{-# LANGUAGE CPP          #-}
{-# LANGUAGE BangPatterns #-}

{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

{-
(c) The University of Glasgow, 1994-2006


Core pass to saturate constructors and PrimOps
-}

module GHC.CoreToStg.Prep
   ( corePrepPgm
   , corePrepExpr
   , mkConvertNumLiteral
   )
where

#include "HsVersions.h"

import GHC.Prelude

import GHC.Platform
import GHC.Platform.Ways

import GHC.Driver.Session
import GHC.Driver.Env
import GHC.Driver.Ppr

import GHC.Tc.Utils.Env
import GHC.Unit

import GHC.Builtin.Names
import GHC.Builtin.PrimOps
import GHC.Builtin.Types
import GHC.Builtin.Types.Prim ( realWorldStatePrimTy )
import GHC.Types.Id.Make ( realWorldPrimId, mkPrimOpId )

import GHC.Core.Utils
import GHC.Core.Opt.Arity
import GHC.Core.FVs
import GHC.Core.Opt.Monad ( CoreToDo(..) )
import GHC.Core.Lint    ( endPassIO )
import GHC.Core
import GHC.Core.Make hiding( FloatBind(..) )   -- We use our own FloatBind here
import GHC.Core.Type
import GHC.Core.Coercion
import GHC.Core.TyCon
import GHC.Core.DataCon
import GHC.Core.Opt.OccurAnal
import GHC.Core.TyCo.Rep( UnivCoProvenance(..) )


import GHC.Data.Maybe
import GHC.Data.OrdList
import GHC.Data.FastString

import GHC.Utils.Error
import GHC.Utils.Misc
import GHC.Utils.Panic
import GHC.Utils.Outputable
import GHC.Utils.Monad  ( mapAccumLM )
import GHC.Utils.Logger

import GHC.Types.Demand
import GHC.Types.Var
import GHC.Types.Var.Set
import GHC.Types.Var.Env
import GHC.Types.Id
import GHC.Types.Id.Info
import GHC.Types.Basic
import GHC.Types.Name   ( NamedThing(..), nameSrcSpan, isInternalName )
import GHC.Types.SrcLoc ( SrcSpan(..), realSrcLocSpan, mkRealSrcLoc )
import GHC.Types.Literal
import GHC.Types.Tickish
import GHC.Types.TyThing
import GHC.Types.CostCentre ( CostCentre, ccFromThisModule )
import GHC.Types.Unique.Supply

import GHC.Data.Pair
import Data.List        ( unfoldr )
import Data.Functor.Identity
import Control.Monad
import qualified Data.Set as S

{-
-- ---------------------------------------------------------------------------
-- Note [CorePrep Overview]
-- ---------------------------------------------------------------------------

The goal of this pass is to prepare for code generation.

1.  Saturate constructor and primop applications.

2.  Convert to A-normal form; that is, function arguments
    are always variables.

    * Use case for strict arguments:
        f E ==> case E of x -> f x
        (where f is strict)

    * Use let for non-trivial lazy arguments
        f E ==> let x = E in f x
        (were f is lazy and x is non-trivial)

3.  Similarly, convert any unboxed lets into cases.
    [I'm experimenting with leaving 'ok-for-speculation'
     rhss in let-form right up to this point.]

4.  Ensure that *value* lambdas only occur as the RHS of a binding
    (The code generator can't deal with anything else.)
    Type lambdas are ok, however, because the code gen discards them.

5.  [Not any more; nuked Jun 2002] Do the seq/par munging.

6.  Clone all local Ids.
    This means that all such Ids are unique, rather than the
    weaker guarantee of no clashes which the simplifier provides.
    And that is what the code generator needs.

    We don't clone TyVars or CoVars. The code gen doesn't need that,
    and doing so would be tiresome because then we'd need
    to substitute in types and coercions.

