tock-mirror/transformations/SimplifyExprs.hs

602 lines
26 KiB
Haskell

{-
Tock: a compiler for parallel languages
Copyright (C) 2007, 2008 University of Kent
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program. If not, see <http://www.gnu.org/licenses/>.
-}
-- | Simplify expressions in the AST.
module SimplifyExprs where
import Control.Monad.State
import Data.Generics
import qualified Data.Map as Map
import qualified AST as A
import CompState
import Errors
import EvalConstants
import Metadata
import Pass
import qualified Properties as Prop
import ShowCode
import Traversal
import Types
import Utils
simplifyExprs :: [Pass A.AST]
simplifyExprs =
[ functionsToProcs
, removeAfter
, expandArrayLiterals
, pullRepCounts
, pullUp False
, transformConstr
]
-- These are a special case, and do not get pulled up, nor turned into PROCs:
builtInOperatorFunction :: A.Name -> Bool
builtInOperatorFunction = (`elem` occamBuiltInOperatorFunctions) . A.nameName
-- | Convert FUNCTION declarations to PROCs.
functionsToProcs :: PassOn A.Specification
functionsToProcs = pass "Convert FUNCTIONs to PROCs"
(Prop.agg_namesDone ++ [Prop.expressionTypesChecked, Prop.parUsageChecked,
Prop.functionTypesChecked])
[Prop.functionsRemoved]
(applyBottomUpM doSpecification)
where
doSpecification :: A.Specification -> PassM A.Specification
doSpecification (A.Specification m n (A.Function mf smrm rts fs evp))
| not (builtInOperatorFunction n)
= do -- Create new names for the return values.
specs <- sequence [makeNonceVariable "return_formal" mf t A.Abbrev | t <- rts]
let names = [n | A.Specification mf n _ <- specs]
-- Note the return types so we can fix calls later.
modify $ (\ps -> ps { csFunctionReturns = Map.insert (A.nameName n) rts (csFunctionReturns ps) })
-- Turn the value process into an assignment process.
let p = fmap (vpToSeq m n [A.Variable mf n | n <- names]) evp
let st = A.Proc mf smrm (fs ++ [A.Formal A.Abbrev t n | (t, n) <- zip rts names]) p
-- Build a new specification and redefine the function.
let spec = A.Specification m n st
let nd = A.NameDef {
A.ndMeta = mf,
A.ndName = A.nameName n,
A.ndOrigName = A.nameName n,
A.ndSpecType = st,
A.ndAbbrevMode = A.Original,
A.ndNameSource = A.NameUser,
A.ndPlacement = A.Unplaced
}
defineName n nd
return spec
doSpecification s = return s
vpToSeq :: Meta -> A.Name -> [A.Variable] -> Either (A.Structured A.ExpressionList) A.Process -> A.Process
vpToSeq m n vs (Left el) = A.Seq m $ vpToSeq' el vs
vpToSeq _ n vs (Right p) = subst p
where
subst :: Data t => t -> t
subst = doGenericSubst `extT` doAssignSubst
doGenericSubst :: Data t => t -> t
doGenericSubst = gmapT subst `extT` (id :: String -> String) `extT` (id :: Meta -> Meta)
doAssignSubst :: A.Process -> A.Process
doAssignSubst ass@(A.Assign m [A.Variable _ dest] el) = if (A.nameName dest == A.nameName n) then (A.Assign m vs el) else ass
doAssignSubst p = doGenericSubst p
vpToSeq' :: A.Structured A.ExpressionList -> [A.Variable] -> A.Structured A.Process
vpToSeq' (A.Spec m spec s) vs = A.Spec m spec (vpToSeq' s vs)
vpToSeq' (A.ProcThen m p s) vs = A.ProcThen m p (vpToSeq' s vs)
vpToSeq' (A.Only m el) vs = A.Only m $ A.Assign m vs el
-- | Convert AFTER expressions to the equivalent using MINUS (which is how the
-- occam 3 manual defines AFTER).
removeAfter :: PassOn2 A.Expression A.ExpressionList
removeAfter = pass "Convert AFTER to MINUS"
[Prop.expressionTypesChecked]
[Prop.afterRemoved]
(applyBottomUpM2 doExpression doExpressionList)
where
doFunctionCall :: (Meta -> A.Name -> [A.Expression] -> a)
-> Meta -> A.Name -> [A.Expression] -> PassM a
doFunctionCall f m n args
= do mOp <- builtInOperator n
ts <- mapM astTypeOf args
let op s = A.Name (A.nameMeta n) $ occamDefaultOperator s ts
case mOp of
Just "AFTER"
| A.nameName n == occamDefaultOperator "AFTER" [A.Byte, A.Byte] ->
let one = A.Literal m A.Byte $ A.IntLiteral m "1"
oneTwoSeven = A.Literal m A.Byte $ A.IntLiteral m "127"
in return $ f m (op "<")
[A.FunctionCall m (op "MINUS")
[A.FunctionCall m (op "MINUS") args
, one]
,oneTwoSeven]
| otherwise
-> let zero = A.Literal m (head ts) $ A.IntLiteral m "0"
in return $ f m (op ">") [A.FunctionCall m (op "MINUS") args, zero]
_ -> return $ f m n args
doExpression :: A.Expression -> PassM A.Expression
doExpression e@(A.FunctionCall m n args)
= doFunctionCall A.FunctionCall m n args
doExpression e = return e
doExpressionList :: A.ExpressionList -> PassM A.ExpressionList
doExpressionList e@(A.FunctionCallList m n args)
= doFunctionCall A.FunctionCallList m n args
doExpressionList e = return e
-- | For array literals that include other arrays, burst them into their
-- elements.
expandArrayLiterals :: PassOn (A.Structured A.Expression)
expandArrayLiterals = pass "Expand array literals"
[Prop.expressionTypesChecked, Prop.processTypesChecked]
[Prop.arrayLiteralsExpanded]
(applyBottomUpM doArrayElem)
where
doArrayElem :: A.Structured A.Expression -> PassM (A.Structured A.Expression)
doArrayElem ae@(A.Only _ e)
= do t <- astTypeOf e
case (t, e) of
(A.Array ds _, _) -> expand ds e
_ -> return ae
doArrayElem ae = return ae
expand :: [A.Dimension] -> A.Expression -> PassM (A.Structured A.Expression)
expand [] e = return $ A.Only (findMeta e) e
expand (A.UnknownDimension:_) e
= dieP (findMeta e) "array literal containing non-literal array of unknown size"
expand (A.Dimension n:ds) e
= do -- Because it's an array literal, we must know the size.
size <- evalIntExpression n
elems <- sequence [case e of
A.Literal _ _ (A.ArrayListLiteral _ (A.Several _ ls)) ->
return $ ls !! i
_ -> expand ds (A.SubscriptedExpr m
(A.Subscript m A.NoCheck $
makeConstant m i) e)
| i <- [0 .. size - 1]]
return $ A.Several (findMeta e) elems
where m = findMeta e
-- | We pull up the loop (Rep) counts into a temporary expression, whenever the loop
-- count could be modified within the loop. Here are all things that can be replicated:
-- SEQ -- can be altered during the loop, must pull up
-- PAR -- count cannot be modified by code inside the loop (it is used before any PAR branches are run)
-- BUT since we implement replicated pars using a loop that forks off those
-- processes, it seems safest to pull up
-- IF -- cannot be altered during loop; once body executes, loop is effectively broken
-- ALT -- same as IF
-- BUT the programmer could offer to read into the replication count, which
-- could cause all sorts of horrendous problems, so pull up
-- Therefore, we only need to pull up the counts for SEQ, PAR and ALT
--
-- TODO for simplification, we could avoid pulling up replication counts that are known to be constants
--
-- TODO we should also pull up the step counts
pullRepCounts :: PassOn A.Process
pullRepCounts = pass "Pull up replicator counts for SEQs, PARs and ALTs"
(Prop.agg_namesDone ++ Prop.agg_typesDone)
[]
(applyBottomUpM pullRepCountProc)
where
pullRepCountStr :: Data a => Bool -> A.Structured a
-> StateT (A.Structured A.Process -> A.Structured A.Process)
PassM (A.Structured a)
pullRepCountStr addHere (A.Spec m (A.Specification mspec n (A.Rep mrep (A.For mfor
from for step))) scope)
= do t <- lift $ astTypeOf for
spec@(A.Specification _ nonceName _) <- lift $ makeNonceIsExpr "rep_for" mspec t for
let newRepSpec = (A.Rep mrep (A.For mfor from (A.ExprVariable mspec $ A.Variable mspec nonceName) step))
lift $ modifyName n $ \nd -> nd { A.ndSpecType = newRepSpec }
if addHere
then return $ A.Spec mspec spec $
A.Spec m (A.Specification mspec n newRepSpec) scope
else do modify (. A.Spec mspec spec)
return $ A.Spec m (A.Specification mspec n newRepSpec) scope
pullRepCountStr _ s = return s
pullRepCountProc :: Transform A.Process
pullRepCountProc (A.Alt m p body) = evalStateT (pullRepCountStr True body) id >>* A.Alt m p
pullRepCountProc (A.Seq m body) = evalStateT (pullRepCountStr True body) id >>* A.Seq m
pullRepCountProc (A.Par m p body)
= do (body', spec) <- runStateT (pullRepCountStr False body) id
return $ A.Seq m $ spec $ A.Only m $ A.Par m p body'
pullRepCountProc p = return p
transformConstr :: PassOnOps (ExtOpMSP BaseOp)
transformConstr = pass "Transform array constructors into initialisation code"
(Prop.agg_namesDone ++ Prop.agg_typesDone ++ [Prop.subscriptsPulledUp])
[Prop.arrayConstructorsRemoved]
(applyBottomUpMS doStructured)
where
-- For arrays, this takes a constructor expression:
-- VAL type name IS [i = rep | expr]:
-- ...
-- and produces this:
-- type name:
-- PROCTHEN
-- INT indexvar:
-- SEQ
-- indexvar := 0
-- SEQ i = rep
-- SEQ
-- name[indexvar] := expr
-- indexvar := indexvar + 1
-- ...
--
-- For lists, it takes the similar expression and produces:
-- type name:
-- PROCTHEN
-- SEQ i = rep
-- name += [expr]
doStructured :: Data a => A.Structured a -> PassM (A.Structured a)
doStructured (A.Spec m (A.Specification m' n (A.Is _ _ _
(A.ActualExpression expr@(A.Literal m'' t (A.ArrayListLiteral _ (A.Spec _ (A.Specification _
repn (A.Rep _ rep)) repExp)))))) scope)
= do case t of
A.Array {} ->
do indexVarSpec@(A.Specification _ indexName _) <- makeNonceVariable "array_constr_index" m'' A.Int A.Original
let indexVar = A.Variable m'' indexName
(repExp', specs) = stripSpecs repExp
tInner <- trivialSubscriptType m t
-- To avoid confusion in later passes, we must change the abbreviation
-- mode for this thing from ValAbbrev (which it must have been)
-- to Original, since we are now actually declaring it and assigning
-- to it:
modifyName n $ \nd -> nd {A.ndAbbrevMode = A.Original}
incIndex <- incrementIndex indexVar
let body = specs $ A.Several m''
[ assignItem tInner indexVar repExp'
, incIndex ]
body' <- applyBottomUpMS doStructured body
return $ declDest $ A.ProcThen m''
(A.Seq m'' $ A.Spec m'' indexVarSpec $
A.Several m'' [assignIndex0 indexVar,
replicateCode $ body'
])
scope
A.List {} ->
return $ declDest $ A.ProcThen m''
(A.Seq m'' $ replicateCode $ appendItem)
scope
_ -> diePC m $ formatCode "Unsupported type for array constructor: %" t
where
-- Also strips ProcThen
stripSpecs :: A.Structured A.Expression -> (A.Structured A.Expression,
A.Structured A.Process -> A.Structured A.Process)
stripSpecs (A.Spec m spec scope)
= let (result, innerSpecs) = stripSpecs scope in
(result, A.Spec m spec . innerSpecs)
stripSpecs (A.ProcThen m proc body)
= let (result, innerSpecs) = stripSpecs body in
(result, A.ProcThen m proc . innerSpecs)
stripSpecs se = (se, id)
declDest :: Data a => A.Structured a -> A.Structured a
declDest = A.Spec m (A.Specification m' n (A.Declaration m' t))
assignIndex0 :: A.Variable -> A.Structured A.Process
assignIndex0 indexVar = A.Only m'' $ A.Assign m'' [indexVar] $
A.ExpressionList m'' [A.Literal m'' A.Int $ A.IntLiteral m'' "0"]
incrementIndex :: A.Variable -> PassM (A.Structured A.Process)
incrementIndex indexVar
= do indexVar_plus1 <- addOne $ A.ExprVariable m'' indexVar
return $ A.Only m'' $ A.Assign m'' [indexVar] $ A.ExpressionList m'' [indexVar_plus1]
assignItem :: A.Type -> A.Variable -> A.Structured A.Expression -> A.Structured A.Process
assignItem t' indexVar repExp' = A.Only m'' $ A.Assign m'' [A.SubscriptedVariable m''
(A.Subscript m'' A.NoCheck $ A.ExprVariable m'' indexVar) $
A.Variable m'' n] $ A.ExpressionList m'' [
case repExp' of
A.Only _ e -> e
_ -> A.Literal m'' t' $ A.ArrayListLiteral m'' repExp'
]
appendItem :: A.Structured A.Process
appendItem = A.Only m'' $ A.Assign m'' [A.Variable m'' n] $
A.ExpressionList m'' [A.FunctionCall m'' (A.Name m'' "++")
[A.ExprVariable m'' $ A.Variable m'' n
,A.Literal m'' (let A.List tInner = t in tInner) $ A.ArrayListLiteral m'' repExp
]]
replicateCode :: Data a => A.Structured a -> A.Structured a
replicateCode = A.Spec m'' (A.Specification m'' repn (A.Rep m'' rep))
doStructured s = return s
type PullUpOps = ExtOpMSP BaseOp
`ExtOpMP` A.Process
`ExtOpMP` A.Structured A.Expression
`ExtOpMP` A.Specification
`ExtOpMP` A.LiteralRepr
`ExtOpMP` A.Expression
`ExtOpMP` A.Variable
`ExtOpMP` A.ExpressionList
-- | Find things that need to be moved up to their enclosing Structured, and do
-- so.
pullUp :: Bool -> PassOnOps PullUpOps
pullUp pullUpArraysInsideRecords = pass "Pull up definitions"
(Prop.agg_namesDone ++ Prop.agg_typesDone ++ [Prop.functionsRemoved, Prop.seqInputsFlattened])
[Prop.functionCallsRemoved, Prop.subscriptsPulledUp]
recurse
where
ops :: PullUpOps
ops = baseOp
`extOpMS` (ops, doStructured)
`extOpM` doProcess
`extOpM` doRepArray
`extOpM` doSpecification
`extOpM` doLiteralRepr
`extOpM` doExpression
`extOpM` doVariable
`extOpM` doExpressionList
recurse :: RecurseM PassM PullUpOps
recurse = makeRecurseM ops
descend :: DescendM PassM PullUpOps
descend = makeDescendM ops
-- | When we encounter a Structured, create a new pulled items state,
-- recurse over it, then apply whatever pulled items we found to it.
doStructured :: TransformStructured PullUpOps
doStructured s
= do pushPullContext
-- Recurse over the body, then apply the pulled items to it
s' <- descend s >>= applyPulled
-- ... and restore the original pulled items
popPullContext
return s'
doProcActual :: Transform A.Actual
doProcActual a@(A.ActualVariable {}) = descend a
doProcActual a@(A.ActualExpression {}) = descend a
-- Definitely pull up channel arrays and claims:
doProcActual a
= do a' <- recurse a
t <- astTypeOf a
spec@(A.Specification _ n' _)
<- defineNonce m "actual" (A.Is m A.Abbrev t a) A.Abbrev
addPulled (m, Left spec)
return $ A.ActualVariable (A.Variable m n')
where
m = findMeta a
-- | As with doStructured: when we find a process, create a new pulled items
-- context, and if we find any items apply them to it.
doProcess :: A.Process -> PassM A.Process
doProcess p
= do pushPullContext
p' <- case p of
A.ProcCall m n as
-> mapM doProcActual as >>* A.ProcCall m n
_ -> descend p
pulled <- havePulled
p'' <- if pulled
then liftM (A.Seq emptyMeta) $ applyPulled (A.Only emptyMeta p')
else return p'
popPullContext
return p''
-- | There are issues with array constructors. Consider:
-- [i = 0 FOR 10 | [i, i+1]]
-- You cannot pull the inner array literal up past the replicator,
-- because then i will not be in scope. So what we must do is
-- pull the array up to just inside the replicator (while pulling the whole
-- literal up as normal):
-- VAL array_expr_outer IS [i = 3 FOR 5 |
-- VAL array_expr_inner IS [i, i + 1]:
-- array_expr_inner]
-- Then when it is transformed later, it should become:
-- array_expr_outer:
-- PROCTHEN
-- INT array_constr_index:
-- SEQ
-- array_constr_index := 0
-- SEQ i = 3 FOR 5
-- VAL array_expr_inner IS [i, i + 1]:
-- SEQ
-- array_expr_outer[array_constr_index] := array_expr_inner -- itself flattened later!
-- array_constr_index := array_constr_index + 1
doRepArray :: A.Structured A.Expression -> PassM (A.Structured A.Expression)
doRepArray (A.Spec m spec@(A.Specification _ _ (A.Rep {})) scope)
= do -- We descend into the spec before we push a new context,
-- as anything in the spec should be pulled up to the outer context,
-- not inside the replicator
spec' <- descend spec
pushPullContext
scope' <- recurse scope >>= applyPulled
popPullContext
return $ A.Spec m spec' scope'
doRepArray s = descend s
-- | Filter what can be pulled in Specifications.
doSpecification :: A.Specification -> PassM A.Specification
-- Iss might be SubscriptedVars -- which is fine; the backend can deal with that.
doSpecification (A.Specification m n (A.Is m' am t (A.ActualVariable v)))
= do v' <- descend v -- note descend rather than pullUp
return $ A.Specification m n (A.Is m' am t $ A.ActualVariable v')
-- IsExprs might be SubscriptedExprs, and if so we have to convert them.
doSpecification (A.Specification m n (A.Is m' am t (A.ActualExpression e)))
= do e' <- doExpression' e -- note doExpression' rather than recurse
return $ A.Specification m n (A.Is m' am t $ A.ActualExpression e')
-- Convert RetypesExpr into Retypes of a variable.
doSpecification (A.Specification m n (A.RetypesExpr m' am toT e))
= do e' <- doExpression e
fromT <- astTypeOf e'
spec@(A.Specification _ n' _) <- makeNonceIsExpr "retypes_expr" m' fromT e'
addPulled $ (m', Left spec)
return $ A.Specification m n (A.Retypes m' am toT (A.Variable m' n'))
doSpecification s = descend s
-- | Filter what can be pulled in LiteralReprs.
doLiteralRepr :: A.LiteralRepr -> PassM A.LiteralRepr
-- FIXME: We could do away with ArrayElem and have a rule like the below
-- for nested array literals.
-- Don't pull up array expressions that are fields of record literals.
doLiteralRepr (A.RecordLiteral m es)
= do es' <- mapM (if pullUpArraysInsideRecords then doExpression else doExpression') es -- note doExpression' rather than recurse
return $ A.RecordLiteral m es'
doLiteralRepr lr = descend lr
-- | Pull array expressions that aren't already non-subscripted variables.
-- Also pull lists that are literals or constructed
doExpression :: A.Expression -> PassM A.Expression
-- For is-defined, we don't want to pull up:
doExpression e@(A.IsDefined {}) = return e
doExpression e
-- This part handles recursing into the expression first:
= do e' <- doExpression' e
t <- astTypeOf e'
case t of
A.Array _ _ ->
case e' of
A.ExprVariable _ (A.Variable _ _) -> return e'
A.ExprVariable _ (A.DirectedVariable _ _ _) -> return e'
--TODO work out whether to pull up DerefVariable
_ -> pull t e'
A.List _ ->
case e' of
A.Literal {} -> pull t e'
_ -> return e'
A.Record _ ->
case e' of
A.Literal {} -> pull t e'
_ -> return e'
_ -> return e'
where
pull :: A.Type -> A.Expression -> PassM A.Expression
pull t e
= do let m = findMeta e
spec@(A.Specification _ n _) <- makeNonceIsExpr "array_expr" m t e
addPulled $ (m, Left spec)
return $ A.ExprVariable m (A.Variable m n)
-- | Pull any variable subscript that results in an array, or contains a slice.
doVariable :: A.Variable -> PassM A.Variable
doVariable v@(A.SubscriptedVariable m sub _)
= do v' <- if isSlice sub then descend v else descendAfterSubscripts v
t <- astTypeOf v'
case t of
A.Array _ _ ->
do origAM <- abbrevModeOfVariable v'
let am = makeAbbrevAM origAM
spec@(A.Specification _ n _) <- makeNonceIs "array_slice" m t am v'
addPulled $ (m, Left spec)
return $ A.Variable m n
_ -> return v'
where
descendAfterSubscripts (A.SubscriptedVariable m sub v) | not (isSlice sub)
= do sub' <- recurse sub
v' <- descendAfterSubscripts v
return $ A.SubscriptedVariable m sub' v'
descendAfterSubscripts v = doVariable v
isSlice (A.SubscriptFromFor {}) = True
isSlice (A.SubscriptFrom {}) = True
isSlice (A.SubscriptFor {}) = True
isSlice _ = False
doVariable v@(A.DirectedVariable m dir innerV)
= do t <- astTypeOf innerV
case t of
A.Array ds (A.Chan attr innerT) ->
do let ds' = [case d of
A.Dimension {} -> d
A.UnknownDimension -> A.Dimension $ A.ExprVariable m $
specificDimSize i innerV
| (d, i) <- zip ds [0..]]
spec@(A.Specification _ n _) <- makeNonceIs "dir_array" m
(A.Array ds' $ A.ChanEnd dir (dirAttr dir attr) innerT) A.Abbrev v
addPulled $ (m, Left spec)
return $ A.Variable m n
_ -> descend v
doVariable v@(A.DerefVariable m innerV)
= do t <- astTypeOf v
case t of
A.Array ds innerT ->
do let ds' = [case d of
A.Dimension {} -> d
A.UnknownDimension -> A.Dimension $ A.ExprVariable m $
specificDimSize i innerV
| (d, i) <- zip ds [0..]]
spec@(A.Specification _ n _) <- makeNonceIs "mob_array" m
(A.Array ds' innerT) A.Abbrev v
addPulled $ (m, Left spec)
return $ A.Variable m n
_ -> descend v
doVariable v@(A.VariableSizes m _)
= do v' <- descend v
t <- astTypeOf v'
spec@(A.Specification _ n _) <- makeNonceIs "sizes_array" m t A.ValAbbrev v'
addPulled $ (m, Left spec)
return $ A.Variable m n
doVariable v = descend v
-- | Convert a FUNCTION call into some variables and a PROC call.
convertFuncCall :: Meta -> A.Name -> [A.Expression] -> PassM [A.Variable]
convertFuncCall m n es
= do es' <- recurse es
ets <- sequence [astTypeOf e | e <- es']
ps <- get
rts <- case Map.lookup (A.nameName n) (csFunctionReturns ps) of
Nothing -> dieP m "Could not find function returns"
Just x -> return x
specs <- sequence [makeNonceVariable "return_actual" m t A.Original | t <- rts]
sequence_ [addPulled $ (m, Left spec) | spec <- specs]
let names = [n | A.Specification _ n _ <- specs]
let vars = [A.Variable m n | n <- names]
let call = A.ProcCall m n (map A.ActualExpression es' ++ map A.ActualVariable vars)
addPulled $ (m, Right call)
return vars
doExpression' :: A.Expression -> PassM A.Expression
-- Convert single-valued function calls.
doExpression' (A.FunctionCall m n es) | not $ builtInOperatorFunction n
= do [v] <- convertFuncCall m n es
return $ A.ExprVariable m v
-- Convert SubscriptedExprs into SubscriptedVariables.
doExpression' (A.SubscriptedExpr m s e)
= do e' <- recurse e
s' <- recurse s
t <- astTypeOf e'
spec@(A.Specification _ n _) <- makeNonceIsExpr "subscripted_expr" m t e'
addPulled $ (m, Left spec)
return $ A.ExprVariable m (A.SubscriptedVariable m s' (A.Variable m n))
doExpression' e = descend e
doExpressionList :: A.ExpressionList -> PassM A.ExpressionList
-- Convert multi-valued function calls.
doExpressionList (A.FunctionCallList m n es)
| not (builtInOperatorFunction n)
= do vs <- convertFuncCall m n es
return $ A.ExpressionList m [A.ExprVariable m v | v <- vs]
doExpressionList el = descend el