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%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[CoreSyn]{A data type for the Haskell compiler midsection}
\begin{code}
module CoreSyn (
Expr(..), Alt, Bind(..), AltCon(..), Arg, Note(..),
CoreExpr, CoreAlt, CoreBind, CoreArg, CoreBndr,
TaggedExpr, TaggedAlt, TaggedBind, TaggedArg, TaggedBndr(..),
mkLets, mkLams,
mkApps, mkTyApps, mkValApps, mkVarApps,
mkLit, mkIntLitInt, mkIntLit,
mkConApp,
varToCoreExpr,
isTyVar, isId, cmpAltCon, cmpAlt, ltAlt,
bindersOf, bindersOfBinds, rhssOfBind, rhssOfAlts,
collectBinders, collectTyBinders, collectValBinders, collectTyAndValBinders,
collectArgs,
coreExprCc,
flattenBinds,
isValArg, isTypeArg, valArgCount, valBndrCount, isRuntimeArg, isRuntimeVar,
-- Unfoldings
Unfolding(..), UnfoldingGuidance(..), -- Both abstract everywhere but in CoreUnfold.lhs
noUnfolding, evaldUnfolding, mkOtherCon,
unfoldingTemplate, maybeUnfoldingTemplate, otherCons,
isValueUnfolding, isEvaldUnfolding, isCheapUnfolding, isCompulsoryUnfolding,
hasUnfolding, hasSomeUnfolding, neverUnfold,
-- Seq stuff
seqExpr, seqExprs, seqUnfolding,
-- Annotated expressions
AnnExpr, AnnExpr'(..), AnnBind(..), AnnAlt,
deAnnotate, deAnnotate', deAnnAlt, collectAnnBndrs,
-- Core rules
CoreRule(..), -- CoreSubst, CoreTidy, CoreFVs, PprCore only
RuleName, seqRules,
isBuiltinRule, ruleName, isLocalRule, ruleIdName
) where
#include "HsVersions.h"
import StaticFlags ( opt_RuntimeTypes )
import CostCentre ( CostCentre, noCostCentre )
import Var ( Var, Id, TyVar, isTyVar, isId )
import Type ( Type, mkTyVarTy, seqType )
import Name ( Name )
import OccName ( OccName )
import Literal ( Literal, mkMachInt )
import DataCon ( DataCon, dataConWorkId, dataConTag )
import BasicTypes ( Activation )
import FastString
import Outputable
\end{code}
%************************************************************************
%* *
\subsection{The main data types}
%* *
%************************************************************************
These data types are the heart of the compiler
\begin{code}
infixl 8 `App` -- App brackets to the left
data Expr b -- "b" for the type of binders,
= Var Id
| Lit Literal
| App (Expr b) (Arg b)
| Lam b (Expr b)
| Let (Bind b) (Expr b)
| Case (Expr b) b Type [Alt b] -- Binder gets bound to value of scrutinee
-- Invariant: The list of alternatives is ALWAYS EXHAUSTIVE,
-- meaning that it covers all cases that can occur
-- See the example below
--
-- Invariant: The DEFAULT case must be *first*, if it occurs at all
-- Invariant: The remaining cases are in order of increasing
-- tag (for DataAlts)
-- lit (for LitAlts)
-- This makes finding the relevant constructor easy,
-- and makes comparison easier too
| Note Note (Expr b)
| Type Type -- This should only show up at the top
-- level of an Arg
-- An "exhausive" case does not necessarily mention all constructors:
-- data Foo = Red | Green | Blue
--
-- ...case x of
-- Red -> True
-- other -> f (case x of
-- Green -> ...
-- Blue -> ... )
-- The inner case does not need a Red alternative, because x can't be Red at
-- that program point.
type Arg b = Expr b -- Can be a Type
type Alt b = (AltCon, [b], Expr b) -- (DEFAULT, [], rhs) is the default alternative
data AltCon = DataAlt DataCon
| LitAlt Literal
| DEFAULT
deriving (Eq, Ord)
data Bind b = NonRec b (Expr b)
| Rec [(b, (Expr b))]
data Note
= SCC CostCentre
| Coerce
Type -- The to-type: type of whole coerce expression
Type -- The from-type: type of enclosed expression
| InlineCall -- Instructs simplifier to inline
-- the enclosed call
| InlineMe -- Instructs simplifer to treat the enclosed expression
-- as very small, and inline it at its call sites
| CoreNote String -- A generic core annotation, propagated but not used by GHC
-- NOTE: we also treat expressions wrapped in InlineMe as
-- 'cheap' and 'dupable' (in the sense of exprIsCheap, exprIsDupable)
-- What this means is that we obediently inline even things that don't
-- look like valuse. This is sometimes important:
-- {-# INLINE f #-}
-- f = g . h
-- Here, f looks like a redex, and we aren't going to inline (.) because it's
-- inside an INLINE, so it'll stay looking like a redex. Nevertheless, we
-- should inline f even inside lambdas. In effect, we should trust the programmer.
\end{code}
INVARIANTS:
* The RHS of a letrec, and the RHSs of all top-level lets,
must be of LIFTED type.
* The RHS of a let, may be of UNLIFTED type, but only if the expression
is ok-for-speculation. This means that the let can be floated around
without difficulty. e.g.
y::Int# = x +# 1# ok
y::Int# = fac 4# not ok [use case instead]
* The argument of an App can be of any type.
* The simplifier tries to ensure that if the RHS of a let is a constructor
application, its arguments are trivial, so that the constructor can be
inlined vigorously.
%************************************************************************
%* *
\subsection{Transformation rules}
%* *
%************************************************************************
The CoreRule type and its friends are dealt with mainly in CoreRules,
but CoreFVs, Subst, PprCore, CoreTidy also inspect the representation.
A Rule is
"local" if the function it is a rule for is defined in the
same module as the rule itself.
"orphan" if nothing on the LHS is defined in the same module
as the rule itself
\begin{code}
type RuleName = FastString
data CoreRule
= Rule {
ru_name :: RuleName,
ru_act :: Activation, -- When the rule is active
-- Rough-matching stuff
-- see comments with InstEnv.Instance( is_cls, is_rough )
ru_fn :: Name, -- Name of the Id at the head of this rule
ru_rough :: [Maybe Name], -- Name at the head of each argument
-- Proper-matching stuff
-- see comments with InstEnv.Instance( is_tvs, is_tys )
ru_bndrs :: [CoreBndr], -- Forall'd variables
ru_args :: [CoreExpr], -- LHS args
-- And the right-hand side
ru_rhs :: CoreExpr,
-- Locality
ru_local :: Bool, -- The fn at the head of the rule is
-- defined in the same module as the rule
-- Orphan-hood; see comments is InstEnv.Instance( is_orph )
ru_orph :: Maybe OccName }
| BuiltinRule { -- Built-in rules are used for constant folding
ru_name :: RuleName, -- and suchlike. It has no free variables.
ru_fn :: Name, -- Name of the Id at
-- the head of this rule
ru_try :: [CoreExpr] -> Maybe CoreExpr }
isBuiltinRule (BuiltinRule {}) = True
isBuiltinRule _ = False
ruleName :: CoreRule -> RuleName
ruleName = ru_name
ruleIdName :: CoreRule -> Name
ruleIdName = ru_fn
isLocalRule :: CoreRule -> Bool
isLocalRule = ru_local
\end{code}
%************************************************************************
%* *
Unfoldings
%* *
%************************************************************************
The @Unfolding@ type is declared here to avoid numerous loops, but it
should be abstract everywhere except in CoreUnfold.lhs
\begin{code}
data Unfolding
= NoUnfolding
| OtherCon [AltCon] -- It ain't one of these
-- (OtherCon xs) also indicates that something has been evaluated
-- and hence there's no point in re-evaluating it.
-- OtherCon [] is used even for non-data-type values
-- to indicated evaluated-ness. Notably:
-- data C = C !(Int -> Int)
-- case x of { C f -> ... }
-- Here, f gets an OtherCon [] unfolding.
| CompulsoryUnfolding CoreExpr -- There is no "original" definition,
-- so you'd better unfold.
| CoreUnfolding -- An unfolding with redundant cached information
CoreExpr -- Template; binder-info is correct
Bool -- True <=> top level binding
Bool -- exprIsHNF template (cached); it is ok to discard a `seq` on
-- this variable
Bool -- True <=> doesn't waste (much) work to expand inside an inlining
-- Basically it's exprIsCheap
UnfoldingGuidance -- Tells about the *size* of the template.
data UnfoldingGuidance
= UnfoldNever
| UnfoldIfGoodArgs Int -- and "n" value args
[Int] -- Discount if the argument is evaluated.
-- (i.e., a simplification will definitely
-- be possible). One elt of the list per *value* arg.
Int -- The "size" of the unfolding; to be elaborated
-- later. ToDo
Int -- Scrutinee discount: the discount to substract if the thing is in
-- a context (case (thing args) of ...),
-- (where there are the right number of arguments.)
noUnfolding = NoUnfolding
evaldUnfolding = OtherCon []
mkOtherCon = OtherCon
seqUnfolding :: Unfolding -> ()
seqUnfolding (CoreUnfolding e top b1 b2 g)
= seqExpr e `seq` top `seq` b1 `seq` b2 `seq` seqGuidance g
seqUnfolding other = ()
seqGuidance (UnfoldIfGoodArgs n ns a b) = n `seq` sum ns `seq` a `seq` b `seq` ()
seqGuidance other = ()
\end{code}
\begin{code}
unfoldingTemplate :: Unfolding -> CoreExpr
unfoldingTemplate (CoreUnfolding expr _ _ _ _) = expr
unfoldingTemplate (CompulsoryUnfolding expr) = expr
unfoldingTemplate other = panic "getUnfoldingTemplate"
maybeUnfoldingTemplate :: Unfolding -> Maybe CoreExpr
maybeUnfoldingTemplate (CoreUnfolding expr _ _ _ _) = Just expr
maybeUnfoldingTemplate (CompulsoryUnfolding expr) = Just expr
maybeUnfoldingTemplate other = Nothing
otherCons :: Unfolding -> [AltCon]
otherCons (OtherCon cons) = cons
otherCons other = []
isValueUnfolding :: Unfolding -> Bool
-- Returns False for OtherCon
isValueUnfolding (CoreUnfolding _ _ is_evald _ _) = is_evald
isValueUnfolding other = False
isEvaldUnfolding :: Unfolding -> Bool
-- Returns True for OtherCon
isEvaldUnfolding (OtherCon _) = True
isEvaldUnfolding (CoreUnfolding _ _ is_evald _ _) = is_evald
isEvaldUnfolding other = False
isCheapUnfolding :: Unfolding -> Bool
isCheapUnfolding (CoreUnfolding _ _ _ is_cheap _) = is_cheap
isCheapUnfolding other = False
isCompulsoryUnfolding :: Unfolding -> Bool
isCompulsoryUnfolding (CompulsoryUnfolding _) = True
isCompulsoryUnfolding other = False
hasUnfolding :: Unfolding -> Bool
hasUnfolding (CoreUnfolding _ _ _ _ _) = True
hasUnfolding (CompulsoryUnfolding _) = True
hasUnfolding other = False
hasSomeUnfolding :: Unfolding -> Bool
hasSomeUnfolding NoUnfolding = False
hasSomeUnfolding other = True
neverUnfold :: Unfolding -> Bool
neverUnfold NoUnfolding = True
neverUnfold (OtherCon _) = True
neverUnfold (CoreUnfolding _ _ _ _ UnfoldNever) = True
neverUnfold other = False
\end{code}
%************************************************************************
%* *
\subsection{The main data type}
%* *
%************************************************************************
\begin{code}
-- The Ord is needed for the FiniteMap used in the lookForConstructor
-- in SimplEnv. If you declared that lookForConstructor *ignores*
-- constructor-applications with LitArg args, then you could get
-- rid of this Ord.
instance Outputable AltCon where
ppr (DataAlt dc) = ppr dc
ppr (LitAlt lit) = ppr lit
ppr DEFAULT = ptext SLIT("__DEFAULT")
instance Show AltCon where
showsPrec p con = showsPrecSDoc p (ppr con)
cmpAlt :: Alt b -> Alt b -> Ordering
cmpAlt (con1, _, _) (con2, _, _) = con1 `cmpAltCon` con2
ltAlt :: Alt b -> Alt b -> Bool
ltAlt a1 a2 = case a1 `cmpAlt` a2 of { LT -> True; other -> False }
cmpAltCon :: AltCon -> AltCon -> Ordering
-- Compares AltCons within a single list of alternatives
cmpAltCon DEFAULT DEFAULT = EQ
cmpAltCon DEFAULT con = LT
cmpAltCon (DataAlt d1) (DataAlt d2) = dataConTag d1 `compare` dataConTag d2
cmpAltCon (DataAlt _) DEFAULT = GT
cmpAltCon (LitAlt l1) (LitAlt l2) = l1 `compare` l2
cmpAltCon (LitAlt _) DEFAULT = GT
cmpAltCon con1 con2 = WARN( True, text "Comparing incomparable AltCons" <+>
ppr con1 <+> ppr con2 )
LT
\end{code}
%************************************************************************
%* *
\subsection{Useful synonyms}
%* *
%************************************************************************
The common case
\begin{code}
type CoreBndr = Var
type CoreExpr = Expr CoreBndr
type CoreArg = Arg CoreBndr
type CoreBind = Bind CoreBndr
type CoreAlt = Alt CoreBndr
\end{code}
Binders are ``tagged'' with a \tr{t}:
\begin{code}
data TaggedBndr t = TB CoreBndr t -- TB for "tagged binder"
type TaggedBind t = Bind (TaggedBndr t)
type TaggedExpr t = Expr (TaggedBndr t)
type TaggedArg t = Arg (TaggedBndr t)
type TaggedAlt t = Alt (TaggedBndr t)
instance Outputable b => Outputable (TaggedBndr b) where
ppr (TB b l) = char '<' <> ppr b <> comma <> ppr l <> char '>'
instance Outputable b => OutputableBndr (TaggedBndr b) where
pprBndr _ b = ppr b -- Simple
\end{code}
%************************************************************************
%* *
\subsection{Core-constructing functions with checking}
%* *
%************************************************************************
\begin{code}
mkApps :: Expr b -> [Arg b] -> Expr b
mkTyApps :: Expr b -> [Type] -> Expr b
mkValApps :: Expr b -> [Expr b] -> Expr b
mkVarApps :: Expr b -> [Var] -> Expr b
mkApps f args = foldl App f args
mkTyApps f args = foldl (\ e a -> App e (Type a)) f args
mkValApps f args = foldl (\ e a -> App e a) f args
mkVarApps f vars = foldl (\ e a -> App e (varToCoreExpr a)) f vars
mkLit :: Literal -> Expr b
mkIntLit :: Integer -> Expr b
mkIntLitInt :: Int -> Expr b
mkConApp :: DataCon -> [Arg b] -> Expr b
mkLets :: [Bind b] -> Expr b -> Expr b
mkLams :: [b] -> Expr b -> Expr b
mkLit lit = Lit lit
mkConApp con args = mkApps (Var (dataConWorkId con)) args
mkLams binders body = foldr Lam body binders
mkLets binds body = foldr Let body binds
mkIntLit n = Lit (mkMachInt n)
mkIntLitInt n = Lit (mkMachInt (toInteger n))
varToCoreExpr :: CoreBndr -> Expr b
varToCoreExpr v | isId v = Var v
| otherwise = Type (mkTyVarTy v)
\end{code}
%************************************************************************
%* *
\subsection{Simple access functions}
%* *
%************************************************************************
\begin{code}
bindersOf :: Bind b -> [b]
bindersOf (NonRec binder _) = [binder]
bindersOf (Rec pairs) = [binder | (binder, _) <- pairs]
bindersOfBinds :: [Bind b] -> [b]
bindersOfBinds binds = foldr ((++) . bindersOf) [] binds
rhssOfBind :: Bind b -> [Expr b]
rhssOfBind (NonRec _ rhs) = [rhs]
rhssOfBind (Rec pairs) = [rhs | (_,rhs) <- pairs]
rhssOfAlts :: [Alt b] -> [Expr b]
rhssOfAlts alts = [e | (_,_,e) <- alts]
flattenBinds :: [Bind b] -> [(b, Expr b)] -- Get all the lhs/rhs pairs
flattenBinds (NonRec b r : binds) = (b,r) : flattenBinds binds
flattenBinds (Rec prs1 : binds) = prs1 ++ flattenBinds binds
flattenBinds [] = []
\end{code}
We often want to strip off leading lambdas before getting down to
business. @collectBinders@ is your friend.
We expect (by convention) type-, and value- lambdas in that
order.
\begin{code}
collectBinders :: Expr b -> ([b], Expr b)
collectTyBinders :: CoreExpr -> ([TyVar], CoreExpr)
collectValBinders :: CoreExpr -> ([Id], CoreExpr)
collectTyAndValBinders :: CoreExpr -> ([TyVar], [Id], CoreExpr)
collectBinders expr
= go [] expr
where
go bs (Lam b e) = go (b:bs) e
go bs e = (reverse bs, e)
collectTyAndValBinders expr
= (tvs, ids, body)
where
(tvs, body1) = collectTyBinders expr
(ids, body) = collectValBinders body1
collectTyBinders expr
= go [] expr
where
go tvs (Lam b e) | isTyVar b = go (b:tvs) e
go tvs e = (reverse tvs, e)
collectValBinders expr
= go [] expr
where
go ids (Lam b e) | isId b = go (b:ids) e
go ids body = (reverse ids, body)
\end{code}
@collectArgs@ takes an application expression, returning the function
and the arguments to which it is applied.
\begin{code}
collectArgs :: Expr b -> (Expr b, [Arg b])
collectArgs expr
= go expr []
where
go (App f a) as = go f (a:as)
go e as = (e, as)
\end{code}
coreExprCc gets the cost centre enclosing an expression, if any.
It looks inside lambdas because (scc "foo" \x.e) = \x.scc "foo" e
\begin{code}
coreExprCc :: Expr b -> CostCentre
coreExprCc (Note (SCC cc) e) = cc
coreExprCc (Note other_note e) = coreExprCc e
coreExprCc (Lam _ e) = coreExprCc e
coreExprCc other = noCostCentre
\end{code}
%************************************************************************
%* *
\subsection{Predicates}
%* *
%************************************************************************
@isRuntimeVar v@ returns if (Lam v _) really becomes a lambda at runtime,
i.e. if type applications are actual lambdas because types are kept around
at runtime.
Similarly isRuntimeArg.
\begin{code}
isRuntimeVar :: Var -> Bool
isRuntimeVar | opt_RuntimeTypes = \v -> True
| otherwise = \v -> isId v
isRuntimeArg :: CoreExpr -> Bool
isRuntimeArg | opt_RuntimeTypes = \e -> True
| otherwise = \e -> isValArg e
\end{code}
\begin{code}
isValArg (Type _) = False
isValArg other = True
isTypeArg (Type _) = True
isTypeArg other = False
valBndrCount :: [CoreBndr] -> Int
valBndrCount [] = 0
valBndrCount (b : bs) | isId b = 1 + valBndrCount bs
| otherwise = valBndrCount bs
valArgCount :: [Arg b] -> Int
valArgCount [] = 0
valArgCount (Type _ : args) = valArgCount args
valArgCount (other : args) = 1 + valArgCount args
\end{code}
%************************************************************************
%* *
\subsection{Seq stuff}
%* *
%************************************************************************
\begin{code}
seqExpr :: CoreExpr -> ()
seqExpr (Var v) = v `seq` ()
seqExpr (Lit lit) = lit `seq` ()
seqExpr (App f a) = seqExpr f `seq` seqExpr a
seqExpr (Lam b e) = seqBndr b `seq` seqExpr e
seqExpr (Let b e) = seqBind b `seq` seqExpr e
-- gaw 2004
seqExpr (Case e b t as) = seqExpr e `seq` seqBndr b `seq` seqType t `seq` seqAlts as
seqExpr (Note n e) = seqNote n `seq` seqExpr e
seqExpr (Type t) = seqType t
seqExprs [] = ()
seqExprs (e:es) = seqExpr e `seq` seqExprs es
seqNote (Coerce t1 t2) = seqType t1 `seq` seqType t2
seqNote (CoreNote s) = s `seq` ()
seqNote other = ()
seqBndr b = b `seq` ()
seqBndrs [] = ()
seqBndrs (b:bs) = seqBndr b `seq` seqBndrs bs
seqBind (NonRec b e) = seqBndr b `seq` seqExpr e
seqBind (Rec prs) = seqPairs prs
seqPairs [] = ()
seqPairs ((b,e):prs) = seqBndr b `seq` seqExpr e `seq` seqPairs prs
seqAlts [] = ()
seqAlts ((c,bs,e):alts) = seqBndrs bs `seq` seqExpr e `seq` seqAlts alts
seqRules [] = ()
seqRules (Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs } : rules)
= seqBndrs bndrs `seq` seqExprs (rhs:args) `seq` seqRules rules
seqRules (BuiltinRule {} : rules) = seqRules rules
\end{code}
%************************************************************************
%* *
\subsection{Annotated core; annotation at every node in the tree}
%* *
%************************************************************************
\begin{code}
type AnnExpr bndr annot = (annot, AnnExpr' bndr annot)
data AnnExpr' bndr annot
= AnnVar Id
| AnnLit Literal
| AnnLam bndr (AnnExpr bndr annot)
| AnnApp (AnnExpr bndr annot) (AnnExpr bndr annot)
-- gaw 2004
| AnnCase (AnnExpr bndr annot) bndr Type [AnnAlt bndr annot]
| AnnLet (AnnBind bndr annot) (AnnExpr bndr annot)
| AnnNote Note (AnnExpr bndr annot)
| AnnType Type
type AnnAlt bndr annot = (AltCon, [bndr], AnnExpr bndr annot)
data AnnBind bndr annot
= AnnNonRec bndr (AnnExpr bndr annot)
| AnnRec [(bndr, AnnExpr bndr annot)]
\end{code}
\begin{code}
deAnnotate :: AnnExpr bndr annot -> Expr bndr
deAnnotate (_, e) = deAnnotate' e
deAnnotate' (AnnType t) = Type t
deAnnotate' (AnnVar v) = Var v
deAnnotate' (AnnLit lit) = Lit lit
deAnnotate' (AnnLam binder body) = Lam binder (deAnnotate body)
deAnnotate' (AnnApp fun arg) = App (deAnnotate fun) (deAnnotate arg)
deAnnotate' (AnnNote note body) = Note note (deAnnotate body)
deAnnotate' (AnnLet bind body)
= Let (deAnnBind bind) (deAnnotate body)
where
deAnnBind (AnnNonRec var rhs) = NonRec var (deAnnotate rhs)
deAnnBind (AnnRec pairs) = Rec [(v,deAnnotate rhs) | (v,rhs) <- pairs]
-- gaw 2004
deAnnotate' (AnnCase scrut v t alts)
= Case (deAnnotate scrut) v t (map deAnnAlt alts)
deAnnAlt :: AnnAlt bndr annot -> Alt bndr
deAnnAlt (con,args,rhs) = (con,args,deAnnotate rhs)
\end{code}
\begin{code}
collectAnnBndrs :: AnnExpr bndr annot -> ([bndr], AnnExpr bndr annot)
collectAnnBndrs e
= collect [] e
where
collect bs (_, AnnLam b body) = collect (b:bs) body
collect bs body = (reverse bs, body)
\end{code}
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