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 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
26 import qualified VarSet
27 import qualified CoreFVs
28 import qualified CoreUtils
29 import qualified MkCore
30 import Outputable ( showSDoc, ppr, nest )
38 --------------------------------
39 -- Start of transformations
40 --------------------------------
42 --------------------------------
44 --------------------------------
45 eta, etatop :: Transform
46 eta expr | is_fun expr && not (is_lam expr) = do
47 let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
48 id <- mkInternalVar "param" arg_ty
49 change (Lam id (App expr (Var id)))
50 -- Leave all other expressions unchanged
52 etatop = notappargs ("eta", eta)
54 --------------------------------
56 --------------------------------
57 beta, betatop :: Transform
58 -- Substitute arg for x in expr
59 beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr
60 -- Propagate the application into the let
61 beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
62 -- Propagate the application into each of the alternatives
63 beta (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
65 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
66 ty' = CoreUtils.applyTypeToArg ty arg
67 -- Leave all other expressions unchanged
68 beta expr = return expr
69 -- Perform this transform everywhere
70 betatop = everywhere ("beta", beta)
72 --------------------------------
74 --------------------------------
75 -- Try to move casts as much downward as possible.
76 castprop, castproptop :: Transform
77 castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
78 castprop expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
80 alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
81 -- Leave all other expressions unchanged
82 castprop expr = return expr
83 -- Perform this transform everywhere
84 castproptop = everywhere ("castprop", castprop)
86 --------------------------------
87 -- let recursification
88 --------------------------------
89 letrec, letrectop :: Transform
90 letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
91 -- Leave all other expressions unchanged
92 letrec expr = return expr
93 -- Perform this transform everywhere
94 letrectop = everywhere ("letrec", letrec)
96 --------------------------------
98 --------------------------------
99 letsimpl, letsimpltop :: Transform
100 -- Don't simplifiy lets that are already simple
101 letsimpl expr@(Let _ (Var _)) = return expr
102 -- Put the "in ..." value of a let in its own binding, but not when the
103 -- expression is applicable (to prevent loops with inlinefun).
104 letsimpl (Let (Rec binds) expr) | not $ is_applicable expr = do
105 id <- mkInternalVar "foo" (CoreUtils.exprType expr)
106 let bind = (id, expr)
107 change $ Let (Rec (bind:binds)) (Var id)
108 -- Leave all other expressions unchanged
109 letsimpl expr = return expr
110 -- Perform this transform everywhere
111 letsimpltop = everywhere ("letsimpl", letsimpl)
113 --------------------------------
115 --------------------------------
116 letflat, letflattop :: Transform
117 letflat (Let (Rec binds) expr) = do
118 -- Turn each binding into a list of bindings (possibly containing just one
119 -- element, of course)
120 bindss <- Monad.mapM flatbind binds
121 -- Concat all the bindings
122 let binds' = concat bindss
123 -- Return the new let. We don't use change here, since possibly nothing has
124 -- changed. If anything has changed, flatbind has already flagged that
126 return $ Let (Rec binds') expr
128 -- Turns a binding of a let into a multiple bindings, or any other binding
129 -- into a list with just that binding
130 flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
131 flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
132 flatbind (b, expr) = return [(b, expr)]
133 -- Leave all other expressions unchanged
134 letflat expr = return expr
135 -- Perform this transform everywhere
136 letflattop = everywhere ("letflat", letflat)
138 --------------------------------
139 -- Simple let binding removal
140 --------------------------------
141 -- Remove a = b bindings from let expressions everywhere
142 letremovetop :: Transform
143 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> case e of (Var v) | not $ Id.isDataConWorkId v -> True; otherwise -> False))
145 --------------------------------
147 --------------------------------
148 -- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let
149 -- expressions everywhere. This means that any value that still needs to be
150 -- applied to something else (polymorphic values need to be applied to a
151 -- Type) will be inlined, and will eventually be applied to all their
154 -- This is a tricky function, which is prone to create loops in the
155 -- transformations. To fix this, we make sure that no transformation will
156 -- create a new let binding with a function type. These other transformations
157 -- will just not work on those function-typed values at first, but the other
158 -- transformations (in particular β-reduction) should make sure that the type
159 -- of those values eventually becomes primitive.
