{-# LANGUAGE TypeFamilies #-}

-- | The IR tracks aliases, mostly to ensure the soundness of in-place
-- updates, but it can also be used for other things (such as memory
-- optimisations).  This module contains the raw building blocks for
-- determining the aliases of the values produced by expressions.  It
-- also contains some building blocks for inspecting consumption.
--
-- One important caveat is that all aliases computed here are /local/.
-- Thus, they do not take aliases-of-aliases into account.  See
-- "Futhark.Analysis.Alias" if this is not what you want.
module Futhark.IR.Prop.Aliases
  ( subExpAliases,
    expAliases,
    patAliases,
    lookupAliases,
    Aliased (..),
    AliasesOf (..),

    -- * Consumption
    consumedInStm,
    consumedInExp,
    consumedByLambda,

    -- * Extensibility
    AliasTable,
    AliasedOp (..),
    CanBeAliased (..),
  )
where

import Data.Bifunctor (first, second)
import Data.Kind qualified
import Data.List (find, transpose)
import Data.Map qualified as M
import Futhark.IR.Prop (IsOp, NameInfo (..), Scope)
import Futhark.IR.Prop.Names
import Futhark.IR.Prop.Patterns
import Futhark.IR.Prop.Types
import Futhark.IR.Syntax

-- | The class of representations that contain aliasing information.
class (RepTypes rep, AliasedOp (Op rep), AliasesOf (LetDec rep)) => Aliased rep where
  -- | The aliases of the body results.
  bodyAliases :: Body rep -> [Names]

  -- | The variables consumed in the body.
  consumedInBody :: Body rep -> Names

vnameAliases :: VName -> Names
vnameAliases :: VName -> Names
vnameAliases = VName -> Names
oneName

-- | The aliases of a subexpression.
subExpAliases :: SubExp -> Names
subExpAliases :: SubExp -> Names
subExpAliases Constant {} = forall a. Monoid a => a
mempty
subExpAliases (Var VName
v) = VName -> Names
vnameAliases VName
v

basicOpAliases :: BasicOp -> [Names]
basicOpAliases :: BasicOp -> [Names]
basicOpAliases (SubExp SubExp
se) = [SubExp -> Names
subExpAliases SubExp
se]
basicOpAliases (Opaque OpaqueOp
_ SubExp
se) = [SubExp -> Names
subExpAliases SubExp
se]
basicOpAliases (ArrayLit [SubExp]
_ Type
_) = [forall a. Monoid a => a
mempty]
basicOpAliases BinOp {} = [forall a. Monoid a => a
mempty]
basicOpAliases ConvOp {} = [forall a. Monoid a => a
mempty]
basicOpAliases CmpOp {} = [forall a. Monoid a => a
mempty]
basicOpAliases UnOp {} = [forall a. Monoid a => a
mempty]
basicOpAliases (Index VName
ident Slice SubExp
_) = [VName -> Names
vnameAliases VName
ident]
basicOpAliases Update {} = [forall a. Monoid a => a
mempty]
basicOpAliases (FlatIndex VName
ident FlatSlice SubExp
_) = [VName -> Names
vnameAliases VName
ident]
basicOpAliases FlatUpdate {} = [forall a. Monoid a => a
mempty]
basicOpAliases Iota {} = [forall a. Monoid a => a
mempty]
basicOpAliases Replicate {} = [forall a. Monoid a => a
mempty]
basicOpAliases Scratch {} = [forall a. Monoid a => a
mempty]
basicOpAliases (Reshape ReshapeKind
_ Shape
_ VName
e) = [VName -> Names
vnameAliases VName
e]
basicOpAliases (Rearrange [Int]
_ VName
e) = [VName -> Names
vnameAliases VName
e]
basicOpAliases (Rotate [SubExp]
_ VName
e) = [VName -> Names
vnameAliases VName
e]
basicOpAliases Concat {} = [forall a. Monoid a => a
mempty]
basicOpAliases Copy {} = [forall a. Monoid a => a
mempty]
basicOpAliases Manifest {} = [forall a. Monoid a => a
mempty]
basicOpAliases Assert {} = [forall a. Monoid a => a
mempty]
basicOpAliases UpdateAcc {} = [forall a. Monoid a => a
mempty]

matchAliases :: [([Names], Names)] -> [Names]
matchAliases :: [([Names], Names)] -> [Names]
matchAliases [([Names], Names)]
l =
  forall a b. (a -> b) -> [a] -> [b]
map ((Names -> Names -> Names
`namesSubtract` forall a. Monoid a => [a] -> a
mconcat [Names]
conses) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a. Monoid a => [a] -> a
mconcat) forall a b. (a -> b) -> a -> b
$ forall a. [[a]] -> [[a]]
transpose [[Names]]
alses
  where
    ([[Names]]
alses, [Names]
conses) = forall a b. [(a, b)] -> ([a], [b])
unzip [([Names], Names)]
l

funcallAliases :: [(SubExp, Diet)] -> [TypeBase shape Uniqueness] -> [Names]
funcallAliases :: forall shape.
[(SubExp, Diet)] -> [TypeBase shape Uniqueness] -> [Names]
funcallAliases [(SubExp, Diet)]
args [TypeBase shape Uniqueness]
t =
  forall shape.
[TypeBase shape Uniqueness] -> [(Names, Diet)] -> [Names]
returnAliases [TypeBase shape Uniqueness]
t [(SubExp -> Names
subExpAliases SubExp
se, Diet
d) | (SubExp
se, Diet
d) <- [(SubExp, Diet)]
args]

-- | The aliases of an expression, one per non-context value returned.
expAliases :: (Aliased rep) => Exp rep -> [Names]
expAliases :: forall {k} (rep :: k). Aliased rep => Exp rep -> [Names]
expAliases (Match [SubExp]
_ [Case (Body rep)]
cases Body rep
defbody MatchDec (BranchType rep)
_) =
  [([Names], Names)] -> [Names]
matchAliases forall a b. (a -> b) -> a -> b
$ forall {k} {rep :: k}. Aliased rep => Body rep -> ([Names], Names)
onBody Body rep
defbody forall a. a -> [a] -> [a]
: forall a b. (a -> b) -> [a] -> [b]
map (forall {k} {rep :: k}. Aliased rep => Body rep -> ([Names], Names)
onBody forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall body. Case body -> body
caseBody) [Case (Body rep)]
cases
  where
    onBody :: Body rep -> ([Names], Names)
onBody Body rep
body = (forall {k} (rep :: k). Aliased rep => Body rep -> [Names]
bodyAliases Body rep
body, forall {k} (rep :: k). Aliased rep => Body rep -> Names
consumedInBody Body rep
body)
expAliases (BasicOp BasicOp
op) = BasicOp -> [Names]
basicOpAliases BasicOp
op
expAliases (DoLoop [(FParam rep, SubExp)]
merge LoopForm rep
_ Body rep
loopbody) = do
  (FParam rep
p, Names
als) <-
    forall {dec}.
Eq dec =>
[(Param dec, Names)] -> [(Param dec, Names)]
transitive forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. [a] -> [b] -> [(a, b)]
zip [FParam rep]
params forall a b. (a -> b) -> a -> b
$ forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith forall a. Monoid a => a -> a -> a
mappend [Names]
arg_aliases (forall {k} (rep :: k). Aliased rep => Body rep -> [Names]
bodyAliases Body rep
loopbody)
  let als' :: Names
als' = Names
als Names -> Names -> Names
`namesSubtract` Names
param_names
  if forall shape. TypeBase shape Uniqueness -> Bool
unique forall a b. (a -> b) -> a -> b
$ forall dec. DeclTyped dec => Param dec -> DeclType
paramDeclType FParam rep
p
    then forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a. Monoid a => a
mempty
    else forall (f :: * -> *) a. Applicative f => a -> f a
pure Names
als'
  where
    arg_aliases :: [Names]
arg_aliases = forall a b. (a -> b) -> [a] -> [b]
map (SubExp -> Names
subExpAliases forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a, b) -> b
snd) [(FParam rep, SubExp)]
merge
    params :: [FParam rep]
params = forall a b. (a -> b) -> [a] -> [b]
map forall a b. (a, b) -> a
fst [(FParam rep, SubExp)]
merge
    param_names :: Names
param_names = [VName] -> Names
namesFromList forall a b. (a -> b) -> a -> b
$ forall a b. (a -> b) -> [a] -> [b]
map forall dec. Param dec -> VName
paramName [FParam rep]
params
    transitive :: [(Param dec, Names)] -> [(Param dec, Names)]
transitive [(Param dec, Names)]
merge_and_als =
      let merge_and_als' :: [(Param dec, Names)]
merge_and_als' = forall a b. (a -> b) -> [a] -> [b]
map (forall (p :: * -> * -> *) b c a.
Bifunctor p =>
(b -> c) -> p a b -> p a c
second Names -> Names
expand) [(Param dec, Names)]
merge_and_als
       in if [(Param dec, Names)]
merge_and_als' forall a. Eq a => a -> a -> Bool
== [(Param dec, Names)]
merge_and_als
            then [(Param dec, Names)]
merge_and_als
            else [(Param dec, Names)] -> [(Param dec, Names)]
transitive [(Param dec, Names)]
merge_and_als'
      where
        look :: VName -> Names
look VName
v = forall b a. b -> (a -> b) -> Maybe a -> b
maybe forall a. Monoid a => a
mempty forall a b. (a, b) -> b
snd forall a b. (a -> b) -> a -> b
$ forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Maybe a
find ((forall a. Eq a => a -> a -> Bool
== VName
v) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall dec. Param dec -> VName
paramName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a, b) -> a
fst) [(Param dec, Names)]
merge_and_als
        expand :: Names -> Names
expand Names
als = Names
als forall a. Semigroup a => a -> a -> a
<> forall (t :: * -> *) m a.
(Foldable t, Monoid m) =>
(a -> m) -> t a -> m
foldMap VName -> Names
look (Names -> [VName]
namesToList Names
als)
expAliases (Apply Name
_ [(SubExp, Diet)]
args [RetType rep]
t (Safety, SrcLoc, [SrcLoc])
_) =
  forall shape.
[(SubExp, Diet)] -> [TypeBase shape Uniqueness] -> [Names]
funcallAliases [(SubExp, Diet)]
args forall a b. (a -> b) -> a -> b
$ forall a b. (a -> b) -> [a] -> [b]
map forall t. DeclExtTyped t => t -> DeclExtType
declExtTypeOf [RetType rep]
t
expAliases (WithAcc [WithAccInput rep]
inputs Lambda rep
lam) =
  forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap forall {t :: * -> *} {a} {a} {a} {c}.
(Foldable t, Monoid a) =>
(a, t a, c) -> [a]
inputAliases [WithAccInput rep]
inputs forall a. [a] -> [a] -> [a]
++ forall a. Int -> [a] -> [a]
drop Int
num_accs (forall {k} (rep :: k). Aliased rep => Body rep -> [Names]
bodyAliases (forall {k} (rep :: k). Lambda rep -> Body rep
lambdaBody Lambda rep
lam))
  where
    inputAliases :: (a, t a, c) -> [a]
inputAliases (a
_, t a
arrs, c
_) = forall a. Int -> a -> [a]
replicate (forall (t :: * -> *) a. Foldable t => t a -> Int
length t a
arrs) forall a. Monoid a => a
mempty
    num_accs :: Int
num_accs = forall (t :: * -> *) a. Foldable t => t a -> Int
length [WithAccInput rep]
inputs
expAliases (Op Op rep
op) = forall op. AliasedOp op => op -> [Names]
opAliases Op rep
op

returnAliases :: [TypeBase shape Uniqueness] -> [(Names, Diet)] -> [Names]
returnAliases :: forall shape.
[TypeBase shape Uniqueness] -> [(Names, Diet)] -> [Names]
returnAliases [TypeBase shape Uniqueness]
rts [(Names, Diet)]
args = forall a b. (a -> b) -> [a] -> [b]
map TypeBase shape Uniqueness -> Names
returnType' [TypeBase shape Uniqueness]
rts
  where
    returnType' :: TypeBase shape Uniqueness -> Names
returnType' (Array PrimType
_ shape
_ Uniqueness
Nonunique) =
      forall a. Monoid a => [a] -> a
mconcat forall a b. (a -> b) -> a -> b
$ forall a b. (a -> b) -> [a] -> [b]
map (forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry Names -> Diet -> Names
maskAliases) [(Names, Diet)]
args
    returnType' (Array PrimType
_ shape
_ Uniqueness
Unique) =
      forall a. Monoid a => a
mempty
    returnType' (Prim PrimType
_) =
      forall a. Monoid a => a
mempty
    returnType' Acc {} =
      forall a. HasCallStack => [Char] -> a
error [Char]
"returnAliases Acc"
    returnType' Mem {} =
      forall a. Monoid a => [a] -> a
mconcat forall a b. (a -> b) -> a -> b
$ forall a b. (a -> b) -> [a] -> [b]
map (forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry Names -> Diet -> Names
maskAliases) [(Names, Diet)]
args

maskAliases :: Names -> Diet -> Names
maskAliases :: Names -> Diet -> Names
maskAliases Names
_ Diet
Consume = forall a. Monoid a => a
mempty
maskAliases Names
_ Diet
ObservePrim = forall a. Monoid a => a
mempty
maskAliases Names
als Diet
Observe = Names
als

-- | The variables consumed in this statement.
consumedInStm :: Aliased rep => Stm rep -> Names
consumedInStm :: forall {k} (rep :: k). Aliased rep => Stm rep -> Names
consumedInStm = forall {k} (rep :: k). Aliased rep => Exp rep -> Names
consumedInExp forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall {k} (rep :: k). Stm rep -> Exp rep
stmExp

-- | The variables consumed in this expression.
consumedInExp :: (Aliased rep) => Exp rep -> Names
consumedInExp :: forall {k} (rep :: k). Aliased rep => Exp rep -> Names
consumedInExp (Apply Name
_ [(SubExp, Diet)]
args [RetType rep]
_ (Safety, SrcLoc, [SrcLoc])
_) =
  forall a. Monoid a => [a] -> a
mconcat (forall a b. (a -> b) -> [a] -> [b]
map (forall {a}. Monoid a => (a, Diet) -> a
consumeArg forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall (p :: * -> * -> *) a b c.
Bifunctor p =>
(a -> b) -> p a c -> p b c
first SubExp -> Names
subExpAliases) [(SubExp, Diet)]
args)
  where
    consumeArg :: (a, Diet) -> a
consumeArg (a
als, Diet
Consume) = a
als
    consumeArg (a, Diet)
_ = forall a. Monoid a => a
mempty
consumedInExp (Match [SubExp]
_ [Case (Body rep)]
cases Body rep
defbody MatchDec (BranchType rep)
_) =
  forall (t :: * -> *) m a.
(Foldable t, Monoid m) =>
(a -> m) -> t a -> m
foldMap (forall {k} (rep :: k). Aliased rep => Body rep -> Names
consumedInBody forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall body. Case body -> body
caseBody) [Case (Body rep)]
cases forall a. Semigroup a => a -> a -> a
<> forall {k} (rep :: k). Aliased rep => Body rep -> Names
consumedInBody Body rep
defbody
consumedInExp (DoLoop [(FParam rep, SubExp)]
merge LoopForm rep
form Body rep
body) =
  forall a. Monoid a => [a] -> a
mconcat
    ( forall a b. (a -> b) -> [a] -> [b]
map (SubExp -> Names
subExpAliases forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a, b) -> b
snd) forall a b. (a -> b) -> a -> b
$
        forall a. (a -> Bool) -> [a] -> [a]
filter (forall shape. TypeBase shape Uniqueness -> Bool
unique forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall dec. DeclTyped dec => Param dec -> DeclType
paramDeclType forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a, b) -> a
fst) [(FParam rep, SubExp)]
merge
    )
    forall a. Semigroup a => a -> a -> a
<> LoopForm rep -> Names
consumedInForm LoopForm rep
form
  where
    body_consumed :: Names
body_consumed = forall {k} (rep :: k). Aliased rep => Body rep -> Names
consumedInBody Body rep
body
    varConsumed :: (Param (LParamInfo rep), VName) -> Bool
varConsumed = (VName -> Names -> Bool
`nameIn` Names
body_consumed) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall dec. Param dec -> VName
paramName forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (a, b) -> a
fst
    consumedInForm :: LoopForm rep -> Names
consumedInForm (ForLoop VName
_ IntType
_ SubExp
_ [(Param (LParamInfo rep), VName)]
loopvars) =
      [VName] -> Names
namesFromList forall a b. (a -> b) -> a -> b
$ forall a b. (a -> b) -> [a] -> [b]
map forall a b. (a, b) -> b
snd forall a b. (a -> b) -> a -> b
$ forall a. (a -> Bool) -> [a] -> [a]
filter (Param (LParamInfo rep), VName) -> Bool
varConsumed [(Param (LParamInfo rep), VName)]
loopvars
    consumedInForm WhileLoop {} =
      forall a. Monoid a => a
mempty
consumedInExp (WithAcc [WithAccInput rep]
inputs Lambda rep
lam) =
  forall a. Monoid a => [a] -> a
mconcat (forall a b. (a -> b) -> [a] -> [b]
map forall {a} {c}. (a, [VName], c) -> Names
inputConsumed [WithAccInput rep]
inputs)
    forall a. Semigroup a => a -> a -> a
<> ( forall {k} (rep :: k). Aliased rep => Lambda rep -> Names
consumedByLambda Lambda rep
lam
           Names -> Names -> Names
`namesSubtract` [VName] -> Names
namesFromList (forall a b. (a -> b) -> [a] -> [b]
map forall dec. Param dec -> VName
paramName (forall {k} (rep :: k). Lambda rep -> [LParam rep]
lambdaParams Lambda rep
lam))
       )
  where
    inputConsumed :: (a, [VName], c) -> Names
inputConsumed (a
_, [VName]
arrs, c
_) = [VName] -> Names
namesFromList [VName]
arrs
consumedInExp (BasicOp (Update Safety
_ VName
src Slice SubExp
_ SubExp
_)) = VName -> Names
oneName VName
src
consumedInExp (BasicOp (FlatUpdate VName
src FlatSlice SubExp
_ VName
_)) = VName -> Names
oneName VName
src
consumedInExp (BasicOp (UpdateAcc VName
acc [SubExp]
_ [SubExp]
_)) = VName -> Names
oneName VName
acc
consumedInExp (BasicOp BasicOp
_) = forall a. Monoid a => a
mempty
consumedInExp (Op Op rep
op) = forall op. AliasedOp op => op -> Names
consumedInOp Op rep
op

-- | The variables consumed by this lambda.
consumedByLambda :: Aliased rep => Lambda rep -> Names
consumedByLambda :: forall {k} (rep :: k). Aliased rep => Lambda rep -> Names
consumedByLambda = forall {k} (rep :: k). Aliased rep => Body rep -> Names
consumedInBody forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall {k} (rep :: k). Lambda rep -> Body rep
lambdaBody

-- | The aliases of each pattern element (including the context).
patAliases :: AliasesOf dec => Pat dec -> [Names]
patAliases :: forall dec. AliasesOf dec => Pat dec -> [Names]
patAliases = forall a b. (a -> b) -> [a] -> [b]
map (forall a. AliasesOf a => a -> Names
aliasesOf forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall dec. PatElem dec -> dec
patElemDec) forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall dec. Pat dec -> [PatElem dec]
patElems

-- | Something that contains alias information.
class AliasesOf a where
  -- | The alias of the argument element.
  aliasesOf :: a -> Names

instance AliasesOf Names where
  aliasesOf :: Names -> Names
aliasesOf = forall a. a -> a
id

instance AliasesOf dec => AliasesOf (PatElem dec) where
  aliasesOf :: PatElem dec -> Names
aliasesOf = forall a. AliasesOf a => a -> Names
aliasesOf forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall dec. PatElem dec -> dec
patElemDec

-- | Also includes the name itself.
lookupAliases :: AliasesOf (LetDec rep) => VName -> Scope rep -> Names
lookupAliases :: forall {k} (rep :: k).
AliasesOf (LetDec rep) =>
VName -> Scope rep -> Names
lookupAliases VName
v Scope rep
scope =
  case forall k a. Ord k => k -> Map k a -> Maybe a
M.lookup VName
v Scope rep
scope of
    Just (LetName LetDec rep
dec) ->
      VName -> Names
oneName VName
v forall a. Semigroup a => a -> a -> a
<> forall (t :: * -> *) m a.
(Foldable t, Monoid m) =>
(a -> m) -> t a -> m
foldMap (forall {k} (rep :: k).
AliasesOf (LetDec rep) =>
VName -> Scope rep -> Names
`lookupAliases` Scope rep
scope) (Names -> [VName]
namesToList (forall a. AliasesOf a => a -> Names
aliasesOf LetDec rep
dec))
    Maybe (NameInfo rep)
_ -> VName -> Names
oneName VName
v

-- | The class of operations that can produce aliasing and consumption
-- information.
class IsOp op => AliasedOp op where
  opAliases :: op -> [Names]
  consumedInOp :: op -> Names

instance AliasedOp () where
  opAliases :: () -> [Names]
opAliases () = []
  consumedInOp :: () -> Names
consumedInOp () = forall a. Monoid a => a
mempty

-- | Pre-existing aliases for variables.  Used to add transitive
-- aliases.
type AliasTable = M.Map VName Names

-- | The class of operations that can be given aliasing information.
-- This is a somewhat subtle concept that is only used in the
-- simplifier and when using "rep adapters".
class AliasedOp (OpWithAliases op) => CanBeAliased op where
  -- | The op that results when we add aliases to this op.
  type OpWithAliases op :: Data.Kind.Type

  -- | Remove aliases from this op.
  removeOpAliases :: OpWithAliases op -> op

  -- | Add aliases to this op.
  addOpAliases :: AliasTable -> op -> OpWithAliases op

instance CanBeAliased () where
  type OpWithAliases () = ()
  removeOpAliases :: OpWithAliases () -> ()
removeOpAliases = forall a. a -> a
id
  addOpAliases :: AliasTable -> () -> OpWithAliases ()
addOpAliases = forall a b. a -> b -> a
const forall a. a -> a
id