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 -- let recursification
95 --------------------------------
96 letrec, letrectop :: Transform
97 letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
98 -- Leave all other expressions unchanged
99 letrec expr = return expr
100 -- Perform this transform everywhere
101 letrectop = everywhere ("letrec", letrec)
103 --------------------------------
104 -- let simplification
105 --------------------------------
106 letsimpl, letsimpltop :: Transform
107 -- Put the "in ..." value of a let in its own binding, but not when the
108 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
109 letsimpl expr@(Let (Rec binds) res) = do
111 local_var <- Trans.lift $ is_local_var res
112 if not local_var && repr
114 -- If the result is not a local var already (to prevent loops with
115 -- ourselves), extract it.
116 id <- Trans.lift $ mkInternalVar "foo" (CoreUtils.exprType res)
118 change $ Let (Rec (bind:binds)) (Var id)
120 -- If the result is already a local var, don't extract it.
123 -- Leave all other expressions unchanged
124 letsimpl expr = return expr
125 -- Perform this transform everywhere
126 letsimpltop = everywhere ("letsimpl", letsimpl)
128 --------------------------------
130 --------------------------------
131 letflat, letflattop :: Transform
132 letflat (Let (Rec binds) expr) = do
133 -- Turn each binding into a list of bindings (possibly containing just one
134 -- element, of course)
135 bindss <- Monad.mapM flatbind binds
136 -- Concat all the bindings
137 let binds' = concat bindss
138 -- Return the new let. We don't use change here, since possibly nothing has
139 -- changed. If anything has changed, flatbind has already flagged that
141 return $ Let (Rec binds') expr
143 -- Turns a binding of a let into a multiple bindings, or any other binding
144 -- into a list with just that binding
145 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
146 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
147 flatbind (b, expr) = return [(b, expr)]
148 -- Leave all other expressions unchanged
149 letflat expr = return expr
150 -- Perform this transform everywhere
151 letflattop = everywhere ("letflat", letflat)
153 --------------------------------
154 -- Simple let binding removal
155 --------------------------------
156 -- Remove a = b bindings from let expressions everywhere
157 letremovetop :: Transform
158 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
160 --------------------------------
161 -- Unused let binding removal
162 --------------------------------
163 letremoveunused, letremoveunusedtop :: Transform
164 letremoveunused expr@(Let (Rec binds) res) = do
165 -- Filter out all unused binds.
166 let binds' = filter dobind binds
167 -- Only set the changed flag if binds got removed
168 changeif (length binds' /= length binds) (Let (Rec binds') res)
170 bound_exprs = map snd binds
171 -- For each bind check if the bind is used by res or any of the bound
173 dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
174 -- Leave all other expressions unchanged
175 letremoveunused expr = return expr
176 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
178 --------------------------------
180 --------------------------------
181 -- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let
182 -- expressions everywhere. This means that any value that still needs to be
183 -- applied to something else (polymorphic values need to be applied to a
184 -- Type) will be inlined, and will eventually be applied to all their
187 -- This is a tricky function, which is prone to create loops in the
188 -- transformations. To fix this, we make sure that no transformation will
189 -- create a new let binding with a function type. These other transformations
190 -- will just not work on those function-typed values at first, but the other
191 -- transformations (in particular β-reduction) should make sure that the type
192 -- of those values eventually becomes primitive.
193 inlinenonreptop :: Transform
194 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
196 --------------------------------
197 -- Scrutinee simplification
198 --------------------------------
199 scrutsimpl,scrutsimpltop :: Transform
200 -- Don't touch scrutinees that are already simple
201 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
202 -- Replace all other cases with a let that binds the scrutinee and a new
203 -- simple scrutinee, but only when the scrutinee is representable (to prevent
204 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
205 -- will be supported anyway...)