7.  Give each dynamic CCall occurrence a fresh unique; this is
    rather like the cloning step above.

8.  Inject bindings for the "implicit" Ids:
        * Constructor wrappers
        * Constructor workers
    We want curried definitions for all of these in case they
    aren't inlined by some caller.

9.  Replace (lazy e) by e.  See Note [lazyId magic] in GHC.Types.Id.Make
    Also replace (noinline e) by e.

10. Convert bignum literals (LitNatural and LitInteger) into their
    core representation.

11. Uphold tick consistency while doing this: We move ticks out of
    (non-type) applications where we can, and make sure that we
    annotate according to scoping rules when floating.

12. Collect cost centres (including cost centres in unfoldings) if we're in
    profiling mode. We have to do this here beucase we won't have unfoldings
    after this pass (see `zapUnfolding` and Note [Drop unfoldings and rules].

13. Eliminate case clutter in favour of unsafe coercions.
    See Note [Unsafe coercions]

14. Eliminate some magic Ids, specifically
     runRW# (\s. e)  ==>  e[readWorldId/s]
             lazy e  ==>  e
         noinline e  ==>  e
     ToDo:  keepAlive# ...
    This is done in cpeApp

This is all done modulo type applications and abstractions, so that
when type erasure is done for conversion to STG, we don't end up with
any trivial or useless bindings.

Note [Unsafe coercions]
~~~~~~~~~~~~~~~~~~~~~~~
CorePrep does these two transformations:

* Convert empty case to cast with an unsafe coercion
          (case e of {}) ===>  e |> unsafe-co
  See Note [Empty case alternatives] in GHC.Core: if the case
  alternatives are empty, the scrutinee must diverge or raise an
  exception, so we can just dive into it.

  Of course, if the scrutinee *does* return, we may get a seg-fault.
  A belt-and-braces approach would be to persist empty-alternative
  cases to code generator, and put a return point anyway that calls a
  runtime system error function.

  Notice that eliminating empty case can lead to an ill-kinded coercion
      case error @Int "foo" of {}  :: Int#
      ===> error @Int "foo" |> unsafe-co
      where unsafe-co :: Int ~ Int#
  But that's fine because the expression diverges anyway. And it's
  no different to what happened before.

* Eliminate unsafeEqualityProof in favour of an unsafe coercion
          case unsafeEqualityProof of UnsafeRefl g -> e
          ===>  e[unsafe-co/g]
  See (U2) in Note [Implementing unsafeCoerce] in base:Unsafe.Coerce

  Note that this requiresuse ot substitute 'unsafe-co' for 'g', and
  that is the main (current) reason for cpe_tyco_env in CorePrepEnv.
  Tiresome, but not difficult.

These transformations get rid of "case clutter", leaving only casts.
We are doing no further significant tranformations, so the reasons
for the case forms have disappeared. And it is extremely helpful for
the ANF-ery, CoreToStg, and backends, if trivial expressions really do
look trivial. #19700 was an example.

In both cases, the "unsafe-co" is just (UnivCo ty1 ty2 CorePrepProv).

Note [CorePrep invariants]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Here is the syntax of the Core produced by CorePrep:

    Trivial expressions
       arg ::= lit |  var
              | arg ty  |  /\a. arg
              | truv co  |  /\c. arg  |  arg |> co

    Applications
       app ::= lit  |  var  |  app arg  |  app ty  | app co | app |> co

    Expressions
       body ::= app
              | let(rec) x = rhs in body     -- Boxed only
              | case body of pat -> body
              | /\a. body | /\c. body
              | body |> co

    Right hand sides (only place where value lambdas can occur)
       rhs ::= /\a.rhs  |  \x.rhs  |  body

We define a synonym for each of these non-terminals.  Functions
with the corresponding name produce a result in that syntax.
-}

type CpeArg  = CoreExpr    -- Non-terminal 'arg'
type CpeApp  = CoreExpr    -- Non-terminal 'app'
type CpeBody = CoreExpr    -- Non-terminal 'body'
type CpeRhs  = CoreExpr    -- Non-terminal 'rhs'

{-
************************************************************************
*                                                                      *
                Top level stuff
*                                                                      *
************************************************************************
-}

corePrepPgm :: HscEnv -> Module -> ModLocation -> CoreProgram -> [TyCon]
            -> IO (CoreProgram, S.Set CostCentre)
corePrepPgm :: HscEnv
-> Module
-> ModLocation
-> CoreProgram
-> [TyCon]
-> IO (CoreProgram, Set CostCentre)
corePrepPgm HscEnv
hsc_env Module
this_mod ModLocation
mod_loc CoreProgram
binds [TyCon]
data_tycons =
    Logger
-> DynFlags
-> SDoc
-> ((CoreProgram, Set CostCentre) -> ())
-> IO (CoreProgram, Set CostCentre)
-> IO (CoreProgram, Set CostCentre)
forall (m :: * -> *) a.
MonadIO m =>
Logger -> DynFlags -> SDoc -> (a -> ()) -> m a -> m a
withTiming Logger
logger DynFlags
dflags
               (String -> SDoc
text String
"CorePrep"SDoc -> SDoc -> SDoc
<+>SDoc -> SDoc
brackets (Module -> SDoc
forall a. Outputable a => a -> SDoc
ppr Module
this_mod))
               (\(CoreProgram
a,Set CostCentre
b) -> CoreProgram
a CoreProgram -> Set CostCentre -> Set CostCentre
forall a b. [a] -> b -> b
`seqList` Set CostCentre
b Set CostCentre -> () -> ()
`seq` ()) (IO (CoreProgram, Set CostCentre)
 -> IO (CoreProgram, Set CostCentre))
-> IO (CoreProgram, Set CostCentre)
-> IO (CoreProgram, Set CostCentre)
forall a b. (a -> b) -> a -> b
$ do
    UniqSupply
us <- Char -> IO UniqSupply
mkSplitUniqSupply Char
's'
    CorePrepEnv
initialCorePrepEnv <- HscEnv -> IO CorePrepEnv
mkInitialCorePrepEnv HscEnv
hsc_env

    let cost_centres :: Set CostCentre
cost_centres
          | Way
WayProf Way -> Set Way -> Bool
forall a. Ord a => a -> Set a -> Bool
`S.member` DynFlags -> Set Way
ways DynFlags
dflags
          = Module -> CoreProgram -> Set CostCentre
collectCostCentres Module
this_mod CoreProgram
binds
          | Bool
otherwise
          = Set CostCentre
forall a. Set a
S.empty

        implicit_binds :: CoreProgram
implicit_binds = DynFlags -> ModLocation -> [TyCon] -> CoreProgram
mkDataConWorkers DynFlags
dflags ModLocation
mod_loc [TyCon]
data_tycons
            -- NB: we must feed mkImplicitBinds through corePrep too
            -- so that they are suitably cloned and eta-expanded

        binds_out :: CoreProgram
binds_out = UniqSupply -> UniqSM CoreProgram -> CoreProgram
forall a. UniqSupply -> UniqSM a -> a
initUs_ UniqSupply
us (UniqSM CoreProgram -> CoreProgram)
-> UniqSM CoreProgram -> CoreProgram
forall a b. (a -> b) -> a -> b
$ do
                      Floats
floats1 <- CorePrepEnv -> CoreProgram -> UniqSM Floats
corePrepTopBinds CorePrepEnv
initialCorePrepEnv CoreProgram
binds
                      Floats
floats2 <- CorePrepEnv -> CoreProgram -> UniqSM Floats
corePrepTopBinds CorePrepEnv
initialCorePrepEnv CoreProgram
implicit_binds
                      CoreProgram -> UniqSM CoreProgram
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats -> CoreProgram
deFloatTop (Floats
floats1 Floats -> Floats -> Floats
`appendFloats` Floats
floats2))

    HscEnv
-> PrintUnqualified
-> CoreToDo
-> CoreProgram
-> [CoreRule]
-> IO ()
endPassIO HscEnv
hsc_env PrintUnqualified
alwaysQualify CoreToDo
CorePrep CoreProgram
binds_out []
    (CoreProgram, Set CostCentre) -> IO (CoreProgram, Set CostCentre)
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreProgram
binds_out, Set CostCentre
cost_centres)
  where
    dflags :: DynFlags
dflags = HscEnv -> DynFlags
hsc_dflags HscEnv
hsc_env
    logger :: Logger
logger = HscEnv -> Logger
hsc_logger HscEnv
hsc_env

corePrepExpr :: HscEnv -> CoreExpr -> IO CoreExpr
corePrepExpr :: HscEnv -> CpeBody -> IO CpeBody
corePrepExpr HscEnv
hsc_env CpeBody
expr = do
    let dflags :: DynFlags
dflags = HscEnv -> DynFlags
hsc_dflags HscEnv
hsc_env
    let logger :: Logger
logger = HscEnv -> Logger
hsc_logger HscEnv
hsc_env
    Logger
-> DynFlags -> SDoc -> (CpeBody -> ()) -> IO CpeBody -> IO CpeBody
forall (m :: * -> *) a.
MonadIO m =>
Logger -> DynFlags -> SDoc -> (a -> ()) -> m a -> m a
withTiming Logger
logger DynFlags
dflags (String -> SDoc
text String
"CorePrep [expr]") (\CpeBody
e -> CpeBody
e CpeBody -> () -> ()
`seq` ()) (IO CpeBody -> IO CpeBody) -> IO CpeBody -> IO CpeBody
forall a b. (a -> b) -> a -> b
$ do
      UniqSupply
us <- Char -> IO UniqSupply
mkSplitUniqSupply Char
's'
      CorePrepEnv
initialCorePrepEnv <- HscEnv -> IO CorePrepEnv
mkInitialCorePrepEnv HscEnv
hsc_env
      let new_expr :: CpeBody
new_expr = UniqSupply -> UniqSM CpeBody -> CpeBody
forall a. UniqSupply -> UniqSM a -> a
initUs_ UniqSupply
us (CorePrepEnv -> CpeBody -> UniqSM CpeBody
cpeBodyNF CorePrepEnv
initialCorePrepEnv CpeBody
expr)
      Logger
-> DynFlags -> DumpFlag -> String -> DumpFormat -> SDoc -> IO ()
dumpIfSet_dyn Logger
logger DynFlags
dflags DumpFlag
Opt_D_dump_prep String
"CorePrep" DumpFormat
FormatCore (CpeBody -> SDoc
forall a. Outputable a => a -> SDoc
ppr CpeBody
new_expr)
      CpeBody -> IO CpeBody
forall (m :: * -> *) a. Monad m => a -> m a
return CpeBody
new_expr

corePrepTopBinds :: CorePrepEnv -> [CoreBind] -> UniqSM Floats
-- Note [Floating out of top level bindings]
corePrepTopBinds :: CorePrepEnv -> CoreProgram -> UniqSM Floats
corePrepTopBinds CorePrepEnv
initialCorePrepEnv CoreProgram
binds
