{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-}

{-# LANGUAGE CPP #-}
module CoreOpt (
        -- ** Simple expression optimiser
        simpleOptPgm, simpleOptExpr, simpleOptExprWith,

        -- ** Join points
        joinPointBinding_maybe, joinPointBindings_maybe,

        -- ** Predicates on expressions
        exprIsConApp_maybe, exprIsLiteral_maybe, exprIsLambda_maybe,

        -- ** Coercions and casts
        pushCoArg, pushCoValArg, pushCoTyArg, collectBindersPushingCo
    ) where

#include "HsVersions.h"

import GhcPrelude

import CoreArity( etaExpandToJoinPoint )

import CoreSyn
import CoreSubst
import CoreUtils
import CoreFVs
import {-#SOURCE #-} CoreUnfold ( mkUnfolding )
import MkCore ( FloatBind(..) )
import PprCore  ( pprCoreBindings, pprRules )
import OccurAnal( occurAnalyseExpr, occurAnalysePgm )
import Literal  ( Literal(LitString) )
import Id
import IdInfo   ( unfoldingInfo, setUnfoldingInfo, setRuleInfo, IdInfo (..) )
import Var      ( isNonCoVarId )
import VarSet
import VarEnv
import DataCon
import Demand( etaExpandStrictSig )
import OptCoercion ( optCoercion )
import Type     hiding ( substTy, extendTvSubst, extendCvSubst, extendTvSubstList
                       , isInScope, substTyVarBndr, cloneTyVarBndr )
import Coercion hiding ( substCo, substCoVarBndr )
import TyCon        ( tyConArity )
import TysWiredIn
import PrelNames
import BasicTypes
import Module       ( Module )
import ErrUtils
import DynFlags
import Outputable
import Pair
import Util
import Maybes       ( orElse )
import FastString
import Data.List
import qualified Data.ByteString as BS

{-
************************************************************************
*                                                                      *
        The Simple Optimiser
*                                                                      *
************************************************************************

Note [The simple optimiser]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The simple optimiser is a lightweight, pure (non-monadic) function
that rapidly does a lot of simple optimisations, including

  - inlining things that occur just once,
      or whose RHS turns out to be trivial
  - beta reduction
  - case of known constructor
  - dead code elimination

It does NOT do any call-site inlining; it only inlines a function if
it can do so unconditionally, dropping the binding.  It thereby
guarantees to leave no un-reduced beta-redexes.

It is careful to follow the guidance of "Secrets of the GHC inliner",
and in particular the pre-inline-unconditionally and
post-inline-unconditionally story, to do effective beta reduction on
functions called precisely once, without repeatedly optimising the same
expression.  In fact, the simple optimiser is a good example of this
little dance in action; the full Simplifier is a lot more complicated.

-}

simpleOptExpr :: DynFlags -> CoreExpr -> CoreExpr
-- See Note [The simple optimiser]
-- Do simple optimisation on an expression
-- The optimisation is very straightforward: just
-- inline non-recursive bindings that are used only once,
-- or where the RHS is trivial
--
-- We also inline bindings that bind a Eq# box: see
-- See Note [Getting the map/coerce RULE to work].
--
-- Also we convert functions to join points where possible (as
-- the occurrence analyser does most of the work anyway).
--
-- The result is NOT guaranteed occurrence-analysed, because
-- in  (let x = y in ....) we substitute for x; so y's occ-info
-- may change radically

simpleOptExpr :: DynFlags -> CoreExpr -> CoreExpr
simpleOptExpr DynFlags
dflags CoreExpr
expr
  = -- pprTrace "simpleOptExpr" (ppr init_subst $$ ppr expr)
    DynFlags -> Subst -> CoreExpr -> CoreExpr
simpleOptExprWith DynFlags
dflags Subst
init_subst CoreExpr
expr
  where
    init_subst :: Subst
init_subst = InScopeSet -> Subst
mkEmptySubst (VarSet -> InScopeSet
mkInScopeSet (CoreExpr -> VarSet
exprFreeVars CoreExpr
expr))
        -- It's potentially important to make a proper in-scope set
        -- Consider  let x = ..y.. in \y. ...x...
        -- Then we should remember to clone y before substituting
        -- for x.  It's very unlikely to occur, because we probably
        -- won't *be* substituting for x if it occurs inside a
        -- lambda.
        --
        -- It's a bit painful to call exprFreeVars, because it makes
        -- three passes instead of two (occ-anal, and go)

simpleOptExprWith :: DynFlags -> Subst -> InExpr -> OutExpr
-- See Note [The simple optimiser]
simpleOptExprWith :: DynFlags -> Subst -> CoreExpr -> CoreExpr
simpleOptExprWith DynFlags
dflags Subst
subst CoreExpr
expr
  = HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
init_env (CoreExpr -> CoreExpr
occurAnalyseExpr CoreExpr
expr)
  where
    init_env :: SimpleOptEnv
init_env = SOE :: DynFlags -> IdEnv SimpleClo -> Subst -> SimpleOptEnv
SOE { soe_dflags :: DynFlags
soe_dflags = DynFlags
dflags
                   , soe_inl :: IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
forall a. VarEnv a
emptyVarEnv
                   , soe_subst :: Subst
soe_subst = Subst
subst }

----------------------
simpleOptPgm :: DynFlags -> Module
             -> CoreProgram -> [CoreRule]
             -> IO (CoreProgram, [CoreRule])
-- See Note [The simple optimiser]
simpleOptPgm :: DynFlags
-> Module
-> CoreProgram
-> [CoreRule]
-> IO (CoreProgram, [CoreRule])
simpleOptPgm DynFlags
dflags Module
this_mod CoreProgram
binds [CoreRule]
rules
  = do { DynFlags -> DumpFlag -> String -> SDoc -> IO ()
dumpIfSet_dyn DynFlags
dflags DumpFlag
Opt_D_dump_occur_anal String
"Occurrence analysis"
                       (CoreProgram -> SDoc
forall b. OutputableBndr b => [Bind b] -> SDoc
pprCoreBindings CoreProgram
occ_anald_binds SDoc -> SDoc -> SDoc
$$ [CoreRule] -> SDoc
pprRules [CoreRule]
rules );

       ; (CoreProgram, [CoreRule]) -> IO (CoreProgram, [CoreRule])
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreProgram -> CoreProgram
forall a. [a] -> [a]
reverse CoreProgram
binds', [CoreRule]
rules') }
  where
    occ_anald_binds :: CoreProgram
occ_anald_binds  = Module
-> (Id -> Bool)
-> (Activation -> Bool)
-> [CoreRule]
-> CoreProgram
-> CoreProgram
occurAnalysePgm Module
this_mod
                          (\Id
_ -> Bool
True)  {- All unfoldings active -}
                          (\Activation
_ -> Bool
False) {- No rules active -}
                          [CoreRule]
rules CoreProgram
binds

    (SimpleOptEnv
final_env, CoreProgram
binds') = ((SimpleOptEnv, CoreProgram)
 -> InBind -> (SimpleOptEnv, CoreProgram))
-> (SimpleOptEnv, CoreProgram)
-> CoreProgram
-> (SimpleOptEnv, CoreProgram)
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' (SimpleOptEnv, CoreProgram)
-> InBind -> (SimpleOptEnv, CoreProgram)
do_one (DynFlags -> SimpleOptEnv
emptyEnv DynFlags
dflags, []) CoreProgram
occ_anald_binds
    final_subst :: Subst
final_subst = SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
final_env

    rules' :: [CoreRule]
rules' = Subst -> [CoreRule] -> [CoreRule]
substRulesForImportedIds Subst
final_subst [CoreRule]
rules
             -- We never unconditionally inline into rules,
             -- hence paying just a substitution

    do_one :: (SimpleOptEnv, CoreProgram)
-> InBind -> (SimpleOptEnv, CoreProgram)
do_one (SimpleOptEnv
env, CoreProgram
binds') InBind
bind
      = case SimpleOptEnv
-> InBind -> TopLevelFlag -> (SimpleOptEnv, Maybe InBind)
simple_opt_bind SimpleOptEnv
env InBind
bind TopLevelFlag
TopLevel of
          (SimpleOptEnv
env', Maybe InBind
Nothing)    -> (SimpleOptEnv
env', CoreProgram
binds')
          (SimpleOptEnv
env', Just InBind
bind') -> (SimpleOptEnv
env', InBind
bind'InBind -> CoreProgram -> CoreProgram
forall a. a -> [a] -> [a]
:CoreProgram
binds')

-- In these functions the substitution maps InVar -> OutExpr

----------------------
type SimpleClo = (SimpleOptEnv, InExpr)

data SimpleOptEnv
  = SOE { SimpleOptEnv -> DynFlags
soe_dflags :: DynFlags
        , SimpleOptEnv -> IdEnv SimpleClo
soe_inl   :: IdEnv SimpleClo
             -- Deals with preInlineUnconditionally; things
             -- that occur exactly once and are inlined
             -- without having first been simplified

        , SimpleOptEnv -> Subst
soe_subst :: Subst
             -- Deals with cloning; includes the InScopeSet
        }

instance Outputable SimpleOptEnv where
  ppr :: SimpleOptEnv -> SDoc
ppr (SOE { soe_inl :: SimpleOptEnv -> IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
inl, soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst })
    = String -> SDoc
text String
"SOE {" SDoc -> SDoc -> SDoc
<+> [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"soe_inl   =" SDoc -> SDoc -> SDoc
<+> IdEnv SimpleClo -> SDoc
forall a. Outputable a => a -> SDoc
ppr IdEnv SimpleClo
inl
                            , String -> SDoc
text String
"soe_subst =" SDoc -> SDoc -> SDoc
<+> Subst -> SDoc
forall a. Outputable a => a -> SDoc
ppr Subst
subst ]
                   SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"}"

emptyEnv :: DynFlags -> SimpleOptEnv
emptyEnv :: DynFlags -> SimpleOptEnv
emptyEnv DynFlags
dflags
  = SOE :: DynFlags -> IdEnv SimpleClo -> Subst -> SimpleOptEnv
SOE { soe_dflags :: DynFlags
soe_dflags = DynFlags
dflags
        , soe_inl :: IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
forall a. VarEnv a
emptyVarEnv
        , soe_subst :: Subst
soe_subst = Subst
emptySubst }

soeZapSubst :: SimpleOptEnv -> SimpleOptEnv
soeZapSubst :: SimpleOptEnv -> SimpleOptEnv
soeZapSubst env :: SimpleOptEnv
env@(SOE { soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst })
  = SimpleOptEnv
env { soe_inl :: IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
forall a. VarEnv a
emptyVarEnv, soe_subst :: Subst
soe_subst = Subst -> Subst
zapSubstEnv Subst
subst }

soeSetInScope :: SimpleOptEnv -> SimpleOptEnv -> SimpleOptEnv
-- Take in-scope set from env1, and the rest from env2
soeSetInScope :: SimpleOptEnv -> SimpleOptEnv -> SimpleOptEnv
soeSetInScope (SOE { soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst1 })
              env2 :: SimpleOptEnv
env2@(SOE { soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst2 })
  = SimpleOptEnv
env2 { soe_subst :: Subst
soe_subst = Subst -> InScopeSet -> Subst
setInScope Subst
subst2 (Subst -> InScopeSet
substInScope Subst
subst1) }

---------------
simple_opt_clo :: SimpleOptEnv -> SimpleClo -> OutExpr
simple_opt_clo :: SimpleOptEnv -> SimpleClo -> CoreExpr
simple_opt_clo SimpleOptEnv
env (SimpleOptEnv
e_env, CoreExpr
e)
  = HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr (SimpleOptEnv -> SimpleOptEnv -> SimpleOptEnv
soeSetInScope SimpleOptEnv
env SimpleOptEnv
e_env) CoreExpr
e

simple_opt_expr :: HasCallStack => SimpleOptEnv -> InExpr -> OutExpr
simple_opt_expr :: SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env CoreExpr
expr
  = CoreExpr -> CoreExpr
go CoreExpr
expr
  where
    subst :: Subst
subst        = SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
env
    in_scope :: InScopeSet
in_scope     = Subst -> InScopeSet
substInScope Subst
subst
    in_scope_env :: (InScopeSet, IdUnfoldingFun)
in_scope_env = (InScopeSet
in_scope, IdUnfoldingFun
simpleUnfoldingFun)

    go :: CoreExpr -> CoreExpr
go (Var Id
v)
       | Just SimpleClo
clo <- IdEnv SimpleClo -> Id -> Maybe SimpleClo
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv (SimpleOptEnv -> IdEnv SimpleClo
soe_inl SimpleOptEnv
env) Id
v
       = SimpleOptEnv -> SimpleClo -> CoreExpr
simple_opt_clo SimpleOptEnv
env SimpleClo
clo
       | Bool
otherwise
       = SDoc -> Subst -> Id -> CoreExpr
lookupIdSubst (String -> SDoc
text String
"simpleOptExpr") (SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
env) Id
v

    go (App CoreExpr
e1 CoreExpr
e2)      = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env CoreExpr
e1 [(SimpleOptEnv
env,CoreExpr
e2)]
    go (Type Type
ty)        = Type -> CoreExpr
forall b. Type -> Expr b
Type     (Subst -> Type -> Type
substTy Subst
subst Type
ty)
    go (Coercion Coercion
co)    = Coercion -> CoreExpr
forall b. Coercion -> Expr b
Coercion (DynFlags -> TCvSubst -> Coercion -> Coercion
optCoercion (SimpleOptEnv -> DynFlags
soe_dflags SimpleOptEnv
env) (Subst -> TCvSubst
getTCvSubst Subst
subst) Coercion
co)
    go (Lit Literal
lit)        = Literal -> CoreExpr
forall b. Literal -> Expr b
Lit Literal
lit
    go (Tick Tickish Id
tickish CoreExpr
e) = Tickish Id -> CoreExpr -> CoreExpr
mkTick (Subst -> Tickish Id -> Tickish Id
substTickish Subst
subst Tickish Id
tickish) (CoreExpr -> CoreExpr
go CoreExpr
e)
    go (Cast CoreExpr
e Coercion
co)      | Coercion -> Bool
isReflCo Coercion
co' = CoreExpr -> CoreExpr
go CoreExpr
e
                        | Bool
otherwise    = CoreExpr -> Coercion -> CoreExpr
forall b. Expr b -> Coercion -> Expr b
Cast (CoreExpr -> CoreExpr
go CoreExpr
e) Coercion
co'
                        where
                          co' :: Coercion
co' = DynFlags -> TCvSubst -> Coercion -> Coercion
optCoercion (SimpleOptEnv -> DynFlags
soe_dflags SimpleOptEnv
env) (Subst -> TCvSubst
getTCvSubst Subst
subst) Coercion
co