206 scrutsimpl expr@(Case scrut b ty alts) = do
210 id <- Trans.lift $ mkInternalVar "scrut" (CoreUtils.exprType scrut)
211 change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
214 -- Leave all other expressions unchanged
215 scrutsimpl expr = return expr
216 -- Perform this transform everywhere
217 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
219 --------------------------------
220 -- Case binder wildening
221 --------------------------------
222 casesimpl, casesimpltop :: Transform
223 -- This is already a selector case (or, if x does not appear in bndrs, a very
224 -- simple case statement that will be removed by caseremove below). Just leave
226 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
227 -- Make sure that all case alternatives have only wild binders and simple
229 -- This is done by creating a new let binding for each non-wild binder, which
230 -- is bound to a new simple selector case statement and for each complex
231 -- expression. We do this only for representable types, to prevent loops with
233 casesimpl expr@(Case scrut b ty alts) = do
234 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
235 let bindings = concat bindingss
236 -- Replace the case with a let with bindings and a case
237 let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
238 -- If there are no non-wild binders, or this case is already a simple
239 -- selector (i.e., a single alt with exactly one binding), already a simple
240 -- selector altan no bindings (i.e., no wild binders in the original case),
241 -- don't change anything, otherwise, replace the case.
242 if null bindings then return expr else change newlet
244 -- Generate a single wild binder, since they are all the same
245 wild = MkCore.mkWildBinder
246 -- Wilden the binders of one alt, producing a list of bindings as a
248 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
249 doalt (con, bndrs, expr) = do
250 -- Make each binder wild, if possible
251 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
252 let (newbndrs, bindings_maybe) = unzip bndrs_res
253 -- Extract a complex expression, if possible. For this we check if any of
254 -- the new list of bndrs are used by expr. We can't use free_vars here,
255 -- since that looks at the old bndrs.
256 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) $ expr
257 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
258 -- Create a new alternative
259 let newalt = (con, newbndrs, expr')
260 let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe)
261 return (bindings, newalt)
263 -- Make wild alternatives for each binder
264 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
265 -- A set of all the binders that are used by the expression
266 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
267 -- Look at the ith binder in the case alternative. Return a new binder
268 -- for it (either the same one, or a wild one) and optionally a let
269 -- binding containing a case expression.
270 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
272 repr <- isRepr (Var b)
273 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
274 -- in expr, this means that b is unused if expr does not use it.)
275 let wild = not (VarSet.elemVarSet b free_vars)
276 -- Create a new binding for any representable binder that is not
277 -- already wild and is representable (to prevent loops with
279 if (not wild) && repr
281 -- Create on new binder that will actually capture a value in this
282 -- case statement, and return it.
283 let bty = (Id.idType b)
284 id <- Trans.lift $ mkInternalVar "sel" bty
285 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
286 let caseexpr = Case scrut b bty [(con, binders, Var id)]
287 return (wildbndrs!!i, Just (b, caseexpr))
289 -- Just leave the original binder in place, and don't generate an
290 -- extra selector case.
292 -- Process the expression of a case alternative. Accepts an expression
293 -- and whether this expression uses any of the binders in the
294 -- alternative. Returns an optional new binding and a new expression.
295 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
296 doexpr expr uses_bndrs = do
297 local_var <- Trans.lift $ is_local_var expr
299 -- Extract any expressions that do not use any binders from this
300 -- alternative, is not a local var already and is representable (to
301 -- prevent loops with inlinenonrep).
302 if (not uses_bndrs) && (not local_var) && repr
304 id <- Trans.lift $ mkInternalVar "caseval" (CoreUtils.exprType expr)
305 -- We don't flag a change here, since casevalsimpl will do that above
306 -- based on Just we return here.