  = CorePrepEnv -> CoreProgram -> UniqSM Floats
go CorePrepEnv
initialCorePrepEnv CoreProgram
binds
  where
    go :: CorePrepEnv -> CoreProgram -> UniqSM Floats
go CorePrepEnv
_   []             = Floats -> UniqSM Floats
forall (m :: * -> *) a. Monad m => a -> m a
return Floats
emptyFloats
    go CorePrepEnv
env (CoreBind
bind : CoreProgram
binds) = do (CorePrepEnv
env', Floats
floats, Maybe CoreBind
maybe_new_bind)
                                 <- TopLevelFlag
-> CorePrepEnv
-> CoreBind
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
cpeBind TopLevelFlag
TopLevel CorePrepEnv
env CoreBind
bind
                               MASSERT(isNothing maybe_new_bind)
                                 -- Only join points get returned this way by
                                 -- cpeBind, and no join point may float to top
                               Floats
floatss <- CorePrepEnv -> CoreProgram -> UniqSM Floats
go CorePrepEnv
env' CoreProgram
binds
                               Floats -> UniqSM Floats
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats Floats -> Floats -> Floats
`appendFloats` Floats
floatss)

mkDataConWorkers :: DynFlags -> ModLocation -> [TyCon] -> [CoreBind]
-- See Note [Data constructor workers]
-- c.f. Note [Injecting implicit bindings] in GHC.Iface.Tidy
mkDataConWorkers :: DynFlags -> ModLocation -> [TyCon] -> CoreProgram
mkDataConWorkers DynFlags
dflags ModLocation
mod_loc [TyCon]
data_tycons
  = [ Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
id (Name -> CpeBody -> CpeBody
tick_it (DataCon -> Name
forall a. NamedThing a => a -> Name
getName DataCon
data_con) (Id -> CpeBody
forall b. Id -> Expr b
Var Id
id))
                                -- The ice is thin here, but it works
    | TyCon
tycon <- [TyCon]
data_tycons,     -- CorePrep will eta-expand it
      DataCon
data_con <- TyCon -> [DataCon]
tyConDataCons TyCon
tycon,
      let id :: Id
id = DataCon -> Id
dataConWorkId DataCon
data_con
    ]
 where
   -- If we want to generate debug info, we put a source note on the
   -- worker. This is useful, especially for heap profiling.
   tick_it :: Name -> CpeBody -> CpeBody
tick_it Name
name
     | DynFlags -> Int
debugLevel DynFlags
dflags Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0                = CpeBody -> CpeBody
forall a. a -> a
id
     | RealSrcSpan RealSrcSpan
span Maybe BufSpan
_ <- Name -> SrcSpan
nameSrcSpan Name
name = RealSrcSpan -> CpeBody -> CpeBody
tick RealSrcSpan
span
     | Just String
file <- ModLocation -> Maybe String
ml_hs_file ModLocation
mod_loc       = RealSrcSpan -> CpeBody -> CpeBody
tick (String -> RealSrcSpan
span1 String
file)
     | Bool
otherwise                             = RealSrcSpan -> CpeBody -> CpeBody
tick (String -> RealSrcSpan
span1 String
"???")
     where tick :: RealSrcSpan -> CpeBody -> CpeBody
tick RealSrcSpan
span  = CoreTickish -> CpeBody -> CpeBody
forall b. CoreTickish -> Expr b -> Expr b
Tick (RealSrcSpan -> String -> CoreTickish
forall (pass :: TickishPass).
RealSrcSpan -> String -> GenTickish pass
SourceNote RealSrcSpan
span (String -> CoreTickish) -> String -> CoreTickish
forall a b. (a -> b) -> a -> b
$ DynFlags -> SDoc -> String
showSDoc DynFlags
dflags (Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name))
           span1 :: String -> RealSrcSpan
span1 String
file = RealSrcLoc -> RealSrcSpan
realSrcLocSpan (RealSrcLoc -> RealSrcSpan) -> RealSrcLoc -> RealSrcSpan
forall a b. (a -> b) -> a -> b
$ FastString -> Int -> Int -> RealSrcLoc
mkRealSrcLoc (String -> FastString
mkFastString String
file) Int
1 Int
1

{-
Note [Floating out of top level bindings]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NB: we do need to float out of top-level bindings
Consider        x = length [True,False]
We want to get
                s1 = False : []
                s2 = True  : s1
                x  = length s2

We return a *list* of bindings, because we may start with
        x* = f (g y)
where x is demanded, in which case we want to finish with
