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) 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.Pretty
44 --------------------------------
45 -- Start of transformations
46 --------------------------------
48 --------------------------------
50 --------------------------------
51 eta, etatop :: Transform
52 eta expr | is_fun expr && not (is_lam expr) = do
53 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
54 id <- mkInternalVar "param" arg_ty
55 change (Lam id (App expr (Var id)))
56 -- Leave all other expressions unchanged
58 etatop = notappargs ("eta", eta)
60 --------------------------------
62 --------------------------------
63 beta, betatop :: Transform
64 -- Substitute arg for x in expr
65 beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr
66 -- Propagate the application into the let
67 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
68 -- Propagate the application into each of the alternatives
69 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
71 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
72 ty' = CoreUtils.applyTypeToArg ty arg
73 -- Leave all other expressions unchanged
74 beta expr = return expr
75 -- Perform this transform everywhere
76 betatop = everywhere ("beta", beta)
78 --------------------------------
80 --------------------------------
81 -- Try to move casts as much downward as possible.
82 castprop, castproptop :: Transform
83 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
84 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
86 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
87 -- Leave all other expressions unchanged
88 castprop expr = return expr
89 -- Perform this transform everywhere
90 castproptop = everywhere ("castprop", castprop)
92 --------------------------------
93 -- let recursification
94 --------------------------------
95 letrec, letrectop :: Transform
96 letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
97 -- Leave all other expressions unchanged
98 letrec expr = return expr
99 -- Perform this transform everywhere
100 letrectop = everywhere ("letrec", letrec)
102 --------------------------------
103 -- let simplification
104 --------------------------------
105 letsimpl, letsimpltop :: Transform
106 -- Put the "in ..." value of a let in its own binding, but not when the
107 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
108 letsimpl expr@(Let (Rec binds) res) = do
110 local_var <- Trans.lift $ is_local_var res
111 if not local_var && repr
113 -- If the result is not a local var already (to prevent loops with
114 -- ourselves), extract it.
115 id <- mkInternalVar "foo" (CoreUtils.exprType res)
117 change $ Let (Rec (bind:binds)) (Var id)
119 -- If the result is already a local var, don't extract it.
122 -- Leave all other expressions unchanged
123 letsimpl expr = return expr
124 -- Perform this transform everywhere
125 letsimpltop = everywhere ("letsimpl", letsimpl)
127 --------------------------------
129 --------------------------------
130 letflat, letflattop :: Transform
131 letflat (Let (Rec binds) expr) = do
132 -- Turn each binding into a list of bindings (possibly containing just one
133 -- element, of course)
134 bindss <- Monad.mapM flatbind binds
135 -- Concat all the bindings
136 let binds' = concat bindss
137 -- Return the new let. We don't use change here, since possibly nothing has
138 -- changed. If anything has changed, flatbind has already flagged that
140 return $ Let (Rec binds') expr
142 -- Turns a binding of a let into a multiple bindings, or any other binding
143 -- into a list with just that binding
144 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
145 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
146 flatbind (b, expr) = return [(b, expr)]
147 -- Leave all other expressions unchanged
148 letflat expr = return expr
149 -- Perform this transform everywhere
150 letflattop = everywhere ("letflat", letflat)
152 --------------------------------
153 -- Simple let binding removal
154 --------------------------------
155 -- Remove a = b bindings from let expressions everywhere
156 letremovetop :: Transform
157 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
159 --------------------------------
161 --------------------------------
162 -- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let
163 -- expressions everywhere. This means that any value that still needs to be
164 -- applied to something else (polymorphic values need to be applied to a
165 -- Type) will be inlined, and will eventually be applied to all their
168 -- This is a tricky function, which is prone to create loops in the
169 -- transformations. To fix this, we make sure that no transformation will
170 -- create a new let binding with a function type. These other transformations
171 -- will just not work on those function-typed values at first, but the other
172 -- transformations (in particular β-reduction) should make sure that the type
173 -- of those values eventually becomes primitive.
