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 if is_wild b || Type.isFunTy (Id.idType b)
217 -- Don't create extra bindings for binders that are already wild, or
218 -- for binders that bind function types (to prevent loops with
222 -- Create on new binder that will actually capture a value in this
223 -- case statement, and return it
224 let bty = (Id.idType b)
225 id <- mkInternalVar "sel" bty
226 let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
227 return $ Just (b, Case scrut b bty [(con, binders, Var id)])
228 -- Leave all other expressions unchanged
229 casewild expr = return expr
230 -- Perform this transform everywhere
231 casewildtop = everywhere ("casewild", casewild)
233 --------------------------------
234 -- Case value simplification
235 --------------------------------
236 casevalsimpl, casevalsimpltop :: Transform
237 casevalsimpl expr@(Case scrut b ty alts) = do
238 -- Try to simplify each alternative, resulting in an optional binding and a
240 (bindings_maybe, alts') <- (Monad.liftM unzip) $ mapM doalt alts
241 let bindings = Maybe.catMaybes bindings_maybe
242 -- Create a new let around the case, that binds of the cases values.
243 let newlet = Let (Rec bindings) (Case scrut b ty alts')
244 -- If there were no values that needed and allowed simplification, don't
246 if null bindings then return expr else change newlet
248 doalt :: CoreAlt -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreAlt)
249 -- Don't simplify values that are already simple
250 doalt alt@(con, bndrs, Var _) = return (Nothing, alt)
251 -- Simplify each alt by creating a new id, binding the case value to it and
252 -- replacing the case value with that id. Only do this when the case value
253 -- does not use any of the binders bound by this alternative, for that would
254 -- cause those binders to become unbound when moving the value outside of
255 -- the case statement. Also, don't create a binding for applicable
256 -- expressions, to prevent loops with inlinefun.
257 doalt (con, bndrs, expr) | (not usesvars) && (not $ is_applicable expr) = do
258 id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
259 -- We don't flag a change here, since casevalsimpl will do that above
260 -- based on Just we return here.
261 return $ (Just (id, expr), (con, bndrs, Var id))
262 -- Find if any of the binders are used by expr
263 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
264 -- Don't simplify anything else
265 doalt alt = return (Nothing, alt)
266 -- Leave all other expressions unchanged
267 casevalsimpl expr = return expr
268 -- Perform this transform everywhere
269 casevalsimpltop = everywhere ("casevalsimpl", casevalsimpl)
271 --------------------------------
273 --------------------------------
274 -- Remove case statements that have only a single alternative and only wild
276 caseremove, caseremovetop :: Transform
277 -- Replace a useless case by the value of its single alternative
278 caseremove (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
279 -- Find if any of the binders are used by expr
280 where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
281 -- Leave all other expressions unchanged
282 caseremove expr = return expr
283 -- Perform this transform everywhere
284 caseremovetop = everywhere ("caseremove", caseremove)
286 --------------------------------
287 -- Application simplification
288 --------------------------------
289 -- Make sure that all arguments in an application are simple variables.
290 appsimpl, appsimpltop :: Transform
291 -- Don't simplify arguments that are already simple. Do simplify datacons,
292 -- however, since we can't portmap literals.
293 appsimpl expr@(App f (Var v)) | not $ Id.isDataConWorkId v = return expr
294 -- Simplify all non-applicable (to prevent loops with inlinefun) arguments,
295 -- except for type arguments (since a let can't bind type vars, only a lambda
296 -- can). Do this by introducing a new Let that binds the argument and passing
297 -- the new binder in the application.
298 appsimpl (App f expr) | (not $ is_applicable expr) && (not $ CoreSyn.isTypeArg expr) = do
299 id <- mkInternalVar "arg" (CoreUtils.exprType expr)
300 change $ Let (Rec [(id, expr)]) (App f (Var id))
301 -- Leave all other expressions unchanged
302 appsimpl expr = return expr
303 -- Perform this transform everywhere
304 appsimpltop = everywhere ("appsimpl", appsimpl)
307 --------------------------------
308 -- Type argument propagation
309 --------------------------------
310 -- Remove all applications to type arguments, by duplicating the function
311 -- called with the type application in its new definition. We leave
312 -- dictionaries that might be associated with the type untouched, the funprop
313 -- transform should propagate these later on.
314 typeprop, typeproptop :: Transform
315 -- Transform any function that is applied to a type argument. Since type
316 -- arguments are always the first ones to apply and we'll remove all type
317 -- arguments, we can simply do them one by one. We only propagate type
318 -- arguments without any free tyvars, since tyvars those wouldn't be in scope
319 -- in the new function.
320 typeprop expr@(App (Var f) arg@(Type ty)) | not $ has_free_tyvars arg = do
321 body_maybe <- Trans.lift $ getGlobalBind f
324 let newbody = App body (Type ty)
325 -- Create a new function with the same name but a new body
326 newf <- mkFunction f newbody
327 -- Replace the application with this new function
329 -- If we don't have a body for the function called, leave it unchanged (it
330 -- should be a primitive function then).
331 Nothing -> return expr
332 -- Leave all other expressions unchanged
333 typeprop expr = return expr
334 -- Perform this transform everywhere
335 typeproptop = everywhere ("typeprop", typeprop)
338 --------------------------------
339 -- Function-typed argument propagation
340 --------------------------------
341 -- Remove all applications to function-typed arguments, by duplication the
342 -- function called with the function-typed parameter replaced by the free
343 -- variables of the argument passed in.
344 funprop, funproptop :: Transform
345 -- Transform any application of a named function (i.e., skip applications of
346 -- lambda's). Also skip applications that have arguments with free type
347 -- variables, since we can't inline those.
348 funprop expr@(App _ _) | is_var fexpr && not (any has_free_tyvars args) = do
349 -- Find the body of the function called
350 body_maybe <- Trans.lift $ getGlobalBind f
353 -- Process each of the arguments in turn
354 (args', changed) <- Writer.listen $ mapM doarg args
355 -- See if any of the arguments changed
356 case Monoid.getAny changed of
358 let (newargs', newparams', oldargs) = unzip3 args'
359 let newargs = concat newargs'
360 let newparams = concat newparams'
361 -- Create a new body that consists of a lambda for all new arguments and
362 -- the old body applied to some arguments.
363 let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
364 -- Create a new function with the same name but a new body
365 newf <- mkFunction f newbody
366 -- Replace the original application with one of the new function to the
368 change $ MkCore.mkCoreApps (Var newf) newargs
370 -- Don't change the expression if none of the arguments changed
373 -- If we don't have a body for the function called, leave it unchanged (it
374 -- should be a primitive function then).
375 Nothing -> return expr
377 -- Find the function called and the arguments
378 (fexpr, args) = collectArgs expr
381 -- Process a single argument and return (args, bndrs, arg), where args are
382 -- the arguments to replace the given argument in the original
383 -- application, bndrs are the binders to include in the top-level lambda
384 -- in the new function body, and arg is the argument to apply to the old
386 doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
387 doarg arg | is_fun arg = do
388 bndrs <- Trans.lift getGlobalBinders
389 -- Find interesting free variables, each of which should be passed to
390 -- the new function instead of the original function argument.
392 -- Interesting vars are those that are local, but not available from the
393 -- top level scope (functions from this module are defined as local, but
394 -- they're not local to this function, so we can freely move references
395 -- to them into another function).
396 let interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
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)
401 -- Non-functiontyped arguments can be unchanged. Note that this handles
402 -- both values and types.
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 funprop expr = return expr
411 -- Perform this transform everywhere
412 funproptop = everywhere ("funprop", funprop)
415 -- TODO: introduce top level let if needed?
417 --------------------------------
418 -- End of transformations
419 --------------------------------
424 -- What transforms to run?
425 transforms = [typeproptop, funproptop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinefuntop, appsimpltop]
427 -- Turns the given bind into VHDL
429 UniqSupply.UniqSupply -- ^ A UniqSupply we can use
430 -> [(CoreBndr, CoreExpr)] -- ^ All bindings we know (i.e., in the current module)
431 -> [CoreBndr] -- ^ The bindings to generate VHDL for (i.e., the top level bindings)
432 -> [Bool] -- ^ For each of the bindings to generate VHDL for, if it is stateful
433 -> [(CoreBndr, CoreExpr)] -- ^ The resulting VHDL
435 normalizeModule uniqsupply bindings generate_for statefuls = runTransformSession uniqsupply $ do
436 -- Put all the bindings in this module in the tsBindings map
437 putA tsBindings (Map.fromList bindings)
438 -- (Recursively) normalize each of the requested bindings
439 mapM normalizeBind generate_for
440 -- Get all initial bindings and the ones we produced
441 bindings_map <- getA tsBindings
442 let bindings = Map.assocs bindings_map
443 normalized_bindings <- getA tsNormalized
444 -- But return only the normalized bindings
445 return $ filter ((flip VarSet.elemVarSet normalized_bindings) . fst) bindings
447 normalizeBind :: CoreBndr -> TransformSession ()
449 -- Don't normalize global variables, these should be either builtin
450 -- functions or data constructors.
451 Monad.when (Var.isLocalIdVar bndr) $ do
452 -- Skip binders that have a polymorphic type, since it's impossible to
453 -- create polymorphic hardware.
454 if is_poly (Var bndr)
456 -- This should really only happen at the top level... TODO: Give
457 -- a different error if this happens down in the recursion.
458 error $ "Function " ++ show bndr ++ " is polymorphic, can't normalize"
460 normalized_funcs <- getA tsNormalized
461 -- See if this function was normalized already
462 if VarSet.elemVarSet bndr normalized_funcs
464 -- Yup, don't do it again
467 -- Nope, note that it has been and do it.
468 modA tsNormalized (flip VarSet.extendVarSet bndr)
469 expr_maybe <- getGlobalBind bndr
472 -- Introduce an empty Let at the top level, so there will always be
473 -- a let in the expression (none of the transformations will remove
475 let expr' = Let (Rec []) expr
476 -- Normalize this expression
477 trace ("Transforming " ++ (show bndr) ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
478 expr' <- dotransforms transforms expr'
479 trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
480 -- And store the normalized version in the session
481 modA tsBindings (Map.insert bndr expr')
482 -- Find all vars used with a function type. All of these should be global
483 -- binders (i.e., functions used), since any local binders with a function
484 -- type should have been inlined already.
485 let used_funcs_set = CoreFVs.exprSomeFreeVars (\v -> (Type.isFunTy . snd . Type.splitForAllTys . Id.idType) v) expr'
486 let used_funcs = VarSet.varSetElems used_funcs_set
487 -- Process each of the used functions recursively
488 mapM normalizeBind used_funcs
490 -- We don't have a value for this binder. This really shouldn't
491 -- happen for local id's...
492 Nothing -> error $ "No value found for binder " ++ pprString bndr ++ "? This should not happen!"