2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
8 -- | CoreSyn holds all the main data types for use by for the Glasgow Haskell Compiler midsection
11 Expr(..), Alt, Bind(..), AltCon(..), Arg, Note(..),
12 CoreExpr, CoreAlt, CoreBind, CoreArg, CoreBndr,
13 TaggedExpr, TaggedAlt, TaggedBind, TaggedArg, TaggedBndr(..),
15 -- ** 'Expr' construction
17 mkApps, mkTyApps, mkVarApps,
19 mkIntLit, mkIntLitInt,
20 mkWordLit, mkWordLitWord,
21 mkCharLit, mkStringLit,
22 mkFloatLit, mkFloatLitFloat,
23 mkDoubleLit, mkDoubleLitDouble,
26 varToCoreExpr, varsToCoreExprs,
28 isTyVar, isId, cmpAltCon, cmpAlt, ltAlt,
30 -- ** Simple 'Expr' access functions and predicates
31 bindersOf, bindersOfBinds, rhssOfBind, rhssOfAlts,
32 collectBinders, collectTyBinders, collectValBinders, collectTyAndValBinders,
33 collectArgs, coreExprCc, flattenBinds,
35 isValArg, isTypeArg, valArgCount, valBndrCount, isRuntimeArg, isRuntimeVar,
37 -- * Unfolding data types
38 Unfolding(..), UnfoldingGuidance(..), InlineRuleInfo(..), InlSatFlag(..),
39 -- Abstract everywhere but in CoreUnfold.lhs
41 -- ** Constructing 'Unfolding's
42 noUnfolding, evaldUnfolding, mkOtherCon,
44 -- ** Predicates and deconstruction on 'Unfolding'
45 unfoldingTemplate, setUnfoldingTemplate,
46 maybeUnfoldingTemplate, otherCons, unfoldingArity,
47 isValueUnfolding, isEvaldUnfolding, isCheapUnfolding,
48 isExpandableUnfolding, isConLikeUnfolding,
49 isInlineRule, isInlineRule_maybe, isClosedUnfolding, hasSomeUnfolding,
50 isStableUnfolding, canUnfold, neverUnfoldGuidance,
53 seqExpr, seqExprs, seqUnfolding,
55 -- * Annotated expression data types
56 AnnExpr, AnnExpr'(..), AnnBind(..), AnnAlt,
58 -- ** Operations on annotations
59 deAnnotate, deAnnotate', deAnnAlt, collectAnnBndrs,
61 -- * Core rule data types
62 CoreRule(..), -- CoreSubst, CoreTidy, CoreFVs, PprCore only
65 -- ** Operations on 'CoreRule's
66 seqRules, ruleArity, ruleName, ruleIdName, ruleActivation_maybe,
68 isBuiltinRule, isLocalRule
71 #include "HsVersions.h"
87 infixl 4 `mkApps`, `mkTyApps`, `mkVarApps`
88 -- Left associative, so that we can say (f `mkTyApps` xs `mkVarApps` ys)
91 %************************************************************************
93 \subsection{The main data types}
95 %************************************************************************
97 These data types are the heart of the compiler
100 infixl 8 `App` -- App brackets to the left
102 -- | This is the data type that represents GHCs core intermediate language. Currently
103 -- GHC uses System FC <http://research.microsoft.com/~simonpj/papers/ext-f/> for this purpose,
104 -- which is closely related to the simpler and better known System F <http://en.wikipedia.org/wiki/System_F>.
106 -- We get from Haskell source to this Core language in a number of stages:
108 -- 1. The source code is parsed into an abstract syntax tree, which is represented
109 -- by the data type 'HsExpr.HsExpr' with the names being 'RdrName.RdrNames'
111 -- 2. This syntax tree is /renamed/, which attaches a 'Unique.Unique' to every 'RdrName.RdrName'
112 -- (yielding a 'Name.Name') to disambiguate identifiers which are lexically identical.
113 -- For example, this program:
116 -- f x = let f x = x + 1
120 -- Would be renamed by having 'Unique's attached so it looked something like this:
123 -- f_1 x_2 = let f_3 x_4 = x_4 + 1
127 -- 3. The resulting syntax tree undergoes type checking (which also deals with instantiating
128 -- type class arguments) to yield a 'HsExpr.HsExpr' type that has 'Id.Id' as it's names.
130 -- 4. Finally the syntax tree is /desugared/ from the expressive 'HsExpr.HsExpr' type into
131 -- this 'Expr' type, which has far fewer constructors and hence is easier to perform
132 -- optimization, analysis and code generation on.
134 -- The type parameter @b@ is for the type of binders in the expression tree.
136 = Var Id -- ^ Variables
137 | Lit Literal -- ^ Primitive literals
138 | App (Expr b) (Arg b) -- ^ Applications: note that the argument may be a 'Type'.
140 -- See "CoreSyn#let_app_invariant" for another invariant
141 | Lam b (Expr b) -- ^ Lambda abstraction
142 | Let (Bind b) (Expr b) -- ^ Recursive and non recursive @let@s. Operationally
143 -- this corresponds to allocating a thunk for the things
144 -- bound and then executing the sub-expression.
146 -- #top_level_invariant#
147 -- #letrec_invariant#
149 -- The right hand sides of all top-level and recursive @let@s
150 -- /must/ be of lifted type (see "Type#type_classification" for
151 -- the meaning of /lifted/ vs. /unlifted/).
153 -- #let_app_invariant#
154 -- The right hand side of of a non-recursive 'Let' _and_ the argument of an 'App',
155 -- /may/ be of unlifted type, but only if the expression
156 -- is ok-for-speculation. This means that the let can be floated around
157 -- without difficulty. For example, this is OK:
159 -- > y::Int# = x +# 1#
161 -- But this is not, as it may affect termination if the expression is floated out:
163 -- > y::Int# = fac 4#
165 -- In this situation you should use @case@ rather than a @let@. The function
166 -- 'CoreUtils.needsCaseBinding' can help you determine which to generate, or
167 -- alternatively use 'MkCore.mkCoreLet' rather than this constructor directly,
168 -- which will generate a @case@ if necessary
171 -- We allow a /non-recursive/ let to bind a type variable, thus:
173 -- > Let (NonRec tv (Type ty)) body
175 -- This can be very convenient for postponing type substitutions until
176 -- the next run of the simplifier.
178 -- At the moment, the rest of the compiler only deals with type-let
179 -- in a Let expression, rather than at top level. We may want to revist
181 | Case (Expr b) b Type [Alt b] -- ^ Case split. Operationally this corresponds to evaluating
182 -- the scrutinee (expression examined) to weak head normal form
183 -- and then examining at most one level of resulting constructor (i.e. you
184 -- cannot do nested pattern matching directly with this).
186 -- The binder gets bound to the value of the scrutinee,
187 -- and the 'Type' must be that of all the case alternatives
190 -- This is one of the more complicated elements of the Core language, and comes
191 -- with a number of restrictions:
193 -- The 'DEFAULT' case alternative must be first in the list, if it occurs at all.
195 -- The remaining cases are in order of increasing
196 -- tag (for 'DataAlts') or
197 -- lit (for 'LitAlts').
198 -- This makes finding the relevant constructor easy, and makes comparison easier too.
200 -- The list of alternatives must be exhaustive. An /exhaustive/ case
201 -- does not necessarily mention all constructors:
204 -- data Foo = Red | Green | Blue
207 -- other -> f (case x of
212 -- The inner case does not need a @Red@ alternative, because @x@ can't be @Red@ at
213 -- that program point.
214 | Cast (Expr b) Coercion -- ^ Cast an expression to a particular type. This is used to implement @newtype@s
215 -- (a @newtype@ constructor or destructor just becomes a 'Cast' in Core) and GADTs.
216 | Note Note (Expr b) -- ^ Notes. These allow general information to be
217 -- added to expressions in the syntax tree
218 | Type Type -- ^ A type: this should only show up at the top
221 -- | Type synonym for expressions that occur in function argument positions.
222 -- Only 'Arg' should contain a 'Type' at top level, general 'Expr' should not
225 -- | A case split alternative. Consists of the constructor leading to the alternative,
226 -- the variables bound from the constructor, and the expression to be executed given that binding.
227 -- The default alternative is @(DEFAULT, [], rhs)@
228 type Alt b = (AltCon, [b], Expr b)
230 -- | A case alternative constructor (i.e. pattern match)
231 data AltCon = DataAlt DataCon -- ^ A plain data constructor: @case e of { Foo x -> ... }@.
232 -- Invariant: the 'DataCon' is always from a @data@ type, and never from a @newtype@
233 | LitAlt Literal -- ^ A literal: @case e of { 1 -> ... }@
234 | DEFAULT -- ^ Trivial alternative: @case e of { _ -> ... }@
237 -- | Binding, used for top level bindings in a module and local bindings in a @let@.
238 data Bind b = NonRec b (Expr b)
239 | Rec [(b, (Expr b))]
242 -------------------------- CoreSyn INVARIANTS ---------------------------
244 Note [CoreSyn top-level invariant]
245 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
246 See #toplevel_invariant#
248 Note [CoreSyn letrec invariant]
249 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
250 See #letrec_invariant#
252 Note [CoreSyn let/app invariant]
253 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
254 See #let_app_invariant#
256 This is intially enforced by DsUtils.mkCoreLet and mkCoreApp
258 Note [CoreSyn case invariants]
259 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
260 See #case_invariants#
262 Note [CoreSyn let goal]
263 ~~~~~~~~~~~~~~~~~~~~~~~
264 * The simplifier tries to ensure that if the RHS of a let is a constructor
265 application, its arguments are trivial, so that the constructor can be
275 -- | Allows attaching extra information to points in expressions rather than e.g. identifiers.
277 = SCC CostCentre -- ^ A cost centre annotation for profiling
278 | CoreNote String -- ^ A generic core annotation, propagated but not used by GHC
282 %************************************************************************
284 \subsection{Transformation rules}
286 %************************************************************************
288 The CoreRule type and its friends are dealt with mainly in CoreRules,
289 but CoreFVs, Subst, PprCore, CoreTidy also inspect the representation.
292 -- | A 'CoreRule' is:
294 -- * \"Local\" if the function it is a rule for is defined in the
295 -- same module as the rule itself.
297 -- * \"Orphan\" if nothing on the LHS is defined in the same module
298 -- as the rule itself
301 ru_name :: RuleName, -- ^ Name of the rule, for communication with the user
302 ru_act :: Activation, -- ^ When the rule is active
304 -- Rough-matching stuff
305 -- see comments with InstEnv.Instance( is_cls, is_rough )
306 ru_fn :: Name, -- ^ Name of the 'Id.Id' at the head of this rule
307 ru_rough :: [Maybe Name], -- ^ Name at the head of each argument to the left hand side
309 -- Proper-matching stuff
310 -- see comments with InstEnv.Instance( is_tvs, is_tys )
311 ru_bndrs :: [CoreBndr], -- ^ Variables quantified over
312 ru_args :: [CoreExpr], -- ^ Left hand side arguments
314 -- And the right-hand side
315 ru_rhs :: CoreExpr, -- ^ Right hand side of the rule
316 -- Occurrence info is guaranteed correct
317 -- See Note [OccInfo in unfoldings and rules]
320 ru_local :: Bool -- ^ @True@ iff the fn at the head of the rule is
321 -- defined in the same module as the rule
322 -- and is not an implicit 'Id' (like a record selector,
323 -- class operation, or data constructor)
325 -- NB: ru_local is *not* used to decide orphan-hood
326 -- c.g. MkIface.coreRuleToIfaceRule
329 -- | Built-in rules are used for constant folding
330 -- and suchlike. They have no free variables.
332 ru_name :: RuleName, -- ^ As above
333 ru_fn :: Name, -- ^ As above
334 ru_nargs :: Int, -- ^ Number of arguments that 'ru_try' consumes,
335 -- if it fires, including type arguments
336 ru_try :: [CoreExpr] -> Maybe CoreExpr
337 -- ^ This function does the rewrite. It given too many
338 -- arguments, it simply discards them; the returned 'CoreExpr'
339 -- is just the rewrite of 'ru_fn' applied to the first 'ru_nargs' args
341 -- See Note [Extra args in rule matching] in Rules.lhs
343 isBuiltinRule :: CoreRule -> Bool
344 isBuiltinRule (BuiltinRule {}) = True
345 isBuiltinRule _ = False
347 -- | The number of arguments the 'ru_fn' must be applied
348 -- to before the rule can match on it
349 ruleArity :: CoreRule -> Int
350 ruleArity (BuiltinRule {ru_nargs = n}) = n
351 ruleArity (Rule {ru_args = args}) = length args
353 ruleName :: CoreRule -> RuleName
356 ruleActivation_maybe :: CoreRule -> Maybe Activation
357 ruleActivation_maybe (BuiltinRule { }) = Nothing
358 ruleActivation_maybe (Rule { ru_act = act }) = Just act
360 -- | The 'Name' of the 'Id.Id' at the head of the rule left hand side
361 ruleIdName :: CoreRule -> Name
364 isLocalRule :: CoreRule -> Bool
365 isLocalRule = ru_local
367 -- | Set the 'Name' of the 'Id.Id' at the head of the rule left hand side
368 setRuleIdName :: Name -> CoreRule -> CoreRule
369 setRuleIdName nm ru = ru { ru_fn = nm }
373 %************************************************************************
377 %************************************************************************
379 The @Unfolding@ type is declared here to avoid numerous loops
382 -- | Records the /unfolding/ of an identifier, which is approximately the form the
383 -- identifier would have if we substituted its definition in for the identifier.
384 -- This type should be treated as abstract everywhere except in "CoreUnfold"
386 = NoUnfolding -- ^ We have no information about the unfolding
388 | OtherCon [AltCon] -- ^ It ain't one of these constructors.
389 -- @OtherCon xs@ also indicates that something has been evaluated
390 -- and hence there's no point in re-evaluating it.
391 -- @OtherCon []@ is used even for non-data-type values
392 -- to indicated evaluated-ness. Notably:
394 -- > data C = C !(Int -> Int)
395 -- > case x of { C f -> ... }
397 -- Here, @f@ gets an @OtherCon []@ unfolding.
399 | DFunUnfolding DataCon [CoreExpr]
400 -- The Unfolding of a DFunId
401 -- df = /\a1..am. \d1..dn. MkD (op1 a1..am d1..dn)
402 -- (op2 a1..am d1..dn)
403 -- where Arity = n, the number of dict args to the dfun
404 -- The [CoreExpr] are the superclasses and methods [op1,op2],
405 -- in positional order.
406 -- They are usually variables, but can be trivial expressions
407 -- instead (e.g. a type application).
409 | CoreUnfolding { -- An unfolding for an Id with no pragma, or perhaps a NOINLINE pragma
410 -- (For NOINLINE, the phase, if any, is in the InlinePragInfo for this Id.)
411 uf_tmpl :: CoreExpr, -- Template; occurrence info is correct
412 uf_arity :: Arity, -- Number of value arguments expected
413 uf_is_top :: Bool, -- True <=> top level binding
414 uf_is_value :: Bool, -- exprIsHNF template (cached); it is ok to discard a `seq` on
416 uf_is_conlike :: Bool, -- True <=> application of constructor or CONLIKE function
417 -- Cached version of exprIsConLike
418 uf_is_cheap :: Bool, -- True <=> doesn't waste (much) work to expand inside an inlining
419 -- Cached version of exprIsCheap
420 uf_expandable :: Bool, -- True <=> can expand in RULE matching
421 -- Cached version of exprIsExpandable
422 uf_guidance :: UnfoldingGuidance -- Tells about the *size* of the template.
424 -- ^ An unfolding with redundant cached information. Parameters:
426 -- uf_tmpl: Template used to perform unfolding;
427 -- NB: Occurrence info is guaranteed correct:
428 -- see Note [OccInfo in unfoldings and rules]
430 -- uf_is_top: Is this a top level binding?
432 -- uf_is_value: 'exprIsHNF' template (cached); it is ok to discard a 'seq' on
435 -- uf_is_cheap: Does this waste only a little work if we expand it inside an inlining?
436 -- Basically this is a cached version of 'exprIsCheap'
438 -- uf_guidance: Tells us about the /size/ of the unfolding template
440 ------------------------------------------------
441 -- | 'UnfoldingGuidance' says when unfolding should take place
442 data UnfoldingGuidance
443 = InlineRule { -- Be very keen to inline this; See Note [InlineRules]
444 -- The uf_tmpl is the *original* RHS; do *not* replace it on
445 -- each simlifier run. Hence, the *actual* RHS of the function
446 -- may be different by now, because it may have been optimised.
448 ir_sat :: InlSatFlag,
449 ir_info :: InlineRuleInfo
452 | UnfoldIfGoodArgs { -- Arose from a normal Id; the info here is the
453 -- result of a simple analysis of the RHS
455 ug_args :: [Int], -- Discount if the argument is evaluated.
456 -- (i.e., a simplification will definitely
457 -- be possible). One elt of the list per *value* arg.
459 ug_size :: Int, -- The "size" of the unfolding.
461 ug_res :: Int -- Scrutinee discount: the discount to substract if the thing is in
462 } -- a context (case (thing args) of ...),
463 -- (where there are the right number of arguments.)
465 | UnfoldNever -- A variant of UnfoldIfGoodArgs, used for big RHSs
468 = InlAlways -- Inline absolutely always, however boring the context.
469 -- There is /no original definition/. Only a few primop-like things
470 -- have this property (see MkId.lhs, calls to mkCompulsoryUnfolding).
472 | InlSmall -- The RHS is very small (eg no bigger than a call), so inline any
473 -- /saturated/ application, regardless of context
474 -- See Note [INLINE for small functions] in CoreUnfold
478 | InlWrapper Id -- This unfolding is a the wrapper in a
479 -- worker/wrapper split from the strictness analyser
480 -- Used to abbreviate the uf_tmpl in interface files
481 -- which don't need to contain the RHS;
482 -- it can be derived from the strictness info
483 -- [In principle this is orthogonal to the InlSmall/InVanilla thing,
484 -- but it's convenient to have it here.]
486 data InlSatFlag = InlSat | InlUnSat
487 -- Specifies whether to INLINE only if the thing is applied to 'arity' args
489 ------------------------------------------------
490 noUnfolding :: Unfolding
491 -- ^ There is no known 'Unfolding'
492 evaldUnfolding :: Unfolding
493 -- ^ This unfolding marks the associated thing as being evaluated
495 noUnfolding = NoUnfolding
496 evaldUnfolding = OtherCon []
498 mkOtherCon :: [AltCon] -> Unfolding
499 mkOtherCon = OtherCon
501 seqUnfolding :: Unfolding -> ()
502 seqUnfolding (CoreUnfolding { uf_tmpl = e, uf_is_top = top,
503 uf_is_value = b1, uf_is_cheap = b2,
504 uf_expandable = b3, uf_is_conlike = b4,
505 uf_arity = a, uf_guidance = g})
506 = seqExpr e `seq` top `seq` b1 `seq` a `seq` b2 `seq` b3 `seq` b4 `seq` seqGuidance g
510 seqGuidance :: UnfoldingGuidance -> ()
511 seqGuidance (UnfoldIfGoodArgs ns n b) = n `seq` sum ns `seq` b `seq` ()
516 -- | Retrieves the template of an unfolding: panics if none is known
517 unfoldingTemplate :: Unfolding -> CoreExpr
518 unfoldingTemplate = uf_tmpl
520 setUnfoldingTemplate :: Unfolding -> CoreExpr -> Unfolding
521 setUnfoldingTemplate unf rhs = unf { uf_tmpl = rhs }
523 -- | Retrieves the template of an unfolding if possible
524 maybeUnfoldingTemplate :: Unfolding -> Maybe CoreExpr
525 maybeUnfoldingTemplate (CoreUnfolding { uf_tmpl = expr }) = Just expr
526 maybeUnfoldingTemplate _ = Nothing
528 -- | The constructors that the unfolding could never be:
529 -- returns @[]@ if no information is available
530 otherCons :: Unfolding -> [AltCon]
531 otherCons (OtherCon cons) = cons
534 -- | Determines if it is certainly the case that the unfolding will
535 -- yield a value (something in HNF): returns @False@ if unsure
536 isValueUnfolding :: Unfolding -> Bool
537 -- Returns False for OtherCon
538 isValueUnfolding (CoreUnfolding { uf_is_value = is_evald }) = is_evald
539 isValueUnfolding _ = False
541 -- | Determines if it possibly the case that the unfolding will
542 -- yield a value. Unlike 'isValueUnfolding' it returns @True@
544 isEvaldUnfolding :: Unfolding -> Bool
545 -- Returns True for OtherCon
546 isEvaldUnfolding (OtherCon _) = True
547 isEvaldUnfolding (CoreUnfolding { uf_is_value = is_evald }) = is_evald
548 isEvaldUnfolding _ = False
550 -- | @True@ if the unfolding is a constructor application, the application
551 -- of a CONLIKE function or 'OtherCon'
552 isConLikeUnfolding :: Unfolding -> Bool
553 isConLikeUnfolding (OtherCon _) = True
554 isConLikeUnfolding (CoreUnfolding { uf_is_conlike = con }) = con
555 isConLikeUnfolding _ = False
557 -- | Is the thing we will unfold into certainly cheap?
558 isCheapUnfolding :: Unfolding -> Bool
559 isCheapUnfolding (CoreUnfolding { uf_is_cheap = is_cheap }) = is_cheap
560 isCheapUnfolding _ = False
562 isExpandableUnfolding :: Unfolding -> Bool
563 isExpandableUnfolding (CoreUnfolding { uf_expandable = is_expable }) = is_expable
564 isExpandableUnfolding _ = False
566 isInlineRule :: Unfolding -> Bool
567 isInlineRule (CoreUnfolding { uf_guidance = InlineRule {}}) = True
568 isInlineRule _ = False
570 isInlineRule_maybe :: Unfolding -> Maybe (InlineRuleInfo, InlSatFlag)
571 isInlineRule_maybe (CoreUnfolding { uf_guidance =
572 InlineRule { ir_info = inl, ir_sat = sat } }) = Just (inl,sat)
573 isInlineRule_maybe _ = Nothing
575 isStableUnfolding :: Unfolding -> Bool
576 -- True of unfoldings that should not be overwritten
577 -- by a CoreUnfolding for the RHS of a let-binding
578 isStableUnfolding (CoreUnfolding { uf_guidance = InlineRule {} }) = True
579 isStableUnfolding (DFunUnfolding {}) = True
580 isStableUnfolding _ = False
582 unfoldingArity :: Unfolding -> Arity
583 unfoldingArity (CoreUnfolding { uf_arity = arity }) = arity
584 unfoldingArity _ = panic "unfoldingArity"
586 isClosedUnfolding :: Unfolding -> Bool -- No free variables
587 isClosedUnfolding (CoreUnfolding {}) = False
588 isClosedUnfolding _ = True
590 -- | Only returns False if there is no unfolding information available at all
591 hasSomeUnfolding :: Unfolding -> Bool
592 hasSomeUnfolding NoUnfolding = False
593 hasSomeUnfolding _ = True
595 neverUnfoldGuidance :: UnfoldingGuidance -> Bool
596 neverUnfoldGuidance UnfoldNever = True
597 neverUnfoldGuidance _ = False
599 canUnfold :: Unfolding -> Bool
600 canUnfold (CoreUnfolding { uf_guidance = g }) = not (neverUnfoldGuidance g)
609 you intend that calls (f e) are replaced by <rhs>[e/x] So we
610 should capture (\x.<rhs>) in the Unfolding of 'f', and never meddle
611 with it. Meanwhile, we can optimise <rhs> to our heart's content,
612 leaving the original unfolding intact in Unfolding of 'f'.
614 So the representation of an Unfolding has changed quite a bit
615 (see CoreSyn). An INLINE pragma gives rise to an InlineRule
618 Moreover, it's only used when 'f' is applied to the
619 specified number of arguments; that is, the number of argument on
620 the LHS of the '=' sign in the original source definition.
621 For example, (.) is now defined in the libraries like this
623 (.) f g = \x -> f (g x)
624 so that it'll inline when applied to two arguments. If 'x' appeared
627 it'd only inline when applied to three arguments. This slightly-experimental
628 change was requested by Roman, but it seems to make sense.
630 See also Note [Inlining an InlineRule] in CoreUnfold.
633 Note [OccInfo in unfoldings and rules]
634 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
635 In unfoldings and rules, we guarantee that the template is occ-analysed,
636 so that the occurence info on the binders is correct. This is important,
637 because the Simplifier does not re-analyse the template when using it. If
638 the occurrence info is wrong
639 - We may get more simpifier iterations than necessary, because
640 once-occ info isn't there
641 - More seriously, we may get an infinite loop if there's a Rec
642 without a loop breaker marked
645 %************************************************************************
647 \subsection{The main data type}
649 %************************************************************************
652 -- The Ord is needed for the FiniteMap used in the lookForConstructor
653 -- in SimplEnv. If you declared that lookForConstructor *ignores*
654 -- constructor-applications with LitArg args, then you could get
657 instance Outputable AltCon where
658 ppr (DataAlt dc) = ppr dc
659 ppr (LitAlt lit) = ppr lit
660 ppr DEFAULT = ptext (sLit "__DEFAULT")
662 instance Show AltCon where
663 showsPrec p con = showsPrecSDoc p (ppr con)
665 cmpAlt :: Alt b -> Alt b -> Ordering
666 cmpAlt (con1, _, _) (con2, _, _) = con1 `cmpAltCon` con2
668 ltAlt :: Alt b -> Alt b -> Bool
669 ltAlt a1 a2 = (a1 `cmpAlt` a2) == LT
671 cmpAltCon :: AltCon -> AltCon -> Ordering
672 -- ^ Compares 'AltCon's within a single list of alternatives
673 cmpAltCon DEFAULT DEFAULT = EQ
674 cmpAltCon DEFAULT _ = LT
676 cmpAltCon (DataAlt d1) (DataAlt d2) = dataConTag d1 `compare` dataConTag d2
677 cmpAltCon (DataAlt _) DEFAULT = GT
678 cmpAltCon (LitAlt l1) (LitAlt l2) = l1 `compare` l2
679 cmpAltCon (LitAlt _) DEFAULT = GT
681 cmpAltCon con1 con2 = WARN( True, text "Comparing incomparable AltCons" <+>
682 ppr con1 <+> ppr con2 )
686 %************************************************************************
688 \subsection{Useful synonyms}
690 %************************************************************************
693 -- | The common case for the type of binders and variables when
694 -- we are manipulating the Core language within GHC
696 -- | Expressions where binders are 'CoreBndr's
697 type CoreExpr = Expr CoreBndr
698 -- | Argument expressions where binders are 'CoreBndr's
699 type CoreArg = Arg CoreBndr
700 -- | Binding groups where binders are 'CoreBndr's
701 type CoreBind = Bind CoreBndr
702 -- | Case alternatives where binders are 'CoreBndr's
703 type CoreAlt = Alt CoreBndr
706 %************************************************************************
710 %************************************************************************
713 -- | Binders are /tagged/ with a t
714 data TaggedBndr t = TB CoreBndr t -- TB for "tagged binder"
716 type TaggedBind t = Bind (TaggedBndr t)
717 type TaggedExpr t = Expr (TaggedBndr t)
718 type TaggedArg t = Arg (TaggedBndr t)
719 type TaggedAlt t = Alt (TaggedBndr t)
721 instance Outputable b => Outputable (TaggedBndr b) where
722 ppr (TB b l) = char '<' <> ppr b <> comma <> ppr l <> char '>'
724 instance Outputable b => OutputableBndr (TaggedBndr b) where
725 pprBndr _ b = ppr b -- Simple
729 %************************************************************************
731 \subsection{Core-constructing functions with checking}
733 %************************************************************************
736 -- | Apply a list of argument expressions to a function expression in a nested fashion. Prefer to
737 -- use 'CoreUtils.mkCoreApps' if possible
738 mkApps :: Expr b -> [Arg b] -> Expr b
739 -- | Apply a list of type argument expressions to a function expression in a nested fashion
740 mkTyApps :: Expr b -> [Type] -> Expr b
741 -- | Apply a list of type or value variables to a function expression in a nested fashion
742 mkVarApps :: Expr b -> [Var] -> Expr b
743 -- | Apply a list of argument expressions to a data constructor in a nested fashion. Prefer to
744 -- use 'MkCore.mkCoreConApps' if possible
745 mkConApp :: DataCon -> [Arg b] -> Expr b
747 mkApps f args = foldl App f args
748 mkTyApps f args = foldl (\ e a -> App e (Type a)) f args
749 mkVarApps f vars = foldl (\ e a -> App e (varToCoreExpr a)) f vars
750 mkConApp con args = mkApps (Var (dataConWorkId con)) args
753 -- | Create a machine integer literal expression of type @Int#@ from an @Integer@.
754 -- If you want an expression of type @Int@ use 'MkCore.mkIntExpr'
755 mkIntLit :: Integer -> Expr b
756 -- | Create a machine integer literal expression of type @Int#@ from an @Int@.
757 -- If you want an expression of type @Int@ use 'MkCore.mkIntExpr'
758 mkIntLitInt :: Int -> Expr b
760 mkIntLit n = Lit (mkMachInt n)
761 mkIntLitInt n = Lit (mkMachInt (toInteger n))
763 -- | Create a machine word literal expression of type @Word#@ from an @Integer@.
764 -- If you want an expression of type @Word@ use 'MkCore.mkWordExpr'
765 mkWordLit :: Integer -> Expr b
766 -- | Create a machine word literal expression of type @Word#@ from a @Word@.
767 -- If you want an expression of type @Word@ use 'MkCore.mkWordExpr'
768 mkWordLitWord :: Word -> Expr b
770 mkWordLit w = Lit (mkMachWord w)
771 mkWordLitWord w = Lit (mkMachWord (toInteger w))
773 -- | Create a machine character literal expression of type @Char#@.
774 -- If you want an expression of type @Char@ use 'MkCore.mkCharExpr'
775 mkCharLit :: Char -> Expr b
776 -- | Create a machine string literal expression of type @Addr#@.
777 -- If you want an expression of type @String@ use 'MkCore.mkStringExpr'
778 mkStringLit :: String -> Expr b
780 mkCharLit c = Lit (mkMachChar c)
781 mkStringLit s = Lit (mkMachString s)
783 -- | Create a machine single precision literal expression of type @Float#@ from a @Rational@.
784 -- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr'
785 mkFloatLit :: Rational -> Expr b
786 -- | Create a machine single precision literal expression of type @Float#@ from a @Float@.
787 -- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr'
788 mkFloatLitFloat :: Float -> Expr b
790 mkFloatLit f = Lit (mkMachFloat f)
791 mkFloatLitFloat f = Lit (mkMachFloat (toRational f))
793 -- | Create a machine double precision literal expression of type @Double#@ from a @Rational@.
794 -- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr'
795 mkDoubleLit :: Rational -> Expr b
796 -- | Create a machine double precision literal expression of type @Double#@ from a @Double@.
797 -- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr'
798 mkDoubleLitDouble :: Double -> Expr b
800 mkDoubleLit d = Lit (mkMachDouble d)
801 mkDoubleLitDouble d = Lit (mkMachDouble (toRational d))
803 -- | Bind all supplied binding groups over an expression in a nested let expression. Prefer to
804 -- use 'CoreUtils.mkCoreLets' if possible
805 mkLets :: [Bind b] -> Expr b -> Expr b
806 -- | Bind all supplied binders over an expression in a nested lambda expression. Prefer to
807 -- use 'CoreUtils.mkCoreLams' if possible
808 mkLams :: [b] -> Expr b -> Expr b
810 mkLams binders body = foldr Lam body binders
811 mkLets binds body = foldr Let body binds
814 -- | Create a binding group where a type variable is bound to a type. Per "CoreSyn#type_let",
815 -- this can only be used to bind something in a non-recursive @let@ expression
816 mkTyBind :: TyVar -> Type -> CoreBind
817 mkTyBind tv ty = NonRec tv (Type ty)
819 -- | Convert a binder into either a 'Var' or 'Type' 'Expr' appropriately
820 varToCoreExpr :: CoreBndr -> Expr b
821 varToCoreExpr v | isId v = Var v
822 | otherwise = Type (mkTyVarTy v)
824 varsToCoreExprs :: [CoreBndr] -> [Expr b]
825 varsToCoreExprs vs = map varToCoreExpr vs
829 %************************************************************************
831 \subsection{Simple access functions}
833 %************************************************************************
836 -- | Extract every variable by this group
837 bindersOf :: Bind b -> [b]
838 bindersOf (NonRec binder _) = [binder]
839 bindersOf (Rec pairs) = [binder | (binder, _) <- pairs]
841 -- | 'bindersOf' applied to a list of binding groups
842 bindersOfBinds :: [Bind b] -> [b]
843 bindersOfBinds binds = foldr ((++) . bindersOf) [] binds
845 rhssOfBind :: Bind b -> [Expr b]
846 rhssOfBind (NonRec _ rhs) = [rhs]
847 rhssOfBind (Rec pairs) = [rhs | (_,rhs) <- pairs]
849 rhssOfAlts :: [Alt b] -> [Expr b]
850 rhssOfAlts alts = [e | (_,_,e) <- alts]
852 -- | Collapse all the bindings in the supplied groups into a single
853 -- list of lhs\/rhs pairs suitable for binding in a 'Rec' binding group
854 flattenBinds :: [Bind b] -> [(b, Expr b)]
855 flattenBinds (NonRec b r : binds) = (b,r) : flattenBinds binds
856 flattenBinds (Rec prs1 : binds) = prs1 ++ flattenBinds binds
861 -- | We often want to strip off leading lambdas before getting down to
862 -- business. This function is your friend.
863 collectBinders :: Expr b -> ([b], Expr b)
864 -- | Collect as many type bindings as possible from the front of a nested lambda
865 collectTyBinders :: CoreExpr -> ([TyVar], CoreExpr)
866 -- | Collect as many value bindings as possible from the front of a nested lambda
867 collectValBinders :: CoreExpr -> ([Id], CoreExpr)
868 -- | Collect type binders from the front of the lambda first,
869 -- then follow up by collecting as many value bindings as possible
870 -- from the resulting stripped expression
871 collectTyAndValBinders :: CoreExpr -> ([TyVar], [Id], CoreExpr)
876 go bs (Lam b e) = go (b:bs) e
877 go bs e = (reverse bs, e)
879 collectTyAndValBinders expr
882 (tvs, body1) = collectTyBinders expr
883 (ids, body) = collectValBinders body1
885 collectTyBinders expr
888 go tvs (Lam b e) | isTyVar b = go (b:tvs) e
889 go tvs e = (reverse tvs, e)
891 collectValBinders expr
894 go ids (Lam b e) | isId b = go (b:ids) e
895 go ids body = (reverse ids, body)
899 -- | Takes a nested application expression and returns the the function
900 -- being applied and the arguments to which it is applied
901 collectArgs :: Expr b -> (Expr b, [Arg b])
905 go (App f a) as = go f (a:as)
910 -- | Gets the cost centre enclosing an expression, if any.
911 -- It looks inside lambdas because @(scc \"foo\" \\x.e) = \\x. scc \"foo\" e@
912 coreExprCc :: Expr b -> CostCentre
913 coreExprCc (Note (SCC cc) _) = cc
914 coreExprCc (Note _ e) = coreExprCc e
915 coreExprCc (Lam _ e) = coreExprCc e
916 coreExprCc _ = noCostCentre
919 %************************************************************************
921 \subsection{Predicates}
923 %************************************************************************
925 At one time we optionally carried type arguments through to runtime.
926 @isRuntimeVar v@ returns if (Lam v _) really becomes a lambda at runtime,
927 i.e. if type applications are actual lambdas because types are kept around
928 at runtime. Similarly isRuntimeArg.
931 -- | Will this variable exist at runtime?
932 isRuntimeVar :: Var -> Bool
935 -- | Will this argument expression exist at runtime?
936 isRuntimeArg :: CoreExpr -> Bool
937 isRuntimeArg = isValArg
939 -- | Returns @False@ iff the expression is a 'Type' expression at its top level
940 isValArg :: Expr b -> Bool
941 isValArg (Type _) = False
944 -- | Returns @True@ iff the expression is a 'Type' expression at its top level
945 isTypeArg :: Expr b -> Bool
946 isTypeArg (Type _) = True
949 -- | The number of binders that bind values rather than types
950 valBndrCount :: [CoreBndr] -> Int
951 valBndrCount = count isId
953 -- | The number of argument expressions that are values rather than types at their top level
954 valArgCount :: [Arg b] -> Int
955 valArgCount = count isValArg
959 %************************************************************************
961 \subsection{Seq stuff}
963 %************************************************************************
966 seqExpr :: CoreExpr -> ()
967 seqExpr (Var v) = v `seq` ()
968 seqExpr (Lit lit) = lit `seq` ()
969 seqExpr (App f a) = seqExpr f `seq` seqExpr a
970 seqExpr (Lam b e) = seqBndr b `seq` seqExpr e
971 seqExpr (Let b e) = seqBind b `seq` seqExpr e
972 seqExpr (Case e b t as) = seqExpr e `seq` seqBndr b `seq` seqType t `seq` seqAlts as
973 seqExpr (Cast e co) = seqExpr e `seq` seqType co
974 seqExpr (Note n e) = seqNote n `seq` seqExpr e
975 seqExpr (Type t) = seqType t
977 seqExprs :: [CoreExpr] -> ()
979 seqExprs (e:es) = seqExpr e `seq` seqExprs es
981 seqNote :: Note -> ()
982 seqNote (CoreNote s) = s `seq` ()
985 seqBndr :: CoreBndr -> ()
986 seqBndr b = b `seq` ()
988 seqBndrs :: [CoreBndr] -> ()
990 seqBndrs (b:bs) = seqBndr b `seq` seqBndrs bs
992 seqBind :: Bind CoreBndr -> ()
993 seqBind (NonRec b e) = seqBndr b `seq` seqExpr e
994 seqBind (Rec prs) = seqPairs prs
996 seqPairs :: [(CoreBndr, CoreExpr)] -> ()
998 seqPairs ((b,e):prs) = seqBndr b `seq` seqExpr e `seq` seqPairs prs
1000 seqAlts :: [CoreAlt] -> ()
1002 seqAlts ((c,bs,e):alts) = c `seq` seqBndrs bs `seq` seqExpr e `seq` seqAlts alts
1004 seqRules :: [CoreRule] -> ()
1006 seqRules (Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs } : rules)
1007 = seqBndrs bndrs `seq` seqExprs (rhs:args) `seq` seqRules rules
1008 seqRules (BuiltinRule {} : rules) = seqRules rules
1011 %************************************************************************
1013 \subsection{Annotated core}
1015 %************************************************************************
1018 -- | Annotated core: allows annotation at every node in the tree
1019 type AnnExpr bndr annot = (annot, AnnExpr' bndr annot)
1021 -- | A clone of the 'Expr' type but allowing annotation at every tree node
1022 data AnnExpr' bndr annot
1025 | AnnLam bndr (AnnExpr bndr annot)
1026 | AnnApp (AnnExpr bndr annot) (AnnExpr bndr annot)
1027 | AnnCase (AnnExpr bndr annot) bndr Type [AnnAlt bndr annot]
1028 | AnnLet (AnnBind bndr annot) (AnnExpr bndr annot)
1029 | AnnCast (AnnExpr bndr annot) Coercion
1030 | AnnNote Note (AnnExpr bndr annot)
1033 -- | A clone of the 'Alt' type but allowing annotation at every tree node
1034 type AnnAlt bndr annot = (AltCon, [bndr], AnnExpr bndr annot)
1036 -- | A clone of the 'Bind' type but allowing annotation at every tree node
1037 data AnnBind bndr annot
1038 = AnnNonRec bndr (AnnExpr bndr annot)
1039 | AnnRec [(bndr, AnnExpr bndr annot)]
1043 deAnnotate :: AnnExpr bndr annot -> Expr bndr
1044 deAnnotate (_, e) = deAnnotate' e
1046 deAnnotate' :: AnnExpr' bndr annot -> Expr bndr
1047 deAnnotate' (AnnType t) = Type t
1048 deAnnotate' (AnnVar v) = Var v
1049 deAnnotate' (AnnLit lit) = Lit lit
1050 deAnnotate' (AnnLam binder body) = Lam binder (deAnnotate body)
1051 deAnnotate' (AnnApp fun arg) = App (deAnnotate fun) (deAnnotate arg)
1052 deAnnotate' (AnnCast e co) = Cast (deAnnotate e) co
1053 deAnnotate' (AnnNote note body) = Note note (deAnnotate body)
1055 deAnnotate' (AnnLet bind body)
1056 = Let (deAnnBind bind) (deAnnotate body)
1058 deAnnBind (AnnNonRec var rhs) = NonRec var (deAnnotate rhs)
1059 deAnnBind (AnnRec pairs) = Rec [(v,deAnnotate rhs) | (v,rhs) <- pairs]
1061 deAnnotate' (AnnCase scrut v t alts)
1062 = Case (deAnnotate scrut) v t (map deAnnAlt alts)
1064 deAnnAlt :: AnnAlt bndr annot -> Alt bndr
1065 deAnnAlt (con,args,rhs) = (con,args,deAnnotate rhs)
1069 -- | As 'collectBinders' but for 'AnnExpr' rather than 'Expr'
1070 collectAnnBndrs :: AnnExpr bndr annot -> ([bndr], AnnExpr bndr annot)
1074 collect bs (_, AnnLam b body) = collect (b:bs) body
1075 collect bs body = (reverse bs, body)