160 inlinefuntop :: Transform
161 inlinefuntop = everywhere ("inlinefun", inlinebind (is_applicable . snd))
163 --------------------------------
164 -- Scrutinee simplification
165 --------------------------------
166 scrutsimpl,scrutsimpltop :: Transform
167 -- Don't touch scrutinees that are already simple
168 scrutsimpl expr@(Case (Var _) _ _ _) = return expr
169 -- Replace all other cases with a let that binds the scrutinee and a new
170 -- simple scrutinee, but not when the scrutinee is applicable (to prevent
171 -- loops with inlinefun, though I don't think a scrutinee can be
173 scrutsimpl (Case scrut b ty alts) | not $ is_applicable scrut = do
174 id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
175 change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
176 -- Leave all other expressions unchanged
177 scrutsimpl expr = return expr
178 -- Perform this transform everywhere
179 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
181 --------------------------------
182 -- Case binder wildening
183 --------------------------------
184 casewild, casewildtop :: Transform
185 casewild expr@(Case scrut b ty alts) = do
186 (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
187 let bindings = concat bindingss
188 -- Replace the case with a let with bindings and a case
189 let newlet = (Let (Rec bindings) (Case scrut b ty alts'))
190 -- If there are no non-wild binders, or this case is already a simple
191 -- selector (i.e., a single alt with exactly one binding), already a simple
192 -- selector altan no bindings (i.e., no wild binders in the original case),
193 -- don't change anything, otherwise, replace the case.
194 if null bindings || length alts == 1 && length bindings == 1 then return expr else change newlet
196 -- Generate a single wild binder, since they are all the same
198 -- Wilden the binders of one alt, producing a list of bindings as a
200 doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
201 doalt (con, bndrs, expr) = do
202 bindings_maybe <- Monad.zipWithM mkextracts bndrs [0..]
203 let bindings = Maybe.catMaybes bindings_maybe
204 -- We replace the binders with wild binders only. We can leave expr
205 -- unchanged, since the new bindings bind the same vars as the original
207 let newalt = (con, wildbndrs, expr)
208 return (bindings, newalt)
210 -- Make all binders wild
211 wildbndrs = map (\bndr -> Id.mkWildId (Id.idType bndr)) bndrs
212 -- Creates a case statement to retrieve the ith element from the scrutinee
213 -- and binds that to b.
214 mkextracts :: CoreBndr -> Int -> TransformMonad (Maybe (CoreBndr, CoreExpr))
216 -- TODO: Use free variables instead of is_wild. is_wild is a hack.
217 if is_wild b || Type.isFunTy (Id.idType b)
218 -- Don't create extra bindings for binders that are already wild, or
219 -- for binders that bind function types (to prevent loops with
223 -- Create on new binder that will actually capture a value in this
224 -- case statement, and return it
225 let bty = (Id.idType b)
226 id <- mkInternalVar "sel" bty
227 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
228 return $ Just (b, Case scrut b bty [(con, binders, Var id)])
229 -- Leave all other expressions unchanged
230 casewild expr = return expr
231 -- Perform this transform everywhere
232 casewildtop = everywhere ("casewild", casewild)
234 --------------------------------
235 -- Case value simplification
236 --------------------------------
237 casevalsimpl, casevalsimpltop :: Transform
238 casevalsimpl expr@(Case scrut b ty alts) = do
239 -- Try to simplify each alternative, resulting in an optional binding and a
241 (bindings_maybe, alts') <- (Monad.liftM unzip) $ mapM doalt alts
242 let bindings = Maybe.catMaybes bindings_maybe
243 -- Create a new let around the case, that binds of the cases values.
