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(..), UnfoldingSource(..),
39 -- Abstract everywhere but in CoreUnfold.lhs
41 -- ** Constructing 'Unfolding's
42 noUnfolding, evaldUnfolding, mkOtherCon,
43 unSaturatedOk, needSaturated, boringCxtOk, boringCxtNotOk,
45 -- ** Predicates and deconstruction on 'Unfolding'
46 unfoldingTemplate, setUnfoldingTemplate,
47 maybeUnfoldingTemplate, otherCons, unfoldingArity,
48 isValueUnfolding, isEvaldUnfolding, isCheapUnfolding,
49 isExpandableUnfolding, isConLikeUnfolding, isCompulsoryUnfolding,
50 isInlineRule, isInlineRule_maybe, isClosedUnfolding, hasSomeUnfolding,
51 isStableUnfolding, canUnfold, neverUnfoldGuidance, isInlineRuleSource,
54 seqExpr, seqExprs, seqUnfolding,
56 -- * Annotated expression data types
57 AnnExpr, AnnExpr'(..), AnnBind(..), AnnAlt,
59 -- ** Operations on annotations
60 deAnnotate, deAnnotate', deAnnAlt, collectAnnBndrs,
62 -- * Core rule data types
63 CoreRule(..), -- CoreSubst, CoreTidy, CoreFVs, PprCore only
64 RuleName, IdUnfoldingFun,
66 -- ** Operations on 'CoreRule's
67 seqRules, ruleArity, ruleName, ruleIdName, ruleActivation_maybe,
69 isBuiltinRule, isLocalRule
72 #include "HsVersions.h"
88 infixl 4 `mkApps`, `mkTyApps`, `mkVarApps`
89 -- Left associative, so that we can say (f `mkTyApps` xs `mkVarApps` ys)
92 %************************************************************************
94 \subsection{The main data types}
96 %************************************************************************
98 These data types are the heart of the compiler
101 infixl 8 `App` -- App brackets to the left
103 -- | This is the data type that represents GHCs core intermediate language. Currently
104 -- GHC uses System FC <http://research.microsoft.com/~simonpj/papers/ext-f/> for this purpose,
105 -- which is closely related to the simpler and better known System F <http://en.wikipedia.org/wiki/System_F>.
107 -- We get from Haskell source to this Core language in a number of stages:
109 -- 1. The source code is parsed into an abstract syntax tree, which is represented
110 -- by the data type 'HsExpr.HsExpr' with the names being 'RdrName.RdrNames'
112 -- 2. This syntax tree is /renamed/, which attaches a 'Unique.Unique' to every 'RdrName.RdrName'
113 -- (yielding a 'Name.Name') to disambiguate identifiers which are lexically identical.
114 -- For example, this program:
117 -- f x = let f x = x + 1
121 -- Would be renamed by having 'Unique's attached so it looked something like this:
124 -- f_1 x_2 = let f_3 x_4 = x_4 + 1
128 -- 3. The resulting syntax tree undergoes type checking (which also deals with instantiating
129 -- type class arguments) to yield a 'HsExpr.HsExpr' type that has 'Id.Id' as it's names.
131 -- 4. Finally the syntax tree is /desugared/ from the expressive 'HsExpr.HsExpr' type into
132 -- this 'Expr' type, which has far fewer constructors and hence is easier to perform
133 -- optimization, analysis and code generation on.
135 -- The type parameter @b@ is for the type of binders in the expression tree.
137 = Var Id -- ^ Variables
138 | Lit Literal -- ^ Primitive literals
139 | App (Expr b) (Arg b) -- ^ Applications: note that the argument may be a 'Type'.
141 -- See "CoreSyn#let_app_invariant" for another invariant
142 | Lam b (Expr b) -- ^ Lambda abstraction
143 | Let (Bind b) (Expr b) -- ^ Recursive and non recursive @let@s. Operationally
144 -- this corresponds to allocating a thunk for the things
145 -- bound and then executing the sub-expression.
147 -- #top_level_invariant#
148 -- #letrec_invariant#
150 -- The right hand sides of all top-level and recursive @let@s
151 -- /must/ be of lifted type (see "Type#type_classification" for
152 -- the meaning of /lifted/ vs. /unlifted/).
154 -- #let_app_invariant#
155 -- The right hand side of of a non-recursive 'Let' _and_ the argument of an 'App',
156 -- /may/ be of unlifted type, but only if the expression
157 -- is ok-for-speculation. This means that the let can be floated around
158 -- without difficulty. For example, this is OK:
160 -- > y::Int# = x +# 1#
162 -- But this is not, as it may affect termination if the expression is floated out:
164 -- > y::Int# = fac 4#
166 -- In this situation you should use @case@ rather than a @let@. The function
167 -- 'CoreUtils.needsCaseBinding' can help you determine which to generate, or
168 -- alternatively use 'MkCore.mkCoreLet' rather than this constructor directly,
169 -- which will generate a @case@ if necessary
172 -- We allow a /non-recursive/ let to bind a type variable, thus:
174 -- > Let (NonRec tv (Type ty)) body
176 -- This can be very convenient for postponing type substitutions until
177 -- the next run of the simplifier.
179 -- At the moment, the rest of the compiler only deals with type-let
180 -- in a Let expression, rather than at top level. We may want to revist
182 | Case (Expr b) b Type [Alt b] -- ^ Case split. Operationally this corresponds to evaluating
183 -- the scrutinee (expression examined) to weak head normal form
184 -- and then examining at most one level of resulting constructor (i.e. you
185 -- cannot do nested pattern matching directly with this).
187 -- The binder gets bound to the value of the scrutinee,
188 -- and the 'Type' must be that of all the case alternatives
191 -- This is one of the more complicated elements of the Core language, and comes
192 -- with a number of restrictions:
194 -- The 'DEFAULT' case alternative must be first in the list, if it occurs at all.
196 -- The remaining cases are in order of increasing
197 -- tag (for 'DataAlts') or
198 -- lit (for 'LitAlts').
199 -- This makes finding the relevant constructor easy, and makes comparison easier too.
201 -- The list of alternatives must be exhaustive. An /exhaustive/ case
202 -- does not necessarily mention all constructors:
205 -- data Foo = Red | Green | Blue
208 -- other -> f (case x of
213 -- The inner case does not need a @Red@ alternative, because @x@ can't be @Red@ at
214 -- that program point.
215 | Cast (Expr b) Coercion -- ^ Cast an expression to a particular type. This is used to implement @newtype@s
216 -- (a @newtype@ constructor or destructor just becomes a 'Cast' in Core) and GADTs.
217 | Note Note (Expr b) -- ^ Notes. These allow general information to be
218 -- added to expressions in the syntax tree
219 | Type Type -- ^ A type: this should only show up at the top
222 -- | Type synonym for expressions that occur in function argument positions.
223 -- Only 'Arg' should contain a 'Type' at top level, general 'Expr' should not
226 -- | A case split alternative. Consists of the constructor leading to the alternative,
227 -- the variables bound from the constructor, and the expression to be executed given that binding.
228 -- The default alternative is @(DEFAULT, [], rhs)@
229 type Alt b = (AltCon, [b], Expr b)
231 -- | A case alternative constructor (i.e. pattern match)
232 data AltCon = DataAlt DataCon -- ^ A plain data constructor: @case e of { Foo x -> ... }@.
233 -- Invariant: the 'DataCon' is always from a @data@ type, and never from a @newtype@
234 | LitAlt Literal -- ^ A literal: @case e of { 1 -> ... }@
235 | DEFAULT -- ^ Trivial alternative: @case e of { _ -> ... }@
238 -- | Binding, used for top level bindings in a module and local bindings in a @let@.
239 data Bind b = NonRec b (Expr b)
240 | Rec [(b, (Expr b))]
243 -------------------------- CoreSyn INVARIANTS ---------------------------
245 Note [CoreSyn top-level invariant]
246 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
247 See #toplevel_invariant#
249 Note [CoreSyn letrec invariant]
250 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
251 See #letrec_invariant#
253 Note [CoreSyn let/app invariant]
254 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
255 See #let_app_invariant#
257 This is intially enforced by DsUtils.mkCoreLet and mkCoreApp
259 Note [CoreSyn case invariants]
260 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
261 See #case_invariants#
263 Note [CoreSyn let goal]
264 ~~~~~~~~~~~~~~~~~~~~~~~
265 * The simplifier tries to ensure that if the RHS of a let is a constructor
266 application, its arguments are trivial, so that the constructor can be
276 -- | Allows attaching extra information to points in expressions rather than e.g. identifiers.
278 = SCC CostCentre -- ^ A cost centre annotation for profiling
279 | CoreNote String -- ^ A generic core annotation, propagated but not used by GHC
283 %************************************************************************
285 \subsection{Transformation rules}
287 %************************************************************************
289 The CoreRule type and its friends are dealt with mainly in CoreRules,
290 but CoreFVs, Subst, PprCore, CoreTidy also inspect the representation.
293 -- | A 'CoreRule' is:
295 -- * \"Local\" if the function it is a rule for is defined in the
296 -- same module as the rule itself.
298 -- * \"Orphan\" if nothing on the LHS is defined in the same module
299 -- as the rule itself
302 ru_name :: RuleName, -- ^ Name of the rule, for communication with the user
303 ru_act :: Activation, -- ^ When the rule is active
305 -- Rough-matching stuff
306 -- see comments with InstEnv.Instance( is_cls, is_rough )
307 ru_fn :: Name, -- ^ Name of the 'Id.Id' at the head of this rule
308 ru_rough :: [Maybe Name], -- ^ Name at the head of each argument to the left hand side
310 -- Proper-matching stuff
311 -- see comments with InstEnv.Instance( is_tvs, is_tys )
312 ru_bndrs :: [CoreBndr], -- ^ Variables quantified over
313 ru_args :: [CoreExpr], -- ^ Left hand side arguments
315 -- And the right-hand side
316 ru_rhs :: CoreExpr, -- ^ Right hand side of the rule
317 -- Occurrence info is guaranteed correct
318 -- See Note [OccInfo in unfoldings and rules]
321 ru_local :: Bool -- ^ @True@ iff the fn at the head of the rule is
322 -- defined in the same module as the rule
323 -- and is not an implicit 'Id' (like a record selector,
324 -- class operation, or data constructor)
326 -- NB: ru_local is *not* used to decide orphan-hood
327 -- c.g. MkIface.coreRuleToIfaceRule
330 -- | Built-in rules are used for constant folding
331 -- and suchlike. They have no free variables.
333 ru_name :: RuleName, -- ^ As above
334 ru_fn :: Name, -- ^ As above
335 ru_nargs :: Int, -- ^ Number of arguments that 'ru_try' consumes,
336 -- if it fires, including type arguments
337 ru_try :: IdUnfoldingFun -> [CoreExpr] -> Maybe CoreExpr
338 -- ^ This function does the rewrite. It given too many
339 -- arguments, it simply discards them; the returned 'CoreExpr'
340 -- is just the rewrite of 'ru_fn' applied to the first 'ru_nargs' args
342 -- See Note [Extra args in rule matching] in Rules.lhs
344 type IdUnfoldingFun = Id -> Unfolding
345 -- A function that embodies how to unfold an Id if you need
346 -- to do that in the Rule. The reason we need to pass this info in
347 -- is that whether an Id is unfoldable depends on the simplifier phase
349 isBuiltinRule :: CoreRule -> Bool
350 isBuiltinRule (BuiltinRule {}) = True
351 isBuiltinRule _ = False
353 -- | The number of arguments the 'ru_fn' must be applied
354 -- to before the rule can match on it
355 ruleArity :: CoreRule -> Int
356 ruleArity (BuiltinRule {ru_nargs = n}) = n
357 ruleArity (Rule {ru_args = args}) = length args
359 ruleName :: CoreRule -> RuleName
362 ruleActivation_maybe :: CoreRule -> Maybe Activation
363 ruleActivation_maybe (BuiltinRule { }) = Nothing
364 ruleActivation_maybe (Rule { ru_act = act }) = Just act
366 -- | The 'Name' of the 'Id.Id' at the head of the rule left hand side
367 ruleIdName :: CoreRule -> Name
370 isLocalRule :: CoreRule -> Bool
371 isLocalRule = ru_local
373 -- | Set the 'Name' of the 'Id.Id' at the head of the rule left hand side
374 setRuleIdName :: Name -> CoreRule -> CoreRule
375 setRuleIdName nm ru = ru { ru_fn = nm }
379 %************************************************************************
383 %************************************************************************
385 The @Unfolding@ type is declared here to avoid numerous loops
388 -- | Records the /unfolding/ of an identifier, which is approximately the form the
389 -- identifier would have if we substituted its definition in for the identifier.
390 -- This type should be treated as abstract everywhere except in "CoreUnfold"
392 = NoUnfolding -- ^ We have no information about the unfolding
394 | OtherCon [AltCon] -- ^ It ain't one of these constructors.
395 -- @OtherCon xs@ also indicates that something has been evaluated
396 -- and hence there's no point in re-evaluating it.
397 -- @OtherCon []@ is used even for non-data-type values
398 -- to indicated evaluated-ness. Notably:
400 -- > data C = C !(Int -> Int)
401 -- > case x of { C f -> ... }
403 -- Here, @f@ gets an @OtherCon []@ unfolding.
405 | DFunUnfolding DataCon [CoreExpr]
406 -- The Unfolding of a DFunId
407 -- df = /\a1..am. \d1..dn. MkD (op1 a1..am d1..dn)
408 -- (op2 a1..am d1..dn)
409 -- where Arity = n, the number of dict args to the dfun
410 -- The [CoreExpr] are the superclasses and methods [op1,op2],
411 -- in positional order.
412 -- They are usually variables, but can be trivial expressions
413 -- instead (e.g. a type application).
415 | CoreUnfolding { -- An unfolding for an Id with no pragma, or perhaps a NOINLINE pragma
416 -- (For NOINLINE, the phase, if any, is in the InlinePragInfo for this Id.)
417 uf_tmpl :: CoreExpr, -- Template; occurrence info is correct
418 uf_src :: UnfoldingSource, -- Where the unfolding came from
419 uf_is_top :: Bool, -- True <=> top level binding
420 uf_arity :: Arity, -- Number of value arguments expected
421 uf_is_value :: Bool, -- exprIsHNF template (cached); it is ok to discard a `seq` on
423 uf_is_conlike :: Bool, -- True <=> application of constructor or CONLIKE function
424 -- Cached version of exprIsConLike
425 uf_is_cheap :: Bool, -- True <=> doesn't waste (much) work to expand inside an inlining
426 -- Cached version of exprIsCheap
427 uf_expandable :: Bool, -- True <=> can expand in RULE matching
428 -- Cached version of exprIsExpandable
429 uf_guidance :: UnfoldingGuidance -- Tells about the *size* of the template.
431 -- ^ An unfolding with redundant cached information. Parameters:
433 -- uf_tmpl: Template used to perform unfolding;
434 -- NB: Occurrence info is guaranteed correct:
435 -- see Note [OccInfo in unfoldings and rules]
437 -- uf_is_top: Is this a top level binding?
439 -- uf_is_value: 'exprIsHNF' template (cached); it is ok to discard a 'seq' on
442 -- uf_is_cheap: Does this waste only a little work if we expand it inside an inlining?
443 -- Basically this is a cached version of 'exprIsCheap'
445 -- uf_guidance: Tells us about the /size/ of the unfolding template
447 ------------------------------------------------
449 = InlineCompulsory -- Something that *has* no binding, so you *must* inline it
450 -- Only a few primop-like things have this property
451 -- (see MkId.lhs, calls to mkCompulsoryUnfolding).
452 -- Inline absolutely always, however boring the context.
454 | InlineRule -- From an {-# INLINE #-} pragma; See Note [InlineRules]
456 | InlineWrapper Id -- This unfolding is a the wrapper in a
457 -- worker/wrapper split from the strictness analyser
458 -- The Id is the worker-id
459 -- Used to abbreviate the uf_tmpl in interface files
460 -- which don't need to contain the RHS;
461 -- it can be derived from the strictness info
463 | InlineRhs -- The current rhs of the function
465 -- For InlineRhs, the uf_tmpl is replaced each time around
466 -- For all the others we leave uf_tmpl alone
469 -- | 'UnfoldingGuidance' says when unfolding should take place
470 data UnfoldingGuidance
471 = UnfWhen { -- Inline without thinking about the *size* of the uf_tmpl
472 -- Used (a) for small *and* cheap unfoldings
473 -- (b) for INLINE functions
474 -- See Note [INLINE for small functions] in CoreUnfold
475 ug_unsat_ok :: Bool, -- True <=> ok to inline even if unsaturated
476 ug_boring_ok :: Bool -- True <=> ok to inline even if the context is boring
479 | UnfIfGoodArgs { -- Arose from a normal Id; the info here is the
480 -- result of a simple analysis of the RHS
482 ug_args :: [Int], -- Discount if the argument is evaluated.
483 -- (i.e., a simplification will definitely
484 -- be possible). One elt of the list per *value* arg.
486 ug_size :: Int, -- The "size" of the unfolding.
488 ug_res :: Int -- Scrutinee discount: the discount to substract if the thing is in
489 } -- a context (case (thing args) of ...),
490 -- (where there are the right number of arguments.)
492 | UnfNever -- The RHS is big, so don't inline it
494 -- Constants for the UnfWhen constructor
495 needSaturated, unSaturatedOk :: Bool
496 needSaturated = False
499 boringCxtNotOk, boringCxtOk :: Bool
501 boringCxtNotOk = False
503 ------------------------------------------------
504 noUnfolding :: Unfolding
505 -- ^ There is no known 'Unfolding'
506 evaldUnfolding :: Unfolding
507 -- ^ This unfolding marks the associated thing as being evaluated
509 noUnfolding = NoUnfolding
510 evaldUnfolding = OtherCon []
512 mkOtherCon :: [AltCon] -> Unfolding
513 mkOtherCon = OtherCon
515 seqUnfolding :: Unfolding -> ()
516 seqUnfolding (CoreUnfolding { uf_tmpl = e, uf_is_top = top,
517 uf_is_value = b1, uf_is_cheap = b2,
518 uf_expandable = b3, uf_is_conlike = b4,
519 uf_arity = a, uf_guidance = g})
520 = seqExpr e `seq` top `seq` b1 `seq` a `seq` b2 `seq` b3 `seq` b4 `seq` seqGuidance g
524 seqGuidance :: UnfoldingGuidance -> ()
525 seqGuidance (UnfIfGoodArgs ns n b) = n `seq` sum ns `seq` b `seq` ()
530 isInlineRuleSource :: UnfoldingSource -> Bool
531 isInlineRuleSource InlineCompulsory = True
532 isInlineRuleSource InlineRule = True
533 isInlineRuleSource (InlineWrapper {}) = True
534 isInlineRuleSource InlineRhs = False
536 -- | Retrieves the template of an unfolding: panics if none is known
537 unfoldingTemplate :: Unfolding -> CoreExpr
538 unfoldingTemplate = uf_tmpl
540 setUnfoldingTemplate :: Unfolding -> CoreExpr -> Unfolding
541 setUnfoldingTemplate unf rhs = unf { uf_tmpl = rhs }
543 -- | Retrieves the template of an unfolding if possible
544 maybeUnfoldingTemplate :: Unfolding -> Maybe CoreExpr
545 maybeUnfoldingTemplate (CoreUnfolding { uf_tmpl = expr }) = Just expr
546 maybeUnfoldingTemplate _ = Nothing
548 -- | The constructors that the unfolding could never be:
549 -- returns @[]@ if no information is available
550 otherCons :: Unfolding -> [AltCon]
551 otherCons (OtherCon cons) = cons
554 -- | Determines if it is certainly the case that the unfolding will
555 -- yield a value (something in HNF): returns @False@ if unsure
556 isValueUnfolding :: Unfolding -> Bool
557 -- Returns False for OtherCon
558 isValueUnfolding (CoreUnfolding { uf_is_value = is_evald }) = is_evald
559 isValueUnfolding _ = False
561 -- | Determines if it possibly the case that the unfolding will
562 -- yield a value. Unlike 'isValueUnfolding' it returns @True@
564 isEvaldUnfolding :: Unfolding -> Bool
565 -- Returns True for OtherCon
566 isEvaldUnfolding (OtherCon _) = True
567 isEvaldUnfolding (CoreUnfolding { uf_is_value = is_evald }) = is_evald
568 isEvaldUnfolding _ = False
570 -- | @True@ if the unfolding is a constructor application, the application
571 -- of a CONLIKE function or 'OtherCon'
572 isConLikeUnfolding :: Unfolding -> Bool
573 isConLikeUnfolding (OtherCon _) = True
574 isConLikeUnfolding (CoreUnfolding { uf_is_conlike = con }) = con
575 isConLikeUnfolding _ = False
577 -- | Is the thing we will unfold into certainly cheap?
578 isCheapUnfolding :: Unfolding -> Bool
579 isCheapUnfolding (CoreUnfolding { uf_is_cheap = is_cheap }) = is_cheap
580 isCheapUnfolding _ = False
582 isExpandableUnfolding :: Unfolding -> Bool
583 isExpandableUnfolding (CoreUnfolding { uf_expandable = is_expable }) = is_expable
584 isExpandableUnfolding _ = False
586 isInlineRule :: Unfolding -> Bool
587 isInlineRule (CoreUnfolding { uf_src = src }) = isInlineRuleSource src
588 isInlineRule _ = False
590 isInlineRule_maybe :: Unfolding -> Maybe (UnfoldingSource, Bool)
591 isInlineRule_maybe (CoreUnfolding { uf_src = src, uf_guidance = guide })
592 | isInlineRuleSource src
593 = Just (src, unsat_ok)
595 unsat_ok = case guide of
596 UnfWhen unsat_ok _ -> unsat_ok
598 isInlineRule_maybe _ = Nothing
600 isCompulsoryUnfolding :: Unfolding -> Bool
601 isCompulsoryUnfolding (CoreUnfolding { uf_src = InlineCompulsory }) = True
602 isCompulsoryUnfolding _ = False
604 isStableUnfolding :: Unfolding -> Bool
605 -- True of unfoldings that should not be overwritten
606 -- by a CoreUnfolding for the RHS of a let-binding
607 isStableUnfolding (CoreUnfolding { uf_src = src }) = isInlineRuleSource src
608 isStableUnfolding (DFunUnfolding {}) = True
609 isStableUnfolding _ = False
611 unfoldingArity :: Unfolding -> Arity
612 unfoldingArity (CoreUnfolding { uf_arity = arity }) = arity
613 unfoldingArity _ = panic "unfoldingArity"
615 isClosedUnfolding :: Unfolding -> Bool -- No free variables
616 isClosedUnfolding (CoreUnfolding {}) = False
617 isClosedUnfolding _ = True
619 -- | Only returns False if there is no unfolding information available at all
620 hasSomeUnfolding :: Unfolding -> Bool
621 hasSomeUnfolding NoUnfolding = False
622 hasSomeUnfolding _ = True
624 neverUnfoldGuidance :: UnfoldingGuidance -> Bool
625 neverUnfoldGuidance UnfNever = True
626 neverUnfoldGuidance _ = False
628 canUnfold :: Unfolding -> Bool
629 canUnfold (CoreUnfolding { uf_guidance = g }) = not (neverUnfoldGuidance g)
638 you intend that calls (f e) are replaced by <rhs>[e/x] So we
639 should capture (\x.<rhs>) in the Unfolding of 'f', and never meddle
640 with it. Meanwhile, we can optimise <rhs> to our heart's content,
641 leaving the original unfolding intact in Unfolding of 'f'.
643 So the representation of an Unfolding has changed quite a bit
644 (see CoreSyn). An INLINE pragma gives rise to an InlineRule
647 Moreover, it's only used when 'f' is applied to the
648 specified number of arguments; that is, the number of argument on
649 the LHS of the '=' sign in the original source definition.
650 For example, (.) is now defined in the libraries like this
652 (.) f g = \x -> f (g x)
653 so that it'll inline when applied to two arguments. If 'x' appeared
656 it'd only inline when applied to three arguments. This slightly-experimental
657 change was requested by Roman, but it seems to make sense.
659 See also Note [Inlining an InlineRule] in CoreUnfold.
662 Note [OccInfo in unfoldings and rules]
663 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
664 In unfoldings and rules, we guarantee that the template is occ-analysed,
665 so that the occurence info on the binders is correct. This is important,
666 because the Simplifier does not re-analyse the template when using it. If
667 the occurrence info is wrong
668 - We may get more simpifier iterations than necessary, because
669 once-occ info isn't there
670 - More seriously, we may get an infinite loop if there's a Rec
671 without a loop breaker marked
674 %************************************************************************
676 \subsection{The main data type}
678 %************************************************************************
681 -- The Ord is needed for the FiniteMap used in the lookForConstructor
682 -- in SimplEnv. If you declared that lookForConstructor *ignores*
683 -- constructor-applications with LitArg args, then you could get
686 instance Outputable AltCon where
687 ppr (DataAlt dc) = ppr dc
688 ppr (LitAlt lit) = ppr lit
689 ppr DEFAULT = ptext (sLit "__DEFAULT")
691 instance Show AltCon where
692 showsPrec p con = showsPrecSDoc p (ppr con)
694 cmpAlt :: Alt b -> Alt b -> Ordering
695 cmpAlt (con1, _, _) (con2, _, _) = con1 `cmpAltCon` con2
697 ltAlt :: Alt b -> Alt b -> Bool
698 ltAlt a1 a2 = (a1 `cmpAlt` a2) == LT
700 cmpAltCon :: AltCon -> AltCon -> Ordering
701 -- ^ Compares 'AltCon's within a single list of alternatives
702 cmpAltCon DEFAULT DEFAULT = EQ
703 cmpAltCon DEFAULT _ = LT
705 cmpAltCon (DataAlt d1) (DataAlt d2) = dataConTag d1 `compare` dataConTag d2
706 cmpAltCon (DataAlt _) DEFAULT = GT
707 cmpAltCon (LitAlt l1) (LitAlt l2) = l1 `compare` l2
708 cmpAltCon (LitAlt _) DEFAULT = GT
710 cmpAltCon con1 con2 = WARN( True, text "Comparing incomparable AltCons" <+>
711 ppr con1 <+> ppr con2 )
715 %************************************************************************
717 \subsection{Useful synonyms}
719 %************************************************************************
722 -- | The common case for the type of binders and variables when
723 -- we are manipulating the Core language within GHC
725 -- | Expressions where binders are 'CoreBndr's
726 type CoreExpr = Expr CoreBndr
727 -- | Argument expressions where binders are 'CoreBndr's
728 type CoreArg = Arg CoreBndr
729 -- | Binding groups where binders are 'CoreBndr's
730 type CoreBind = Bind CoreBndr
731 -- | Case alternatives where binders are 'CoreBndr's
732 type CoreAlt = Alt CoreBndr
735 %************************************************************************
739 %************************************************************************
742 -- | Binders are /tagged/ with a t
743 data TaggedBndr t = TB CoreBndr t -- TB for "tagged binder"
745 type TaggedBind t = Bind (TaggedBndr t)
746 type TaggedExpr t = Expr (TaggedBndr t)
747 type TaggedArg t = Arg (TaggedBndr t)
748 type TaggedAlt t = Alt (TaggedBndr t)
750 instance Outputable b => Outputable (TaggedBndr b) where
751 ppr (TB b l) = char '<' <> ppr b <> comma <> ppr l <> char '>'
753 instance Outputable b => OutputableBndr (TaggedBndr b) where
754 pprBndr _ b = ppr b -- Simple
758 %************************************************************************
760 \subsection{Core-constructing functions with checking}
762 %************************************************************************
765 -- | Apply a list of argument expressions to a function expression in a nested fashion. Prefer to
766 -- use 'CoreUtils.mkCoreApps' if possible
767 mkApps :: Expr b -> [Arg b] -> Expr b
768 -- | Apply a list of type argument expressions to a function expression in a nested fashion
769 mkTyApps :: Expr b -> [Type] -> Expr b
770 -- | Apply a list of type or value variables to a function expression in a nested fashion
771 mkVarApps :: Expr b -> [Var] -> Expr b
772 -- | Apply a list of argument expressions to a data constructor in a nested fashion. Prefer to
773 -- use 'MkCore.mkCoreConApps' if possible
774 mkConApp :: DataCon -> [Arg b] -> Expr b
776 mkApps f args = foldl App f args
777 mkTyApps f args = foldl (\ e a -> App e (Type a)) f args
778 mkVarApps f vars = foldl (\ e a -> App e (varToCoreExpr a)) f vars
779 mkConApp con args = mkApps (Var (dataConWorkId con)) args
782 -- | Create a machine integer literal expression of type @Int#@ from an @Integer@.
783 -- If you want an expression of type @Int@ use 'MkCore.mkIntExpr'
784 mkIntLit :: Integer -> Expr b
785 -- | Create a machine integer literal expression of type @Int#@ from an @Int@.
786 -- If you want an expression of type @Int@ use 'MkCore.mkIntExpr'
787 mkIntLitInt :: Int -> Expr b
789 mkIntLit n = Lit (mkMachInt n)
790 mkIntLitInt n = Lit (mkMachInt (toInteger n))
792 -- | Create a machine word literal expression of type @Word#@ from an @Integer@.
793 -- If you want an expression of type @Word@ use 'MkCore.mkWordExpr'
794 mkWordLit :: Integer -> Expr b
795 -- | Create a machine word literal expression of type @Word#@ from a @Word@.
796 -- If you want an expression of type @Word@ use 'MkCore.mkWordExpr'
797 mkWordLitWord :: Word -> Expr b
799 mkWordLit w = Lit (mkMachWord w)
800 mkWordLitWord w = Lit (mkMachWord (toInteger w))
802 -- | Create a machine character literal expression of type @Char#@.
803 -- If you want an expression of type @Char@ use 'MkCore.mkCharExpr'
804 mkCharLit :: Char -> Expr b
805 -- | Create a machine string literal expression of type @Addr#@.
806 -- If you want an expression of type @String@ use 'MkCore.mkStringExpr'
807 mkStringLit :: String -> Expr b
809 mkCharLit c = Lit (mkMachChar c)
810 mkStringLit s = Lit (mkMachString s)
812 -- | Create a machine single precision literal expression of type @Float#@ from a @Rational@.
813 -- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr'
814 mkFloatLit :: Rational -> Expr b
815 -- | Create a machine single precision literal expression of type @Float#@ from a @Float@.
816 -- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr'
817 mkFloatLitFloat :: Float -> Expr b
819 mkFloatLit f = Lit (mkMachFloat f)
820 mkFloatLitFloat f = Lit (mkMachFloat (toRational f))
822 -- | Create a machine double precision literal expression of type @Double#@ from a @Rational@.
823 -- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr'
824 mkDoubleLit :: Rational -> Expr b
825 -- | Create a machine double precision literal expression of type @Double#@ from a @Double@.
826 -- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr'
827 mkDoubleLitDouble :: Double -> Expr b
829 mkDoubleLit d = Lit (mkMachDouble d)
830 mkDoubleLitDouble d = Lit (mkMachDouble (toRational d))
832 -- | Bind all supplied binding groups over an expression in a nested let expression. Prefer to
833 -- use 'CoreUtils.mkCoreLets' if possible
834 mkLets :: [Bind b] -> Expr b -> Expr b
835 -- | Bind all supplied binders over an expression in a nested lambda expression. Prefer to
836 -- use 'CoreUtils.mkCoreLams' if possible
837 mkLams :: [b] -> Expr b -> Expr b
839 mkLams binders body = foldr Lam body binders
840 mkLets binds body = foldr Let body binds
843 -- | Create a binding group where a type variable is bound to a type. Per "CoreSyn#type_let",
844 -- this can only be used to bind something in a non-recursive @let@ expression
845 mkTyBind :: TyVar -> Type -> CoreBind
846 mkTyBind tv ty = NonRec tv (Type ty)
848 -- | Convert a binder into either a 'Var' or 'Type' 'Expr' appropriately
849 varToCoreExpr :: CoreBndr -> Expr b
850 varToCoreExpr v | isId v = Var v
851 | otherwise = Type (mkTyVarTy v)
853 varsToCoreExprs :: [CoreBndr] -> [Expr b]
854 varsToCoreExprs vs = map varToCoreExpr vs
858 %************************************************************************
860 \subsection{Simple access functions}
862 %************************************************************************
865 -- | Extract every variable by this group
866 bindersOf :: Bind b -> [b]
867 bindersOf (NonRec binder _) = [binder]
868 bindersOf (Rec pairs) = [binder | (binder, _) <- pairs]
870 -- | 'bindersOf' applied to a list of binding groups
871 bindersOfBinds :: [Bind b] -> [b]
872 bindersOfBinds binds = foldr ((++) . bindersOf) [] binds
874 rhssOfBind :: Bind b -> [Expr b]
875 rhssOfBind (NonRec _ rhs) = [rhs]
876 rhssOfBind (Rec pairs) = [rhs | (_,rhs) <- pairs]
878 rhssOfAlts :: [Alt b] -> [Expr b]
879 rhssOfAlts alts = [e | (_,_,e) <- alts]
881 -- | Collapse all the bindings in the supplied groups into a single
882 -- list of lhs\/rhs pairs suitable for binding in a 'Rec' binding group
883 flattenBinds :: [Bind b] -> [(b, Expr b)]
884 flattenBinds (NonRec b r : binds) = (b,r) : flattenBinds binds
885 flattenBinds (Rec prs1 : binds) = prs1 ++ flattenBinds binds
890 -- | We often want to strip off leading lambdas before getting down to
891 -- business. This function is your friend.
892 collectBinders :: Expr b -> ([b], Expr b)
893 -- | Collect as many type bindings as possible from the front of a nested lambda
894 collectTyBinders :: CoreExpr -> ([TyVar], CoreExpr)
895 -- | Collect as many value bindings as possible from the front of a nested lambda
896 collectValBinders :: CoreExpr -> ([Id], CoreExpr)
897 -- | Collect type binders from the front of the lambda first,
898 -- then follow up by collecting as many value bindings as possible
899 -- from the resulting stripped expression
900 collectTyAndValBinders :: CoreExpr -> ([TyVar], [Id], CoreExpr)
905 go bs (Lam b e) = go (b:bs) e
906 go bs e = (reverse bs, e)
908 collectTyAndValBinders expr
911 (tvs, body1) = collectTyBinders expr
912 (ids, body) = collectValBinders body1
914 collectTyBinders expr
917 go tvs (Lam b e) | isTyVar b = go (b:tvs) e
918 go tvs e = (reverse tvs, e)
920 collectValBinders expr
923 go ids (Lam b e) | isId b = go (b:ids) e
924 go ids body = (reverse ids, body)
928 -- | Takes a nested application expression and returns the the function
929 -- being applied and the arguments to which it is applied
930 collectArgs :: Expr b -> (Expr b, [Arg b])
934 go (App f a) as = go f (a:as)
939 -- | Gets the cost centre enclosing an expression, if any.
940 -- It looks inside lambdas because @(scc \"foo\" \\x.e) = \\x. scc \"foo\" e@
941 coreExprCc :: Expr b -> CostCentre
942 coreExprCc (Note (SCC cc) _) = cc
943 coreExprCc (Note _ e) = coreExprCc e
944 coreExprCc (Lam _ e) = coreExprCc e
945 coreExprCc _ = noCostCentre
948 %************************************************************************
950 \subsection{Predicates}
952 %************************************************************************
954 At one time we optionally carried type arguments through to runtime.
955 @isRuntimeVar v@ returns if (Lam v _) really becomes a lambda at runtime,
956 i.e. if type applications are actual lambdas because types are kept around
957 at runtime. Similarly isRuntimeArg.
960 -- | Will this variable exist at runtime?
961 isRuntimeVar :: Var -> Bool
964 -- | Will this argument expression exist at runtime?
965 isRuntimeArg :: CoreExpr -> Bool
966 isRuntimeArg = isValArg
968 -- | Returns @False@ iff the expression is a 'Type' expression at its top level
969 isValArg :: Expr b -> Bool
970 isValArg (Type _) = False
973 -- | Returns @True@ iff the expression is a 'Type' expression at its top level
974 isTypeArg :: Expr b -> Bool
975 isTypeArg (Type _) = True
978 -- | The number of binders that bind values rather than types
979 valBndrCount :: [CoreBndr] -> Int
980 valBndrCount = count isId
982 -- | The number of argument expressions that are values rather than types at their top level
983 valArgCount :: [Arg b] -> Int
984 valArgCount = count isValArg
988 %************************************************************************
990 \subsection{Seq stuff}
992 %************************************************************************
995 seqExpr :: CoreExpr -> ()
996 seqExpr (Var v) = v `seq` ()
997 seqExpr (Lit lit) = lit `seq` ()
998 seqExpr (App f a) = seqExpr f `seq` seqExpr a
999 seqExpr (Lam b e) = seqBndr b `seq` seqExpr e
1000 seqExpr (Let b e) = seqBind b `seq` seqExpr e
1001 seqExpr (Case e b t as) = seqExpr e `seq` seqBndr b `seq` seqType t `seq` seqAlts as
1002 seqExpr (Cast e co) = seqExpr e `seq` seqType co
1003 seqExpr (Note n e) = seqNote n `seq` seqExpr e
1004 seqExpr (Type t) = seqType t
1006 seqExprs :: [CoreExpr] -> ()
1008 seqExprs (e:es) = seqExpr e `seq` seqExprs es
1010 seqNote :: Note -> ()
1011 seqNote (CoreNote s) = s `seq` ()
1014 seqBndr :: CoreBndr -> ()
1015 seqBndr b = b `seq` ()
1017 seqBndrs :: [CoreBndr] -> ()
1019 seqBndrs (b:bs) = seqBndr b `seq` seqBndrs bs
1021 seqBind :: Bind CoreBndr -> ()
1022 seqBind (NonRec b e) = seqBndr b `seq` seqExpr e
1023 seqBind (Rec prs) = seqPairs prs
1025 seqPairs :: [(CoreBndr, CoreExpr)] -> ()
1027 seqPairs ((b,e):prs) = seqBndr b `seq` seqExpr e `seq` seqPairs prs
1029 seqAlts :: [CoreAlt] -> ()
1031 seqAlts ((c,bs,e):alts) = c `seq` seqBndrs bs `seq` seqExpr e `seq` seqAlts alts
1033 seqRules :: [CoreRule] -> ()
1035 seqRules (Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs } : rules)
1036 = seqBndrs bndrs `seq` seqExprs (rhs:args) `seq` seqRules rules
1037 seqRules (BuiltinRule {} : rules) = seqRules rules
1040 %************************************************************************
1042 \subsection{Annotated core}
1044 %************************************************************************
1047 -- | Annotated core: allows annotation at every node in the tree
1048 type AnnExpr bndr annot = (annot, AnnExpr' bndr annot)
1050 -- | A clone of the 'Expr' type but allowing annotation at every tree node
1051 data AnnExpr' bndr annot
1054 | AnnLam bndr (AnnExpr bndr annot)
1055 | AnnApp (AnnExpr bndr annot) (AnnExpr bndr annot)
1056 | AnnCase (AnnExpr bndr annot) bndr Type [AnnAlt bndr annot]
1057 | AnnLet (AnnBind bndr annot) (AnnExpr bndr annot)
1058 | AnnCast (AnnExpr bndr annot) Coercion
1059 | AnnNote Note (AnnExpr bndr annot)
1062 -- | A clone of the 'Alt' type but allowing annotation at every tree node
1063 type AnnAlt bndr annot = (AltCon, [bndr], AnnExpr bndr annot)
1065 -- | A clone of the 'Bind' type but allowing annotation at every tree node
1066 data AnnBind bndr annot
1067 = AnnNonRec bndr (AnnExpr bndr annot)
1068 | AnnRec [(bndr, AnnExpr bndr annot)]
1072 deAnnotate :: AnnExpr bndr annot -> Expr bndr
1073 deAnnotate (_, e) = deAnnotate' e
1075 deAnnotate' :: AnnExpr' bndr annot -> Expr bndr
1076 deAnnotate' (AnnType t) = Type t
1077 deAnnotate' (AnnVar v) = Var v
1078 deAnnotate' (AnnLit lit) = Lit lit
1079 deAnnotate' (AnnLam binder body) = Lam binder (deAnnotate body)
1080 deAnnotate' (AnnApp fun arg) = App (deAnnotate fun) (deAnnotate arg)
1081 deAnnotate' (AnnCast e co) = Cast (deAnnotate e) co
1082 deAnnotate' (AnnNote note body) = Note note (deAnnotate body)
1084 deAnnotate' (AnnLet bind body)
1085 = Let (deAnnBind bind) (deAnnotate body)
1087 deAnnBind (AnnNonRec var rhs) = NonRec var (deAnnotate rhs)
1088 deAnnBind (AnnRec pairs) = Rec [(v,deAnnotate rhs) | (v,rhs) <- pairs]
1090 deAnnotate' (AnnCase scrut v t alts)
1091 = Case (deAnnotate scrut) v t (map deAnnAlt alts)
1093 deAnnAlt :: AnnAlt bndr annot -> Alt bndr
1094 deAnnAlt (con,args,rhs) = (con,args,deAnnotate rhs)
1098 -- | As 'collectBinders' but for 'AnnExpr' rather than 'Expr'
1099 collectAnnBndrs :: AnnExpr bndr annot -> ([bndr], AnnExpr bndr annot)
1103 collect bs (_, AnnLam b body) = collect (b:bs) body
1104 collect bs body = (reverse bs, body)