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) where
11 import qualified Maybe
12 import qualified "transformers" Control.Monad.Trans as Trans
13 import qualified Control.Monad as Monad
14 import qualified Control.Monad.Trans.Writer as Writer
15 import qualified Data.Map as Map
16 import qualified Data.Monoid as Monoid
21 import qualified UniqSupply
22 import qualified CoreUtils
24 import qualified TcType
27 import qualified VarSet
28 import qualified NameSet
29 import qualified CoreFVs
30 import qualified CoreUtils
31 import qualified MkCore
32 import qualified HscTypes
33 import Outputable ( showSDoc, ppr, nest )
36 import CLasH.Normalize.NormalizeTypes
37 import CLasH.Translator.TranslatorTypes
38 import CLasH.Normalize.NormalizeTools
39 import CLasH.VHDL.VHDLTypes
40 import qualified CLasH.Utils as Utils
41 import CLasH.Utils.Core.CoreTools
42 import CLasH.Utils.Core.BinderTools
43 import CLasH.Utils.Pretty
45 --------------------------------
46 -- Start of transformations
47 --------------------------------
49 --------------------------------
51 --------------------------------
52 eta, etatop :: Transform
53 eta expr | is_fun expr && not (is_lam expr) = do
54 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
55 id <- Trans.lift $ mkInternalVar "param" arg_ty
56 change (Lam id (App expr (Var id)))
57 -- Leave all other expressions unchanged
59 etatop = notappargs ("eta", eta)
61 --------------------------------
63 --------------------------------
64 beta, betatop :: Transform
65 -- Substitute arg for x in expr
66 beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr
67 -- Propagate the application into the let
68 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
69 -- Propagate the application into each of the alternatives
70 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
72 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
73 ty' = CoreUtils.applyTypeToArg ty arg
74 -- Leave all other expressions unchanged
75 beta expr = return expr
76 -- Perform this transform everywhere
77 betatop = everywhere ("beta", beta)
79 --------------------------------
81 --------------------------------
82 -- Try to move casts as much downward as possible.
83 castprop, castproptop :: Transform
84 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
85 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
87 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
88 -- Leave all other expressions unchanged
89 castprop expr = return expr
90 -- Perform this transform everywhere
91 castproptop = everywhere ("castprop", castprop)
93 --------------------------------
94 -- Cast simplification. Mostly useful for state packing and unpacking, but
95 -- perhaps for others as well.
96 --------------------------------
97 castsimpl, castsimpltop :: Transform
98 castsimpl expr@(Cast val ty) = do
99 -- Don't extract values that are already simpl
100 local_var <- Trans.lift $ is_local_var val
101 -- Don't extract values that are not representable, to prevent loops with
104 if (not local_var) && repr
106 -- Generate a binder for the expression
107 id <- Trans.lift $ mkBinderFor val "castval"
108 -- Extract the expression
109 change $ Let (Rec [(id, val)]) (Cast (Var id) ty)
112 -- Leave all other expressions unchanged
113 castsimpl expr = return expr
114 -- Perform this transform everywhere
115 castsimpltop = everywhere ("castsimpl", castsimpl)
117 --------------------------------
118 -- let recursification
119 --------------------------------
120 letrec, letrectop :: Transform
121 letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
122 -- Leave all other expressions unchanged
123 letrec expr = return expr
124 -- Perform this transform everywhere
125 letrectop = everywhere ("letrec", letrec)
127 --------------------------------
128 -- let simplification
129 --------------------------------
130 letsimpl, letsimpltop :: Transform
131 -- Put the "in ..." value of a let in its own binding, but not when the
132 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
133 letsimpl expr@(Let (Rec binds) res) = do
135 local_var <- Trans.lift $ is_local_var res
136 if not local_var && repr
138 -- If the result is not a local var already (to prevent loops with
139 -- ourselves), extract it.
140 id <- Trans.lift $ mkInternalVar "foo" (CoreUtils.exprType res)
142 change $ Let (Rec (bind:binds)) (Var id)
144 -- If the result is already a local var, don't extract it.
147 -- Leave all other expressions unchanged
148 letsimpl expr = return expr
149 -- Perform this transform everywhere
150 letsimpltop = everywhere ("letsimpl", letsimpl)
152 --------------------------------
154 --------------------------------
155 letflat, letflattop :: Transform
156 letflat (Let (Rec binds) expr) = do
157 -- Turn each binding into a list of bindings (possibly containing just one
158 -- element, of course)
159 bindss <- Monad.mapM flatbind binds
160 -- Concat all the bindings
161 let binds' = concat bindss
162 -- Return the new let. We don't use change here, since possibly nothing has
163 -- changed. If anything has changed, flatbind has already flagged that
165 return $ Let (Rec binds') expr
167 -- Turns a binding of a let into a multiple bindings, or any other binding
168 -- into a list with just that binding
169 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
170 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
171 flatbind (b, expr) = return [(b, expr)]
172 -- Leave all other expressions unchanged
173 letflat expr = return expr
174 -- Perform this transform everywhere
175 letflattop = everywhere ("letflat", letflat)
177 --------------------------------
178 -- Simple let binding removal
179 --------------------------------
180 -- Remove a = b bindings from let expressions everywhere
181 letremovetop :: Transform
182 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
184 --------------------------------
185 -- Unused let binding removal
186 --------------------------------
187 letremoveunused, letremoveunusedtop :: Transform
188 letremoveunused expr@(Let (Rec binds) res) = do
189 -- Filter out all unused binds.
190 let binds' = filter dobind binds
191 -- Only set the changed flag if binds got removed
192 changeif (length binds' /= length binds) (Let (Rec binds') res)
194 bound_exprs = map snd binds
195 -- For each bind check if the bind is used by res or any of the bound
197 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
198 -- Leave all other expressions unchanged
199 letremoveunused expr = return expr
200 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
202 --------------------------------
204 --------------------------------
205 -- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let
206 -- expressions everywhere. This means that any value that still needs to be
207 -- applied to something else (polymorphic values need to be applied to a
208 -- Type) will be inlined, and will eventually be applied to all their
211 -- This is a tricky function, which is prone to create loops in the
212 -- transformations. To fix this, we make sure that no transformation will
213 -- create a new let binding with a function type. These other transformations
214 -- will just not work on those function-typed values at first, but the other
215 -- transformations (in particular β-reduction) should make sure that the type
216 -- of those values eventually becomes primitive.
217 inlinenonreptop :: Transform
218 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
220 --------------------------------
221 -- Scrutinee simplification
222 --------------------------------
223 scrutsimpl,scrutsimpltop :: Transform
224 -- Don't touch scrutinees that are already simple
225 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
226 -- Replace all other cases with a let that binds the scrutinee and a new
227 -- simple scrutinee, but only when the scrutinee is representable (to prevent
228 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
229 -- will be supported anyway...)
230 scrutsimpl expr@(Case scrut b ty alts) = do
234 id <- Trans.lift $ mkInternalVar "scrut" (CoreUtils.exprType scrut)
235 change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
238 -- Leave all other expressions unchanged
239 scrutsimpl expr = return expr
240 -- Perform this transform everywhere
241 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
243 --------------------------------
244 -- Case binder wildening
245 --------------------------------
246 casesimpl, casesimpltop :: Transform
247 -- This is already a selector case (or, if x does not appear in bndrs, a very
248 -- simple case statement that will be removed by caseremove below). Just leave
250 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
251 -- Make sure that all case alternatives have only wild binders and simple
253 -- This is done by creating a new let binding for each non-wild binder, which
254 -- is bound to a new simple selector case statement and for each complex
255 -- expression. We do this only for representable types, to prevent loops with
257 casesimpl expr@(Case scrut b ty alts) = do
258 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
259 let bindings = concat bindingss
260 -- Replace the case with a let with bindings and a case
261 let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
262 -- If there are no non-wild binders, or this case is already a simple
263 -- selector (i.e., a single alt with exactly one binding), already a simple
264 -- selector altan no bindings (i.e., no wild binders in the original case),
265 -- don't change anything, otherwise, replace the case.
266 if null bindings then return expr else change newlet
268 -- Generate a single wild binder, since they are all the same
269 wild = MkCore.mkWildBinder
270 -- Wilden the binders of one alt, producing a list of bindings as a
272 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
273 doalt (con, bndrs, expr) = do
274 -- Make each binder wild, if possible
275 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
276 let (newbndrs, bindings_maybe) = unzip bndrs_res
277 -- Extract a complex expression, if possible. For this we check if any of
278 -- the new list of bndrs are used by expr. We can't use free_vars here,
279 -- since that looks at the old bndrs.
280 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) $ expr
281 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
282 -- Create a new alternative
283 let newalt = (con, newbndrs, expr')
284 let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe)
285 return (bindings, newalt)
287 -- Make wild alternatives for each binder
288 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
289 -- A set of all the binders that are used by the expression
290 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
291 -- Look at the ith binder in the case alternative. Return a new binder
292 -- for it (either the same one, or a wild one) and optionally a let
293 -- binding containing a case expression.
294 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
296 repr <- isRepr (Var b)
297 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
298 -- in expr, this means that b is unused if expr does not use it.)
299 let wild = not (VarSet.elemVarSet b free_vars)
300 -- Create a new binding for any representable binder that is not
301 -- already wild and is representable (to prevent loops with
303 if (not wild) && repr
305 -- Create on new binder that will actually capture a value in this
306 -- case statement, and return it.
307 let bty = (Id.idType b)
308 id <- Trans.lift $ mkInternalVar "sel" bty
309 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
310 let caseexpr = Case scrut b bty [(con, binders, Var id)]
311 return (wildbndrs!!i, Just (b, caseexpr))
313 -- Just leave the original binder in place, and don't generate an
314 -- extra selector case.
316 -- Process the expression of a case alternative. Accepts an expression
317 -- and whether this expression uses any of the binders in the
318 -- alternative. Returns an optional new binding and a new expression.
319 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
320 doexpr expr uses_bndrs = do
321 local_var <- Trans.lift $ is_local_var expr
323 -- Extract any expressions that do not use any binders from this
324 -- alternative, is not a local var already and is representable (to
325 -- prevent loops with inlinenonrep).
326 if (not uses_bndrs) && (not local_var) && repr
328 id <- Trans.lift $ mkInternalVar "caseval" (CoreUtils.exprType expr)
329 -- We don't flag a change here, since casevalsimpl will do that above
330 -- based on Just we return here.
331 return $ (Just (id, expr), Var id)
333 -- Don't simplify anything else
334 return (Nothing, expr)
335 -- Leave all other expressions unchanged
336 casesimpl expr = return expr
337 -- Perform this transform everywhere
338 casesimpltop = everywhere ("casesimpl", casesimpl)
340 --------------------------------
342 --------------------------------
343 -- Remove case statements that have only a single alternative and only wild
345 caseremove, caseremovetop :: Transform
346 -- Replace a useless case by the value of its single alternative
347 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
348 -- Find if any of the binders are used by expr
349 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
350 -- Leave all other expressions unchanged
351 caseremove expr = return expr
352 -- Perform this transform everywhere
353 caseremovetop = everywhere ("caseremove", caseremove)
355 --------------------------------
356 -- Argument extraction
357 --------------------------------
358 -- Make sure that all arguments of a representable type are simple variables.
359 appsimpl, appsimpltop :: Transform
360 -- Simplify all representable arguments. Do this by introducing a new Let
361 -- that binds the argument and passing the new binder in the application.
362 appsimpl expr@(App f arg) = do
363 -- Check runtime representability
365 local_var <- Trans.lift $ is_local_var arg
366 if repr && not local_var
367 then do -- Extract representable arguments
368 id <- Trans.lift $ mkInternalVar "arg" (CoreUtils.exprType arg)
369 change $ Let (Rec [(id, arg)]) (App f (Var id))
370 else -- Leave non-representable arguments unchanged
372 -- Leave all other expressions unchanged
373 appsimpl expr = return expr
374 -- Perform this transform everywhere
375 appsimpltop = everywhere ("appsimpl", appsimpl)
377 --------------------------------
378 -- Function-typed argument propagation
379 --------------------------------
380 -- Remove all applications to function-typed arguments, by duplication the
381 -- function called with the function-typed parameter replaced by the free
382 -- variables of the argument passed in.
383 argprop, argproptop :: Transform
384 -- Transform any application of a named function (i.e., skip applications of
385 -- lambda's). Also skip applications that have arguments with free type
386 -- variables, since we can't inline those.
387 argprop expr@(App _ _) | is_var fexpr = do
388 -- Find the body of the function called
389 body_maybe <- Trans.lift $ getGlobalBind f
392 -- Process each of the arguments in turn
393 (args', changed) <- Writer.listen $ mapM doarg args
394 -- See if any of the arguments changed
395 case Monoid.getAny changed of
397 let (newargs', newparams', oldargs) = unzip3 args'
398 let newargs = concat newargs'
399 let newparams = concat newparams'
400 -- Create a new body that consists of a lambda for all new arguments and
401 -- the old body applied to some arguments.
402 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
403 -- Create a new function with the same name but a new body
404 newf <- Trans.lift $ mkFunction f newbody
405 -- Replace the original application with one of the new function to the
407 change $ MkCore.mkCoreApps (Var newf) newargs
409 -- Don't change the expression if none of the arguments changed
412 -- If we don't have a body for the function called, leave it unchanged (it
413 -- should be a primitive function then).
414 Nothing -> return expr
416 -- Find the function called and the arguments
417 (fexpr, args) = collectArgs expr
420 -- Process a single argument and return (args, bndrs, arg), where args are
421 -- the arguments to replace the given argument in the original
422 -- application, bndrs are the binders to include in the top-level lambda
423 -- in the new function body, and arg is the argument to apply to the old
425 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
428 bndrs <- Trans.lift getGlobalBinders
429 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
430 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
432 -- Propagate all complex arguments that are not representable, but not
433 -- arguments with free type variables (since those would require types
434 -- not known yet, which will always be known eventually).
435 -- Find interesting free variables, each of which should be passed to
436 -- the new function instead of the original function argument.
438 -- Interesting vars are those that are local, but not available from the
439 -- top level scope (functions from this module are defined as local, but
440 -- they're not local to this function, so we can freely move references
441 -- to them into another function).
442 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
443 -- Mark the current expression as changed
445 return (map Var free_vars, free_vars, arg)
447 -- Representable types will not be propagated, and arguments with free
448 -- type variables will be propagated later.
449 -- TODO: preserve original naming?
450 id <- Trans.lift $ mkBinderFor arg "param"
451 -- Just pass the original argument to the new function, which binds it
452 -- to a new id and just pass that new id to the old function body.
453 return ([arg], [id], mkReferenceTo id)
454 -- Leave all other expressions unchanged
455 argprop expr = return expr
456 -- Perform this transform everywhere
457 argproptop = everywhere ("argprop", argprop)
459 --------------------------------
460 -- Function-typed argument extraction
461 --------------------------------
462 -- This transform takes any function-typed argument that cannot be propagated
463 -- (because the function that is applied to it is a builtin function), and
464 -- puts it in a brand new top level binder. This allows us to for example
465 -- apply map to a lambda expression This will not conflict with inlinenonrep,
466 -- since that only inlines local let bindings, not top level bindings.
467 funextract, funextracttop :: Transform
468 funextract expr@(App _ _) | is_var fexpr = do
469 body_maybe <- Trans.lift $ getGlobalBind f
471 -- We don't have a function body for f, so we can perform this transform.
473 -- Find the new arguments
474 args' <- mapM doarg args
475 -- And update the arguments. We use return instead of changed, so the
476 -- changed flag doesn't get set if none of the args got changed.
477 return $ MkCore.mkCoreApps fexpr args'
478 -- We have a function body for f, leave this application to funprop
479 Just _ -> return expr
481 -- Find the function called and the arguments
482 (fexpr, args) = collectArgs expr
484 -- Change any arguments that have a function type, but are not simple yet
485 -- (ie, a variable or application). This means to create a new function
486 -- for map (\f -> ...) b, but not for map (foo a) b.
488 -- We could use is_applicable here instead of is_fun, but I think
489 -- arguments to functions could only have forall typing when existential
490 -- typing is enabled. Not sure, though.
491 doarg arg | not (is_simple arg) && is_fun arg = do
492 -- Create a new top level binding that binds the argument. Its body will
493 -- be extended with lambda expressions, to take any free variables used
494 -- by the argument expression.
495 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
496 let body = MkCore.mkCoreLams free_vars arg
497 id <- Trans.lift $ mkBinderFor body "fun"
498 Trans.lift $ addGlobalBind id body
499 -- Replace the argument with a reference to the new function, applied to
501 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
502 -- Leave all other arguments untouched
503 doarg arg = return arg
505 -- Leave all other expressions unchanged
506 funextract expr = return expr
507 -- Perform this transform everywhere
508 funextracttop = everywhere ("funextract", funextract)
510 --------------------------------
511 -- End of transformations
512 --------------------------------
517 -- What transforms to run?
518 transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop]
520 -- | Returns the normalized version of the given function.
522 CoreBndr -- ^ The function to get
523 -> TranslatorSession CoreExpr -- The normalized function body
525 getNormalized bndr = Utils.makeCached bndr tsNormalized $ do
526 if is_poly (Var bndr)
528 -- This should really only happen at the top level... TODO: Give
529 -- a different error if this happens down in the recursion.
530 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
532 expr <- getBinding bndr
533 normalizeExpr (show bndr) expr
535 -- | Normalize an expression
537 String -- ^ What are we normalizing? For debug output only.
538 -> CoreSyn.CoreExpr -- ^ The expression to normalize
539 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
541 normalizeExpr what expr = do
542 -- Introduce an empty Let at the top level, so there will always be
543 -- a let in the expression (none of the transformations will remove
545 let expr' = Let (Rec []) expr
546 -- Normalize this expression
547 trace ("Transforming " ++ what ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
548 expr'' <- dotransforms transforms expr'
549 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr'')) $ return ()
552 -- | Get the value that is bound to the given binder at top level. Fails when
553 -- there is no such binding.
555 CoreBndr -- ^ The binder to get the expression for
556 -> TranslatorSession CoreExpr -- ^ The value bound to the binder
558 getBinding bndr = Utils.makeCached bndr tsBindings $ do
559 -- If the binding isn't in the "cache" (bindings map), then we can't create
560 -- it out of thin air, so return an error.
561 error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr