop :: Transform
651 funextract expr@(App _ _) | is_var fexpr = do
652 body_maybe <- Trans.lift $ getGlobalBind f
654 -- We don't have a function body for f, so we can perform this transform.
656 -- Find the new arguments
657 args' <- mapM doarg args
658 -- And update the arguments. We use return instead of changed, so the
659 -- changed flag doesn't get set if none of the args got changed.
660 return $ MkCore.mkCoreApps fexpr args'
661 -- We have a function body for f, leave this application to funprop
662 Just _ -> return expr
664 -- Find the function called and the arguments
665 (fexpr, args) = collectArgs expr
667 -- Change any arguments that have a function type, but are not simple yet
668 -- (ie, a variable or application). This means to create a new function
669 -- for map (\f -> ...) b, but not for map (foo a) b.
671 -- We could use is_applicable here instead of is_fun, but I think
672 -- arguments to functions could only have forall typing when existential
673 -- typing is enabled. Not sure, though.
674 doarg arg | not (is_simple arg) && is_fun arg = do
675 -- Create a new top level binding that binds the argument. Its body will
676 -- be extended with lambda expressions, to take any free variables used
677 -- by the argument expression.
678 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
679 let body = MkCore.mkCoreLams free_vars arg
680 id <- Trans.lift $ mkBinderFor body "fun"
681 Trans.lift $ addGlobalBind id body
682 -- Replace the argument with a reference to the new function, applied to
684 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
685 -- Leave all other arguments untouched
686 doarg arg = return arg
688 -- Leave all other expressions unchanged
689 funextract expr = return expr
690 -- Perform this transform everywhere
691 funextracttop = everywhere ("funextract", funextract)
693 --------------------------------
694 -- Ensure that a function that just returns another function (or rather,
695 -- another top-level binder) is still properly normalized. This is a temporary
696 -- solution, we should probably integrate this pass with lambdasimpl and
698 --------------------------------
699 simplrestop expr@(Lam _ _) = return expr
700 simplrestop expr@(Let _ _) = return expr
701 simplrestop expr = do
702 local_var <- Trans.lift $ is_local_var expr
703 -- Don't extract values that are not representable, to prevent loops with
706 if local_var || not repr
710 id <- Trans.lift $ mkBinderFor expr "res"
711 change $ Let (NonRec id expr) (Var id)
712 --------------------------------
713 -- End of transformations
714 --------------------------------
719 -- What transforms to run?
720 transforms = [inlinetopleveltop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, scrutbndrremovetop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
722 -- | Returns the normalized version of the given function.
724 CoreBndr -- ^ The function to get
725 -> TranslatorSession CoreExpr -- The normalized function body
727 getNormalized bndr = Utils.makeCached bndr tsNormalized $ do
728 if is_poly (Var bndr)
730 -- This should really only happen at the top level... TODO: Give
731 -- a different error if this happens down in the recursion.
732 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
734 expr <- getBinding bndr
735 normalizeExpr (show bndr) expr
737 -- | Normalize an expression
739 String -- ^ What are we normalizing? For debug output only.
740 -> CoreSyn.CoreExpr -- ^ The expression to normalize
741 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
743 normalizeExpr what expr = do
744 expr_uniqued <- genUniques expr
745 -- Normalize this expression
746 trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
747 expr' <- dotransforms transforms expr_uniqued
748 trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
751 -- | Get the value that is bound to the given binder at top level. Fails when
752 -- there is no such binding.
754 CoreBndr -- ^ The binder to get the expression for
755 -> TranslatorSession CoreExpr -- ^ The value bound to the binder
757 getBinding bndr = Utils.makeCached bndr tsBindings $ do
758 -- If the binding isn't in the "cache" (bindings map), then we can't create
759 -- it out of thin air, so return an error.
760 error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr
762 -- | Split a normalized expression into the argument binders, top level
763 -- bindings and the result binder.
765 CoreExpr -- ^ The normalized expression
766 -> ([CoreBndr], [Binding], CoreBndr)
767 splitNormalized expr = (args, binds, res)
769 (args, letexpr) = CoreSyn.collectBinders expr
770 (binds, resexpr) = flattenLets letexpr
771 res = case resexpr of
773 _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"