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 not when the scrutinee is applicable (to prevent
183 -- loops with inlinefun, though I don't think a scrutinee can be
185 scrutsimpl (Case scrut b ty alts) | not $ is_applicable scrut = do
186 id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
187 change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
188 -- Leave all other expressions unchanged
189 scrutsimpl expr = return expr
190 -- Perform this transform everywhere
191 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
193 --------------------------------
194 -- Case binder wildening
195 --------------------------------
196 casewild, casewildtop :: Transform
197 casewild expr@(Case scrut b ty alts) = do
198 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
199 let bindings = concat bindingss
200 -- Replace the case with a let with bindings and a case
201 let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
202 -- If there are no non-wild binders, or this case is already a simple
203 -- selector (i.e., a single alt with exactly one binding), already a simple
204 -- selector altan no bindings (i.e., no wild binders in the original case),
205 -- don't change anything, otherwise, replace the case.
206 if null bindings || length alts == 1 && length bindings == 1 then return expr else change newlet
208 -- Generate a single wild binder, since they are all the same
209 wild = MkCore.mkWildBinder
210 -- Wilden the binders of one alt, producing a list of bindings as a
212 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
213 doalt (con, bndrs, expr) = do
214 bindings_maybe <- Monad.zipWithM mkextracts bndrs [0..]
215 let bindings = Maybe.catMaybes bindings_maybe
216 -- We replace the binders with wild binders only. We can leave expr
217 -- unchanged, since the new bindings bind the same vars as the original
219 let newalt = (con, wildbndrs, expr)
220 return (bindings, newalt)
222 -- Make all binders wild
223 wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
224 -- A set of all the binders that are used by the expression
225 free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
226 -- Creates a case statement to retrieve the ith element from the scrutinee
227 -- and binds that to b.
228 mkextracts :: CoreBndr -> Int -> TransformMonad (Maybe (CoreBndr, CoreExpr))
230 if not (VarSet.elemVarSet b free_vars) || Type.isFunTy (Id.idType b)
231 -- Don't create extra bindings for binders that are already wild
232 -- (e.g. not in the free variables of expr, so unused), or for
233 -- binders that bind function types (to prevent loops with
237 -- Create on new binder that will actually capture a value in this
238 -- case statement, and return it
239 let bty = (Id.idType b)
240 id <- mkInternalVar "sel" bty
241 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
242 return $ Just (b, Case scrut b bty [(con, binders, Var id)])
243 -- Leave all other expressions unchanged
244 casewild expr = return expr
245 -- Perform this transform everywhere
246 casewildtop = everywhere ("casewild", casewild)
248 --------------------------------
249 -- Case value simplification
250 --------------------------------
251 casevalsimpl, casevalsimpltop :: Transform
252 casevalsimpl expr@(Case scrut b ty alts) = do
253 -- Try to simplify each alternative, resulting in an optional binding and a
255 (bindings_maybe, alts') <- (Monad.liftM unzip) $ mapM doalt alts
256 let bindings = Maybe.catMaybes bindings_maybe
257 -- Create a new let around the case, that binds of the cases values.
258 let newlet = Let (Rec bindings) (Case scrut b ty alts')
259 -- If there were no values that needed and allowed simplification, don't
261 if null bindings then return expr else change newlet
263 doalt :: CoreAlt -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreAlt)
264 -- Don't simplify values that are already simple
265 doalt alt@(con, bndrs, Var _) = return (Nothing, alt)
266 -- Simplify each alt by creating a new id, binding the case value to it and
267 -- replacing the case value with that id. Only do this when the case value
268 -- does not use any of the binders bound by this alternative, for that would
269 -- cause those binders to become unbound when moving the value outside of
270 -- the case statement. Also, don't create a binding for applicable
271 -- expressions, to prevent loops with inlinefun.
272 doalt (con, bndrs, expr) | (not usesvars) && (not $ is_applicable expr) = do
273 id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
274 -- We don't flag a change here, since casevalsimpl will do that above
275 -- based on Just we return here.
276 return $ (Just (id, expr), (con, bndrs, Var id))
277 -- Find if any of the binders are used by expr
278 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
279 -- Don't simplify anything else
280 doalt alt = return (Nothing, alt)
281 -- Leave all other expressions unchanged
282 casevalsimpl expr = return expr
283 -- Perform this transform everywhere
284 casevalsimpltop = everywhere ("casevalsimpl", casevalsimpl)
286 --------------------------------
288 --------------------------------
289 -- Remove case statements that have only a single alternative and only wild
291 caseremove, caseremovetop :: Transform
292 -- Replace a useless case by the value of its single alternative
293 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
294 -- Find if any of the binders are used by expr
295 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
296 -- Leave all other expressions unchanged
297 caseremove expr = return expr
298 -- Perform this transform everywhere
299 caseremovetop = everywhere ("caseremove", caseremove)
301 --------------------------------
302 -- Argument extraction
303 --------------------------------
304 -- Make sure that all arguments of a representable type are simple variables.