174 inlinenonreptop :: Transform
175 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
177 --------------------------------
178 -- Scrutinee simplification
179 --------------------------------
180 scrutsimpl,scrutsimpltop :: Transform
181 -- Don't touch scrutinees that are already simple
182 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
183 -- Replace all other cases with a let that binds the scrutinee and a new
184 -- simple scrutinee, but only when the scrutinee is representable (to prevent
185 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
186 -- will be supported anyway...)
187 scrutsimpl expr@(Case scrut b ty alts) = do
191 id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
192 change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
195 -- Leave all other expressions unchanged
196 scrutsimpl expr = return expr
197 -- Perform this transform everywhere
198 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
200 --------------------------------
201 -- Case binder wildening
202 --------------------------------
203 casesimpl, casesimpltop :: Transform
204 -- This is already a selector case (or, if x does not appear in bndrs, a very
205 -- simple case statement that will be removed by caseremove below). Just leave
207 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
208 -- Make sure that all case alternatives have only wild binders and simple
210 -- This is done by creating a new let binding for each non-wild binder, which
211 -- is bound to a new simple selector case statement and for each complex
212 -- expression. We do this only for representable types, to prevent loops with
214 casesimpl expr@(Case scrut b ty alts) = do
215 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
216 let bindings = concat bindingss
217 -- Replace the case with a let with bindings and a case
218 let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
219 -- If there are no non-wild binders, or this case is already a simple
220 -- selector (i.e., a single alt with exactly one binding), already a simple
221 -- selector altan no bindings (i.e., no wild binders in the original case),
222 -- don't change anything, otherwise, replace the case.
223 if null bindings then return expr else change newlet
225 -- Generate a single wild binder, since they are all the same
226 wild = MkCore.mkWildBinder
227 -- Wilden the binders of one alt, producing a list of bindings as a
229 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
230 doalt (con, bndrs, expr) = do
231 -- Make each binder wild, if possible
232 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
233 let (newbndrs, bindings_maybe) = unzip bndrs_res
234 -- Extract a complex expression, if possible. For this we check if any of
235 -- the new list of bndrs are used by expr. We can't use free_vars here,
236 -- since that looks at the old bndrs.
237 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) $ expr
238 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
239 -- Create a new alternative
240 let newalt = (con, newbndrs, expr')
241 let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe)
242 return (bindings, newalt)
244 -- Make wild alternatives for each binder
245 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
246 -- A set of all the binders that are used by the expression
247 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
248 -- Look at the ith binder in the case alternative. Return a new binder
249 -- for it (either the same one, or a wild one) and optionally a let
250 -- binding containing a case expression.
251 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
253 repr <- isRepr (Var b)
254 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
255 -- in expr, this means that b is unused if expr does not use it.)
256 let wild = not (VarSet.elemVarSet b free_vars)
257 -- Create a new binding for any representable binder that is not
258 -- already wild and is representable (to prevent loops with
260 if (not wild) && repr
262 -- Create on new binder that will actually capture a value in this
263 -- case statement, and return it.
264 let bty = (Id.idType b)
265 id <- mkInternalVar "sel" bty
266 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
267 let caseexpr = Case scrut b bty [(con, binders, Var id)]
268 return (wildbndrs!!i, Just (b, caseexpr))
270 -- Just leave the original binder in place, and don't generate an
271 -- extra selector case.
273 -- Process the expression of a case alternative. Accepts an expression
274 -- and whether this expression uses any of the binders in the
275 -- alternative. Returns an optional new binding and a new expression.
276 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
277 doexpr expr uses_bndrs = do
278 local_var <- Trans.lift $ is_local_var expr
280 -- Extract any expressions that do not use any binders from this
281 -- alternative, is not a local var already and is representable (to
282 -- prevent loops with inlinenonrep).
283 if (not uses_bndrs) && (not local_var) && repr
285 id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
286 -- We don't flag a change here, since casevalsimpl will do that above
287 -- based on Just we return here.
288 return $ (Just (id, expr), Var id)
290 -- Don't simplify anything else
291 return (Nothing, expr)
292 -- Leave all other expressions unchanged
293 casesimpl expr = return expr
294 -- Perform this transform everywhere
295 casesimpltop = everywhere ("casesimpl", casesimpl)
297 --------------------------------
299 --------------------------------
300 -- Remove case statements that have only a single alternative and only wild
302 caseremove, caseremovetop :: Transform
303 -- Replace a useless case by the value of its single alternative
304 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
305 -- Find if any of the binders are used by expr
306 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
307 -- Leave all other expressions unchanged
308 caseremove expr = return expr
309 -- Perform this transform everywhere
310 caseremovetop = everywhere ("caseremove", caseremove)
312 --------------------------------
313 -- Argument extraction
314 --------------------------------
315 -- Make sure that all arguments of a representable type are simple variables.
316 appsimpl, appsimpltop :: Transform
317 -- Simplify all representable arguments. Do this by introducing a new Let
318 -- that binds the argument and passing the new binder in the application.
319 appsimpl expr@(App f arg) = do
320 -- Check runtime representability
322 local_var <- Trans.lift $ is_local_var arg
323 if repr && not local_var
324 then do -- Extract representable arguments
325 id <- mkInternalVar "arg" (CoreUtils.exprType arg)
326 change $ Let (Rec [(id, arg)]) (App f (Var id))
327 else -- Leave non-representable arguments unchanged
329 -- Leave all other expressions unchanged
330 appsimpl expr = return expr
331 -- Perform this transform everywhere
332 appsimpltop = everywhere ("appsimpl", appsimpl)
334 --------------------------------
335 -- Function-typed argument propagation
336 --------------------------------
337 -- Remove all applications to function-typed arguments, by duplication the
338 -- function called with the function-typed parameter replaced by the free
339 -- variables of the argument passed in.
340 argprop, argproptop :: Transform
341 -- Transform any application of a named function (i.e., skip applications of
342 -- lambda's). Also skip applications that have arguments with free type
343 -- variables, since we can't inline those.
344 argprop expr@(App _ _) | is_var fexpr = do
345 -- Find the body of the function called
346 body_maybe <- Trans.lift $ getGlobalBind f
349 -- Process each of the arguments in turn
350 (args', changed) <- Writer.listen $ mapM doarg args
351 -- See if any of the arguments changed
352 case Monoid.getAny changed of
354 let (newargs', newparams', oldargs) = unzip3 args'
355 let newargs = concat newargs'
356 let newparams = concat newparams'
357 -- Create a new body that consists of a lambda for all new arguments and
358 -- the old body applied to some arguments.
359 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
360 -- Create a new function with the same name but a new body
361 newf <- mkFunction f newbody
362 -- Replace the original application with one of the new function to the
364 change $ MkCore.mkCoreApps (Var newf) newargs
366 -- Don't change the expression if none of the arguments changed
369 -- If we don't have a body for the function called, leave it unchanged (it
370 -- should be a primitive function then).
371 Nothing -> return expr
373 -- Find the function called and the arguments
374 (fexpr, args) = collectArgs expr
377 -- Process a single argument and return (args, bndrs, arg), where args are
378 -- the arguments to replace the given argument in the original
379 -- application, bndrs are the binders to include in the top-level lambda
380 -- in the new function body, and arg is the argument to apply to the old
382 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
385 bndrs <- Trans.lift getGlobalBinders
386 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
387 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
389 -- Propagate all complex arguments that are not representable, but not
390 -- arguments with free type variables (since those would require types
391 -- not known yet, which will always be known eventually).
392 -- Find interesting free variables, each of which should be passed to
393 -- the new function instead of the original function argument.
395 -- Interesting vars are those that are local, but not available from the
396 -- top level scope (functions from this module are defined as local, but
397 -- they're not local to this function, so we can freely move references
398 -- to them into another function).
