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 (normalizeModule) 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.Normalize.NormalizeTools
38 import CLasH.VHDL.VHDLTypes
39 import CLasH.Utils.Core.CoreTools
40 import CLasH.Utils.Pretty
42 --------------------------------
43 -- Start of transformations
44 --------------------------------
46 --------------------------------
48 --------------------------------
49 eta, etatop :: Transform
50 eta expr | is_fun expr && not (is_lam expr) = do
51 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
52 id <- mkInternalVar "param" arg_ty
53 change (Lam id (App expr (Var id)))
54 -- Leave all other expressions unchanged
56 etatop = notappargs ("eta", eta)
58 --------------------------------
60 --------------------------------
61 beta, betatop :: Transform
62 -- Substitute arg for x in expr
63 beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr
64 -- Propagate the application into the let
65 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
66 -- Propagate the application into each of the alternatives
67 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
69 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
70 ty' = CoreUtils.applyTypeToArg ty arg
71 -- Leave all other expressions unchanged
72 beta expr = return expr
73 -- Perform this transform everywhere
74 betatop = everywhere ("beta", beta)
76 --------------------------------
78 --------------------------------
79 -- Try to move casts as much downward as possible.
80 castprop, castproptop :: Transform
81 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
82 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
84 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
85 -- Leave all other expressions unchanged
86 castprop expr = return expr
87 -- Perform this transform everywhere
88 castproptop = everywhere ("castprop", castprop)
90 --------------------------------
91 -- let recursification
92 --------------------------------
93 letrec, letrectop :: Transform
94 letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
95 -- Leave all other expressions unchanged
96 letrec expr = return expr
97 -- Perform this transform everywhere
98 letrectop = everywhere ("letrec", letrec)
100 --------------------------------
101 -- let simplification
102 --------------------------------
103 letsimpl, letsimpltop :: Transform
104 -- Put the "in ..." value of a let in its own binding, but not when the
105 -- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
106 letsimpl expr@(Let (Rec binds) res) = do
108 local_var <- Trans.lift $ is_local_var res
109 if not local_var && repr
111 -- If the result is not a local var already (to prevent loops with
112 -- ourselves), extract it.
113 id <- mkInternalVar "foo" (CoreUtils.exprType res)
115 change $ Let (Rec (bind:binds)) (Var id)
117 -- If the result is already a local var, don't extract it.
120 -- Leave all other expressions unchanged
121 letsimpl expr = return expr
122 -- Perform this transform everywhere
123 letsimpltop = everywhere ("letsimpl", letsimpl)
125 --------------------------------
127 --------------------------------
128 letflat, letflattop :: Transform
129 letflat (Let (Rec binds) expr) = do
130 -- Turn each binding into a list of bindings (possibly containing just one
131 -- element, of course)
132 bindss <- Monad.mapM flatbind binds
133 -- Concat all the bindings
134 let binds' = concat bindss
135 -- Return the new let. We don't use change here, since possibly nothing has
136 -- changed. If anything has changed, flatbind has already flagged that
138 return $ Let (Rec binds') expr
140 -- Turns a binding of a let into a multiple bindings, or any other binding
141 -- into a list with just that binding
142 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
143 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
144 flatbind (b, expr) = return [(b, expr)]
145 -- Leave all other expressions unchanged
146 letflat expr = return expr
147 -- Perform this transform everywhere
148 letflattop = everywhere ("letflat", letflat)
150 --------------------------------
151 -- Simple let binding removal
152 --------------------------------
153 -- Remove a = b bindings from let expressions everywhere
154 letremovetop :: Transform
155 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
157 --------------------------------
159 --------------------------------
160 -- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let
161 -- expressions everywhere. This means that any value that still needs to be
162 -- applied to something else (polymorphic values need to be applied to a
163 -- Type) will be inlined, and will eventually be applied to all their
166 -- This is a tricky function, which is prone to create loops in the
167 -- transformations. To fix this, we make sure that no transformation will
168 -- create a new let binding with a function type. These other transformations
169 -- will just not work on those function-typed values at first, but the other
170 -- transformations (in particular β-reduction) should make sure that the type
171 -- of those values eventually becomes primitive.
172 inlinenonreptop :: Transform
173 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
175 --------------------------------
176 -- Scrutinee simplification
177 --------------------------------
178 scrutsimpl,scrutsimpltop :: Transform
179 -- Don't touch scrutinees that are already simple
180 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
181 -- Replace all other cases with a let that binds the scrutinee and a new
182 -- simple scrutinee, but only when the scrutinee is representable (to prevent
183 -- loops with inlinenonrep, though I don't think a non-representable scrutinee
184 -- will be supported anyway...)
185 scrutsimpl expr@(Case scrut b ty alts) = do
189 id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
190 change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
193 -- Leave all other expressions unchanged
194 scrutsimpl expr = return expr
195 -- Perform this transform everywhere
196 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
198 --------------------------------
199 -- Case binder wildening
200 --------------------------------
201 casesimpl, casesimpltop :: Transform
202 -- This is already a selector case (or, if x does not appear in bndrs, a very
203 -- simple case statement that will be removed by caseremove below). Just leave
205 casesimpl expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
206 -- Make sure that all case alternatives have only wild binders and simple
208 -- This is done by creating a new let binding for each non-wild binder, which
209 -- is bound to a new simple selector case statement and for each complex
210 -- expression. We do this only for representable types, to prevent loops with
212 casesimpl expr@(Case scrut b ty alts) = do
213 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
214 let bindings = concat bindingss
215 -- Replace the case with a let with bindings and a case
216 let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
217 -- If there are no non-wild binders, or this case is already a simple
218 -- selector (i.e., a single alt with exactly one binding), already a simple
219 -- selector altan no bindings (i.e., no wild binders in the original case),
220 -- don't change anything, otherwise, replace the case.
221 if null bindings then return expr else change newlet
223 -- Generate a single wild binder, since they are all the same
224 wild = MkCore.mkWildBinder
225 -- Wilden the binders of one alt, producing a list of bindings as a
227 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
228 doalt (con, bndrs, expr) = do
229 -- Make each binder wild, if possible
230 bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
231 let (newbndrs, bindings_maybe) = unzip bndrs_res
232 -- Extract a complex expression, if possible. For this we check if any of
233 -- the new list of bndrs are used by expr. We can't use free_vars here,
234 -- since that looks at the old bndrs.
235 let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) $ expr
236 (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
237 -- Create a new alternative
238 let newalt = (con, newbndrs, expr')
239 let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe)
240 return (bindings, newalt)
242 -- Make wild alternatives for each binder
243 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
244 -- A set of all the binders that are used by the expression
245 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
246 -- Look at the ith binder in the case alternative. Return a new binder
247 -- for it (either the same one, or a wild one) and optionally a let
248 -- binding containing a case expression.
249 dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
251 repr <- isRepr (Var b)
252 -- Is b wild (e.g., not a free var of expr. Since b is only in scope
253 -- in expr, this means that b is unused if expr does not use it.)
254 let wild = not (VarSet.elemVarSet b free_vars)
255 -- Create a new binding for any representable binder that is not
256 -- already wild and is representable (to prevent loops with
258 if (not wild) && repr
260 -- Create on new binder that will actually capture a value in this
261 -- case statement, and return it.
262 let bty = (Id.idType b)
263 id <- mkInternalVar "sel" bty
264 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
265 let caseexpr = Case scrut b bty [(con, binders, Var id)]
266 return (wildbndrs!!i, Just (b, caseexpr))
268 -- Just leave the original binder in place, and don't generate an
269 -- extra selector case.
271 -- Process the expression of a case alternative. Accepts an expression
272 -- and whether this expression uses any of the binders in the
273 -- alternative. Returns an optional new binding and a new expression.
274 doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
275 doexpr expr uses_bndrs = do
276 local_var <- Trans.lift $ is_local_var expr
278 -- Extract any expressions that do not use any binders from this
279 -- alternative, is not a local var already and is representable (to
280 -- prevent loops with inlinenonrep).
281 if (not uses_bndrs) && (not local_var) && repr
283 id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
284 -- We don't flag a change here, since casevalsimpl will do that above
285 -- based on Just we return here.
286 return $ (Just (id, expr), Var id)
288 -- Don't simplify anything else
289 return (Nothing, expr)
290 -- Leave all other expressions unchanged
291 casesimpl expr = return expr
292 -- Perform this transform everywhere
293 casesimpltop = everywhere ("casesimpl", casesimpl)
295 --------------------------------
297 --------------------------------
298 -- Remove case statements that have only a single alternative and only wild
300 caseremove, caseremovetop :: Transform
301 -- Replace a useless case by the value of its single alternative
302 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
303 -- Find if any of the binders are used by expr
304 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
305 -- Leave all other expressions unchanged
306 caseremove expr = return expr
307 -- Perform this transform everywhere
308 caseremovetop = everywhere ("caseremove", caseremove)
310 --------------------------------
311 -- Argument extraction
312 --------------------------------
313 -- Make sure that all arguments of a representable type are simple variables.
314 appsimpl, appsimpltop :: Transform
315 -- Simplify all representable arguments. Do this by introducing a new Let
316 -- that binds the argument and passing the new binder in the application.
317 appsimpl expr@(App f arg) = do
318 -- Check runtime representability
320 local_var <- Trans.lift $ is_local_var arg
321 if repr && not local_var
322 then do -- Extract representable arguments
323 id <- mkInternalVar "arg" (CoreUtils.exprType arg)
324 change $ Let (Rec [(id, arg)]) (App f (Var id))
325 else -- Leave non-representable arguments unchanged
327 -- Leave all other expressions unchanged
328 appsimpl expr = return expr
329 -- Perform this transform everywhere
330 appsimpltop = everywhere ("appsimpl", appsimpl)
332 --------------------------------
333 -- Function-typed argument propagation
334 --------------------------------
335 -- Remove all applications to function-typed arguments, by duplication the
336 -- function called with the function-typed parameter replaced by the free
337 -- variables of the argument passed in.
338 argprop, argproptop :: Transform
339 -- Transform any application of a named function (i.e., skip applications of
340 -- lambda's). Also skip applications that have arguments with free type
341 -- variables, since we can't inline those.
342 argprop expr@(App _ _) | is_var fexpr = do
343 -- Find the body of the function called
344 body_maybe <- Trans.lift $ getGlobalBind f
347 -- Process each of the arguments in turn
348 (args', changed) <- Writer.listen $ mapM doarg args
349 -- See if any of the arguments changed
350 case Monoid.getAny changed of
352 let (newargs', newparams', oldargs) = unzip3 args'
353 let newargs = concat newargs'
354 let newparams = concat newparams'
355 -- Create a new body that consists of a lambda for all new arguments and
356 -- the old body applied to some arguments.
357 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
358 -- Create a new function with the same name but a new body
359 newf <- mkFunction f newbody
360 -- Replace the original application with one of the new function to the
362 change $ MkCore.mkCoreApps (Var newf) newargs
364 -- Don't change the expression if none of the arguments changed
367 -- If we don't have a body for the function called, leave it unchanged (it
368 -- should be a primitive function then).
369 Nothing -> return expr
371 -- Find the function called and the arguments
372 (fexpr, args) = collectArgs expr
375 -- Process a single argument and return (args, bndrs, arg), where args are
376 -- the arguments to replace the given argument in the original
377 -- application, bndrs are the binders to include in the top-level lambda
378 -- in the new function body, and arg is the argument to apply to the old
380 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
383 bndrs <- Trans.lift getGlobalBinders
384 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
385 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
387 -- Propagate all complex arguments that are not representable, but not
388 -- arguments with free type variables (since those would require types
389 -- not known yet, which will always be known eventually).
390 -- Find interesting free variables, each of which should be passed to
391 -- the new function instead of the original function argument.
393 -- Interesting vars are those that are local, but not available from the
394 -- top level scope (functions from this module are defined as local, but
395 -- they're not local to this function, so we can freely move references
396 -- to them into another function).
397 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
398 -- Mark the current expression as changed
400 return (map Var free_vars, free_vars, arg)
402 -- Representable types will not be propagated, and arguments with free
403 -- type variables will be propagated later.
404 -- TODO: preserve original naming?
405 id <- mkBinderFor arg "param"
406 -- Just pass the original argument to the new function, which binds it
407 -- to a new id and just pass that new id to the old function body.
408 return ([arg], [id], mkReferenceTo id)
409 -- Leave all other expressions unchanged
410 argprop expr = return expr
411 -- Perform this transform everywhere
412 argproptop = everywhere ("argprop", argprop)
414 --------------------------------
415 -- Function-typed argument extraction
416 --------------------------------
417 -- This transform takes any function-typed argument that cannot be propagated
418 -- (because the function that is applied to it is a builtin function), and
419 -- puts it in a brand new top level binder. This allows us to for example
420 -- apply map to a lambda expression This will not conflict with inlinenonrep,
421 -- since that only inlines local let bindings, not top level bindings.
422 funextract, funextracttop :: Transform
423 funextract expr@(App _ _) | is_var fexpr = do
424 body_maybe <- Trans.lift $ getGlobalBind f
426 -- We don't have a function body for f, so we can perform this transform.
428 -- Find the new arguments
429 args' <- mapM doarg args
430 -- And update the arguments. We use return instead of changed, so the
431 -- changed flag doesn't get set if none of the args got changed.
432 return $ MkCore.mkCoreApps fexpr args'
433 -- We have a function body for f, leave this application to funprop
434 Just _ -> return expr
436 -- Find the function called and the arguments
437 (fexpr, args) = collectArgs expr
439 -- Change any arguments that have a function type, but are not simple yet
440 -- (ie, a variable or application). This means to create a new function
441 -- for map (\f -> ...) b, but not for map (foo a) b.
443 -- We could use is_applicable here instead of is_fun, but I think
444 -- arguments to functions could only have forall typing when existential
445 -- typing is enabled. Not sure, though.
446 doarg arg | not (is_simple arg) && is_fun arg = do
447 -- Create a new top level binding that binds the argument. Its body will
448 -- be extended with lambda expressions, to take any free variables used
449 -- by the argument expression.
450 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
451 let body = MkCore.mkCoreLams free_vars arg
452 id <- mkBinderFor body "fun"
453 Trans.lift $ addGlobalBind id body
454 -- Replace the argument with a reference to the new function, applied to
456 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
457 -- Leave all other arguments untouched
458 doarg arg = return arg
460 -- Leave all other expressions unchanged
461 funextract expr = return expr
462 -- Perform this transform everywhere
463 funextracttop = everywhere ("funextract", funextract)
465 --------------------------------
466 -- End of transformations
467 --------------------------------
472 -- What transforms to run?
473 transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop]
475 -- Turns the given bind into VHDL
478 -> UniqSupply.UniqSupply -- ^ A UniqSupply we can use
479 -> [(CoreBndr, CoreExpr)] -- ^ All bindings we know (i.e., in the current module)
481 -> [CoreBndr] -- ^ The bindings to generate VHDL for (i.e., the top level bindings)
482 -> [Bool] -- ^ For each of the bindings to generate VHDL for, if it is stateful
483 -> ([(CoreBndr, CoreExpr)], [(CoreBndr, CoreExpr)], TypeState) -- ^ The resulting VHDL
485 normalizeModule env uniqsupply bindings testexprs generate_for statefuls = runTransformSession env uniqsupply $ do
486 testbinds <- mapM (\x -> do { v <- mkBinderFor' x "test" ; return (v,x) } ) testexprs
487 let testbinders = (map fst testbinds)
488 -- Put all the bindings in this module in the tsBindings map
489 putA tsBindings (Map.fromList (bindings ++ testbinds))
490 -- (Recursively) normalize each of the requested bindings
491 mapM normalizeBind (generate_for ++ testbinders)
492 -- Get all initial bindings and the ones we produced
493 bindings_map <- getA tsBindings
494 let bindings = Map.assocs bindings_map
495 normalized_binders' <- getA tsNormalized
496 let normalized_binders = VarSet.delVarSetList normalized_binders' testbinders
497 let ret_testbinds = zip testbinders (Maybe.catMaybes $ map (\x -> lookup x bindings) testbinders)
498 let ret_binds = filter ((`VarSet.elemVarSet` normalized_binders) . fst) bindings
499 typestate <- getA tsType
500 -- But return only the normalized bindings
501 return $ (ret_binds, ret_testbinds, typestate)
503 normalizeBind :: CoreBndr -> TransformSession ()
505 -- Don't normalize global variables, these should be either builtin
506 -- functions or data constructors.
507 Monad.when (Var.isLocalId bndr) $ do
508 -- Skip binders that have a polymorphic type, since it's impossible to
509 -- create polymorphic hardware.
510 if is_poly (Var bndr)
512 -- This should really only happen at the top level... TODO: Give
513 -- a different error if this happens down in the recursion.
514 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
516 normalized_funcs <- getA tsNormalized
517 -- See if this function was normalized already
518 if VarSet.elemVarSet bndr normalized_funcs
520 -- Yup, don't do it again
523 -- Nope, note that it has been and do it.
524 modA tsNormalized (flip VarSet.extendVarSet bndr)
525 expr_maybe <- getGlobalBind bndr
528 -- Introduce an empty Let at the top level, so there will always be
529 -- a let in the expression (none of the transformations will remove
531 let expr' = Let (Rec []) expr
532 -- Normalize this expression
533 trace ("Transforming " ++ (show bndr) ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
534 expr' <- dotransforms transforms expr'
535 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
536 -- And store the normalized version in the session
537 modA tsBindings (Map.insert bndr expr')
538 -- Find all vars used with a function type. All of these should be global
539 -- binders (i.e., functions used), since any local binders with a function
540 -- type should have been inlined already.
541 bndrs <- getGlobalBinders
542 let used_funcs_set = CoreFVs.exprSomeFreeVars (\v -> not (Id.isDictId v) && v `elem` bndrs) expr'
543 let used_funcs = VarSet.varSetElems used_funcs_set
544 -- Process each of the used functions recursively
545 mapM normalizeBind used_funcs
547 -- We don't have a value for this binder. This really shouldn't
548 -- happen for local id's...
549 Nothing -> error $ "\nNormalize.normalizeBind: No value found for binder " ++ pprString bndr ++ "? This should not happen!"