    go (Let InBind
bind CoreExpr
body)  = case SimpleOptEnv
-> InBind -> TopLevelFlag -> (SimpleOptEnv, Maybe InBind)
simple_opt_bind SimpleOptEnv
env InBind
bind TopLevelFlag
NotTopLevel of
                             (SimpleOptEnv
env', Maybe InBind
Nothing)   -> HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env' CoreExpr
body
                             (SimpleOptEnv
env', Just InBind
bind) -> InBind -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let InBind
bind (HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env' CoreExpr
body)

    go lam :: CoreExpr
lam@(Lam {})     = SimpleOptEnv -> [Id] -> CoreExpr -> CoreExpr
go_lam SimpleOptEnv
env [] CoreExpr
lam
    go (Case CoreExpr
e Id
b Type
ty [Alt Id]
as)
       -- See Note [Getting the map/coerce RULE to work]
      | Id -> Bool
isDeadBinder Id
b
      , Just (InScopeSet
_, [], DataCon
con, [Type]
_tys, [CoreExpr]
es) <- (InScopeSet, IdUnfoldingFun)
-> CoreExpr
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
exprIsConApp_maybe (InScopeSet, IdUnfoldingFun)
in_scope_env CoreExpr
e'
        -- We don't need to be concerned about floats when looking for coerce.
      , Just (AltCon
altcon, [Id]
bs, CoreExpr
rhs) <- AltCon -> [Alt Id] -> Maybe (Alt Id)
forall a b. AltCon -> [(AltCon, a, b)] -> Maybe (AltCon, a, b)
findAlt (DataCon -> AltCon
DataAlt DataCon
con) [Alt Id]
as
      = case AltCon
altcon of
          AltCon
DEFAULT -> CoreExpr -> CoreExpr
go CoreExpr
rhs
          AltCon
_       -> (Maybe (Id, CoreExpr) -> CoreExpr -> CoreExpr)
-> CoreExpr -> [Maybe (Id, CoreExpr)] -> CoreExpr
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Maybe (Id, CoreExpr) -> CoreExpr -> CoreExpr
wrapLet (HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env' CoreExpr
rhs) [Maybe (Id, CoreExpr)]
mb_prs
            where
              (SimpleOptEnv
env', [Maybe (Id, CoreExpr)]
mb_prs) = (SimpleOptEnv
 -> (Id, CoreExpr) -> (SimpleOptEnv, Maybe (Id, CoreExpr)))
-> SimpleOptEnv
-> [(Id, CoreExpr)]
-> (SimpleOptEnv, [Maybe (Id, CoreExpr)])
forall (t :: * -> *) a b c.
Traversable t =>
(a -> b -> (a, c)) -> a -> t b -> (a, t c)
mapAccumL (TopLevelFlag
-> SimpleOptEnv
-> (Id, CoreExpr)
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_out_bind TopLevelFlag
NotTopLevel) SimpleOptEnv
env ([(Id, CoreExpr)] -> (SimpleOptEnv, [Maybe (Id, CoreExpr)]))
-> [(Id, CoreExpr)] -> (SimpleOptEnv, [Maybe (Id, CoreExpr)])
forall a b. (a -> b) -> a -> b
$
                               String -> [Id] -> [CoreExpr] -> [(Id, CoreExpr)]
forall a b. String -> [a] -> [b] -> [(a, b)]
zipEqual String
"simpleOptExpr" [Id]
bs [CoreExpr]
es

         -- Note [Getting the map/coerce RULE to work]
      | Id -> Bool
isDeadBinder Id
b
      , [(AltCon
DEFAULT, [Id]
_, CoreExpr
rhs)] <- [Alt Id]
as
      , Type -> Bool
isCoVarType (Id -> Type
varType Id
b)
      , (Var Id
fun, [CoreExpr]
_args) <- CoreExpr -> (CoreExpr, [CoreExpr])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs CoreExpr
e
      , Id
fun Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
coercibleSCSelIdKey
         -- without this last check, we get #11230
      = CoreExpr -> CoreExpr
go CoreExpr
rhs

      | Bool
otherwise
      = CoreExpr -> Id -> Type -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case CoreExpr
e' Id
b' (Subst -> Type -> Type
substTy Subst
subst Type
ty)
                   ((Alt Id -> Alt Id) -> [Alt Id] -> [Alt Id]
forall a b. (a -> b) -> [a] -> [b]
map (SimpleOptEnv -> Alt Id -> Alt Id
forall a.
SimpleOptEnv -> (a, [Id], CoreExpr) -> (a, [Id], CoreExpr)
go_alt SimpleOptEnv
env') [Alt Id]
as)
      where
        e' :: CoreExpr
e' = CoreExpr -> CoreExpr
go CoreExpr
e
        (SimpleOptEnv
env', Id
b') = SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_bndr SimpleOptEnv
env Id
b

    ----------------------
    go_alt :: SimpleOptEnv -> (a, [Id], CoreExpr) -> (a, [Id], CoreExpr)
go_alt SimpleOptEnv
env (a
con, [Id]
bndrs, CoreExpr
rhs)
      = (a
con, [Id]
bndrs', HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env' CoreExpr
rhs)
      where
        (SimpleOptEnv
env', [Id]
bndrs') = SimpleOptEnv -> [Id] -> (SimpleOptEnv, [Id])
subst_opt_bndrs SimpleOptEnv
env [Id]
bndrs

    ----------------------
    -- go_lam tries eta reduction
    go_lam :: SimpleOptEnv -> [Id] -> CoreExpr -> CoreExpr
go_lam SimpleOptEnv
env [Id]
bs' (Lam Id
b CoreExpr
e)
       = SimpleOptEnv -> [Id] -> CoreExpr -> CoreExpr
go_lam SimpleOptEnv
env' (Id
b'Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
:[Id]
bs') CoreExpr
e
       where
         (SimpleOptEnv
env', Id
b') = SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_bndr SimpleOptEnv
env Id
b
    go_lam SimpleOptEnv
env [Id]
bs' CoreExpr
e
       | Just CoreExpr
etad_e <- [Id] -> CoreExpr -> Maybe CoreExpr
tryEtaReduce [Id]
bs CoreExpr
e' = CoreExpr
etad_e
       | Bool
otherwise                         = [Id] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
bs CoreExpr
e'
       where
         bs :: [Id]
bs = [Id] -> [Id]
forall a. [a] -> [a]
reverse [Id]
bs'
         e' :: CoreExpr
e' = HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env CoreExpr
e

----------------------
-- simple_app collects arguments for beta reduction
simple_app :: SimpleOptEnv -> InExpr -> [SimpleClo] -> CoreExpr

simple_app :: SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env (Var Id
v) [SimpleClo]
as
  | Just (SimpleOptEnv
env', CoreExpr
e) <- IdEnv SimpleClo -> Id -> Maybe SimpleClo
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv (SimpleOptEnv -> IdEnv SimpleClo
soe_inl SimpleOptEnv
env) Id
v
  = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app (SimpleOptEnv -> SimpleOptEnv -> SimpleOptEnv
soeSetInScope SimpleOptEnv
env SimpleOptEnv
env') CoreExpr
e [SimpleClo]
as

  | let unf :: Unfolding
unf = IdUnfoldingFun
idUnfolding Id
v
  , Unfolding -> Bool
isCompulsoryUnfolding (IdUnfoldingFun
idUnfolding Id
v)
  , Activation -> Bool
isAlwaysActive (Id -> Activation
idInlineActivation Id
v)
    -- See Note [Unfold compulsory unfoldings in LHSs]
  = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app (SimpleOptEnv -> SimpleOptEnv
soeZapSubst SimpleOptEnv
env) (Unfolding -> CoreExpr
unfoldingTemplate Unfolding
unf) [SimpleClo]
as

  | Bool
otherwise
  , let out_fn :: CoreExpr
out_fn = SDoc -> Subst -> Id -> CoreExpr
lookupIdSubst (String -> SDoc
text String
"simple_app") (SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
env) Id
v
  = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
finish_app SimpleOptEnv
env CoreExpr
out_fn [SimpleClo]
as

simple_app SimpleOptEnv
env (App CoreExpr
e1 CoreExpr
e2) [SimpleClo]
as
  = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env CoreExpr
e1 ((SimpleOptEnv
env, CoreExpr
e2) SimpleClo -> [SimpleClo] -> [SimpleClo]
forall a. a -> [a] -> [a]
: [SimpleClo]
as)

simple_app SimpleOptEnv
env (Lam Id
b CoreExpr
e) (SimpleClo
a:[SimpleClo]
as)
  = Maybe (Id, CoreExpr) -> CoreExpr -> CoreExpr
wrapLet Maybe (Id, CoreExpr)
mb_pr (SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env' CoreExpr
e [SimpleClo]
as)
  where
     (SimpleOptEnv
env', Maybe (Id, CoreExpr)
mb_pr) = SimpleOptEnv
-> Id
-> Maybe Id
-> SimpleClo
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_bind_pair SimpleOptEnv
env Id
b Maybe Id
forall a. Maybe a
Nothing SimpleClo
a TopLevelFlag
NotTopLevel

simple_app SimpleOptEnv
env (Tick Tickish Id
t CoreExpr
e) [SimpleClo]
as
  -- Okay to do "(Tick t e) x ==> Tick t (e x)"?
  | Tickish Id
t Tickish Id -> TickishScoping -> Bool
forall id. Tickish id -> TickishScoping -> Bool
`tickishScopesLike` TickishScoping
SoftScope
  = Tickish Id -> CoreExpr -> CoreExpr
mkTick Tickish Id
t (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$ SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env CoreExpr
e [SimpleClo]
as

-- (let x = e in b) a1 .. an  =>  let x = e in (b a1 .. an)
-- The let might appear there as a result of inlining
-- e.g.   let f = let x = e in b
--        in f a1 a2
--   (#13208)
-- However, do /not/ do this transformation for join points
--    See Note [simple_app and join points]
simple_app SimpleOptEnv
env (Let InBind
bind CoreExpr
body) [SimpleClo]
args
  = case SimpleOptEnv
-> InBind -> TopLevelFlag -> (SimpleOptEnv, Maybe InBind)
simple_opt_bind SimpleOptEnv
env InBind
bind TopLevelFlag
NotTopLevel of
      (SimpleOptEnv
env', Maybe InBind
Nothing)   -> SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env' CoreExpr
body [SimpleClo]
args
      (SimpleOptEnv
env', Just InBind
bind')
        | InBind -> Bool
isJoinBind InBind
bind' -> SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
finish_app SimpleOptEnv
env CoreExpr
expr' [SimpleClo]
args
        | Bool
otherwise        -> InBind -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let InBind
bind' (SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
simple_app SimpleOptEnv
env' CoreExpr
body [SimpleClo]
args)
        where
          expr' :: CoreExpr
expr' = InBind -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let InBind
bind' (HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env' CoreExpr
body)

simple_app SimpleOptEnv
env CoreExpr
e [SimpleClo]
as
  = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
finish_app SimpleOptEnv
env (HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env CoreExpr
e) [SimpleClo]
as

finish_app :: SimpleOptEnv -> OutExpr -> [SimpleClo] -> OutExpr
finish_app :: SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
finish_app SimpleOptEnv
_ CoreExpr
fun []
  = CoreExpr
fun
finish_app SimpleOptEnv
env CoreExpr
fun (SimpleClo
arg:[SimpleClo]
args)
  = SimpleOptEnv -> CoreExpr -> [SimpleClo] -> CoreExpr
finish_app SimpleOptEnv
env (CoreExpr -> CoreExpr -> CoreExpr
forall b. Expr b -> Expr b -> Expr b
App CoreExpr
fun (SimpleOptEnv -> SimpleClo -> CoreExpr
simple_opt_clo SimpleOptEnv
env SimpleClo
arg)) [SimpleClo]
args

----------------------
simple_opt_bind :: SimpleOptEnv -> InBind -> TopLevelFlag
                -> (SimpleOptEnv, Maybe OutBind)
simple_opt_bind :: SimpleOptEnv
-> InBind -> TopLevelFlag -> (SimpleOptEnv, Maybe InBind)
simple_opt_bind SimpleOptEnv
env (NonRec Id
b CoreExpr
r) TopLevelFlag
top_level
  = (SimpleOptEnv
env', case Maybe (Id, CoreExpr)
mb_pr of
            Maybe (Id, CoreExpr)
Nothing    -> Maybe InBind
forall a. Maybe a
Nothing
            Just (Id
b,CoreExpr
r) -> InBind -> Maybe InBind
forall a. a -> Maybe a
Just (Id -> CoreExpr -> InBind
forall b. b -> Expr b -> Bind b
NonRec Id
b CoreExpr
r))
  where
    (Id
b', CoreExpr
r') = Id -> CoreExpr -> Maybe (Id, CoreExpr)
joinPointBinding_maybe Id
b CoreExpr
r Maybe (Id, CoreExpr) -> (Id, CoreExpr) -> (Id, CoreExpr)
forall a. Maybe a -> a -> a
`orElse` (Id
b, CoreExpr
r)
    (SimpleOptEnv
env', Maybe (Id, CoreExpr)
mb_pr) = SimpleOptEnv
-> Id
-> Maybe Id
-> SimpleClo
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_bind_pair SimpleOptEnv
env Id
b' Maybe Id
forall a. Maybe a
Nothing (SimpleOptEnv
env,CoreExpr
r') TopLevelFlag
top_level

simple_opt_bind SimpleOptEnv
env (Rec [(Id, CoreExpr)]
prs) TopLevelFlag
top_level
  = (SimpleOptEnv
env'', Maybe InBind
res_bind)
  where
    res_bind :: Maybe InBind
res_bind          = InBind -> Maybe InBind
forall a. a -> Maybe a
Just ([(Id, CoreExpr)] -> InBind
forall b. [(b, Expr b)] -> Bind b
Rec ([(Id, CoreExpr)] -> [(Id, CoreExpr)]
forall a. [a] -> [a]
reverse [(Id, CoreExpr)]
rev_prs'))
    prs' :: [(Id, CoreExpr)]
prs'              = [(Id, CoreExpr)] -> Maybe [(Id, CoreExpr)]
joinPointBindings_maybe [(Id, CoreExpr)]
prs Maybe [(Id, CoreExpr)] -> [(Id, CoreExpr)] -> [(Id, CoreExpr)]
forall a. Maybe a -> a -> a
`orElse` [(Id, CoreExpr)]
prs
    (SimpleOptEnv
env', [Id]
bndrs')    = SimpleOptEnv -> [Id] -> (SimpleOptEnv, [Id])
subst_opt_bndrs SimpleOptEnv
env (((Id, CoreExpr) -> Id) -> [(Id, CoreExpr)] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map (Id, CoreExpr) -> Id
forall a b. (a, b) -> a
fst [(Id, CoreExpr)]
prs')
    (SimpleOptEnv
env'', [(Id, CoreExpr)]
rev_prs') = ((SimpleOptEnv, [(Id, CoreExpr)])
 -> ((Id, CoreExpr), Id) -> (SimpleOptEnv, [(Id, CoreExpr)]))
-> (SimpleOptEnv, [(Id, CoreExpr)])
-> [((Id, CoreExpr), Id)]
-> (SimpleOptEnv, [(Id, CoreExpr)])
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' (SimpleOptEnv, [(Id, CoreExpr)])
-> ((Id, CoreExpr), Id) -> (SimpleOptEnv, [(Id, CoreExpr)])
do_pr (SimpleOptEnv
env', []) ([(Id, CoreExpr)]
prs' [(Id, CoreExpr)] -> [Id] -> [((Id, CoreExpr), Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
bndrs')
    do_pr :: (SimpleOptEnv, [(Id, CoreExpr)])
-> ((Id, CoreExpr), Id) -> (SimpleOptEnv, [(Id, CoreExpr)])
do_pr (SimpleOptEnv
env, [(Id, CoreExpr)]
prs) ((Id
b,CoreExpr
r), Id
b')
       = (SimpleOptEnv
env', case Maybe (Id, CoreExpr)
mb_pr of
                  Just (Id, CoreExpr)
pr -> (Id, CoreExpr)
pr (Id, CoreExpr) -> [(Id, CoreExpr)] -> [(Id, CoreExpr)]
forall a. a -> [a] -> [a]
: [(Id, CoreExpr)]
prs
                  Maybe (Id, CoreExpr)
Nothing -> [(Id, CoreExpr)]
prs)
       where
         (SimpleOptEnv
env', Maybe (Id, CoreExpr)
mb_pr) = SimpleOptEnv
-> Id
-> Maybe Id
-> SimpleClo
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_bind_pair SimpleOptEnv
env Id
b (Id -> Maybe Id
forall a. a -> Maybe a
Just Id
b') (SimpleOptEnv
env,CoreExpr
r) TopLevelFlag
top_level

----------------------
simple_bind_pair :: SimpleOptEnv
                 -> InVar -> Maybe OutVar
                 -> SimpleClo
                 -> TopLevelFlag
                 -> (SimpleOptEnv, Maybe (OutVar, OutExpr))
    -- (simple_bind_pair subst in_var out_rhs)
    --   either extends subst with (in_var -> out_rhs)
    --   or     returns Nothing
simple_bind_pair :: SimpleOptEnv
-> Id
-> Maybe Id
-> SimpleClo
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_bind_pair env :: SimpleOptEnv
env@(SOE { soe_inl :: SimpleOptEnv -> IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
inl_env, soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst })
                 Id
in_bndr Maybe Id
mb_out_bndr clo :: SimpleClo
clo@(SimpleOptEnv
rhs_env, CoreExpr
in_rhs)
                 TopLevelFlag
top_level
  | Type Type
ty <- CoreExpr
in_rhs        -- let a::* = TYPE ty in <body>
  , let out_ty :: Type
out_ty = Subst -> Type -> Type
substTy (SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
rhs_env) Type
ty
  = ASSERT( isTyVar in_bndr )
    (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst -> Id -> Type -> Subst
extendTvSubst Subst
subst Id
in_bndr Type
out_ty }, Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing)

  | Coercion Coercion
co <- CoreExpr
in_rhs
  , let out_co :: Coercion
out_co = DynFlags -> TCvSubst -> Coercion -> Coercion
optCoercion (SimpleOptEnv -> DynFlags
soe_dflags SimpleOptEnv
env) (Subst -> TCvSubst
getTCvSubst (SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
rhs_env)) Coercion
co
  = ASSERT( isCoVar in_bndr )
    (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst -> Id -> Coercion -> Subst
extendCvSubst Subst
subst Id
in_bndr Coercion
out_co }, Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing)

  | ASSERT2( isNonCoVarId in_bndr, ppr in_bndr )
    -- The previous two guards got rid of tyvars and coercions
    -- See Note [CoreSyn type and coercion invariant] in CoreSyn
    Bool
pre_inline_unconditionally
  = (SimpleOptEnv
env { soe_inl :: IdEnv SimpleClo
soe_inl = IdEnv SimpleClo -> Id -> SimpleClo -> IdEnv SimpleClo
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv IdEnv SimpleClo
inl_env Id
in_bndr SimpleClo
clo }, Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing)

  | Bool
otherwise
  = SimpleOptEnv
-> Id
-> Maybe Id
-> CoreExpr
-> OccInfo
-> Bool
-> Bool
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_out_bind_pair SimpleOptEnv
env Id
in_bndr Maybe Id
mb_out_bndr CoreExpr
out_rhs
                         OccInfo
occ Bool
active Bool
stable_unf TopLevelFlag
top_level
  where
    stable_unf :: Bool
stable_unf = Unfolding -> Bool
isStableUnfolding (IdUnfoldingFun
idUnfolding Id
in_bndr)
    active :: Bool
active     = Activation -> Bool
isAlwaysActive (Id -> Activation
idInlineActivation Id
in_bndr)
    occ :: OccInfo
occ        = Id -> OccInfo
idOccInfo Id
in_bndr

    out_rhs :: CoreExpr
out_rhs | Just Int
join_arity <- Id -> Maybe Int
isJoinId_maybe Id
in_bndr
            = Int -> CoreExpr
simple_join_rhs Int
join_arity
            | Bool
otherwise
            = SimpleOptEnv -> SimpleClo -> CoreExpr
simple_opt_clo SimpleOptEnv
env SimpleClo
clo

    simple_join_rhs :: Int -> CoreExpr
simple_join_rhs Int
join_arity -- See Note [Preserve join-binding arity]
      = [Id] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
join_bndrs' (HasCallStack => SimpleOptEnv -> CoreExpr -> CoreExpr
SimpleOptEnv -> CoreExpr -> CoreExpr
simple_opt_expr SimpleOptEnv
env_body CoreExpr
join_body)
      where
        env0 :: SimpleOptEnv
env0 = SimpleOptEnv -> SimpleOptEnv -> SimpleOptEnv
soeSetInScope SimpleOptEnv
env SimpleOptEnv
rhs_env
        ([Id]
join_bndrs, CoreExpr
join_body) = Int -> CoreExpr -> ([Id], CoreExpr)
forall b. Int -> Expr b -> ([b], Expr b)
collectNBinders Int
join_arity CoreExpr
in_rhs
        (SimpleOptEnv
env_body, [Id]
join_bndrs') = SimpleOptEnv -> [Id] -> (SimpleOptEnv, [Id])
subst_opt_bndrs SimpleOptEnv
env0 [Id]
join_bndrs

    pre_inline_unconditionally :: Bool
    pre_inline_unconditionally :: Bool
pre_inline_unconditionally
       | Id -> Bool
isExportedId Id
in_bndr     = Bool
False
       | Bool
stable_unf               = Bool
False
       | Bool -> Bool
not Bool
active               = Bool
False    -- Note [Inline prag in simplOpt]
       | Bool -> Bool
not (OccInfo -> Bool
safe_to_inline OccInfo
occ) = Bool
False
       | Bool
otherwise                = Bool
True

        -- Unconditionally safe to inline
    safe_to_inline :: OccInfo -> Bool
    safe_to_inline :: OccInfo -> Bool
safe_to_inline (IAmALoopBreaker {}) = Bool
False
    safe_to_inline OccInfo
IAmDead              = Bool
True
    safe_to_inline occ :: OccInfo
occ@(OneOcc {})      =  Bool -> Bool
not (OccInfo -> Bool
occ_in_lam OccInfo
occ)
                                        Bool -> Bool -> Bool
&& OccInfo -> Bool
occ_one_br OccInfo
occ
    safe_to_inline (ManyOccs {})        = Bool
False

-------------------
simple_out_bind :: TopLevelFlag
                -> SimpleOptEnv
                -> (InVar, OutExpr)
                -> (SimpleOptEnv, Maybe (OutVar, OutExpr))
simple_out_bind :: TopLevelFlag
-> SimpleOptEnv
-> (Id, CoreExpr)
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_out_bind TopLevelFlag
top_level env :: SimpleOptEnv
env@(SOE { soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst }) (Id
in_bndr, CoreExpr
out_rhs)
  | Type Type
out_ty <- CoreExpr
out_rhs
  = ASSERT( isTyVar in_bndr )
    (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst -> Id -> Type -> Subst
extendTvSubst Subst
subst Id
in_bndr Type
out_ty }, Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing)

  | Coercion Coercion
out_co <- CoreExpr
out_rhs
  = ASSERT( isCoVar in_bndr )
    (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst -> Id -> Coercion -> Subst
extendCvSubst Subst
subst Id
in_bndr Coercion
out_co }, Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing)

  | Bool
otherwise
  = SimpleOptEnv
-> Id
-> Maybe Id
-> CoreExpr
-> OccInfo
-> Bool
-> Bool
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_out_bind_pair SimpleOptEnv
env Id
in_bndr Maybe Id
forall a. Maybe a
Nothing CoreExpr
out_rhs
                         (Id -> OccInfo
idOccInfo Id
in_bndr) Bool
True Bool
False TopLevelFlag
top_level

-------------------
simple_out_bind_pair :: SimpleOptEnv
                     -> InId -> Maybe OutId -> OutExpr
                     -> OccInfo -> Bool -> Bool -> TopLevelFlag
                     -> (SimpleOptEnv, Maybe (OutVar, OutExpr))
simple_out_bind_pair :: SimpleOptEnv
-> Id
-> Maybe Id
-> CoreExpr
-> OccInfo
-> Bool
-> Bool
-> TopLevelFlag
-> (SimpleOptEnv, Maybe (Id, CoreExpr))
simple_out_bind_pair SimpleOptEnv
env Id
in_bndr Maybe Id
mb_out_bndr CoreExpr
out_rhs
                     OccInfo
occ_info Bool
active Bool
stable_unf TopLevelFlag
top_level
  | ASSERT2( isNonCoVarId in_bndr, ppr in_bndr )
    -- Type and coercion bindings are caught earlier
    -- See Note [CoreSyn type and coercion invariant]
    Bool
post_inline_unconditionally
  = ( SimpleOptEnv
env' { soe_subst :: Subst
soe_subst = Subst -> Id -> CoreExpr -> Subst
extendIdSubst (SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
env) Id
in_bndr CoreExpr
out_rhs }
    , Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing)

  | Bool
otherwise
  = ( SimpleOptEnv
env', (Id, CoreExpr) -> Maybe (Id, CoreExpr)
forall a. a -> Maybe a
Just (Id
out_bndr, CoreExpr
out_rhs) )
  where
    (SimpleOptEnv
env', Id
bndr1) = case Maybe Id
mb_out_bndr of
                      Just Id
out_bndr -> (SimpleOptEnv
env, Id
out_bndr)
                      Maybe Id
Nothing       -> SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_bndr SimpleOptEnv
env Id
in_bndr
    out_bndr :: Id
out_bndr = SimpleOptEnv -> Id -> TopLevelFlag -> CoreExpr -> Id -> Id
add_info SimpleOptEnv
env' Id
in_bndr TopLevelFlag
top_level CoreExpr
out_rhs Id
bndr1

    post_inline_unconditionally :: Bool
    post_inline_unconditionally :: Bool
post_inline_unconditionally
       | Id -> Bool
isExportedId Id
in_bndr  = Bool
False -- Note [Exported Ids and trivial RHSs]
       | Bool
stable_unf            = Bool
False -- Note [Stable unfoldings and postInlineUnconditionally]
       | Bool -> Bool
not Bool
active            = Bool
False --     in SimplUtils
       | Bool
is_loop_breaker       = Bool
False -- If it's a loop-breaker of any kind, don't inline
                                       -- because it might be referred to "earlier"
       | CoreExpr -> Bool
exprIsTrivial CoreExpr
out_rhs = Bool
True
       | Bool
coercible_hack        = Bool
True
       | Bool
otherwise             = Bool
False

    is_loop_breaker :: Bool
is_loop_breaker = OccInfo -> Bool
isWeakLoopBreaker OccInfo
occ_info

    -- See Note [Getting the map/coerce RULE to work]
    coercible_hack :: Bool
coercible_hack | (Var Id
fun, [CoreExpr]
args) <- CoreExpr -> (CoreExpr, [CoreExpr])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs CoreExpr
out_rhs
                   , Just DataCon
dc <- Id -> Maybe DataCon
isDataConWorkId_maybe Id
fun
                   , DataCon
dc DataCon -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
heqDataConKey Bool -> Bool -> Bool
|| DataCon
dc DataCon -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
coercibleDataConKey
                   = (CoreExpr -> Bool) -> [CoreExpr] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all CoreExpr -> Bool
exprIsTrivial [CoreExpr]
args
                   | Bool
otherwise
                   = Bool
False

{- Note [Exported Ids and trivial RHSs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We obviously do not want to unconditionally inline an Id that is exported.
In SimplUtils, Note [Top level and postInlineUnconditionally], we
explain why we don't inline /any/ top-level things unconditionally, even
trivial ones.  But we do here!  Why?  In the simple optimiser

  * We do no rule rewrites
  * We do no call-site inlining

Those differences obviate the reasons for not inlining a trivial rhs,
and increase the benefit for doing so.  So we unconditionally inline trivial
rhss here.

Note [Preserve join-binding arity]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Be careful /not/ to eta-reduce the RHS of a join point, lest we lose
the join-point arity invariant.  #15108 was caused by simplifying
the RHS with simple_opt_expr, which does eta-reduction.  Solution:
simplify the RHS of a join point by simplifying under the lambdas
(which of course should be there).

Note [simple_app and join points]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In general for let-bindings we can do this:
   (let { x = e } in b) a  ==>  let { x = e } in b a

But not for join points!  For two reasons:

- We would need to push the continuation into the RHS:
   (join { j = e } in b) a  ==>  let { j' = e a } in b[j'/j] a
                                      NB ----^^
  and also change the type of j, hence j'.
  That's a bit sophisticated for the very simple optimiser.

- We might end up with something like
    join { j' = e a } in
    (case blah of        )
    (  True  -> j' void# ) a
    (  False -> blah     )
  and now the call to j' doesn't look like a tail call, and
  Lint may reject.  I say "may" because this is /explicitly/
  allowed in the "Compiling without Continuations" paper
  (Section 3, "Managing \Delta").  But GHC currently does not
  allow this slightly-more-flexible form.  See CoreSyn
  Note [Join points are less general than the paper].

The simple thing to do is to disable this transformation
for join points in the simple optimiser

Note [The Let-Unfoldings Invariant]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A program has the Let-Unfoldings property iff:

- For every let-bound variable f, whether top-level or nested, whether
  recursive or not:
  - Both the binding Id of f, and every occurence Id of f, has an idUnfolding.
  - For non-INLINE things, that unfolding will be f's right hand sids
  - For INLINE things (which have a "stable" unfolding) that unfolding is
    semantically equivalent to f's RHS, but derived from the original RHS of f
    rather that its current RHS.

Informally, we can say that in a program that has the Let-Unfoldings property,
all let-bound Id's have an explicit unfolding attached to them.

Currently, the simplifier guarantees the Let-Unfoldings invariant for anything
it outputs.

-}

----------------------
subst_opt_bndrs :: SimpleOptEnv -> [InVar] -> (SimpleOptEnv, [OutVar])
subst_opt_bndrs :: SimpleOptEnv -> [Id] -> (SimpleOptEnv, [Id])
subst_opt_bndrs SimpleOptEnv
env [Id]
bndrs = (SimpleOptEnv -> Id -> (SimpleOptEnv, Id))
-> SimpleOptEnv -> [Id] -> (SimpleOptEnv, [Id])
forall (t :: * -> *) a b c.
Traversable t =>
(a -> b -> (a, c)) -> a -> t b -> (a, t c)
mapAccumL SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_bndr SimpleOptEnv
env [Id]
bndrs

subst_opt_bndr :: SimpleOptEnv -> InVar -> (SimpleOptEnv, OutVar)
subst_opt_bndr :: SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_bndr SimpleOptEnv
env Id
bndr
  | Id -> Bool
isTyVar Id
bndr  = (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst
subst_tv }, Id
tv')
  | Id -> Bool
isCoVar Id
bndr  = (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst
subst_cv }, Id
cv')
  | Bool
otherwise     = SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_id_bndr SimpleOptEnv
env Id
bndr
  where
    subst :: Subst
subst           = SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
env
    (Subst
subst_tv, Id
tv') = Subst -> Id -> (Subst, Id)
substTyVarBndr Subst
subst Id
bndr
    (Subst
subst_cv, Id
cv') = Subst -> Id -> (Subst, Id)
substCoVarBndr Subst
subst Id
bndr

subst_opt_id_bndr :: SimpleOptEnv -> InId -> (SimpleOptEnv, OutId)
-- Nuke all fragile IdInfo, unfolding, and RULES; it gets added back later by
-- add_info.
--
-- Rather like SimplEnv.substIdBndr
--
-- It's important to zap fragile OccInfo (which CoreSubst.substIdBndr
-- carefully does not do) because simplOptExpr invalidates it

subst_opt_id_bndr :: SimpleOptEnv -> Id -> (SimpleOptEnv, Id)
subst_opt_id_bndr env :: SimpleOptEnv
env@(SOE { soe_subst :: SimpleOptEnv -> Subst
soe_subst = Subst
subst, soe_inl :: SimpleOptEnv -> IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
inl }) Id
old_id
  = (SimpleOptEnv
env { soe_subst :: Subst
soe_subst = Subst
new_subst, soe_inl :: IdEnv SimpleClo
soe_inl = IdEnv SimpleClo
new_inl }, Id
new_id)
  where
    Subst InScopeSet
in_scope IdSubstEnv
id_subst TvSubstEnv
tv_subst CvSubstEnv
cv_subst = Subst
subst

    id1 :: Id
id1    = InScopeSet -> Id -> Id
uniqAway InScopeSet
in_scope Id
old_id
    id2 :: Id
id2    = Id -> Type -> Id
setIdType Id
id1 (Subst -> Type -> Type
substTy Subst
subst (Id -> Type
idType Id
old_id))
    new_id :: Id
new_id = Id -> Id
zapFragileIdInfo Id
id2
             -- Zaps rules, unfolding, and fragile OccInfo
             -- The unfolding and rules will get added back later, by add_info

    new_in_scope :: InScopeSet
new_in_scope = InScopeSet
in_scope InScopeSet -> Id -> InScopeSet
`extendInScopeSet` Id
new_id

    no_change :: Bool
no_change = Id
new_id Id -> Id -> Bool
forall a. Eq a => a -> a -> Bool
== Id
old_id

        -- Extend the substitution if the unique has changed,
        -- See the notes with substTyVarBndr for the delSubstEnv
    new_id_subst :: IdSubstEnv
new_id_subst
      | Bool
no_change = IdSubstEnv -> Id -> IdSubstEnv
forall a. VarEnv a -> Id -> VarEnv a
delVarEnv IdSubstEnv
id_subst Id
old_id
      | Bool
otherwise = IdSubstEnv -> Id -> CoreExpr -> IdSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv IdSubstEnv
id_subst Id
old_id (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
new_id)

    new_subst :: Subst
new_subst = InScopeSet -> IdSubstEnv -> TvSubstEnv -> CvSubstEnv -> Subst
Subst InScopeSet
new_in_scope IdSubstEnv
new_id_subst TvSubstEnv
tv_subst CvSubstEnv
cv_subst
    new_inl :: IdEnv SimpleClo
new_inl   = IdEnv SimpleClo -> Id -> IdEnv SimpleClo
forall a. VarEnv a -> Id -> VarEnv a
delVarEnv IdEnv SimpleClo
inl Id
old_id

----------------------
add_info :: SimpleOptEnv -> InVar -> TopLevelFlag -> OutExpr -> OutVar -> OutVar
add_info :: SimpleOptEnv -> Id -> TopLevelFlag -> CoreExpr -> Id -> Id
add_info SimpleOptEnv
env Id
old_bndr TopLevelFlag
top_level CoreExpr
new_rhs Id
new_bndr
 | Id -> Bool
isTyVar Id
old_bndr = Id
new_bndr
 | Bool
otherwise        = Id -> IdInfo -> Id
lazySetIdInfo Id
new_bndr IdInfo
new_info
 where
   subst :: Subst
subst    = SimpleOptEnv -> Subst
soe_subst SimpleOptEnv
env
   dflags :: DynFlags
dflags   = SimpleOptEnv -> DynFlags
soe_dflags SimpleOptEnv
env
   old_info :: IdInfo
old_info = HasDebugCallStack => Id -> IdInfo
Id -> IdInfo
idInfo Id
old_bndr

   -- Add back in the rules and unfolding which were
   -- removed by zapFragileIdInfo in subst_opt_id_bndr.
   --
   -- See Note [The Let-Unfoldings Invariant]
   new_info :: IdInfo
new_info = HasDebugCallStack => Id -> IdInfo
Id -> IdInfo
idInfo Id
new_bndr IdInfo -> RuleInfo -> IdInfo
`setRuleInfo`      RuleInfo
new_rules
                              IdInfo -> Unfolding -> IdInfo
`setUnfoldingInfo` Unfolding
new_unfolding

   old_rules :: RuleInfo
old_rules = IdInfo -> RuleInfo
ruleInfo IdInfo
old_info
   new_rules :: RuleInfo
new_rules = Subst -> Id -> RuleInfo -> RuleInfo
substSpec Subst
subst Id
new_bndr RuleInfo
old_rules

   old_unfolding :: Unfolding
old_unfolding = IdInfo -> Unfolding
unfoldingInfo IdInfo
old_info
   new_unfolding :: Unfolding
new_unfolding | Unfolding -> Bool
isStableUnfolding Unfolding
old_unfolding
                 = Subst -> Unfolding -> Unfolding
substUnfolding Subst
subst Unfolding
old_unfolding
                 | Bool
otherwise
                 = Unfolding
unfolding_from_rhs

   unfolding_from_rhs :: Unfolding
unfolding_from_rhs = DynFlags
-> UnfoldingSource -> Bool -> Bool -> CoreExpr -> Unfolding
mkUnfolding DynFlags
dflags UnfoldingSource
InlineRhs
                                    (TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_level)
                                    Bool
False -- may be bottom or not
                                    CoreExpr
new_rhs

simpleUnfoldingFun :: IdUnfoldingFun
simpleUnfoldingFun :: IdUnfoldingFun
simpleUnfoldingFun Id
id
  | Activation -> Bool
isAlwaysActive (Id -> Activation
idInlineActivation Id
id) = IdUnfoldingFun
idUnfolding Id
id
  | Bool
otherwise                              = Unfolding
noUnfolding

wrapLet :: Maybe (Id,CoreExpr) -> CoreExpr -> CoreExpr
wrapLet :: Maybe (Id, CoreExpr) -> CoreExpr -> CoreExpr
wrapLet Maybe (Id, CoreExpr)
Nothing      CoreExpr
body = CoreExpr
body
wrapLet (Just (Id
b,CoreExpr
r)) CoreExpr
body = InBind -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let (Id -> CoreExpr -> InBind
forall b. b -> Expr b -> Bind b
NonRec Id
b CoreExpr
r) CoreExpr
body

{-
Note [Inline prag in simplOpt]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If there's an INLINE/NOINLINE pragma that restricts the phase in
which the binder can be inlined, we don't inline here; after all,
we don't know what phase we're in.  Here's an example

  foo :: Int -> Int -> Int
  {-# INLINE foo #-}
  foo m n = inner m
     where
       {-# INLINE [1] inner #-}
       inner m = m+n

  bar :: Int -> Int
  bar n = foo n 1

When inlining 'foo' in 'bar' we want the let-binding for 'inner'
to remain visible until Phase 1

Note [Unfold compulsory unfoldings in LHSs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When the user writes `RULES map coerce = coerce` as a rule, the rule
will only ever match if simpleOptExpr replaces coerce by its unfolding
on the LHS, because that is the core that the rule matching engine
will find. So do that for everything that has a compulsory
unfolding. Also see Note [Desugaring coerce as cast] in Desugar.

However, we don't want to inline 'seq', which happens to also have a
compulsory unfolding, so we only do this unfolding only for things
that are always-active.  See Note [User-defined RULES for seq] in MkId.

Note [Getting the map/coerce RULE to work]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We wish to allow the "map/coerce" RULE to fire:

  {-# RULES "map/coerce" map coerce = coerce #-}

The naive core produced for this is

  forall a b (dict :: Coercible * a b).
    map @a @b (coerce @a @b @dict) = coerce @[a] @[b] @dict'

  where dict' :: Coercible [a] [b]
        dict' = ...

This matches literal uses of `map coerce` in code, but that's not what we
want. We want it to match, say, `map MkAge` (where newtype Age = MkAge Int)
too. Some of this is addressed by compulsorily unfolding coerce on the LHS,
yielding

  forall a b (dict :: Coercible * a b).
    map @a @b (\(x :: a) -> case dict of
      MkCoercible (co :: a ~R# b) -> x |> co) = ...

Getting better. But this isn't exactly what gets produced. This is because
Coercible essentially has ~R# as a superclass, and superclasses get eagerly
extracted during solving. So we get this:

  forall a b (dict :: Coercible * a b).
    case Coercible_SCSel @* @a @b dict of
      _ [Dead] -> map @a @b (\(x :: a) -> case dict of
                               MkCoercible (co :: a ~R# b) -> x |> co) = ...

Unfortunately, this still abstracts over a Coercible dictionary. We really
want it to abstract over the ~R# evidence. So, we have Desugar.unfold_coerce,
which transforms the above to (see also Note [Desugaring coerce as cast] in
Desugar)

  forall a b (co :: a ~R# b).
    let dict = MkCoercible @* @a @b co in
    case Coercible_SCSel @* @a @b dict of
      _ [Dead] -> map @a @b (\(x :: a) -> case dict of
         MkCoercible (co :: a ~R# b) -> x |> co) = let dict = ... in ...

Now, we need simpleOptExpr to fix this up. It does so by taking three
separate actions:
  1. Inline certain non-recursive bindings. The choice whether to inline
     is made in simple_bind_pair. Note the rather specific check for
     MkCoercible in there.

  2. Stripping case expressions like the Coercible_SCSel one.
     See the `Case` case of simple_opt_expr's `go` function.

  3. Look for case expressions that unpack something that was
     just packed and inline them. This is also done in simple_opt_expr's
     `go` function.

This is all a fair amount of special-purpose hackery, but it's for
a good cause. And it won't hurt other RULES and such that it comes across.


************************************************************************
*                                                                      *
                Join points
*                                                                      *
************************************************************************
-}

-- | Returns Just (bndr,rhs) if the binding is a join point:
-- If it's a JoinId, just return it
-- If it's not yet a JoinId but is always tail-called,
--    make it into a JoinId and return it.
-- In the latter case, eta-expand the RHS if necessary, to make the
-- lambdas explicit, as is required for join points
--
-- Precondition: the InBndr has been occurrence-analysed,
--               so its OccInfo is valid
joinPointBinding_maybe :: InBndr -> InExpr -> Maybe (InBndr, InExpr)
joinPointBinding_maybe :: Id -> CoreExpr -> Maybe (Id, CoreExpr)
joinPointBinding_maybe Id
bndr CoreExpr
rhs
  | Bool -> Bool
not (Id -> Bool
isId Id
bndr)
  = Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing

  | Id -> Bool
isJoinId Id
bndr
  = (Id, CoreExpr) -> Maybe (Id, CoreExpr)
forall a. a -> Maybe a
Just (Id
bndr, CoreExpr
rhs)

  | AlwaysTailCalled Int
join_arity <- OccInfo -> TailCallInfo
tailCallInfo (Id -> OccInfo
idOccInfo Id
bndr)
  , ([Id]
bndrs, CoreExpr
body) <- Int -> CoreExpr -> ([Id], CoreExpr)
etaExpandToJoinPoint Int
join_arity CoreExpr
rhs
  , let str_sig :: StrictSig
str_sig   = Id -> StrictSig
idStrictness Id
bndr
        str_arity :: Int
str_arity = (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
bndrs  -- Strictness demands are for Ids only
        join_bndr :: Id
join_bndr = Id
bndr Id -> Int -> Id
`asJoinId`        Int
join_arity
                         Id -> StrictSig -> Id
`setIdStrictness` Int -> StrictSig -> StrictSig
etaExpandStrictSig Int
str_arity StrictSig
str_sig
  = (Id, CoreExpr) -> Maybe (Id, CoreExpr)
forall a. a -> Maybe a
Just (Id
join_bndr, [Id] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
bndrs CoreExpr
body)

  | Bool
otherwise
  = Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing

joinPointBindings_maybe :: [(InBndr, InExpr)] -> Maybe [(InBndr, InExpr)]
joinPointBindings_maybe :: [(Id, CoreExpr)] -> Maybe [(Id, CoreExpr)]
joinPointBindings_maybe [(Id, CoreExpr)]
bndrs
  = ((Id, CoreExpr) -> Maybe (Id, CoreExpr))
-> [(Id, CoreExpr)] -> Maybe [(Id, CoreExpr)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ((Id -> CoreExpr -> Maybe (Id, CoreExpr))
-> (Id, CoreExpr) -> Maybe (Id, CoreExpr)
forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry Id -> CoreExpr -> Maybe (Id, CoreExpr)
joinPointBinding_maybe) [(Id, CoreExpr)]
bndrs


{- Note [Strictness and join points]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have

   let f = \x.  if x>200 then e1 else e1

and we know that f is strict in x.  Then if we subsequently
discover that f is an arity-2 join point, we'll eta-expand it to

   let f = \x y.  if x>200 then e1 else e1

and now it's only strict if applied to two arguments.  So we should
adjust the strictness info.

A more common case is when

   f = \x. error ".."

and again its arity increases (#15517)
-}

{- *********************************************************************
*                                                                      *
         exprIsConApp_maybe
*                                                                      *
************************************************************************

Note [exprIsConApp_maybe]
~~~~~~~~~~~~~~~~~~~~~~~~~
exprIsConApp_maybe is a very important function.  There are two principal
uses:
  * case e of { .... }
  * cls_op e, where cls_op is a class operation

In both cases you want to know if e is of form (C e1..en) where C is
a data constructor.

However e might not *look* as if


Note [exprIsConApp_maybe on literal strings]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See #9400 and #13317.

Conceptually, a string literal "abc" is just ('a':'b':'c':[]), but in Core
they are represented as unpackCString# "abc"# by MkCore.mkStringExprFS, or
unpackCStringUtf8# when the literal contains multi-byte UTF8 characters.

For optimizations we want to be able to treat it as a list, so they can be
decomposed when used in a case-statement. exprIsConApp_maybe detects those
calls to unpackCString# and returns:

Just (':', [Char], ['a', unpackCString# "bc"]).

We need to be careful about UTF8 strings here. ""# contains a ByteString, so
we must parse it back into a FastString to split off the first character.
That way we can treat unpackCString# and unpackCStringUtf8# in the same way.

We must also be caeful about
   lvl = "foo"#
   ...(unpackCString# lvl)...
to ensure that we see through the let-binding for 'lvl'.  Hence the
(exprIsLiteral_maybe .. arg) in the guard before the call to
dealWithStringLiteral.

Note [Push coercions in exprIsConApp_maybe]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In #13025 I found a case where we had
    op (df @t1 @t2)     -- op is a ClassOp
where
    df = (/\a b. K e1 e2) |> g

To get this to come out we need to simplify on the fly
   ((/\a b. K e1 e2) |> g) @t1 @t2

Hence the use of pushCoArgs.

Note [exprIsConApp_maybe on data constructors with wrappers]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Problem:
- some data constructors have wrappers
- these wrappers inline late (see MkId Note [Activation for data constructor wrappers])
- but we still want case-of-known-constructor to fire early.

Example:
   data T = MkT !Int
   $WMkT n = case n of n' -> MkT n'   -- Wrapper for MkT
   foo x = case $WMkT e of MkT y -> blah

Here we want the case-of-known-constructor transformation to fire, giving
   foo x = case e of x' -> let y = x' in blah

Here's how exprIsConApp_maybe achieves this:

0.  Start with scrutinee = $WMkT e

1.  Inline $WMkT on-the-fly.  That's why data-constructor wrappers are marked
    as expandable. (See CoreUtils.isExpandableApp.) Now we have
      scrutinee = (\n. case n of n' -> MkT n') e

2.  Beta-reduce the application, generating a floated 'let'.
    See Note [beta-reduction in exprIsConApp_maybe] below.  Now we have
      scrutinee = case n of n' -> MkT n'
      with floats {Let n = e}

3.  Float the "case x of x' ->" binding out.  Now we have
      scrutinee = MkT n'
      with floats {Let n = e; case n of n' ->}

And now we have a known-constructor MkT that we can return.

Notice that both (2) and (3) require exprIsConApp_maybe to gather and return
a bunch of floats, both let and case bindings.

Note [beta-reduction in exprIsConApp_maybe]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The unfolding a definition (_e.g._ a let-bound variable or a datacon wrapper) is
typically a function. For instance, take the wrapper for MkT in Note
[exprIsConApp_maybe on data constructors with wrappers]:

    $WMkT n = case n of { n' -> T n' }

If `exprIsConApp_maybe` is trying to analyse `$MkT arg`, upon unfolding of $MkT,
it will see

   (\n -> case n of { n' -> T n' }) arg

In order to go progress, `exprIsConApp_maybe` must perform a beta-reduction.

We don't want to blindly substitute `arg` in the body of the function, because
it duplicates work. We can (and, in fact, used to) substitute `arg` in the body,
but only when `arg` is a variable (or something equally work-free).

But, because of Note [exprIsConApp_maybe on data constructors with wrappers],
'exprIsConApp_maybe' now returns floats. So, instead, we can beta-reduce
_always_:

    (\x -> body) arg

Is transformed into

   let x = arg in body

Which, effectively, means emitting a float `let x = arg` and recursively
analysing the body.

For newtypes, this strategy requires that their wrappers have compulsory unfoldings.
Suppose we have
   newtype T a b where
     MkT :: a -> T b a   -- Note args swapped

This defines a worker function MkT, a wrapper function $WMkT, and an axT:
   $WMkT :: forall a b. a -> T b a
   $WMkT = /\b a. \(x:a). MkT a b x    -- A real binding

   MkT :: forall a b. a -> T a b
   MkT = /\a b. \(x:a). x |> (ax a b)  -- A compulsory unfolding

   axiom axT :: a ~R# T a b

Now we are optimising
   case $WMkT (I# 3) |> sym axT of I# y -> ...
we clearly want to simplify this. If $WMkT did not have a compulsory
unfolding, we would end up with
   let a = I#3 in case a of I# y -> ...
because in general, we do this on-the-fly beta-reduction
   (\x. e) blah  -->  let x = blah in e
and then float the the let.  (Substitution would risk duplicating 'blah'.)

But if the case-of-known-constructor doesn't actually fire (i.e.
exprIsConApp_maybe does not return Just) then nothing happens, and nothing
will happen the next time either.

See test T16254, which checks the behavior of newtypes.
-}

data ConCont = CC [CoreExpr] Coercion
                  -- Substitution already applied

-- | Returns @Just ([b1..bp], dc, [t1..tk], [x1..xn])@ if the argument
-- expression is a *saturated* constructor application of the form @let b1 in
-- .. let bp in dc t1..tk x1 .. xn@, where t1..tk are the
-- *universally-quantified* type args of 'dc'. Floats can also be (and most
-- likely are) single-alternative case expressions. Why does
-- 'exprIsConApp_maybe' return floats? We may have to look through lets and
-- cases to detect that we are in the presence of a data constructor wrapper. In
-- this case, we need to return the lets and cases that we traversed. See Note
-- [exprIsConApp_maybe on data constructors with wrappers]. Data constructor wrappers
-- are unfolded late, but we really want to trigger case-of-known-constructor as
-- early as possible. See also Note [Activation for data constructor wrappers]
-- in MkId.
--
-- We also return the incoming InScopeSet, augmented with
-- the binders from any [FloatBind] that we return
exprIsConApp_maybe :: InScopeEnv -> CoreExpr
                   -> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
exprIsConApp_maybe :: (InScopeSet, IdUnfoldingFun)
-> CoreExpr
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
exprIsConApp_maybe (InScopeSet
in_scope, IdUnfoldingFun
id_unf) CoreExpr
expr
  = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go (InScopeSet -> Either InScopeSet Subst
forall a b. a -> Either a b
Left InScopeSet
in_scope) [] CoreExpr
expr ([CoreExpr] -> Coercion -> ConCont
CC [] (Type -> Coercion
mkRepReflCo (CoreExpr -> Type
exprType CoreExpr
expr)))
  where
    go :: Either InScopeSet Subst
             -- Left in-scope  means "empty substitution"
             -- Right subst    means "apply this substitution to the CoreExpr"
             -- NB: in the call (go subst floats expr cont)
             --     the substitution applies to 'expr', but /not/ to 'floats' or 'cont'
       -> [FloatBind] -> CoreExpr -> ConCont
             -- Notice that the floats here are in reverse order
       -> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
    go :: Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
subst [FloatBind]
floats (Tick Tickish Id
t CoreExpr
expr) ConCont
cont
       | Bool -> Bool
not (Tickish Id -> Bool
forall id. Tickish id -> Bool
tickishIsCode Tickish Id
t) = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
subst [FloatBind]
floats CoreExpr
expr ConCont
cont

    go Either InScopeSet Subst
subst [FloatBind]
floats (Cast CoreExpr
expr Coercion
co1) (CC [CoreExpr]
args Coercion
co2)
       | Just ([CoreExpr]
args', MCoercion
m_co1') <- Coercion -> [CoreExpr] -> Maybe ([CoreExpr], MCoercion)
pushCoArgs (Either InScopeSet Subst -> Coercion -> Coercion
forall a. Either a Subst -> Coercion -> Coercion
subst_co Either InScopeSet Subst
subst Coercion
co1) [CoreExpr]
args
            -- See Note [Push coercions in exprIsConApp_maybe]
       = case MCoercion
m_co1' of
           MCo Coercion
co1' -> Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
subst [FloatBind]
floats CoreExpr
expr ([CoreExpr] -> Coercion -> ConCont
CC [CoreExpr]
args' (Coercion
co1' Coercion -> Coercion -> Coercion
`mkTransCo` Coercion
co2))
           MCoercion
MRefl    -> Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
subst [FloatBind]
floats CoreExpr
expr ([CoreExpr] -> Coercion -> ConCont
CC [CoreExpr]
args' Coercion
co2)

    go Either InScopeSet Subst
subst [FloatBind]
floats (App CoreExpr
fun CoreExpr
arg) (CC [CoreExpr]
args Coercion
co)
       = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
subst [FloatBind]
floats CoreExpr
fun ([CoreExpr] -> Coercion -> ConCont
CC (Either InScopeSet Subst -> CoreExpr -> CoreExpr
forall a. Either a Subst -> CoreExpr -> CoreExpr
subst_expr Either InScopeSet Subst
subst CoreExpr
arg CoreExpr -> [CoreExpr] -> [CoreExpr]
forall a. a -> [a] -> [a]
: [CoreExpr]
args) Coercion
co)

    go Either InScopeSet Subst
subst [FloatBind]
floats (Lam Id
bndr CoreExpr
body) (CC (CoreExpr
arg:[CoreExpr]
args) Coercion
co)
       | CoreExpr -> Bool
exprIsTrivial CoreExpr
arg          -- Don't duplicate stuff!
       = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go (Either InScopeSet Subst
-> Id -> CoreExpr -> Either InScopeSet Subst
forall a.
Either InScopeSet Subst -> Id -> CoreExpr -> Either a Subst
extend Either InScopeSet Subst
subst Id
bndr CoreExpr
arg) [FloatBind]
floats CoreExpr
body ([CoreExpr] -> Coercion -> ConCont
CC [CoreExpr]
args Coercion
co)
       | Bool
otherwise
       = let (Either a Subst
subst', Id
bndr') = Either InScopeSet Subst -> Id -> (Either a Subst, Id)
forall a. Either InScopeSet Subst -> Id -> (Either a Subst, Id)
subst_bndr Either InScopeSet Subst
subst Id
bndr
             float :: FloatBind
float           = InBind -> FloatBind
FloatLet (Id -> CoreExpr -> InBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr' CoreExpr
arg)
         in Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
forall a. Either a Subst
subst' (FloatBind
floatFloatBind -> [FloatBind] -> [FloatBind]
forall a. a -> [a] -> [a]
:[FloatBind]
floats) CoreExpr
body ([CoreExpr] -> Coercion -> ConCont
CC [CoreExpr]
args Coercion
co)

    go Either InScopeSet Subst
subst [FloatBind]
floats (Let (NonRec Id
bndr CoreExpr
rhs) CoreExpr
expr) ConCont
cont
       = let rhs' :: CoreExpr
rhs'            = Either InScopeSet Subst -> CoreExpr -> CoreExpr
forall a. Either a Subst -> CoreExpr -> CoreExpr
subst_expr Either InScopeSet Subst
subst CoreExpr
rhs
             (Either a Subst
subst', Id
bndr') = Either InScopeSet Subst -> Id -> (Either a Subst, Id)
forall a. Either InScopeSet Subst -> Id -> (Either a Subst, Id)
subst_bndr Either InScopeSet Subst
subst Id
bndr
             float :: FloatBind
float           = InBind -> FloatBind
FloatLet (Id -> CoreExpr -> InBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr' CoreExpr
rhs')
         in Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
forall a. Either a Subst
subst' (FloatBind
floatFloatBind -> [FloatBind] -> [FloatBind]
forall a. a -> [a] -> [a]
:[FloatBind]
floats) CoreExpr
expr ConCont
cont

    go Either InScopeSet Subst
subst [FloatBind]
floats (Case CoreExpr
scrut Id
b Type
_ [(AltCon
con, [Id]
vars, CoreExpr
expr)]) ConCont
cont
       = let
          scrut' :: CoreExpr
scrut'           = Either InScopeSet Subst -> CoreExpr -> CoreExpr
forall a. Either a Subst -> CoreExpr -> CoreExpr
subst_expr Either InScopeSet Subst
subst CoreExpr
scrut
          (Either a Subst
subst', Id
b')     = Either InScopeSet Subst -> Id -> (Either a Subst, Id)
forall a. Either InScopeSet Subst -> Id -> (Either a Subst, Id)
subst_bndr Either InScopeSet Subst
subst Id
b
          (Either InScopeSet Subst
subst'', [Id]
vars') = Either InScopeSet Subst -> [Id] -> (Either InScopeSet Subst, [Id])
forall (t :: * -> *).
Traversable t =>
Either InScopeSet Subst -> t Id -> (Either InScopeSet Subst, t Id)
subst_bndrs Either InScopeSet Subst
forall a. Either a Subst
subst' [Id]
vars
          float :: FloatBind
float            = CoreExpr -> Id -> AltCon -> [Id] -> FloatBind
FloatCase CoreExpr
scrut' Id
b' AltCon
con [Id]
vars'
         in
           Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go Either InScopeSet Subst
subst'' (FloatBind
floatFloatBind -> [FloatBind] -> [FloatBind]
forall a. a -> [a] -> [a]
:[FloatBind]
floats) CoreExpr
expr ConCont
cont

    go (Right Subst
sub) [FloatBind]
floats (Var Id
v) ConCont
cont
       = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go (InScopeSet -> Either InScopeSet Subst
forall a b. a -> Either a b
Left (Subst -> InScopeSet
substInScope Subst
sub))
            [FloatBind]
floats
            (SDoc -> Subst -> Id -> CoreExpr
lookupIdSubst (String -> SDoc
text String
"exprIsConApp" SDoc -> SDoc -> SDoc
<+> CoreExpr -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreExpr
expr) Subst
sub Id
v)
            ConCont
cont

    go (Left InScopeSet
in_scope) [FloatBind]
floats (Var Id
fun) cont :: ConCont
cont@(CC [CoreExpr]
args Coercion
co)

        | Just DataCon
con <- Id -> Maybe DataCon
isDataConWorkId_maybe Id
fun
        , (CoreExpr -> Bool) -> [CoreExpr] -> Int
forall a. (a -> Bool) -> [a] -> Int
count CoreExpr -> Bool
forall b. Expr b -> Bool
isValArg [CoreExpr]
args Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Id -> Int
idArity Id
fun
        = InScopeSet
-> [FloatBind]
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
succeedWith InScopeSet
in_scope [FloatBind]
floats (Maybe (DataCon, [Type], [CoreExpr])
 -> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr]))
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
forall a b. (a -> b) -> a -> b
$
          DataCon
-> [CoreExpr] -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
pushCoDataCon DataCon
con [CoreExpr]
args Coercion
co

        -- Look through data constructor wrappers: they inline late (See Note
        -- [Activation for data constructor wrappers]) but we want to do
        -- case-of-known-constructor optimisation eagerly.
        | Id -> Bool
isDataConWrapId Id
fun
        , let rhs :: CoreExpr
rhs = Unfolding -> CoreExpr
uf_tmpl (IdUnfoldingFun
realIdUnfolding Id
fun)
        = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go (InScopeSet -> Either InScopeSet Subst
forall a b. a -> Either a b
Left InScopeSet
in_scope) [FloatBind]
floats CoreExpr
rhs ConCont
cont

        -- Look through dictionary functions; see Note [Unfolding DFuns]
        | DFunUnfolding { df_bndrs :: Unfolding -> [Id]
df_bndrs = [Id]
bndrs, df_con :: Unfolding -> DataCon
df_con = DataCon
con, df_args :: Unfolding -> [CoreExpr]
df_args = [CoreExpr]
dfun_args } <- Unfolding
unfolding
        , [Id]
bndrs [Id] -> [CoreExpr] -> Bool
forall a b. [a] -> [b] -> Bool
`equalLength` [CoreExpr]
args    -- See Note [DFun arity check]
        , let subst :: Subst
subst = InScopeSet -> [(Id, CoreExpr)] -> Subst
mkOpenSubst InScopeSet
in_scope ([Id]
bndrs [Id] -> [CoreExpr] -> [(Id, CoreExpr)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [CoreExpr]
args)
        = InScopeSet
-> [FloatBind]
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
succeedWith InScopeSet
in_scope [FloatBind]
floats (Maybe (DataCon, [Type], [CoreExpr])
 -> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr]))
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
forall a b. (a -> b) -> a -> b
$
          DataCon
-> [CoreExpr] -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
pushCoDataCon DataCon
con ((CoreExpr -> CoreExpr) -> [CoreExpr] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map (SDoc -> Subst -> CoreExpr -> CoreExpr
substExpr (String -> SDoc
text String
"exprIsConApp1") Subst
subst) [CoreExpr]
dfun_args) Coercion
co

        -- Look through unfoldings, but only arity-zero one;
        -- if arity > 0 we are effectively inlining a function call,
        -- and that is the business of callSiteInline.
        -- In practice, without this test, most of the "hits" were
        -- CPR'd workers getting inlined back into their wrappers,
        | Id -> Int
idArity Id
fun Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0
        , Just CoreExpr
rhs <- Unfolding -> Maybe CoreExpr
expandUnfolding_maybe Unfolding
unfolding
        , let in_scope' :: InScopeSet
in_scope' = InScopeSet -> VarSet -> InScopeSet
extendInScopeSetSet InScopeSet
in_scope (CoreExpr -> VarSet
exprFreeVars CoreExpr
rhs)
        = Either InScopeSet Subst
-> [FloatBind]
-> CoreExpr
-> ConCont
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
go (InScopeSet -> Either InScopeSet Subst
forall a b. a -> Either a b
Left InScopeSet
in_scope') [FloatBind]
floats CoreExpr
rhs ConCont
cont

        -- See Note [exprIsConApp_maybe on literal strings]
        | (Id
fun Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
unpackCStringIdKey) Bool -> Bool -> Bool
||
          (Id
fun Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
unpackCStringUtf8IdKey)
        , [CoreExpr
arg]              <- [CoreExpr]
args
        , Just (LitString ByteString
str) <- (InScopeSet, IdUnfoldingFun) -> CoreExpr -> Maybe Literal
exprIsLiteral_maybe (InScopeSet
in_scope, IdUnfoldingFun
id_unf) CoreExpr
arg
        = InScopeSet
-> [FloatBind]
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
succeedWith InScopeSet
in_scope [FloatBind]
floats (Maybe (DataCon, [Type], [CoreExpr])
 -> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr]))
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
forall a b. (a -> b) -> a -> b
$
          Id -> ByteString -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
dealWithStringLiteral Id
fun ByteString
str Coercion
co
        where
          unfolding :: Unfolding
unfolding = IdUnfoldingFun
id_unf Id
fun

    go Either InScopeSet Subst
_ [FloatBind]
_ CoreExpr
_ ConCont
_ = Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
forall a. Maybe a
Nothing

    succeedWith :: InScopeSet -> [FloatBind]
                -> Maybe (DataCon, [Type], [CoreExpr])
                -> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
    succeedWith :: InScopeSet
-> [FloatBind]
-> Maybe (DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
succeedWith InScopeSet
in_scope [FloatBind]
rev_floats Maybe (DataCon, [Type], [CoreExpr])
x
      = do { (DataCon
con, [Type]
tys, [CoreExpr]
args) <- Maybe (DataCon, [Type], [CoreExpr])
x
           ; let floats :: [FloatBind]
floats = [FloatBind] -> [FloatBind]
forall a. [a] -> [a]
reverse [FloatBind]
rev_floats
           ; (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
-> Maybe (InScopeSet, [FloatBind], DataCon, [Type], [CoreExpr])
forall (m :: * -> *) a. Monad m => a -> m a
return (InScopeSet
in_scope, [FloatBind]
floats, DataCon
con, [Type]
tys, [CoreExpr]
args) }

    ----------------------------
    -- Operations on the (Either InScopeSet CoreSubst)
    -- The Left case is wildly dominant
    subst_co :: Either a Subst -> Coercion -> Coercion
subst_co (Left {}) Coercion
co = Coercion
co
    subst_co (Right Subst
s) Coercion
co = HasCallStack => Subst -> Coercion -> Coercion
Subst -> Coercion -> Coercion
CoreSubst.substCo Subst
s Coercion
co

    subst_expr :: Either a Subst -> CoreExpr -> CoreExpr
subst_expr (Left {}) CoreExpr
e = CoreExpr
e
    subst_expr (Right Subst
s) CoreExpr
e = SDoc -> Subst -> CoreExpr -> CoreExpr
substExpr (String -> SDoc
text String
"exprIsConApp2") Subst
s CoreExpr
e

    subst_bndr :: Either InScopeSet Subst -> Id -> (Either a Subst, Id)
subst_bndr Either InScopeSet Subst
msubst Id
bndr
      = (Subst -> Either a Subst
forall a b. b -> Either a b
Right Subst
subst', Id
bndr')
      where
        (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr Subst
subst Id
bndr
        subst :: Subst
subst = case Either InScopeSet Subst
msubst of
                  Left in_scope -> InScopeSet -> Subst
mkEmptySubst InScopeSet
in_scope
                  Right subst   -> Subst
subst

    subst_bndrs :: Either InScopeSet Subst -> t Id -> (Either InScopeSet Subst, t Id)
subst_bndrs Either InScopeSet Subst
subst t Id
bs = (Either InScopeSet Subst -> Id -> (Either InScopeSet Subst, Id))
-> Either InScopeSet Subst
-> t Id
-> (Either InScopeSet Subst, t Id)
forall (t :: * -> *) a b c.
Traversable t =>
(a -> b -> (a, c)) -> a -> t b -> (a, t c)
mapAccumL Either InScopeSet Subst -> Id -> (Either InScopeSet Subst, Id)
forall a. Either InScopeSet Subst -> Id -> (Either a Subst, Id)
subst_bndr Either InScopeSet Subst
subst t Id
bs

    extend :: Either InScopeSet Subst -> Id -> CoreExpr -> Either a Subst
extend (Left InScopeSet
in_scope) Id
v CoreExpr
e = Subst -> Either a Subst
forall a b. b -> Either a b
Right (Subst -> Id -> CoreExpr -> Subst
extendSubst (InScopeSet -> Subst
mkEmptySubst InScopeSet
in_scope) Id
v CoreExpr
e)
    extend (Right Subst
s)       Id
v CoreExpr
e = Subst -> Either a Subst
forall a b. b -> Either a b
Right (Subst -> Id -> CoreExpr -> Subst
extendSubst Subst
s Id
v CoreExpr
e)


-- See Note [exprIsConApp_maybe on literal strings]
dealWithStringLiteral :: Var -> BS.ByteString -> Coercion
                      -> Maybe (DataCon, [Type], [CoreExpr])

-- This is not possible with user-supplied empty literals, MkCore.mkStringExprFS
-- turns those into [] automatically, but just in case something else in GHC
-- generates a string literal directly.
dealWithStringLiteral :: Id -> ByteString -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
dealWithStringLiteral Id
_   ByteString
str Coercion
co
  | ByteString -> Bool
BS.null ByteString
str
  = DataCon
-> [CoreExpr] -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
pushCoDataCon DataCon
nilDataCon [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
charTy] Coercion
co

dealWithStringLiteral Id
fun ByteString
str Coercion
co
  = let strFS :: FastString
strFS = ByteString -> FastString
mkFastStringByteString ByteString
str

        char :: Expr b
char = DataCon -> [Expr b] -> Expr b
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
charDataCon [Char -> Expr b
forall b. Char -> Expr b
mkCharLit (FastString -> Char
headFS FastString
strFS)]
        charTail :: ByteString
charTail = FastString -> ByteString
bytesFS (FastString -> FastString
tailFS FastString
strFS)

        -- In singleton strings, just add [] instead of unpackCstring# ""#.
        rest :: Expr b
rest = if ByteString -> Bool
BS.null ByteString
charTail
                 then DataCon -> [Expr b] -> Expr b
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
nilDataCon [Type -> Expr b
forall b. Type -> Expr b
Type Type
charTy]
                 else Expr b -> Expr b -> Expr b
forall b. Expr b -> Expr b -> Expr b
App (Id -> Expr b
forall b. Id -> Expr b
Var Id
fun)
                          (Literal -> Expr b
forall b. Literal -> Expr b
Lit (ByteString -> Literal
LitString ByteString
charTail))

    in DataCon
-> [CoreExpr] -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
pushCoDataCon DataCon
consDataCon [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
charTy, CoreExpr
forall b. Expr b
char, CoreExpr
forall b. Expr b
rest] Coercion
co

{-
Note [Unfolding DFuns]
~~~~~~~~~~~~~~~~~~~~~~
DFuns look like

  df :: forall a b. (Eq a, Eq b) -> Eq (a,b)
  df a b d_a d_b = MkEqD (a,b) ($c1 a b d_a d_b)
                               ($c2 a b d_a d_b)

So to split it up we just need to apply the ops $c1, $c2 etc
to the very same args as the dfun.  It takes a little more work
to compute the type arguments to the dictionary constructor.

Note [DFun arity check]
~~~~~~~~~~~~~~~~~~~~~~~
Here we check that the total number of supplied arguments (inclding
type args) matches what the dfun is expecting.  This may be *less*
than the ordinary arity of the dfun: see Note [DFun unfoldings] in CoreSyn
-}

exprIsLiteral_maybe :: InScopeEnv -> CoreExpr -> Maybe Literal
-- Same deal as exprIsConApp_maybe, but much simpler
-- Nevertheless we do need to look through unfoldings for
-- Integer and string literals, which are vigorously hoisted to top level
-- and not subsequently inlined
exprIsLiteral_maybe :: (InScopeSet, IdUnfoldingFun) -> CoreExpr -> Maybe Literal
exprIsLiteral_maybe env :: (InScopeSet, IdUnfoldingFun)
env@(InScopeSet
_, IdUnfoldingFun
id_unf) CoreExpr
e
  = case CoreExpr
e of
      Lit Literal
l     -> Literal -> Maybe Literal
forall a. a -> Maybe a
Just Literal
l
      Tick Tickish Id
_ CoreExpr
e' -> (InScopeSet, IdUnfoldingFun) -> CoreExpr -> Maybe Literal
exprIsLiteral_maybe (InScopeSet, IdUnfoldingFun)
env CoreExpr
e' -- dubious?
      Var Id
v     | Just CoreExpr
rhs <- Unfolding -> Maybe CoreExpr
expandUnfolding_maybe (IdUnfoldingFun
id_unf Id
v)
                -> (InScopeSet, IdUnfoldingFun) -> CoreExpr -> Maybe Literal
exprIsLiteral_maybe (InScopeSet, IdUnfoldingFun)
env CoreExpr
rhs
      CoreExpr
_         -> Maybe Literal
forall a. Maybe a
Nothing

{-
Note [exprIsLambda_maybe]
~~~~~~~~~~~~~~~~~~~~~~~~~~
exprIsLambda_maybe will, given an expression `e`, try to turn it into the form
`Lam v e'` (returned as `Just (v,e')`). Besides using lambdas, it looks through
casts (using the Push rule), and it unfolds function calls if the unfolding
has a greater arity than arguments are present.

Currently, it is used in Rules.match, and is required to make
"map coerce = coerce" match.
-}

exprIsLambda_maybe :: InScopeEnv -> CoreExpr
                      -> Maybe (Var, CoreExpr,[Tickish Id])
    -- See Note [exprIsLambda_maybe]

-- The simple case: It is a lambda already
exprIsLambda_maybe :: (InScopeSet, IdUnfoldingFun)
-> CoreExpr -> Maybe (Id, CoreExpr, [Tickish Id])
exprIsLambda_maybe (InScopeSet, IdUnfoldingFun)
_ (Lam Id
x CoreExpr
e)
    = (Id, CoreExpr, [Tickish Id]) -> Maybe (Id, CoreExpr, [Tickish Id])
forall a. a -> Maybe a
Just (Id
x, CoreExpr
e, [])

-- Still straightforward: Ticks that we can float out of the way
exprIsLambda_maybe (InScopeSet
in_scope_set, IdUnfoldingFun
id_unf) (Tick Tickish Id
t CoreExpr
e)
    | Tickish Id -> Bool
forall id. Tickish id -> Bool
tickishFloatable Tickish Id
t
    , Just (Id
x, CoreExpr
e, [Tickish Id]
ts) <- (InScopeSet, IdUnfoldingFun)
-> CoreExpr -> Maybe (Id, CoreExpr, [Tickish Id])
exprIsLambda_maybe (InScopeSet
in_scope_set, IdUnfoldingFun
id_unf) CoreExpr
e
    = (Id, CoreExpr, [Tickish Id]) -> Maybe (Id, CoreExpr, [Tickish Id])
forall a. a -> Maybe a
Just (Id
x, CoreExpr
e, Tickish Id
tTickish Id -> [Tickish Id] -> [Tickish Id]
forall a. a -> [a] -> [a]
:[Tickish Id]
ts)

-- Also possible: A casted lambda. Push the coercion inside
exprIsLambda_maybe (InScopeSet
in_scope_set, IdUnfoldingFun
id_unf) (Cast CoreExpr
casted_e Coercion
co)
    | Just (Id
x, CoreExpr
e,[Tickish Id]
ts) <- (InScopeSet, IdUnfoldingFun)
-> CoreExpr -> Maybe (Id, CoreExpr, [Tickish Id])
exprIsLambda_maybe (InScopeSet
in_scope_set, IdUnfoldingFun
id_unf) CoreExpr
casted_e
    -- Only do value lambdas.
    -- this implies that x is not in scope in gamma (makes this code simpler)
    , Bool -> Bool
not (Id -> Bool
isTyVar Id
x) Bool -> Bool -> Bool
&& Bool -> Bool
not (Id -> Bool
isCoVar Id
x)
    , ASSERT( not $ x `elemVarSet` tyCoVarsOfCo co) True
    , Just (Id
x',CoreExpr
e') <- InScopeSet -> Id -> CoreExpr -> Coercion -> Maybe (Id, CoreExpr)
pushCoercionIntoLambda InScopeSet
in_scope_set Id
x CoreExpr
e Coercion
co
    , let res :: Maybe (Id, CoreExpr, [Tickish Id])
res = (Id, CoreExpr, [Tickish Id]) -> Maybe (Id, CoreExpr, [Tickish Id])
forall a. a -> Maybe a
Just (Id
x',CoreExpr
e',[Tickish Id]
ts)
    = --pprTrace "exprIsLambda_maybe:Cast" (vcat [ppr casted_e,ppr co,ppr res)])
      Maybe (Id, CoreExpr, [Tickish Id])
res

-- Another attempt: See if we find a partial unfolding
exprIsLambda_maybe (InScopeSet
in_scope_set, IdUnfoldingFun
id_unf) CoreExpr
e
    | (Var Id
f, [CoreExpr]
as, [Tickish Id]
ts) <- (Tickish Id -> Bool)
-> CoreExpr -> (CoreExpr, [CoreExpr], [Tickish Id])
forall b.
(Tickish Id -> Bool) -> Expr b -> (Expr b, [Expr b], [Tickish Id])
collectArgsTicks Tickish Id -> Bool
forall id. Tickish id -> Bool
tickishFloatable CoreExpr
e
    , Id -> Int
idArity Id
f Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> (CoreExpr -> Bool) -> [CoreExpr] -> Int
forall a. (a -> Bool) -> [a] -> Int
count CoreExpr -> Bool
forall b. Expr b -> Bool
isValArg [CoreExpr]
as
    -- Make sure there is hope to get a lambda
    , Just CoreExpr
rhs <- Unfolding -> Maybe CoreExpr
expandUnfolding_maybe (IdUnfoldingFun
id_unf Id
f)
    -- Optimize, for beta-reduction
    , let e' :: CoreExpr
e' = DynFlags -> Subst -> CoreExpr -> CoreExpr
simpleOptExprWith DynFlags
unsafeGlobalDynFlags (InScopeSet -> Subst
mkEmptySubst InScopeSet
in_scope_set) (CoreExpr
rhs CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
`mkApps` [CoreExpr]
as)
    -- Recurse, because of possible casts
    , Just (Id
x', CoreExpr
e'', [Tickish Id]
ts') <- (InScopeSet, IdUnfoldingFun)
-> CoreExpr -> Maybe (Id, CoreExpr, [Tickish Id])
exprIsLambda_maybe (InScopeSet
in_scope_set, IdUnfoldingFun
id_unf) CoreExpr
e'
    , let res :: Maybe (Id, CoreExpr, [Tickish Id])
res = (Id, CoreExpr, [Tickish Id]) -> Maybe (Id, CoreExpr, [Tickish Id])
forall a. a -> Maybe a
Just (Id
x', CoreExpr
e'', [Tickish Id]
ts[Tickish Id] -> [Tickish Id] -> [Tickish Id]
forall a. [a] -> [a] -> [a]
++[Tickish Id]
ts')
    = -- pprTrace "exprIsLambda_maybe:Unfold" (vcat [ppr e, ppr (x',e'')])
      Maybe (Id, CoreExpr, [Tickish Id])
res

exprIsLambda_maybe (InScopeSet, IdUnfoldingFun)
_ CoreExpr
_e
    = -- pprTrace "exprIsLambda_maybe:Fail" (vcat [ppr _e])
      Maybe (Id, CoreExpr, [Tickish Id])
forall a. Maybe a
Nothing


{- *********************************************************************
*                                                                      *
              The "push rules"
*                                                                      *
************************************************************************

Here we implement the "push rules" from FC papers:

* The push-argument rules, where we can move a coercion past an argument.
  We have
      (fun |> co) arg
  and we want to transform it to
    (fun arg') |> co'
  for some suitable co' and tranformed arg'.

* The PushK rule for data constructors.  We have
       (K e1 .. en) |> co
  and we want to tranform to
       (K e1' .. en')
  by pushing the coercion into the arguments
-}

pushCoArgs :: CoercionR -> [CoreArg] -> Maybe ([CoreArg], MCoercion)
pushCoArgs :: Coercion -> [CoreExpr] -> Maybe ([CoreExpr], MCoercion)
pushCoArgs Coercion
co []         = ([CoreExpr], MCoercion) -> Maybe ([CoreExpr], MCoercion)
forall (m :: * -> *) a. Monad m => a -> m a
return ([], Coercion -> MCoercion
MCo Coercion
co)
pushCoArgs Coercion
co (CoreExpr
arg:[CoreExpr]
args) = do { (CoreExpr
arg',  MCoercion
m_co1) <- Coercion -> CoreExpr -> Maybe (CoreExpr, MCoercion)
pushCoArg  Coercion
co  CoreExpr
arg
                              ; case MCoercion
m_co1 of
                                  MCo Coercion
co1 -> do { ([CoreExpr]
args', MCoercion
m_co2) <- Coercion -> [CoreExpr] -> Maybe ([CoreExpr], MCoercion)
pushCoArgs Coercion
co1 [CoreExpr]
args
                                                 ; ([CoreExpr], MCoercion) -> Maybe ([CoreExpr], MCoercion)
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr
arg'CoreExpr -> [CoreExpr] -> [CoreExpr]
forall a. a -> [a] -> [a]
:[CoreExpr]
args', MCoercion
m_co2) }
                                  MCoercion
MRefl  -> ([CoreExpr], MCoercion) -> Maybe ([CoreExpr], MCoercion)
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr
arg'CoreExpr -> [CoreExpr] -> [CoreExpr]
forall a. a -> [a] -> [a]
:[CoreExpr]
args, MCoercion
MRefl) }

pushCoArg :: CoercionR -> CoreArg -> Maybe (CoreArg, MCoercion)
-- We have (fun |> co) arg, and we want to transform it to
--         (fun arg) |> co
-- This may fail, e.g. if (fun :: N) where N is a newtype
-- C.f. simplCast in Simplify.hs
-- 'co' is always Representational
-- If the returned coercion is Nothing, then it would have been reflexive
pushCoArg :: Coercion -> CoreExpr -> Maybe (CoreExpr, MCoercion)
pushCoArg Coercion
co (Type Type
ty) = do { (Type
ty', MCoercion
m_co') <- Coercion -> Type -> Maybe (Type, MCoercion)
pushCoTyArg Coercion
co Type
ty
                            ; (CoreExpr, MCoercion) -> Maybe (CoreExpr, MCoercion)
forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty', MCoercion
m_co') }
pushCoArg Coercion
co CoreExpr
val_arg   = do { (Coercion
arg_co, MCoercion
m_co') <- Coercion -> Maybe (Coercion, MCoercion)
pushCoValArg Coercion
co
                            ; (CoreExpr, MCoercion) -> Maybe (CoreExpr, MCoercion)
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr
val_arg CoreExpr -> Coercion -> CoreExpr
`mkCast` Coercion
arg_co, MCoercion
m_co') }

pushCoTyArg :: CoercionR -> Type -> Maybe (Type, MCoercionR)
-- We have (fun |> co) @ty
-- Push the coercion through to return
--         (fun @ty') |> co'
-- 'co' is always Representational
-- If the returned coercion is Nothing, then it would have been reflexive;
-- it's faster not to compute it, though.
pushCoTyArg :: Coercion -> Type -> Maybe (Type, MCoercion)
pushCoTyArg Coercion
co Type
ty
  -- The following is inefficient - don't do `eqType` here, the coercion
  -- optimizer will take care of it. See #14737.
  -- -- | tyL `eqType` tyR
  -- -- = Just (ty, Nothing)

  | Coercion -> Bool
isReflCo Coercion
co
  = (Type, MCoercion) -> Maybe (Type, MCoercion)
forall a. a -> Maybe a
Just (Type
ty, MCoercion
MRefl)

  | Type -> Bool
isForAllTy_ty Type
tyL
  = ASSERT2( isForAllTy_ty tyR, ppr co $$ ppr ty )
    (Type, MCoercion) -> Maybe (Type, MCoercion)
forall a. a -> Maybe a
Just (Type
ty Type -> Coercion -> Type
`mkCastTy` Coercion
co1, Coercion -> MCoercion
MCo Coercion
co2)

  | Bool
otherwise
  = Maybe (Type, MCoercion)
forall a. Maybe a
Nothing
  where
    Pair Type
tyL Type
tyR = Coercion -> Pair Type
coercionKind Coercion
co
       -- co :: tyL ~ tyR
       -- tyL = forall (a1 :: k1). ty1
       -- tyR = forall (a2 :: k2). ty2

    co1 :: Coercion
co1 = Coercion -> Coercion
mkSymCo (HasDebugCallStack => Role -> Int -> Coercion -> Coercion
Role -> Int -> Coercion -> Coercion
mkNthCo Role
Nominal Int
0 Coercion
co)
       -- co1 :: k2 ~N k1
       -- Note that NthCo can extract a Nominal equality between the
       -- kinds of the types related by a coercion between forall-types.
       -- See the NthCo case in CoreLint.

    co2 :: Coercion
co2 = Coercion -> Coercion -> Coercion
mkInstCo Coercion
co (Role -> Type -> Coercion -> Coercion
mkGReflLeftCo Role
Nominal Type
ty Coercion
co1)
        -- co2 :: ty1[ (ty|>co1)/a1 ] ~ ty2[ ty/a2 ]
        -- Arg of mkInstCo is always nominal, hence mkNomReflCo

pushCoValArg :: CoercionR -> Maybe (Coercion, MCoercion)
-- We have (fun |> co) arg
-- Push the coercion through to return
--         (fun (arg |> co_arg)) |> co_res
-- 'co' is always Representational
-- If the second returned Coercion is actually Nothing, then no cast is necessary;
-- the returned coercion would have been reflexive.
pushCoValArg :: Coercion -> Maybe (Coercion, MCoercion)
pushCoValArg Coercion
co
  -- The following is inefficient - don't do `eqType` here, the coercion
  -- optimizer will take care of it. See #14737.
  -- -- | tyL `eqType` tyR
  -- -- = Just (mkRepReflCo arg, Nothing)

  | Coercion -> Bool
isReflCo Coercion
co
  = (Coercion, MCoercion) -> Maybe (Coercion, MCoercion)
forall a. a -> Maybe a
Just (Type -> Coercion
mkRepReflCo Type
arg, MCoercion
MRefl)

  | Type -> Bool
isFunTy Type
tyL
  , (Coercion
co1, Coercion
co2) <- HasDebugCallStack => Role -> Coercion -> (Coercion, Coercion)
Role -> Coercion -> (Coercion, Coercion)
decomposeFunCo Role
Representational Coercion
co
              -- If   co  :: (tyL1 -> tyL2) ~ (tyR1 -> tyR2)
              -- then co1 :: tyL1 ~ tyR1
              --      co2 :: tyL2 ~ tyR2
  = ASSERT2( isFunTy tyR, ppr co $$ ppr arg )
    (Coercion, MCoercion) -> Maybe (Coercion, MCoercion)
forall a. a -> Maybe a
Just (Coercion -> Coercion
mkSymCo Coercion
co1, Coercion -> MCoercion
MCo Coercion
co2)

  | Bool
otherwise
  = Maybe (Coercion, MCoercion)
forall a. Maybe a
Nothing
  where
    arg :: Type
arg = Type -> Type
funArgTy Type
tyR
    Pair Type
tyL Type
tyR = Coercion -> Pair Type
coercionKind Coercion
co

pushCoercionIntoLambda
    :: InScopeSet -> Var -> CoreExpr -> CoercionR -> Maybe (Var, CoreExpr)
-- This implements the Push rule from the paper on coercions
--    (\x. e) |> co
-- ===>
--    (\x'. e |> co')
pushCoercionIntoLambda :: InScopeSet -> Id -> CoreExpr -> Coercion -> Maybe (Id, CoreExpr)
pushCoercionIntoLambda InScopeSet
in_scope Id
x CoreExpr
e Coercion
co
    | ASSERT(not (isTyVar x) && not (isCoVar x)) True
    , Pair Type
s1s2 Type
t1t2 <- Coercion -> Pair Type
coercionKind Coercion
co
    , Just (Type
_s1,Type
_s2) <- Type -> Maybe (Type, Type)
splitFunTy_maybe Type
s1s2
    , Just (Type
t1,Type
_t2) <- Type -> Maybe (Type, Type)
splitFunTy_maybe Type
t1t2
    = let (Coercion
co1, Coercion
co2) = HasDebugCallStack => Role -> Coercion -> (Coercion, Coercion)
Role -> Coercion -> (Coercion, Coercion)
decomposeFunCo Role
Representational Coercion
co
          -- Should we optimize the coercions here?
          -- Otherwise they might not match too well
          x' :: Id
x' = Id
x Id -> Type -> Id
`setIdType` Type
t1
          in_scope' :: InScopeSet
in_scope' = InScopeSet
in_scope InScopeSet -> Id -> InScopeSet
`extendInScopeSet` Id
x'
          subst :: Subst
subst = Subst -> Id -> CoreExpr -> Subst
extendIdSubst (InScopeSet -> Subst
mkEmptySubst InScopeSet
in_scope')
                                Id
x
                                (CoreExpr -> Coercion -> CoreExpr
mkCast (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
x') Coercion
co1)
      in (Id, CoreExpr) -> Maybe (Id, CoreExpr)
forall a. a -> Maybe a
Just (Id
x', SDoc -> Subst -> CoreExpr -> CoreExpr
substExpr (String -> SDoc
text String
"pushCoercionIntoLambda") Subst
subst CoreExpr
e CoreExpr -> Coercion -> CoreExpr
`mkCast` Coercion
co2)
    | Bool
otherwise
    = String -> SDoc -> Maybe (Id, CoreExpr) -> Maybe (Id, CoreExpr)
forall a. String -> SDoc -> a -> a
pprTrace String
"exprIsLambda_maybe: Unexpected lambda in case" (CoreExpr -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
x CoreExpr
e))
      Maybe (Id, CoreExpr)
forall a. Maybe a
Nothing

pushCoDataCon :: DataCon -> [CoreExpr] -> Coercion
              -> Maybe (DataCon
                       , [Type]      -- Universal type args
                       , [CoreExpr]) -- All other args incl existentials
-- Implement the KPush reduction rule as described in "Down with kinds"
-- The transformation applies iff we have
--      (C e1 ... en) `cast` co
-- where co :: (T t1 .. tn) ~ to_ty
-- The left-hand one must be a T, because exprIsConApp returned True
-- but the right-hand one might not be.  (Though it usually will.)
pushCoDataCon :: DataCon
-> [CoreExpr] -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
pushCoDataCon DataCon
dc [CoreExpr]
dc_args Coercion
co
  | Coercion -> Bool
isReflCo Coercion
co Bool -> Bool -> Bool
|| Type
from_ty Type -> Type -> Bool
`eqType` Type
to_ty  -- try cheap test first
  , let ([CoreExpr]
univ_ty_args, [CoreExpr]
rest_args) = [Id] -> [CoreExpr] -> ([CoreExpr], [CoreExpr])
forall b a. [b] -> [a] -> ([a], [a])
splitAtList (DataCon -> [Id]
dataConUnivTyVars DataCon
dc) [CoreExpr]
dc_args
  = (DataCon, [Type], [CoreExpr])
-> Maybe (DataCon, [Type], [CoreExpr])
forall a. a -> Maybe a
Just (DataCon
dc, (CoreExpr -> Type) -> [CoreExpr] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map CoreExpr -> Type
exprToType [CoreExpr]
univ_ty_args, [CoreExpr]
rest_args)

  | Just (TyCon
to_tc, [Type]
to_tc_arg_tys) <- HasDebugCallStack => Type -> Maybe (TyCon, [Type])
Type -> Maybe (TyCon, [Type])
splitTyConApp_maybe Type
to_ty
  , TyCon
to_tc TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== DataCon -> TyCon
dataConTyCon DataCon
dc
        -- These two tests can fail; we might see
        --      (C x y) `cast` (g :: T a ~ S [a]),
        -- where S is a type function.  In fact, exprIsConApp
        -- will probably not be called in such circumstances,
        -- but there's nothing wrong with it

  = let
        tc_arity :: Int
tc_arity       = TyCon -> Int
tyConArity TyCon
to_tc
        dc_univ_tyvars :: [Id]
dc_univ_tyvars = DataCon -> [Id]
dataConUnivTyVars DataCon
dc
        dc_ex_tcvars :: [Id]
dc_ex_tcvars   = DataCon -> [Id]
dataConExTyCoVars DataCon
dc
        arg_tys :: [Type]
arg_tys        = DataCon -> [Type]
dataConRepArgTys DataCon
dc

        non_univ_args :: [CoreExpr]
non_univ_args  = [Id] -> [CoreExpr] -> [CoreExpr]
forall b a. [b] -> [a] -> [a]
dropList [Id]
dc_univ_tyvars [CoreExpr]
dc_args
        ([CoreExpr]
ex_args, [CoreExpr]
val_args) = [Id] -> [CoreExpr] -> ([CoreExpr], [CoreExpr])
forall b a. [b] -> [a] -> ([a], [a])
splitAtList [Id]
dc_ex_tcvars [CoreExpr]
non_univ_args

        -- Make the "Psi" from the paper
        omegas :: [Coercion]
omegas = Int -> Coercion -> [Role] -> [Coercion]
decomposeCo Int
tc_arity Coercion
co (TyCon -> [Role]
tyConRolesRepresentational TyCon
to_tc)
        (Type -> Coercion
psi_subst, [Type]
to_ex_arg_tys)
          = Role
-> [Id]
-> [Coercion]
-> [Id]
-> [Type]
-> (Type -> Coercion, [Type])
liftCoSubstWithEx Role
Representational
                              [Id]
dc_univ_tyvars
                              [Coercion]
omegas
                              [Id]
dc_ex_tcvars
                              ((CoreExpr -> Type) -> [CoreExpr] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map CoreExpr -> Type
exprToType [CoreExpr]
ex_args)

          -- Cast the value arguments (which include dictionaries)
        new_val_args :: [CoreExpr]
new_val_args = (Type -> CoreExpr -> CoreExpr)
-> [Type] -> [CoreExpr] -> [CoreExpr]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith Type -> CoreExpr -> CoreExpr
cast_arg [Type]
arg_tys [CoreExpr]
val_args
        cast_arg :: Type -> CoreExpr -> CoreExpr
cast_arg Type
arg_ty CoreExpr
arg = CoreExpr -> Coercion -> CoreExpr
mkCast CoreExpr
arg (Type -> Coercion
psi_subst Type
arg_ty)

        to_ex_args :: [Expr b]
to_ex_args = (Type -> Expr b) -> [Type] -> [Expr b]
forall a b. (a -> b) -> [a] -> [b]
map Type -> Expr b
forall b. Type -> Expr b
Type [Type]
to_ex_arg_tys

        dump_doc :: SDoc
dump_doc = [SDoc] -> SDoc
vcat [DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
dc,      [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
dc_univ_tyvars, [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
dc_ex_tcvars,
                         [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
arg_tys, [CoreExpr] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [CoreExpr]
dc_args,
                         [CoreExpr] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [CoreExpr]
ex_args, [CoreExpr] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [CoreExpr]
val_args, Coercion -> SDoc
forall a. Outputable a => a -> SDoc
ppr Coercion
co, Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
from_ty, Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
to_ty, TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
to_tc ]
    in
    ASSERT2( eqType from_ty (mkTyConApp to_tc (map exprToType $ takeList dc_univ_tyvars dc_args)), dump_doc )
    ASSERT2( equalLength val_args arg_tys, dump_doc )
    (DataCon, [Type], [CoreExpr])
-> Maybe (DataCon, [Type], [CoreExpr])
forall a. a -> Maybe a
Just (DataCon
dc, [Type]
to_tc_arg_tys, [CoreExpr]
forall b. [Expr b]
to_ex_args [CoreExpr] -> [CoreExpr] -> [CoreExpr]
forall a. [a] -> [a] -> [a]
++ [CoreExpr]
new_val_args)

  | Bool
otherwise
  = Maybe (DataCon, [Type], [CoreExpr])
forall a. Maybe a
Nothing

  where
    Pair Type
from_ty Type
to_ty = Coercion -> Pair Type
coercionKind Coercion
co

collectBindersPushingCo :: CoreExpr -> ([Var], CoreExpr)
-- Collect lambda binders, pushing coercions inside if possible
-- E.g.   (\x.e) |> g         g :: <Int> -> blah
--        = (\x. e |> Nth 1 g)
--
-- That is,
--
-- collectBindersPushingCo ((\x.e) |> g) === ([x], e |> Nth 1 g)
collectBindersPushingCo :: CoreExpr -> ([Id], CoreExpr)
collectBindersPushingCo CoreExpr
e
  = [Id] -> CoreExpr -> ([Id], CoreExpr)
go [] CoreExpr
e
  where
    -- Peel off lambdas until we hit a cast.
    go :: [Var] -> CoreExpr -> ([Var], CoreExpr)
    -- The accumulator is in reverse order
    go :: [Id] -> CoreExpr -> ([Id], CoreExpr)
go [Id]
bs (Lam Id
b CoreExpr
e)   = [Id] -> CoreExpr -> ([Id], CoreExpr)
go (Id
bId -> [Id] -> [Id]
forall a. a -> [a] -> [a]
:[Id]
bs) CoreExpr
e
    go [Id]
bs (Cast CoreExpr
e Coercion
co) = [Id] -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_c [Id]
bs CoreExpr
e Coercion
co
    go [Id]
bs CoreExpr
e           = ([Id] -> [Id]
forall a. [a] -> [a]
reverse [Id]
bs, CoreExpr
e)

    -- We are in a cast; peel off casts until we hit a lambda.
    go_c :: [Var] -> CoreExpr -> CoercionR -> ([Var], CoreExpr)
    -- (go_c bs e c) is same as (go bs e (e |> c))
    go_c :: [Id] -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_c [Id]
bs (Cast CoreExpr
e Coercion
co1) Coercion
co2 = [Id] -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_c [Id]
bs CoreExpr
e (Coercion
co1 Coercion -> Coercion -> Coercion
`mkTransCo` Coercion
co2)
    go_c [Id]
bs (Lam Id
b CoreExpr
e)    Coercion
co  = [Id] -> Id -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_lam [Id]
bs Id
b CoreExpr
e Coercion
co
    go_c [Id]
bs CoreExpr
e            Coercion
co  = ([Id] -> [Id]
forall a. [a] -> [a]
reverse [Id]
bs, CoreExpr -> Coercion -> CoreExpr
mkCast CoreExpr
e Coercion
co)

    -- We are in a lambda under a cast; peel off lambdas and build a
    -- new coercion for the body.
    go_lam :: [Var] -> Var -> CoreExpr -> CoercionR -> ([Var], CoreExpr)
    -- (go_lam bs b e c) is same as (go_c bs (\b.e) c)
    go_lam :: [Id] -> Id -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_lam [Id]
bs Id
b CoreExpr
e Coercion
co
      | Id -> Bool
isTyVar Id
b
      , let Pair Type
tyL Type
tyR = Coercion -> Pair Type
coercionKind Coercion
co
      , ASSERT( isForAllTy_ty tyL )
        Type -> Bool
isForAllTy_ty Type
tyR
      , Coercion -> Bool
isReflCo (HasDebugCallStack => Role -> Int -> Coercion -> Coercion
Role -> Int -> Coercion -> Coercion
mkNthCo Role
Nominal Int
0 Coercion
co)  -- See Note [collectBindersPushingCo]
      = [Id] -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_c (Id
bId -> [Id] -> [Id]
forall a. a -> [a] -> [a]
:[Id]
bs) CoreExpr
e (Coercion -> Coercion -> Coercion
mkInstCo Coercion
co (Type -> Coercion
mkNomReflCo (Id -> Type
mkTyVarTy Id
b)))

      | Id -> Bool
isCoVar Id
b
      , let Pair Type
tyL Type
tyR = Coercion -> Pair Type
coercionKind Coercion
co
      , ASSERT( isForAllTy_co tyL )
        Type -> Bool
isForAllTy_co Type
tyR
      , Coercion -> Bool
isReflCo (HasDebugCallStack => Role -> Int -> Coercion -> Coercion
Role -> Int -> Coercion -> Coercion
mkNthCo Role
Nominal Int
0 Coercion
co)  -- See Note [collectBindersPushingCo]
      , let cov :: Coercion
cov = Id -> Coercion
mkCoVarCo Id
b
      = [Id] -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_c (Id
bId -> [Id] -> [Id]
forall a. a -> [a] -> [a]
:[Id]
bs) CoreExpr
e (Coercion -> Coercion -> Coercion
mkInstCo Coercion
co (Type -> Coercion
mkNomReflCo (Coercion -> Type
mkCoercionTy Coercion
cov)))

      | Id -> Bool
isId Id
b
      , let Pair Type
tyL Type
tyR = Coercion -> Pair Type
coercionKind Coercion
co
      , ASSERT( isFunTy tyL) isFunTy tyR
      , (Coercion
co_arg, Coercion
co_res) <- HasDebugCallStack => Role -> Coercion -> (Coercion, Coercion)
Role -> Coercion -> (Coercion, Coercion)
decomposeFunCo Role
Representational Coercion
co
      , Coercion -> Bool
isReflCo Coercion
co_arg  -- See Note [collectBindersPushingCo]
      = [Id] -> CoreExpr -> Coercion -> ([Id], CoreExpr)
go_c (Id
bId -> [Id] -> [Id]
forall a. a -> [a] -> [a]
:[Id]
bs) CoreExpr
e Coercion
co_res

      | Bool
otherwise = ([Id] -> [Id]
forall a. [a] -> [a]
reverse [Id]
bs, CoreExpr -> Coercion -> CoreExpr
mkCast (Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
b CoreExpr
e) Coercion
co)

{-

Note [collectBindersPushingCo]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We just look for coercions of form
   <type> -> blah
(and similarly for foralls) to keep this function simple.  We could do
more elaborate stuff, but it'd involve substitution etc.

-}