399 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
400 -- Mark the current expression as changed
402 return (map Var free_vars, free_vars, arg)
404 -- Representable types will not be propagated, and arguments with free
405 -- type variables will be propagated later.
406 -- TODO: preserve original naming?
407 id <- mkBinderFor arg "param"
408 -- Just pass the original argument to the new function, which binds it
409 -- to a new id and just pass that new id to the old function body.
410 return ([arg], [id], mkReferenceTo id)
411 -- Leave all other expressions unchanged
412 argprop expr = return expr
413 -- Perform this transform everywhere
414 argproptop = everywhere ("argprop", argprop)
416 --------------------------------
417 -- Function-typed argument extraction
418 --------------------------------
419 -- This transform takes any function-typed argument that cannot be propagated
420 -- (because the function that is applied to it is a builtin function), and
421 -- puts it in a brand new top level binder. This allows us to for example
422 -- apply map to a lambda expression This will not conflict with inlinenonrep,
423 -- since that only inlines local let bindings, not top level bindings.
424 funextract, funextracttop :: Transform
425 funextract expr@(App _ _) | is_var fexpr = do
426 body_maybe <- Trans.lift $ getGlobalBind f
428 -- We don't have a function body for f, so we can perform this transform.
430 -- Find the new arguments
431 args' <- mapM doarg args
432 -- And update the arguments. We use return instead of changed, so the
433 -- changed flag doesn't get set if none of the args got changed.
434 return $ MkCore.mkCoreApps fexpr args'
435 -- We have a function body for f, leave this application to funprop
436 Just _ -> return expr
438 -- Find the function called and the arguments
439 (fexpr, args) = collectArgs expr
441 -- Change any arguments that have a function type, but are not simple yet
442 -- (ie, a variable or application). This means to create a new function
443 -- for map (\f -> ...) b, but not for map (foo a) b.
445 -- We could use is_applicable here instead of is_fun, but I think
446 -- arguments to functions could only have forall typing when existential
447 -- typing is enabled. Not sure, though.
448 doarg arg | not (is_simple arg) && is_fun arg = do
449 -- Create a new top level binding that binds the argument. Its body will
450 -- be extended with lambda expressions, to take any free variables used
451 -- by the argument expression.
452 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
453 let body = MkCore.mkCoreLams free_vars arg
454 id <- mkBinderFor body "fun"
455 Trans.lift $ addGlobalBind id body
456 -- Replace the argument with a reference to the new function, applied to
458 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
459 -- Leave all other arguments untouched
460 doarg arg = return arg
462 -- Leave all other expressions unchanged
463 funextract expr = return expr
464 -- Perform this transform everywhere
465 funextracttop = everywhere ("funextract", funextract)
467 --------------------------------
468 -- End of transformations
469 --------------------------------
474 -- What transforms to run?
475 transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop]
477 -- | Returns the normalized version of the given function.
479 CoreBndr -- ^ The function to get
480 -> TranslatorSession CoreExpr -- The normalized function body
482 getNormalized bndr = Utils.makeCached bndr tsNormalized $ do
483 if is_poly (Var bndr)
485 -- This should really only happen at the top level... TODO: Give
486 -- a different error if this happens down in the recursion.
487 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
489 expr <- getBinding bndr
490 -- Introduce an empty Let at the top level, so there will always be
491 -- a let in the expression (none of the transformations will remove
493 let expr' = Let (Rec []) expr
494 -- Normalize this expression
495 trace ("Transforming " ++ (show bndr) ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
496 expr'' <- dotransforms transforms expr'
497 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
500 -- | Get the value that is bound to the given binder at top level. Fails when
501 -- there is no such binding.
503 CoreBndr -- ^ The binder to get the expression for
504 -> TranslatorSession CoreExpr -- ^ The value bound to the binder
506 getBinding bndr = Utils.makeCached bndr tsBindings $ do
507 -- If the binding isn't in the "cache" (bindings map), then we can't create
508 -- it out of thin air, so return an error.
509 error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr