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, expandUnfolding_maybe,
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 expandUnfolding_maybe :: Unfolding -> Maybe CoreExpr
587 -- Expand an expandable unfolding; this is used in rule matching
588 -- See Note [Expanding variables] in Rules.lhs
589 -- The key point here is that CONLIKE things can be expanded
590 expandUnfolding_maybe (CoreUnfolding { uf_expandable = True, uf_tmpl = rhs }) = Just rhs
591 expandUnfolding_maybe _ = Nothing
593 isInlineRule :: Unfolding -> Bool
594 isInlineRule (CoreUnfolding { uf_src = src }) = isInlineRuleSource src
595 isInlineRule _ = False
597 isInlineRule_maybe :: Unfolding -> Maybe (UnfoldingSource, Bool)
598 isInlineRule_maybe (CoreUnfolding { uf_src = src, uf_guidance = guide })
599 | isInlineRuleSource src
600 = Just (src, unsat_ok)
602 unsat_ok = case guide of
603 UnfWhen unsat_ok _ -> unsat_ok
605 isInlineRule_maybe _ = Nothing
607 isCompulsoryUnfolding :: Unfolding -> Bool
608 isCompulsoryUnfolding (CoreUnfolding { uf_src = InlineCompulsory }) = True
609 isCompulsoryUnfolding _ = False
611 isStableUnfolding :: Unfolding -> Bool
612 -- True of unfoldings that should not be overwritten
613 -- by a CoreUnfolding for the RHS of a let-binding
614 isStableUnfolding (CoreUnfolding { uf_src = src }) = isInlineRuleSource src
615 isStableUnfolding (DFunUnfolding {}) = True
616 isStableUnfolding _ = False
618 unfoldingArity :: Unfolding -> Arity
619 unfoldingArity (CoreUnfolding { uf_arity = arity }) = arity
620 unfoldingArity _ = panic "unfoldingArity"
622 isClosedUnfolding :: Unfolding -> Bool -- No free variables
623 isClosedUnfolding (CoreUnfolding {}) = False
624 isClosedUnfolding _ = True
626 -- | Only returns False if there is no unfolding information available at all
627 hasSomeUnfolding :: Unfolding -> Bool
628 hasSomeUnfolding NoUnfolding = False
629 hasSomeUnfolding _ = True
631 neverUnfoldGuidance :: UnfoldingGuidance -> Bool
632 neverUnfoldGuidance UnfNever = True
633 neverUnfoldGuidance _ = False
635 canUnfold :: Unfolding -> Bool
636 canUnfold (CoreUnfolding { uf_guidance = g }) = not (neverUnfoldGuidance g)
645 you intend that calls (f e) are replaced by <rhs>[e/x] So we
646 should capture (\x.<rhs>) in the Unfolding of 'f', and never meddle
647 with it. Meanwhile, we can optimise <rhs> to our heart's content,
648 leaving the original unfolding intact in Unfolding of 'f'. For example
649 all xs = foldr (&&) True xs
650 any p = all . map p {-# INLINE any #-}
651 We optimise any's RHS fully, but leave the InlineRule saying "all . map p",
652 which deforests well at the call site.
654 So INLINE pragma gives rise to an InlineRule, which captures the original RHS.
656 Moreover, it's only used when 'f' is applied to the
657 specified number of arguments; that is, the number of argument on
658 the LHS of the '=' sign in the original source definition.
659 For example, (.) is now defined in the libraries like this
661 (.) f g = \x -> f (g x)
662 so that it'll inline when applied to two arguments. If 'x' appeared
665 it'd only inline when applied to three arguments. This slightly-experimental
666 change was requested by Roman, but it seems to make sense.
668 See also Note [Inlining an InlineRule] in CoreUnfold.
671 Note [OccInfo in unfoldings and rules]
672 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
673 In unfoldings and rules, we guarantee that the template is occ-analysed,
674 so that the occurence info on the binders is correct. This is important,
675 because the Simplifier does not re-analyse the template when using it. If
676 the occurrence info is wrong
677 - We may get more simpifier iterations than necessary, because
678 once-occ info isn't there
679 - More seriously, we may get an infinite loop if there's a Rec
680 without a loop breaker marked
683 %************************************************************************
685 \subsection{The main data type}
687 %************************************************************************
690 -- The Ord is needed for the FiniteMap used in the lookForConstructor
691 -- in SimplEnv. If you declared that lookForConstructor *ignores*
692 -- constructor-applications with LitArg args, then you could get
695 instance Outputable AltCon where
696 ppr (DataAlt dc) = ppr dc
697 ppr (LitAlt lit) = ppr lit
698 ppr DEFAULT = ptext (sLit "__DEFAULT")
700 instance Show AltCon where
701 showsPrec p con = showsPrecSDoc p (ppr con)
703 cmpAlt :: Alt b -> Alt b -> Ordering
704 cmpAlt (con1, _, _) (con2, _, _) = con1 `cmpAltCon` con2
706 ltAlt :: Alt b -> Alt b -> Bool
707 ltAlt a1 a2 = (a1 `cmpAlt` a2) == LT
709 cmpAltCon :: AltCon -> AltCon -> Ordering
710 -- ^ Compares 'AltCon's within a single list of alternatives
711 cmpAltCon DEFAULT DEFAULT = EQ
712 cmpAltCon DEFAULT _ = LT
714 cmpAltCon (DataAlt d1) (DataAlt d2) = dataConTag d1 `compare` dataConTag d2
715 cmpAltCon (DataAlt _) DEFAULT = GT
716 cmpAltCon (LitAlt l1) (LitAlt l2) = l1 `compare` l2
717 cmpAltCon (LitAlt _) DEFAULT = GT
719 cmpAltCon con1 con2 = WARN( True, text "Comparing incomparable AltCons" <+>
720 ppr con1 <+> ppr con2 )
724 %************************************************************************
726 \subsection{Useful synonyms}
728 %************************************************************************
731 -- | The common case for the type of binders and variables when
732 -- we are manipulating the Core language within GHC
734 -- | Expressions where binders are 'CoreBndr's
735 type CoreExpr = Expr CoreBndr
736 -- | Argument expressions where binders are 'CoreBndr's
737 type CoreArg = Arg CoreBndr
738 -- | Binding groups where binders are 'CoreBndr's
739 type CoreBind = Bind CoreBndr
740 -- | Case alternatives where binders are 'CoreBndr's
741 type CoreAlt = Alt CoreBndr
744 %************************************************************************
748 %************************************************************************
751 -- | Binders are /tagged/ with a t
752 data TaggedBndr t = TB CoreBndr t -- TB for "tagged binder"
754 type TaggedBind t = Bind (TaggedBndr t)
755 type TaggedExpr t = Expr (TaggedBndr t)
756 type TaggedArg t = Arg (TaggedBndr t)
757 type TaggedAlt t = Alt (TaggedBndr t)
759 instance Outputable b => Outputable (TaggedBndr b) where
760 ppr (TB b l) = char '<' <> ppr b <> comma <> ppr l <> char '>'
762 instance Outputable b => OutputableBndr (TaggedBndr b) where
763 pprBndr _ b = ppr b -- Simple
767 %************************************************************************
769 \subsection{Core-constructing functions with checking}
771 %************************************************************************
774 -- | Apply a list of argument expressions to a function expression in a nested fashion. Prefer to
775 -- use 'CoreUtils.mkCoreApps' if possible
776 mkApps :: Expr b -> [Arg b] -> Expr b
777 -- | Apply a list of type argument expressions to a function expression in a nested fashion
778 mkTyApps :: Expr b -> [Type] -> Expr b
779 -- | Apply a list of type or value variables to a function expression in a nested fashion
780 mkVarApps :: Expr b -> [Var] -> Expr b
781 -- | Apply a list of argument expressions to a data constructor in a nested fashion. Prefer to
782 -- use 'MkCore.mkCoreConApps' if possible
783 mkConApp :: DataCon -> [Arg b] -> Expr b
785 mkApps f args = foldl App f args
786 mkTyApps f args = foldl (\ e a -> App e (Type a)) f args
787 mkVarApps f vars = foldl (\ e a -> App e (varToCoreExpr a)) f vars
788 mkConApp con args = mkApps (Var (dataConWorkId con)) args
791 -- | Create a machine integer literal expression of type @Int#@ from an @Integer@.
792 -- If you want an expression of type @Int@ use 'MkCore.mkIntExpr'
793 mkIntLit :: Integer -> Expr b
794 -- | Create a machine integer literal expression of type @Int#@ from an @Int@.
795 -- If you want an expression of type @Int@ use 'MkCore.mkIntExpr'
796 mkIntLitInt :: Int -> Expr b
798 mkIntLit n = Lit (mkMachInt n)
799 mkIntLitInt n = Lit (mkMachInt (toInteger n))
801 -- | Create a machine word literal expression of type @Word#@ from an @Integer@.
802 -- If you want an expression of type @Word@ use 'MkCore.mkWordExpr'
803 mkWordLit :: Integer -> Expr b
804 -- | Create a machine word literal expression of type @Word#@ from a @Word@.
805 -- If you want an expression of type @Word@ use 'MkCore.mkWordExpr'
806 mkWordLitWord :: Word -> Expr b
808 mkWordLit w = Lit (mkMachWord w)
809 mkWordLitWord w = Lit (mkMachWord (toInteger w))
811 -- | Create a machine character literal expression of type @Char#@.
812 -- If you want an expression of type @Char@ use 'MkCore.mkCharExpr'
813 mkCharLit :: Char -> Expr b
814 -- | Create a machine string literal expression of type @Addr#@.
815 -- If you want an expression of type @String@ use 'MkCore.mkStringExpr'
816 mkStringLit :: String -> Expr b
818 mkCharLit c = Lit (mkMachChar c)
819 mkStringLit s = Lit (mkMachString s)
821 -- | Create a machine single precision literal expression of type @Float#@ from a @Rational@.
822 -- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr'
823 mkFloatLit :: Rational -> Expr b
824 -- | Create a machine single precision literal expression of type @Float#@ from a @Float@.
825 -- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr'
826 mkFloatLitFloat :: Float -> Expr b
828 mkFloatLit f = Lit (mkMachFloat f)
829 mkFloatLitFloat f = Lit (mkMachFloat (toRational f))
831 -- | Create a machine double precision literal expression of type @Double#@ from a @Rational@.
832 -- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr'
833 mkDoubleLit :: Rational -> Expr b
834 -- | Create a machine double precision literal expression of type @Double#@ from a @Double@.
835 -- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr'
836 mkDoubleLitDouble :: Double -> Expr b
838 mkDoubleLit d = Lit (mkMachDouble d)
839 mkDoubleLitDouble d = Lit (mkMachDouble (toRational d))
841 -- | Bind all supplied binding groups over an expression in a nested let expression. Prefer to
842 -- use 'CoreUtils.mkCoreLets' if possible
843 mkLets :: [Bind b] -> Expr b -> Expr b
844 -- | Bind all supplied binders over an expression in a nested lambda expression. Prefer to
845 -- use 'CoreUtils.mkCoreLams' if possible
846 mkLams :: [b] -> Expr b -> Expr b
848 mkLams binders body = foldr Lam body binders
849 mkLets binds body = foldr Let body binds
852 -- | Create a binding group where a type variable is bound to a type. Per "CoreSyn#type_let",
853 -- this can only be used to bind something in a non-recursive @let@ expression
854 mkTyBind :: TyVar -> Type -> CoreBind
855 mkTyBind tv ty = NonRec tv (Type ty)
857 -- | Convert a binder into either a 'Var' or 'Type' 'Expr' appropriately
858 varToCoreExpr :: CoreBndr -> Expr b
859 varToCoreExpr v | isId v = Var v
860 | otherwise = Type (mkTyVarTy v)
862 varsToCoreExprs :: [CoreBndr] -> [Expr b]
863 varsToCoreExprs vs = map varToCoreExpr vs
867 %************************************************************************
869 \subsection{Simple access functions}
871 %************************************************************************
874 -- | Extract every variable by this group
875 bindersOf :: Bind b -> [b]
876 bindersOf (NonRec binder _) = [binder]
877 bindersOf (Rec pairs) = [binder | (binder, _) <- pairs]
879 -- | 'bindersOf' applied to a list of binding groups
880 bindersOfBinds :: [Bind b] -> [b]
881 bindersOfBinds binds = foldr ((++) . bindersOf) [] binds
883 rhssOfBind :: Bind b -> [Expr b]
884 rhssOfBind (NonRec _ rhs) = [rhs]
885 rhssOfBind (Rec pairs) = [rhs | (_,rhs) <- pairs]
887 rhssOfAlts :: [Alt b] -> [Expr b]
888 rhssOfAlts alts = [e | (_,_,e) <- alts]
890 -- | Collapse all the bindings in the supplied groups into a single
891 -- list of lhs\/rhs pairs suitable for binding in a 'Rec' binding group
892 flattenBinds :: [Bind b] -> [(b, Expr b)]
893 flattenBinds (NonRec b r : binds) = (b,r) : flattenBinds binds
894 flattenBinds (Rec prs1 : binds) = prs1 ++ flattenBinds binds
899 -- | We often want to strip off leading lambdas before getting down to
900 -- business. This function is your friend.
901 collectBinders :: Expr b -> ([b], Expr b)
902 -- | Collect as many type bindings as possible from the front of a nested lambda
903 collectTyBinders :: CoreExpr -> ([TyVar], CoreExpr)
904 -- | Collect as many value bindings as possible from the front of a nested lambda
905 collectValBinders :: CoreExpr -> ([Id], CoreExpr)
906 -- | Collect type binders from the front of the lambda first,
907 -- then follow up by collecting as many value bindings as possible
908 -- from the resulting stripped expression
909 collectTyAndValBinders :: CoreExpr -> ([TyVar], [Id], CoreExpr)
914 go bs (Lam b e) = go (b:bs) e
915 go bs e = (reverse bs, e)
917 collectTyAndValBinders expr
920 (tvs, body1) = collectTyBinders expr
921 (ids, body) = collectValBinders body1
923 collectTyBinders expr
926 go tvs (Lam b e) | isTyVar b = go (b:tvs) e
927 go tvs e = (reverse tvs, e)
929 collectValBinders expr
932 go ids (Lam b e) | isId b = go (b:ids) e
933 go ids body = (reverse ids, body)
937 -- | Takes a nested application expression and returns the the function
938 -- being applied and the arguments to which it is applied
939 collectArgs :: Expr b -> (Expr b, [Arg b])
943 go (App f a) as = go f (a:as)
948 -- | Gets the cost centre enclosing an expression, if any.
949 -- It looks inside lambdas because @(scc \"foo\" \\x.e) = \\x. scc \"foo\" e@
950 coreExprCc :: Expr b -> CostCentre
951 coreExprCc (Note (SCC cc) _) = cc
952 coreExprCc (Note _ e) = coreExprCc e
953 coreExprCc (Lam _ e) = coreExprCc e
954 coreExprCc _ = noCostCentre
957 %************************************************************************
959 \subsection{Predicates}
961 %************************************************************************
963 At one time we optionally carried type arguments through to runtime.
964 @isRuntimeVar v@ returns if (Lam v _) really becomes a lambda at runtime,
965 i.e. if type applications are actual lambdas because types are kept around
966 at runtime. Similarly isRuntimeArg.
969 -- | Will this variable exist at runtime?
970 isRuntimeVar :: Var -> Bool
973 -- | Will this argument expression exist at runtime?
974 isRuntimeArg :: CoreExpr -> Bool
975 isRuntimeArg = isValArg
977 -- | Returns @False@ iff the expression is a 'Type' expression at its top level
978 isValArg :: Expr b -> Bool
979 isValArg (Type _) = False
982 -- | Returns @True@ iff the expression is a 'Type' expression at its top level
983 isTypeArg :: Expr b -> Bool
984 isTypeArg (Type _) = True
987 -- | The number of binders that bind values rather than types
988 valBndrCount :: [CoreBndr] -> Int
989 valBndrCount = count isId
991 -- | The number of argument expressions that are values rather than types at their top level
992 valArgCount :: [Arg b] -> Int
993 valArgCount = count isValArg
997 %************************************************************************
999 \subsection{Seq stuff}
1001 %************************************************************************
1004 seqExpr :: CoreExpr -> ()
1005 seqExpr (Var v) = v `seq` ()
1006 seqExpr (Lit lit) = lit `seq` ()
1007 seqExpr (App f a) = seqExpr f `seq` seqExpr a
1008 seqExpr (Lam b e) = seqBndr b `seq` seqExpr e
1009 seqExpr (Let b e) = seqBind b `seq` seqExpr e
1010 seqExpr (Case e b t as) = seqExpr e `seq` seqBndr b `seq` seqType t `seq` seqAlts as
1011 seqExpr (Cast e co) = seqExpr e `seq` seqType co
1012 seqExpr (Note n e) = seqNote n `seq` seqExpr e
1013 seqExpr (Type t) = seqType t
1015 seqExprs :: [CoreExpr] -> ()
1017 seqExprs (e:es) = seqExpr e `seq` seqExprs es
1019 seqNote :: Note -> ()
1020 seqNote (CoreNote s) = s `seq` ()
1023 seqBndr :: CoreBndr -> ()
1024 seqBndr b = b `seq` ()
1026 seqBndrs :: [CoreBndr] -> ()
1028 seqBndrs (b:bs) = seqBndr b `seq` seqBndrs bs
1030 seqBind :: Bind CoreBndr -> ()
1031 seqBind (NonRec b e) = seqBndr b `seq` seqExpr e
1032 seqBind (Rec prs) = seqPairs prs
1034 seqPairs :: [(CoreBndr, CoreExpr)] -> ()
1036 seqPairs ((b,e):prs) = seqBndr b `seq` seqExpr e `seq` seqPairs prs
1038 seqAlts :: [CoreAlt] -> ()
1040 seqAlts ((c,bs,e):alts) = c `seq` seqBndrs bs `seq` seqExpr e `seq` seqAlts alts
1042 seqRules :: [CoreRule] -> ()
1044 seqRules (Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs } : rules)
1045 = seqBndrs bndrs `seq` seqExprs (rhs:args) `seq` seqRules rules
1046 seqRules (BuiltinRule {} : rules) = seqRules rules
1049 %************************************************************************
1051 \subsection{Annotated core}
1053 %************************************************************************
1056 -- | Annotated core: allows annotation at every node in the tree
1057 type AnnExpr bndr annot = (annot, AnnExpr' bndr annot)
1059 -- | A clone of the 'Expr' type but allowing annotation at every tree node
1060 data AnnExpr' bndr annot
1063 | AnnLam bndr (AnnExpr bndr annot)
1064 | AnnApp (AnnExpr bndr annot) (AnnExpr bndr annot)
1065 | AnnCase (AnnExpr bndr annot) bndr Type [AnnAlt bndr annot]
1066 | AnnLet (AnnBind bndr annot) (AnnExpr bndr annot)
1067 | AnnCast (AnnExpr bndr annot) Coercion
1068 | AnnNote Note (AnnExpr bndr annot)
1071 -- | A clone of the 'Alt' type but allowing annotation at every tree node
1072 type AnnAlt bndr annot = (AltCon, [bndr], AnnExpr bndr annot)
1074 -- | A clone of the 'Bind' type but allowing annotation at every tree node
1075 data AnnBind bndr annot
1076 = AnnNonRec bndr (AnnExpr bndr annot)
1077 | AnnRec [(bndr, AnnExpr bndr annot)]
1081 deAnnotate :: AnnExpr bndr annot -> Expr bndr
1082 deAnnotate (_, e) = deAnnotate' e
1084 deAnnotate' :: AnnExpr' bndr annot -> Expr bndr
1085 deAnnotate' (AnnType t) = Type t
1086 deAnnotate' (AnnVar v) = Var v
1087 deAnnotate' (AnnLit lit) = Lit lit
1088 deAnnotate' (AnnLam binder body) = Lam binder (deAnnotate body)
1089 deAnnotate' (AnnApp fun arg) = App (deAnnotate fun) (deAnnotate arg)
1090 deAnnotate' (AnnCast e co) = Cast (deAnnotate e) co
1091 deAnnotate' (AnnNote note body) = Note note (deAnnotate body)
1093 deAnnotate' (AnnLet bind body)
1094 = Let (deAnnBind bind) (deAnnotate body)
1096 deAnnBind (AnnNonRec var rhs) = NonRec var (deAnnotate rhs)
1097 deAnnBind (AnnRec pairs) = Rec [(v,deAnnotate rhs) | (v,rhs) <- pairs]
1099 deAnnotate' (AnnCase scrut v t alts)
1100 = Case (deAnnotate scrut) v t (map deAnnAlt alts)
1102 deAnnAlt :: AnnAlt bndr annot -> Alt bndr
1103 deAnnAlt (con,args,rhs) = (con,args,deAnnotate rhs)
1107 -- | As 'collectBinders' but for 'AnnExpr' rather than 'Expr'
1108 collectAnnBndrs :: AnnExpr bndr annot -> ([bndr], AnnExpr bndr annot)
1112 collect bs (_, AnnLam b body) = collect (b:bs) body
1113 collect bs body = (reverse bs, body)