244 let newlet = Let (Rec bindings) (Case scrut b ty alts')
245 -- If there were no values that needed and allowed simplification, don't
247 if null bindings then return expr else change newlet
249 doalt :: CoreAlt -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreAlt)
250 -- Don't simplify values that are already simple
251 doalt alt@(con, bndrs, Var _) = return (Nothing, alt)
252 -- Simplify each alt by creating a new id, binding the case value to it and
253 -- replacing the case value with that id. Only do this when the case value
254 -- does not use any of the binders bound by this alternative, for that would
255 -- cause those binders to become unbound when moving the value outside of
256 -- the case statement. Also, don't create a binding for applicable
257 -- expressions, to prevent loops with inlinefun.
258 doalt (con, bndrs, expr) | (not usesvars) && (not $ is_applicable expr) = do
259 id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
260 -- We don't flag a change here, since casevalsimpl will do that above
261 -- based on Just we return here.
262 return $ (Just (id, expr), (con, bndrs, Var id))
263 -- Find if any of the binders are used by expr
264 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
265 -- Don't simplify anything else
266 doalt alt = return (Nothing, alt)
267 -- Leave all other expressions unchanged
268 casevalsimpl expr = return expr
269 -- Perform this transform everywhere
270 casevalsimpltop = everywhere ("casevalsimpl", casevalsimpl)
272 --------------------------------
274 --------------------------------
275 -- Remove case statements that have only a single alternative and only wild
277 caseremove, caseremovetop :: Transform
278 -- Replace a useless case by the value of its single alternative
279 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
280 -- Find if any of the binders are used by expr
281 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
282 -- Leave all other expressions unchanged
283 caseremove expr = return expr
284 -- Perform this transform everywhere
285 caseremovetop = everywhere ("caseremove", caseremove)
287 --------------------------------
288 -- Argument extraction
289 --------------------------------
290 -- Make sure that all arguments of a representable type are simple variables.
291 appsimpl, appsimpltop :: Transform
292 -- Don't simplify arguments that are already simple.
293 appsimpl expr@(App f (Var v)) = return expr
294 -- Simplify all representable arguments. Do this by introducing a new Let
295 -- that binds the argument and passing the new binder in the application.
296 appsimpl expr@(App f arg) = do
297 -- Check runtime representability
300 then do -- Extract representable arguments
301 id <- mkInternalVar "arg" (CoreUtils.exprType arg)
302 change $ Let (Rec [(id, arg)]) (App f (Var id))
303 else -- Leave non-representable arguments unchanged
305 -- Leave all other expressions unchanged
306 appsimpl expr = return expr
307 -- Perform this transform everywhere
308 appsimpltop = everywhere ("appsimpl", appsimpl)
310 --------------------------------
311 -- Type argument propagation
312 --------------------------------
313 -- Remove all applications to type arguments, by duplicating the function
314 -- called with the type application in its new definition. We leave
315 -- dictionaries that might be associated with the type untouched, the funprop
316 -- transform should propagate these later on.
317 typeprop, typeproptop :: Transform
318 -- Transform any function that is applied to a type argument. Since type
319 -- arguments are always the first ones to apply and we'll remove all type
320 -- arguments, we can simply do them one by one. We only propagate type
321 -- arguments without any free tyvars, since tyvars those wouldn't be in scope
322 -- in the new function.
323 typeprop expr@(App (Var f) arg@(Type ty)) | not $ has_free_tyvars arg = do
324 body_maybe <- Trans.lift $ getGlobalBind f
327 let newbody = App body (Type ty)
328 -- Create a new function with the same name but a new body
329 newf <- mkFunction f newbody
330 -- Replace the application with this new function
332 -- If we don't have a body for the function called, leave it unchanged (it
333 -- should be a primitive function then).
334 Nothing -> return expr
335 -- Leave all other expressions unchanged
336 typeprop expr = return expr
337 -- Perform this transform everywhere
338 typeproptop = everywhere ("typeprop", typeprop)
341 --------------------------------
342 -- Function-typed argument propagation
343 --------------------------------
344 -- Remove all applications to function-typed arguments, by duplication the
345 -- function called with the function-typed parameter replaced by the free
346 -- variables of the argument passed in.
347 funprop, funproptop :: Transform
348 -- Transform any application of a named function (i.e., skip applications of
349 -- lambda's). Also skip applications that have arguments with free type
350 -- variables, since we can't inline those.
351 funprop expr@(App _ _) | is_var fexpr && not (any has_free_tyvars args) = do
352 -- Find the body of the function called
353 body_maybe <- Trans.lift $ getGlobalBind f
356 -- Process each of the arguments in turn
357 (args', changed) <- Writer.listen $ mapM doarg args
358 -- See if any of the arguments changed
359 case Monoid.getAny changed of
361 let (newargs', newparams', oldargs) = unzip3 args'
362 let newargs = concat newargs'
363 let newparams = concat newparams'
364 -- Create a new body that consists of a lambda for all new arguments and
365 -- the old body applied to some arguments.
366 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
367 -- Create a new function with the same name but a new body
368 newf <- mkFunction f newbody
369 -- Replace the original application with one of the new function to the
371 change $ MkCore.mkCoreApps (Var newf) newargs
373 -- Don't change the expression if none of the arguments changed
376 -- If we don't have a body for the function called, leave it unchanged (it
377 -- should be a primitive function then).
378 Nothing -> return expr
380 -- Find the function called and the arguments
381 (fexpr, args) = collectArgs expr
384 -- Process a single argument and return (args, bndrs, arg), where args are
385 -- the arguments to replace the given argument in the original
386 -- application, bndrs are the binders to include in the top-level lambda
387 -- in the new function body, and arg is the argument to apply to the old
389 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
390 doarg arg | is_fun arg = do
391 bndrs <- Trans.lift getGlobalBinders
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 interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
400 let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
401 -- Mark the current expression as changed
403 return (map Var free_vars, free_vars, arg)
404 -- Non-functiontyped arguments can be unchanged. Note that this handles
405 -- both values and types.
407 -- TODO: preserve original naming?
408 id <- mkBinderFor arg "param"
409 -- Just pass the original argument to the new function, which binds it
410 -- to a new id and just pass that new id to the old function body.
411 return ([arg], [id], mkReferenceTo id)
412 -- Leave all other expressions unchanged
413 funprop expr = return expr
414 -- Perform this transform everywhere
415 funproptop = everywhere ("funprop", funprop)
417 --------------------------------
418 -- Function-typed argument extraction
419 --------------------------------
420 -- This transform takes any function-typed argument that cannot be propagated
421 -- (because the function that is applied to it is a builtin function), and
422 -- puts it in a brand new top level binder. This allows us to for example
423 -- apply map to a lambda expression This will not conflict with inlinefun,
424 -- since that only inlines local let bindings, not top level bindings.
425 funextract, funextracttop :: Transform
426 funextract expr@(App _ _) | is_var fexpr = do
427 body_maybe <- Trans.lift $ getGlobalBind f
429 -- We don't have a function body for f, so we can perform this transform.
431 -- Find the new arguments
432 args' <- mapM doarg args
433 -- And update the arguments. We use return instead of changed, so the
434 -- changed flag doesn't get set if none of the args got changed.
435 return $ MkCore.mkCoreApps fexpr args'
436 -- We have a function body for f, leave this application to funprop
437 Just _ -> return expr
439 -- Find the function called and the arguments
440 (fexpr, args) = collectArgs expr
442 -- Change any arguments that have a function type, but are not simple yet
443 -- (ie, a variable or application). This means to create a new function
444 -- for map (\f -> ...) b, but not for map (foo a) b.
446 -- We could use is_applicable here instead of is_fun, but I think
447 -- arguments to functions could only have forall typing when existential
448 -- typing is enabled. Not sure, though.
449 doarg arg | not (is_simple arg) && is_fun arg = do
450 -- Create a new top level binding that binds the argument. Its body will
451 -- be extended with lambda expressions, to take any free variables used
452 -- by the argument expression.
453 let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
454 let body = MkCore.mkCoreLams free_vars arg
455 id <- mkBinderFor body "fun"
456 Trans.lift $ addGlobalBind id body
457 -- Replace the argument with a reference to the new function, applied to
459 change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
460 -- Leave all other arguments untouched
461 doarg arg = return arg
463 -- Leave all other expressions unchanged
464 funextract expr = return expr
465 -- Perform this transform everywhere
466 funextracttop = everywhere ("funextract", funextract)
468 --------------------------------
469 -- End of transformations
470 --------------------------------
475 -- What transforms to run?
476 transforms = [typeproptop, funproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinefuntop, appsimpltop]
478 -- Turns the given bind into VHDL
480 UniqSupply.UniqSupply -- ^ A UniqSupply we can use
481 -> [(CoreBndr, CoreExpr)] -- ^ All bindings we know (i.e., in the current module)
482 -> [CoreBndr] -- ^ The bindings to generate VHDL for (i.e., the top level bindings)
483 -> [Bool] -- ^ For each of the bindings to generate VHDL for, if it is stateful
484 -> [(CoreBndr, CoreExpr)] -- ^ The resulting VHDL
486 normalizeModule uniqsupply bindings generate_for statefuls = runTransformSession uniqsupply $ do
487 -- Put all the bindings in this module in the tsBindings map
488 putA tsBindings (Map.fromList bindings)
489 -- (Recursively) normalize each of the requested bindings
490 mapM normalizeBind generate_for
491 -- Get all initial bindings and the ones we produced
492 bindings_map <- getA tsBindings
493 let bindings = Map.assocs bindings_map
494 normalized_bindings <- getA tsNormalized
495 -- But return only the normalized bindings
496 return $ filter ((flip VarSet.elemVarSet normalized_bindings) . fst) bindings
498 normalizeBind :: CoreBndr -> TransformSession ()
500 -- Don't normalize global variables, these should be either builtin
501 -- functions or data constructors.
502 Monad.when (Var.isLocalIdVar bndr) $ do
503 -- Skip binders that have a polymorphic type, since it's impossible to
504 -- create polymorphic hardware.
505 if is_poly (Var bndr)
507 -- This should really only happen at the top level... TODO: Give
508 -- a different error if this happens down in the recursion.
509 error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
511 normalized_funcs <- getA tsNormalized
512 -- See if this function was normalized already
513 if VarSet.elemVarSet bndr normalized_funcs
515 -- Yup, don't do it again
518 -- Nope, note that it has been and do it.
519 modA tsNormalized (flip VarSet.extendVarSet bndr)
520 expr_maybe <- getGlobalBind bndr
523 -- Introduce an empty Let at the top level, so there will always be
524 -- a let in the expression (none of the transformations will remove
526 let expr' = Let (Rec []) expr
527 -- Normalize this expression
528 trace ("Transforming " ++ (show bndr) ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
529 expr' <- dotransforms transforms expr'
530 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
531 -- And store the normalized version in the session
532 modA tsBindings (Map.insert bndr expr')
533 -- Find all vars used with a function type. All of these should be global
534 -- binders (i.e., functions used), since any local binders with a function
535 -- type should have been inlined already.
536 let used_funcs_set = CoreFVs.exprSomeFreeVars (\v -> (Type.isFunTy . snd . Type.splitForAllTys . Id.idType) v) expr'
537 let used_funcs = VarSet.varSetElems used_funcs_set
538 -- Process each of the used functions recursively
539 mapM normalizeBind used_funcs
541 -- We don't have a value for this binder. This really shouldn't
542 -- happen for local id's...
543 Nothing -> error $ "\nNormalize.normalizeBind: No value found for binder " ++ pprString bndr ++ "? This should not happen!"