307 return $ (Just (id, expr), Var id)
309 -- Don't simplify anything else
310 return (Nothing, expr)
311 -- Leave all other expressions unchanged
312 casesimpl expr = return expr
313 -- Perform this transform everywhere
314 casesimpltop = everywhere ("casesimpl", casesimpl)
316 --------------------------------
318 --------------------------------
319 -- Remove case statements that have only a single alternative and only wild
321 caseremove, caseremovetop :: Transform
322 -- Replace a useless case by the value of its single alternative
323 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
324 -- Find if any of the binders are used by expr
325 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
326 -- Leave all other expressions unchanged
327 caseremove expr = return expr
328 -- Perform this transform everywhere
329 caseremovetop = everywhere ("caseremove", caseremove)
331 --------------------------------
332 -- Argument extraction
333 --------------------------------
334 -- Make sure that all arguments of a representable type are simple variables.
335 appsimpl, appsimpltop :: Transform
336 -- Simplify all representable arguments. Do this by introducing a new Let
337 -- that binds the argument and passing the new binder in the application.
338 appsimpl expr@(App f arg) = do
339 -- Check runtime representability
341 local_var <- Trans.lift $ is_local_var arg
342 if repr && not local_var
343 then do -- Extract representable arguments
344 id <- Trans.lift $ mkInternalVar "arg" (CoreUtils.exprType arg)
345 change $ Let (Rec [(id, arg)]) (App f (Var id))
346 else -- Leave non-representable arguments unchanged
348 -- Leave all other expressions unchanged
349 appsimpl expr = return expr
350 -- Perform this transform everywhere
351 appsimpltop = everywhere ("appsimpl", appsimpl)
353 --------------------------------
354 -- Function-typed argument propagation
355 --------------------------------
356 -- Remove all applications to function-typed arguments, by duplication the
357 -- function called with the function-typed parameter replaced by the free
358 -- variables of the argument passed in.
359 argprop, argproptop :: Transform
360 -- Transform any application of a named function (i.e., skip applications of
361 -- lambda's). Also skip applications that have arguments with free type
362 -- variables, since we can't inline those.
363 argprop expr@(App _ _) | is_var fexpr = do
364 -- Find the body of the function called
365 body_maybe <- Trans.lift $ getGlobalBind f
368 -- Process each of the arguments in turn
369 (args', changed) <- Writer.listen $ mapM doarg args
370 -- See if any of the arguments changed
371 case Monoid.getAny changed of
373 let (newargs', newparams', oldargs) = unzip3 args'
374 let newargs = concat newargs'
375 let newparams = concat newparams'
376 -- Create a new body that consists of a lambda for all new arguments and
377 -- the old body applied to some arguments.
378 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
379 -- Create a new function with the same name but a new body
380 newf <- Trans.lift $ mkFunction f newbody
381 -- Replace the original application with one of the new function to the
383 change $ MkCore.mkCoreApps (Var newf) newargs
385 -- Don't change the expression if none of the arguments changed
388 -- If we don't have a body for the function called, leave it unchanged (it
389 -- should be a primitive function then).
390 Nothing -> return expr
392 -- Find the function called and the arguments
393 (fexpr, args) = collectArgs expr
396 -- Process a single argument and return (args, bndrs, arg), where args are
397 -- the arguments to replace the given argument in the original
398 -- application, bndrs are the binders to include in the top-level lambda
399 -- in the new function body, and arg is the argument to apply to the old
401 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
404 bndrs <- Trans.lift getGlobalBinders
405 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
406 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
408 -- Propagate all complex arguments that are not representable, but not
409 -- arguments with free type variables (since those would require types
410 -- not known yet, which will always be known eventually).
411 -- Find interesting free variables, each of which should be passed to
412 -- the new function instead of the original function argument.
414 -- Interesting vars are those that are local, but not available from the
415 -- top level scope (functions from this module are defined as local, but
416 -- they're not local to this function, so we can freely move references
417 -- to them into another function).
418 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
419 -- Mark the current expression as changed
421 return (map Var free_vars, free_vars, arg)
423 -- Representable types will not be propagated, and arguments with free
424 -- type variables will be propagated later.
425 -- TODO: preserve original naming?
426 id <- Trans.lift $ mkBinderFor arg "param"
427 -- Just pass the original argument to the new function, which binds it
428 -- to a new id and just pass that new id to the old function body.
429 return ([arg], [id], mkReferenceTo id)
430 -- Leave all other expressions unchanged
431 argprop expr = return expr
432 -- Perform this transform everywhere
433 argproptop = everywhere ("argprop", argprop)
435 --------------------------------
436 -- Function-typed argument extraction
437 --------------------------------
438 -- This transform takes any function-typed argument that cannot be propagated
439 -- (because the function that is applied to it is a builtin function), and
440 -- puts it in a brand new top level binder. This allows us to for example
441 -- apply map to a lambda expression This will not conflict with inlinenonrep,
442 -- since that only inlines local let bindings, not top level bindings.
443 funextract, funextracttop :: Transform
444 funextract expr@(App _ _) | is_var fexpr = do
445 body_maybe <- Trans.lift $ getGlobalBind f
447 -- We don't have a function body for f, so we can perform this transform.
449 -- Find the new arguments
450 args' <- mapM doarg args
451 -- And update the arguments. We use return instead of changed, so the
452 -- changed flag doesn't get set if none of the args got changed.
453 return $ MkCore.mkCoreApps fexpr args'
454 -- We have a function body for f, leave this application to funprop
455 Just _ -> return expr
457 -- Find the function called and the arguments
458 (fexpr, args) = collectArgs expr
460 -- Change any arguments that have a function type, but are not simple yet
461 -- (ie, a variable or application). This means to create a new function
462 -- for map (\f -> ...) b, but not for map (foo a) b.
464 -- We could use is_applicable here instead of is_fun, but I think
465 -- arguments to functions could only have forall typing when existential
466 -- typing is enabled. Not sure, though.
467 doarg arg | not (is_simple arg) && is_fun arg = do
468 -- Create a new top level binding that binds the argument. Its body will
469 -- be extended with lambda expressions, to take any free variables used
470 -- by the argument expression.
471 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
472 let body = MkCore.mkCoreLams free_vars arg
473 id <- Trans.lift $ mkBinderFor body "fun"
474 Trans.lift $ addGlobalBind id body
475 -- Replace the argument with a reference to the new function, applied to
477 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
478 -- Leave all other arguments untouched
479 doarg arg = return arg
481 -- Leave all other expressions unchanged
482 funextract expr = return expr
483 -- Perform this transform everywhere
484 funextracttop = everywhere ("funextract", funextract)
486 --------------------------------
487 -- End of transformations
488 --------------------------------
493 -- What transforms to run?
494 transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop]
496 -- | Returns the normalized version of the given function.
498 CoreBndr -- ^ The function to get
499 -> TranslatorSession CoreExpr -- The normalized function body
501 getNormalized bndr = Utils.makeCached bndr tsNormalized $ do
502 if is_poly (Var bndr)
504 -- This should really only happen at the top level... TODO: Give
505 -- a different error if this happens down in the recursion.
506 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
508 expr <- getBinding bndr
509 normalizeExpr (show bndr) expr
511 -- | Normalize an expression
513 String -- ^ What are we normalizing? For debug output only.
514 -> CoreSyn.CoreExpr -- ^ The expression to normalize
515 -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
517 normalizeExpr what expr = do
518 -- Introduce an empty Let at the top level, so there will always be
519 -- a let in the expression (none of the transformations will remove
521 let expr' = Let (Rec []) expr
522 -- Normalize this expression
523 trace ("Transforming " ++ what ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
524 expr'' <- dotransforms transforms expr'
525 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr'')) $ return ()
528 -- | Get the value that is bound to the given binder at top level. Fails when
529 -- there is no such binding.
531 CoreBndr -- ^ The binder to get the expression for
532 -> TranslatorSession CoreExpr -- ^ The value bound to the binder
534 getBinding bndr = Utils.makeCached bndr tsBindings $ do
535 -- If the binding isn't in the "cache" (bindings map), then we can't create
536 -- it out of thin air, so return an error.
537 error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr