2 -- | Handy functions for creating much Core syntax
4 -- * Constructing normal syntax
6 mkCoreApp, mkCoreApps, mkCoreConApps,
7 mkCoreLams, mkWildCase, mkWildBinder, mkIfThenElse,
9 -- * Constructing boxed literals
10 mkWordExpr, mkWordExprWord,
11 mkIntExpr, mkIntExprInt,
13 mkFloatExpr, mkDoubleExpr,
14 mkCharExpr, mkStringExpr, mkStringExprFS,
16 -- * Constructing general big tuples
20 -- * Constructing small tuples
21 mkCoreVarTup, mkCoreVarTupTy,
22 mkCoreTup, mkCoreTupTy,
24 -- * Constructing big tuples
25 mkBigCoreVarTup, mkBigCoreVarTupTy,
26 mkBigCoreTup, mkBigCoreTupTy,
28 -- * Deconstructing small tuples
29 mkSmallTupleSelector, mkSmallTupleCase,
31 -- * Deconstructing big tuples
32 mkTupleSelector, mkTupleCase,
34 -- * Constructing list expressions
35 mkNilExpr, mkConsExpr, mkListExpr,
36 mkFoldrExpr, mkBuildExpr
39 #include "HsVersions.h"
42 import Var ( setTyVarUnique )
45 import CoreUtils ( exprType, needsCaseBinding, bindNonRec )
54 import TysPrim ( alphaTyVar )
55 import DataCon ( DataCon, dataConWorkId )
59 import Unique ( mkBuiltinUnique )
61 import Util ( notNull, zipEqual )
65 import Data.Char ( ord )
68 infixl 4 `mkCoreApp`, `mkCoreApps`
71 %************************************************************************
73 \subsection{Basic CoreSyn construction}
75 %************************************************************************
78 -- | Bind a binding group over an expression, using a @let@ or @case@ as
79 -- appropriate (see "CoreSyn#let_app_invariant")
80 mkCoreLet :: CoreBind -> CoreExpr -> CoreExpr
81 mkCoreLet (NonRec bndr rhs) body -- See Note [CoreSyn let/app invariant]
82 | needsCaseBinding (idType bndr) rhs
83 = Case rhs bndr (exprType body) [(DEFAULT,[],body)]
87 -- | Bind a list of binding groups over an expression. The leftmost binding
88 -- group becomes the outermost group in the resulting expression
89 mkCoreLets :: [CoreBind] -> CoreExpr -> CoreExpr
90 mkCoreLets binds body = foldr mkCoreLet body binds
92 -- | Construct an expression which represents the application of one expression
94 mkCoreApp :: CoreExpr -> CoreExpr -> CoreExpr
95 -- Check the invariant that the arg of an App is ok-for-speculation if unlifted
96 -- See CoreSyn Note [CoreSyn let/app invariant]
97 mkCoreApp fun (Type ty) = App fun (Type ty)
98 mkCoreApp fun arg = mk_val_app fun arg arg_ty res_ty
100 (arg_ty, res_ty) = splitFunTy (exprType fun)
102 -- | Construct an expression which represents the application of a number of
103 -- expressions to another. The leftmost expression in the list is applied first
104 mkCoreApps :: CoreExpr -> [CoreExpr] -> CoreExpr
105 -- Slightly more efficient version of (foldl mkCoreApp)
107 = go fun (exprType fun) args
110 go fun fun_ty (Type ty : args) = go (App fun (Type ty)) (applyTy fun_ty ty) args
111 go fun fun_ty (arg : args) = go (mk_val_app fun arg arg_ty res_ty) res_ty args
113 (arg_ty, res_ty) = splitFunTy fun_ty
115 -- | Construct an expression which represents the application of a number of
116 -- expressions to that of a data constructor expression. The leftmost expression
117 -- in the list is applied first
118 mkCoreConApps :: DataCon -> [CoreExpr] -> CoreExpr
119 mkCoreConApps con args = mkCoreApps (Var (dataConWorkId con)) args
122 mk_val_app :: CoreExpr -> CoreExpr -> Type -> Type -> CoreExpr
123 mk_val_app fun arg arg_ty _ -- See Note [CoreSyn let/app invariant]
124 | not (needsCaseBinding arg_ty arg)
125 = App fun arg -- The vastly common case
127 mk_val_app fun arg arg_ty res_ty
128 = Case arg arg_id res_ty [(DEFAULT,[],App fun (Var arg_id))]
130 arg_id = mkWildBinder arg_ty
131 -- Lots of shadowing, but it doesn't matter,
132 -- because 'fun ' should not have a free wild-id
134 -- This is Dangerous. But this is the only place we play this
135 -- game, mk_val_app returns an expression that does not have
136 -- have a free wild-id. So the only thing that can go wrong
137 -- is if you take apart this case expression, and pass a
138 -- fragmet of it as the fun part of a 'mk_val_app'.
141 -- | Make a /wildcard binder/. This is typically used when you need a binder
142 -- that you expect to use only at a *binding* site. Do not use it at
143 -- occurrence sites because it has a single, fixed unique, and it's very
144 -- easy to get into difficulties with shadowing. That's why it is used so little.
145 mkWildBinder :: Type -> Id
146 mkWildBinder ty = mkSysLocal (fsLit "wild") (mkBuiltinUnique 1) ty
148 mkWildCase :: CoreExpr -> Type -> Type -> [CoreAlt] -> CoreExpr
149 -- Make a case expression whose case binder is unused
150 -- The alts should not have any occurrences of WildId
151 mkWildCase scrut scrut_ty res_ty alts
152 = Case scrut (mkWildBinder scrut_ty) res_ty alts
154 mkIfThenElse :: CoreExpr -> CoreExpr -> CoreExpr -> CoreExpr
155 mkIfThenElse guard then_expr else_expr
156 -- Not going to be refining, so okay to take the type of the "then" clause
157 = mkWildCase guard boolTy (exprType then_expr)
158 [ (DataAlt falseDataCon, [], else_expr), -- Increasing order of tag!
159 (DataAlt trueDataCon, [], then_expr) ]
162 The functions from this point don't really do anything cleverer than
163 their counterparts in CoreSyn, but they are here for consistency
166 -- | Create a lambda where the given expression has a number of variables
167 -- bound over it. The leftmost binder is that bound by the outermost
168 -- lambda in the result
169 mkCoreLams :: [CoreBndr] -> CoreExpr -> CoreExpr
173 %************************************************************************
175 \subsection{Making literals}
177 %************************************************************************
180 -- | Create a 'CoreExpr' which will evaluate to the given @Int@
181 mkIntExpr :: Integer -> CoreExpr -- Result = I# i :: Int
182 mkIntExpr i = mkConApp intDataCon [mkIntLit i]
184 -- | Create a 'CoreExpr' which will evaluate to the given @Int@
185 mkIntExprInt :: Int -> CoreExpr -- Result = I# i :: Int
186 mkIntExprInt i = mkConApp intDataCon [mkIntLitInt i]
188 -- | Create a 'CoreExpr' which will evaluate to the a @Word@ with the given value
189 mkWordExpr :: Integer -> CoreExpr
190 mkWordExpr w = mkConApp wordDataCon [mkWordLit w]
192 -- | Create a 'CoreExpr' which will evaluate to the given @Word@
193 mkWordExprWord :: Word -> CoreExpr
194 mkWordExprWord w = mkConApp wordDataCon [mkWordLitWord w]
196 -- | Create a 'CoreExpr' which will evaluate to the given @Integer@
197 mkIntegerExpr :: MonadThings m => Integer -> m CoreExpr -- Result :: Integer
199 | inIntRange i -- Small enough, so start from an Int
200 = do integer_id <- lookupId smallIntegerName
201 return (mkSmallIntegerLit integer_id i)
203 -- Special case for integral literals with a large magnitude:
204 -- They are transformed into an expression involving only smaller
205 -- integral literals. This improves constant folding.
207 | otherwise = do -- Big, so start from a string
208 plus_id <- lookupId plusIntegerName
209 times_id <- lookupId timesIntegerName
210 integer_id <- lookupId smallIntegerName
212 lit i = mkSmallIntegerLit integer_id i
213 plus a b = Var plus_id `App` a `App` b
214 times a b = Var times_id `App` a `App` b
216 -- Transform i into (x1 + (x2 + (x3 + (...) * b) * b) * b) with abs xi <= b
217 horner :: Integer -> Integer -> CoreExpr
218 horner b i | abs q <= 1 = if r == 0 || r == i
220 else lit r `plus` lit (i-r)
221 | r == 0 = horner b q `times` lit b
222 | otherwise = lit r `plus` (horner b q `times` lit b)
224 (q,r) = i `quotRem` b
226 return (horner tARGET_MAX_INT i)
228 mkSmallIntegerLit :: Id -> Integer -> CoreExpr
229 mkSmallIntegerLit small_integer i = mkApps (Var small_integer) [mkIntLit i]
232 -- | Create a 'CoreExpr' which will evaluate to the given @Float@
233 mkFloatExpr :: Float -> CoreExpr
234 mkFloatExpr f = mkConApp floatDataCon [mkFloatLitFloat f]
236 -- | Create a 'CoreExpr' which will evaluate to the given @Double@
237 mkDoubleExpr :: Double -> CoreExpr
238 mkDoubleExpr d = mkConApp doubleDataCon [mkDoubleLitDouble d]
241 -- | Create a 'CoreExpr' which will evaluate to the given @Char@
242 mkCharExpr :: Char -> CoreExpr -- Result = C# c :: Int
243 mkCharExpr c = mkConApp charDataCon [mkCharLit c]
245 -- | Create a 'CoreExpr' which will evaluate to the given @String@
246 mkStringExpr :: MonadThings m => String -> m CoreExpr -- Result :: String
247 -- | Create a 'CoreExpr' which will evaluate to a string morally equivalent to the given @FastString@
248 mkStringExprFS :: MonadThings m => FastString -> m CoreExpr -- Result :: String
250 mkStringExpr str = mkStringExprFS (mkFastString str)
254 = return (mkNilExpr charTy)
257 = do let the_char = mkCharExpr (headFS str)
258 return (mkConsExpr charTy the_char (mkNilExpr charTy))
261 = do unpack_id <- lookupId unpackCStringName
262 return (App (Var unpack_id) (Lit (MachStr str)))
265 = do unpack_id <- lookupId unpackCStringUtf8Name
266 return (App (Var unpack_id) (Lit (MachStr str)))
270 safeChar c = ord c >= 1 && ord c <= 0x7F
273 %************************************************************************
275 \subsection{Tuple constructors}
277 %************************************************************************
284 -- GHCs built in tuples can only go up to 'mAX_TUPLE_SIZE' in arity, but
285 -- we might concievably want to build such a massive tuple as part of the
286 -- output of a desugaring stage (notably that for list comprehensions).
288 -- We call tuples above this size \"big tuples\", and emulate them by
289 -- creating and pattern matching on >nested< tuples that are expressible
292 -- Nesting policy: it's better to have a 2-tuple of 10-tuples (3 objects)
293 -- than a 10-tuple of 2-tuples (11 objects), so we want the leaves of any
294 -- construction to be big.
296 -- If you just use the 'mkBigCoreTup', 'mkBigCoreVarTupTy', 'mkTupleSelector'
297 -- and 'mkTupleCase' functions to do all your work with tuples you should be
298 -- fine, and not have to worry about the arity limitation at all.
300 -- | Lifts a \"small\" constructor into a \"big\" constructor by recursive decompositon
301 mkChunkified :: ([a] -> a) -- ^ \"Small\" constructor function, of maximum input arity 'mAX_TUPLE_SIZE'
302 -> [a] -- ^ Possible \"big\" list of things to construct from
303 -> a -- ^ Constructed thing made possible by recursive decomposition
304 mkChunkified small_tuple as = mk_big_tuple (chunkify as)
306 -- Each sub-list is short enough to fit in a tuple
307 mk_big_tuple [as] = small_tuple as
308 mk_big_tuple as_s = mk_big_tuple (chunkify (map small_tuple as_s))
310 chunkify :: [a] -> [[a]]
311 -- ^ Split a list into lists that are small enough to have a corresponding
312 -- tuple arity. The sub-lists of the result all have length <= 'mAX_TUPLE_SIZE'
313 -- But there may be more than 'mAX_TUPLE_SIZE' sub-lists
315 | n_xs <= mAX_TUPLE_SIZE = [xs]
316 | otherwise = split xs
320 split xs = take mAX_TUPLE_SIZE xs : split (drop mAX_TUPLE_SIZE xs)
324 Creating tuples and their types for Core expressions
326 @mkBigCoreVarTup@ builds a tuple; the inverse to @mkTupleSelector@.
328 * If it has only one element, it is the identity function.
330 * If there are more elements than a big tuple can have, it nests
335 -- | Build a small tuple holding the specified variables
336 mkCoreVarTup :: [Id] -> CoreExpr
337 mkCoreVarTup ids = mkCoreTup (map Var ids)
339 -- | Bulid the type of a small tuple that holds the specified variables
340 mkCoreVarTupTy :: [Id] -> Type
341 mkCoreVarTupTy ids = mkCoreTupTy (map idType ids)
343 -- | Build a small tuple holding the specified expressions
344 mkCoreTup :: [CoreExpr] -> CoreExpr
345 mkCoreTup [] = Var unitDataConId
347 mkCoreTup cs = mkConApp (tupleCon Boxed (length cs))
348 (map (Type . exprType) cs ++ cs)
350 -- | Build the type of a small tuple that holds the specified type of thing
351 mkCoreTupTy :: [Type] -> Type
352 mkCoreTupTy [ty] = ty
353 mkCoreTupTy tys = mkTupleTy Boxed (length tys) tys
356 -- | Build a big tuple holding the specified variables
357 mkBigCoreVarTup :: [Id] -> CoreExpr
358 mkBigCoreVarTup ids = mkBigCoreTup (map Var ids)
360 -- | Build the type of a big tuple that holds the specified variables
361 mkBigCoreVarTupTy :: [Id] -> Type
362 mkBigCoreVarTupTy ids = mkBigCoreTupTy (map idType ids)
364 -- | Build a big tuple holding the specified expressions
365 mkBigCoreTup :: [CoreExpr] -> CoreExpr
366 mkBigCoreTup = mkChunkified mkCoreTup
368 -- | Build the type of a big tuple that holds the specified type of thing
369 mkBigCoreTupTy :: [Type] -> Type
370 mkBigCoreTupTy = mkChunkified mkCoreTupTy
373 %************************************************************************
375 \subsection{Tuple destructors}
377 %************************************************************************
380 -- | Builds a selector which scrutises the given
381 -- expression and extracts the one name from the list given.
382 -- If you want the no-shadowing rule to apply, the caller
383 -- is responsible for making sure that none of these names
386 -- If there is just one 'Id' in the tuple, then the selector is
387 -- just the identity.
389 -- If necessary, we pattern match on a \"big\" tuple.
390 mkTupleSelector :: [Id] -- ^ The 'Id's to pattern match the tuple against
391 -> Id -- ^ The 'Id' to select
392 -> Id -- ^ A variable of the same type as the scrutinee
393 -> CoreExpr -- ^ Scrutinee
394 -> CoreExpr -- ^ Selector expression
396 -- mkTupleSelector [a,b,c,d] b v e
398 -- (p,q) -> case p of p {
400 -- We use 'tpl' vars for the p,q, since shadowing does not matter.
402 -- In fact, it's more convenient to generate it innermost first, getting
407 mkTupleSelector vars the_var scrut_var scrut
408 = mk_tup_sel (chunkify vars) the_var
410 mk_tup_sel [vars] the_var = mkSmallTupleSelector vars the_var scrut_var scrut
411 mk_tup_sel vars_s the_var = mkSmallTupleSelector group the_var tpl_v $
412 mk_tup_sel (chunkify tpl_vs) tpl_v
414 tpl_tys = [mkCoreTupTy (map idType gp) | gp <- vars_s]
415 tpl_vs = mkTemplateLocals tpl_tys
416 [(tpl_v, group)] = [(tpl,gp) | (tpl,gp) <- zipEqual "mkTupleSelector" tpl_vs vars_s,
421 -- | Like 'mkTupleSelector' but for tuples that are guaranteed
422 -- never to be \"big\".
424 -- > mkSmallTupleSelector [x] x v e = [| e |]
425 -- > mkSmallTupleSelector [x,y,z] x v e = [| case e of v { (x,y,z) -> x } |]
426 mkSmallTupleSelector :: [Id] -- The tuple args
427 -> Id -- The selected one
428 -> Id -- A variable of the same type as the scrutinee
429 -> CoreExpr -- Scrutinee
431 mkSmallTupleSelector [var] should_be_the_same_var _ scrut
432 = ASSERT(var == should_be_the_same_var)
434 mkSmallTupleSelector vars the_var scrut_var scrut
435 = ASSERT( notNull vars )
436 Case scrut scrut_var (idType the_var)
437 [(DataAlt (tupleCon Boxed (length vars)), vars, Var the_var)]
441 -- | A generalization of 'mkTupleSelector', allowing the body
442 -- of the case to be an arbitrary expression.
444 -- To avoid shadowing, we use uniques to invent new variables.
446 -- If necessary we pattern match on a \"big\" tuple.
447 mkTupleCase :: UniqSupply -- ^ For inventing names of intermediate variables
448 -> [Id] -- ^ The tuple identifiers to pattern match on
449 -> CoreExpr -- ^ Body of the case
450 -> Id -- ^ A variable of the same type as the scrutinee
451 -> CoreExpr -- ^ Scrutinee
453 -- ToDo: eliminate cases where none of the variables are needed.
455 -- mkTupleCase uniqs [a,b,c,d] body v e
456 -- = case e of v { (p,q) ->
457 -- case p of p { (a,b) ->
458 -- case q of q { (c,d) ->
460 mkTupleCase uniqs vars body scrut_var scrut
461 = mk_tuple_case uniqs (chunkify vars) body
463 -- This is the case where don't need any nesting
464 mk_tuple_case _ [vars] body
465 = mkSmallTupleCase vars body scrut_var scrut
467 -- This is the case where we must make nest tuples at least once
468 mk_tuple_case us vars_s body
469 = let (us', vars', body') = foldr one_tuple_case (us, [], body) vars_s
470 in mk_tuple_case us' (chunkify vars') body'
472 one_tuple_case chunk_vars (us, vs, body)
473 = let (us1, us2) = splitUniqSupply us
474 scrut_var = mkSysLocal (fsLit "ds") (uniqFromSupply us1)
475 (mkCoreTupTy (map idType chunk_vars))
476 body' = mkSmallTupleCase chunk_vars body scrut_var (Var scrut_var)
477 in (us2, scrut_var:vs, body')
481 -- | As 'mkTupleCase', but for a tuple that is small enough to be guaranteed
482 -- not to need nesting.
484 :: [Id] -- ^ The tuple args
485 -> CoreExpr -- ^ Body of the case
486 -> Id -- ^ A variable of the same type as the scrutinee
487 -> CoreExpr -- ^ Scrutinee
490 mkSmallTupleCase [var] body _scrut_var scrut
491 = bindNonRec var scrut body
492 mkSmallTupleCase vars body scrut_var scrut
493 -- One branch no refinement?
494 = Case scrut scrut_var (exprType body) [(DataAlt (tupleCon Boxed (length vars)), vars, body)]
497 %************************************************************************
499 \subsection{Common list manipulation expressions}
501 %************************************************************************
503 Call the constructor Ids when building explicit lists, so that they
504 interact well with rules.
507 -- | Makes a list @[]@ for lists of the specified type
508 mkNilExpr :: Type -> CoreExpr
509 mkNilExpr ty = mkConApp nilDataCon [Type ty]
511 -- | Makes a list @(:)@ for lists of the specified type
512 mkConsExpr :: Type -> CoreExpr -> CoreExpr -> CoreExpr
513 mkConsExpr ty hd tl = mkConApp consDataCon [Type ty, hd, tl]
515 -- | Make a list containing the given expressions, where the list has the given type
516 mkListExpr :: Type -> [CoreExpr] -> CoreExpr
517 mkListExpr ty xs = foldr (mkConsExpr ty) (mkNilExpr ty) xs
519 -- | Make a fully applied 'foldr' expression
520 mkFoldrExpr :: MonadThings m
521 => Type -- ^ Element type of the list
522 -> Type -- ^ Fold result type
523 -> CoreExpr -- ^ "Cons" function expression for the fold
524 -> CoreExpr -- ^ "Nil" expression for the fold
525 -> CoreExpr -- ^ List expression being folded acress
527 mkFoldrExpr elt_ty result_ty c n list = do
528 foldr_id <- lookupId foldrName
529 return (Var foldr_id `App` Type elt_ty
535 -- | Make a 'build' expression applied to a locally-bound worker function
536 mkBuildExpr :: (MonadThings m, MonadUnique m)
537 => Type -- ^ Type of list elements to be built
538 -> ((Id, Type) -> (Id, Type) -> m CoreExpr) -- ^ Function that, given information about the 'Id's
539 -- of the binders for the build worker function, returns
540 -- the body of that worker
542 mkBuildExpr elt_ty mk_build_inside = do
543 [n_tyvar] <- newTyVars [alphaTyVar]
544 let n_ty = mkTyVarTy n_tyvar
545 c_ty = mkFunTys [elt_ty, n_ty] n_ty
546 [c, n] <- sequence [mkSysLocalM (fsLit "c") c_ty, mkSysLocalM (fsLit "n") n_ty]
548 build_inside <- mk_build_inside (c, c_ty) (n, n_ty)
550 build_id <- lookupId buildName
551 return $ Var build_id `App` Type elt_ty `App` mkLams [n_tyvar, c, n] build_inside
553 newTyVars tyvar_tmpls = do
555 return (zipWith setTyVarUnique tyvar_tmpls uniqs)