305 appsimpl, appsimpltop :: Transform
306 -- Simplify all representable arguments. Do this by introducing a new Let
307 -- that binds the argument and passing the new binder in the application.
308 appsimpl expr@(App f arg) = do
309 -- Check runtime representability
311 local_var <- Trans.lift $ is_local_var arg
312 if repr && not local_var
313 then do -- Extract representable arguments
314 id <- mkInternalVar "arg" (CoreUtils.exprType arg)
315 change $ Let (Rec [(id, arg)]) (App f (Var id))
316 else -- Leave non-representable arguments unchanged
318 -- Leave all other expressions unchanged
319 appsimpl expr = return expr
320 -- Perform this transform everywhere
321 appsimpltop = everywhere ("appsimpl", appsimpl)
323 --------------------------------
324 -- Function-typed argument propagation
325 --------------------------------
326 -- Remove all applications to function-typed arguments, by duplication the
327 -- function called with the function-typed parameter replaced by the free
328 -- variables of the argument passed in.
329 argprop, argproptop :: Transform
330 -- Transform any application of a named function (i.e., skip applications of
331 -- lambda's). Also skip applications that have arguments with free type
332 -- variables, since we can't inline those.
333 argprop expr@(App _ _) | is_var fexpr = do
334 -- Find the body of the function called
335 body_maybe <- Trans.lift $ getGlobalBind f
338 -- Process each of the arguments in turn
339 (args', changed) <- Writer.listen $ mapM doarg args
340 -- See if any of the arguments changed
341 case Monoid.getAny changed of
343 let (newargs', newparams', oldargs) = unzip3 args'
344 let newargs = concat newargs'
345 let newparams = concat newparams'
346 -- Create a new body that consists of a lambda for all new arguments and
347 -- the old body applied to some arguments.
348 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
349 -- Create a new function with the same name but a new body
350 newf <- mkFunction f newbody
351 -- Replace the original application with one of the new function to the
353 change $ MkCore.mkCoreApps (Var newf) newargs
355 -- Don't change the expression if none of the arguments changed
358 -- If we don't have a body for the function called, leave it unchanged (it
359 -- should be a primitive function then).
360 Nothing -> return expr
362 -- Find the function called and the arguments
363 (fexpr, args) = collectArgs expr
366 -- Process a single argument and return (args, bndrs, arg), where args are
367 -- the arguments to replace the given argument in the original
368 -- application, bndrs are the binders to include in the top-level lambda
369 -- in the new function body, and arg is the argument to apply to the old
371 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
374 bndrs <- Trans.lift getGlobalBinders
375 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
376 if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
378 -- Propagate all complex arguments that are not representable, but not
379 -- arguments with free type variables (since those would require types
380 -- not known yet, which will always be known eventually).
381 -- Find interesting free variables, each of which should be passed to
382 -- the new function instead of the original function argument.
384 -- Interesting vars are those that are local, but not available from the
385 -- top level scope (functions from this module are defined as local, but
386 -- they're not local to this function, so we can freely move references
387 -- to them into another function).
388 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
389 -- Mark the current expression as changed
391 return (map Var free_vars, free_vars, arg)
393 -- Representable types will not be propagated, and arguments with free
394 -- type variables will be propagated later.
395 -- TODO: preserve original naming?
396 id <- mkBinderFor arg "param"
397 -- Just pass the original argument to the new function, which binds it
398 -- to a new id and just pass that new id to the old function body.
399 return ([arg], [id], mkReferenceTo id)
400 -- Leave all other expressions unchanged
401 argprop expr = return expr
402 -- Perform this transform everywhere
403 argproptop = everywhere ("argprop", argprop)
405 --------------------------------
406 -- Function-typed argument extraction
407 --------------------------------
408 -- This transform takes any function-typed argument that cannot be propagated
409 -- (because the function that is applied to it is a builtin function), and
410 -- puts it in a brand new top level binder. This allows us to for example
411 -- apply map to a lambda expression This will not conflict with inlinefun,
412 -- since that only inlines local let bindings, not top level bindings.
413 funextract, funextracttop :: Transform
414 funextract expr@(App _ _) | is_var fexpr = do
415 body_maybe <- Trans.lift $ getGlobalBind f
417 -- We don't have a function body for f, so we can perform this transform.
419 -- Find the new arguments
420 args' <- mapM doarg args
421 -- And update the arguments. We use return instead of changed, so the
422 -- changed flag doesn't get set if none of the args got changed.
423 return $ MkCore.mkCoreApps fexpr args'
424 -- We have a function body for f, leave this application to funprop
425 Just _ -> return expr
427 -- Find the function called and the arguments
428 (fexpr, args) = collectArgs expr
430 -- Change any arguments that have a function type, but are not simple yet
431 -- (ie, a variable or application). This means to create a new function
432 -- for map (\f -> ...) b, but not for map (foo a) b.
434 -- We could use is_applicable here instead of is_fun, but I think
435 -- arguments to functions could only have forall typing when existential
436 -- typing is enabled. Not sure, though.
437 doarg arg | not (is_simple arg) && is_fun arg = do
438 -- Create a new top level binding that binds the argument. Its body will
439 -- be extended with lambda expressions, to take any free variables used
440 -- by the argument expression.
441 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
442 let body = MkCore.mkCoreLams free_vars arg
443 id <- mkBinderFor body "fun"
444 Trans.lift $ addGlobalBind id body
445 -- Replace the argument with a reference to the new function, applied to
447 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
448 -- Leave all other arguments untouched
449 doarg arg = return arg
451 -- Leave all other expressions unchanged
452 funextract expr = return expr
453 -- Perform this transform everywhere
454 funextracttop = everywhere ("funextract", funextract)
456 --------------------------------
457 -- End of transformations
458 --------------------------------
463 -- What transforms to run?
464 transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinenonreptop, appsimpltop]
466 -- Turns the given bind into VHDL
469 -> UniqSupply.UniqSupply -- ^ A UniqSupply we can use
470 -> [(CoreBndr, CoreExpr)] -- ^ All bindings we know (i.e., in the current module)
472 -> [CoreBndr] -- ^ The bindings to generate VHDL for (i.e., the top level bindings)
473 -> [Bool] -- ^ For each of the bindings to generate VHDL for, if it is stateful
474 -> ([(CoreBndr, CoreExpr)], [(CoreBndr, CoreExpr)], TypeState) -- ^ The resulting VHDL
476 normalizeModule env uniqsupply bindings testexprs generate_for statefuls = runTransformSession env uniqsupply $ do
477 testbinds <- mapM (\x -> do { v <- mkBinderFor' x "test" ; return (v,x) } ) testexprs
478 let testbinders = (map fst testbinds)
479 -- Put all the bindings in this module in the tsBindings map
480 putA tsBindings (Map.fromList (bindings ++ testbinds))
481 -- (Recursively) normalize each of the requested bindings
482 mapM normalizeBind (generate_for ++ testbinders)
483 -- Get all initial bindings and the ones we produced
484 bindings_map <- getA tsBindings
485 let bindings = Map.assocs bindings_map
486 normalized_binders' <- getA tsNormalized
487 let normalized_binders = VarSet.delVarSetList normalized_binders' testbinders
488 let ret_testbinds = zip testbinders (Maybe.catMaybes $ map (\x -> lookup x bindings) testbinders)
489 let ret_binds = filter ((`VarSet.elemVarSet` normalized_binders) . fst) bindings
490 typestate <- getA tsType
491 -- But return only the normalized bindings
492 return $ (ret_binds, ret_testbinds, typestate)
494 normalizeBind :: CoreBndr -> TransformSession ()
496 -- Don't normalize global variables, these should be either builtin
497 -- functions or data constructors.
498 Monad.when (Var.isLocalId bndr) $ do
499 -- Skip binders that have a polymorphic type, since it's impossible to
500 -- create polymorphic hardware.
501 if is_poly (Var bndr)
503 -- This should really only happen at the top level... TODO: Give
504 -- a different error if this happens down in the recursion.
505 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
507 normalized_funcs <- getA tsNormalized
508 -- See if this function was normalized already
509 if VarSet.elemVarSet bndr normalized_funcs
511 -- Yup, don't do it again
514 -- Nope, note that it has been and do it.
515 modA tsNormalized (flip VarSet.extendVarSet bndr)
516 expr_maybe <- getGlobalBind bndr
519 -- Introduce an empty Let at the top level, so there will always be
520 -- a let in the expression (none of the transformations will remove
522 let expr' = Let (Rec []) expr
523 -- Normalize this expression
524 trace ("Transforming " ++ (show bndr) ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
525 expr' <- dotransforms transforms expr'
526 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
527 -- And store the normalized version in the session
528 modA tsBindings (Map.insert bndr expr')
529 -- Find all vars used with a function type. All of these should be global
530 -- binders (i.e., functions used), since any local binders with a function
531 -- type should have been inlined already.
532 bndrs <- getGlobalBinders
533 let used_funcs_set = CoreFVs.exprSomeFreeVars (\v -> not (Id.isDictId v) && v `elem` bndrs) expr'
534 let used_funcs = VarSet.varSetElems used_funcs_set
535 -- Process each of the used functions recursively
536 mapM normalizeBind used_funcs
538 -- We don't have a value for this binder. This really shouldn't
539 -- happen for local id's...
540 Nothing -> error $ "\nNormalize.normalizeBind: No value found for binder " ++ pprString bndr ++ "? This should not happen!"