        a = g y
        x* = f a
And then x will actually end up case-bound

Note [Join points and floating]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Join points can float out of other join points but not out of value bindings:

  let z =
    let  w = ... in -- can float
    join k = ... in -- can't float
    ... jump k ...
  join j x1 ... xn =
    let  y = ... in -- can float (but don't want to)
    join h = ... in -- can float (but not much point)
    ... jump h ...
  in ...

Here, the jump to h remains valid if h is floated outward, but the jump to k
does not.

We don't float *out* of join points. It would only be safe to float out of
nullary join points (or ones where the arguments are all either type arguments
or dead binders). Nullary join points aren't ever recursive, so they're always
effectively one-shot functions, which we don't float out of. We *could* float
join points from nullary join points, but there's no clear benefit at this
stage.

Note [Data constructor workers]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create any necessary "implicit" bindings for data con workers.  We
create the rather strange (non-recursive!) binding

        $wC = \x y -> $wC x y

i.e. a curried constructor that allocates.  This means that we can
treat the worker for a constructor like any other function in the rest
of the compiler.  The point here is that CoreToStg will generate a
StgConApp for the RHS, rather than a call to the worker (which would
give a loop).  As Lennart says: the ice is thin here, but it works.

Hmm.  Should we create bindings for dictionary constructors?  They are
always fully applied, and the bindings are just there to support
partial applications. But it's easier to let them through.


Note [Dead code in CorePrep]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Imagine that we got an input program like this (see #4962):

  f :: Show b => Int -> (Int, b -> Maybe Int -> Int)
  f x = (g True (Just x) + g () (Just x), g)
    where
      g :: Show a => a -> Maybe Int -> Int
      g _ Nothing = x
      g y (Just z) = if z > 100 then g y (Just (z + length (show y))) else g y unknown

After specialisation and SpecConstr, we would get something like this:

  f :: Show b => Int -> (Int, b -> Maybe Int -> Int)
  f x = (g$Bool_True_Just x + g$Unit_Unit_Just x, g)
    where
      {-# RULES g $dBool = g$Bool
                g $dUnit = g$Unit #-}
      g = ...
      {-# RULES forall x. g$Bool True (Just x) = g$Bool_True_Just x #-}
      g$Bool = ...
      {-# RULES forall x. g$Unit () (Just x) = g$Unit_Unit_Just x #-}
      g$Unit = ...
      g$Bool_True_Just = ...
      g$Unit_Unit_Just = ...

Note that the g$Bool and g$Unit functions are actually dead code: they
are only kept alive by the occurrence analyser because they are
referred to by the rules of g, which is being kept alive by the fact
that it is used (unspecialised) in the returned pair.

However, at the CorePrep stage there is no way that the rules for g
will ever fire, and it really seems like a shame to produce an output
program that goes to the trouble of allocating a closure for the
unreachable g$Bool and g$Unit functions.

The way we fix this is to:
 * In cloneBndr, drop all unfoldings/rules

 * In deFloatTop, run a simple dead code analyser on each top-level
   RHS to drop the dead local bindings.

The reason we don't just OccAnal the whole output of CorePrep is that
the tidier ensures that all top-level binders are GlobalIds, so they
don't show up in the free variables any longer. So if you run the
occurrence analyser on the output of CoreTidy (or later) you e.g. turn
this program:

  Rec {
  f = ... f ...
  }

Into this one:

  f = ... f ...

(Since f is not considered to be free in its own RHS.)


Note [keepAlive# magic]
~~~~~~~~~~~~~~~~~~~~~~~
When interacting with foreign code, it is often necessary for the user to
extend the lifetime of a heap object beyond the lifetime that would be apparent
from the on-heap references alone. For instance, a program like:

  foreign import safe "hello" hello :: ByteArray# -> IO ()

  callForeign :: IO ()
  callForeign = IO $ \s0 ->
    case newByteArray# n# s0 of (# s1, barr #) ->
      unIO hello barr s1

As-written this program is susceptible to memory-unsafety since there are
no references to `barr` visible to the garbage collector. Consequently, if a
garbage collection happens during the execution of the C function `hello`, it
may be that the array is freed while in use by the foreign function.

To address this, we introduced a new primop, keepAlive#, which "scopes over"
the computation needing the kept-alive value:

  keepAlive# :: forall (ra :: RuntimeRep) (rb :: RuntimeRep) (a :: TYPE a) (b :: TYPE b).
                a -> State# RealWorld -> (State# RealWorld -> b) -> b

When entered, an application (keepAlive# x s k) will apply `k` to the state
token, evaluating it to WHNF. However, during the course of this evaluation
will *guarantee* that `x` is considered to be alive.

There are a few things to note here:

 - we are RuntimeRep-polymorphic in the value to be kept-alive. This is
   necessary since we will often (but not always) be keeping alive something
   unlifted (like a ByteArray#)

 - we are RuntimeRep-polymorphic in the result value since the result may take
   many forms (e.g. a boxed value, a raw state token, or a (# State s, result #).

We implement this operation by desugaring to touch# during CorePrep (see
GHC.CoreToStg.Prep.cpeApp). Specifically,

  keepAlive# x s0 k

is transformed to:

  case k s0 of r ->
  case touch# x realWorld# of s1 ->
    r

Operationally, `keepAlive# x s k` is equivalent to pushing a stack frame with a
pointer to `x` and entering `k s0`. This compilation strategy is safe
because we do no optimization on STG that would drop or re-order the
continuation containing the `touch#`. However, if we were to become more
aggressive in our STG pipeline then we would need to revisit this.

Beyond this CorePrep transformation, there is very little special about
keepAlive#. However, we did explore (and eventually gave up on)
an optimisation which would allow unboxing of constructed product results,
which we describe below.


Lost optimisation: CPR unboxing
--------------------------------
One unfortunate property of this approach is that the simplifier is unable to
unbox the result of a keepAlive# expression. For instance, consider the program:

  case keepAlive# arr s0 (
         \s1 -> case peekInt arr s1 of
                  (# s2, r #) -> I# r
  ) of
    I# x -> ...

This is a surprisingly common pattern, previously used, e.g., in
GHC.IO.Buffer.readWord8Buf. While exploring ideas, we briefly played around
with optimising this away by pushing strict contexts (like the
`case [] of I# x -> ...` above) into keepAlive#'s continuation. While this can
recover unboxing, it can also unfortunately in general change the asymptotic
memory (namely stack) behavior of the program. For instance, consider

  writeN =
    ...
      case keepAlive# x s0 (\s1 -> something s1) of
        (# s2, x #) ->
          writeN ...

As it is tail-recursive, this program will run in constant space. However, if
we push outer case into the continuation we get:

  writeN =

      case keepAlive# x s0 (\s1 ->
        case something s1 of
          (# s2, x #) ->
            writeN ...
      ) of
        ...

Which ends up building a stack which is linear in the recursion depth. For this
reason, we ended up giving up on this optimisation.


Historical note: touch# and its inadequacy
------------------------------------------
Prior to the introduction of `keepAlive#` we instead addressed the need for
lifetime extension with the `touch#` primop:

    touch# :: a -> State# s -> State# s

This operation would ensure that the `a` value passed as the first argument was
considered "alive" at the time the primop application is entered.

For instance, the user might modify `callForeign` as:

  callForeign :: IO ()
  callForeign s0 = IO $ \s0 ->
    case newByteArray# n# s0 of (# s1, barr #) ->
    case unIO hello barr s1 of (# s2, () #) ->
    case touch# barr s2 of s3 ->
      (# s3, () #)

However, in #14346 we discovered that this primop is insufficient in the
presence of simplification. For instance, consider a program like:

  callForeign :: IO ()
  callForeign s0 = IO $ \s0 ->
    case newByteArray# n# s0 of (# s1, barr #) ->
    case unIO (forever $ hello barr) s1 of (# s2, () #) ->
    case touch# barr s2 of s3 ->
      (# s3, () #)

In this case the Simplifier may realize that (forever $ hello barr)
will never return and consequently that the `touch#` that follows is dead code.
As such, it will be dropped, resulting in memory unsoundness.
This unsoundness lead to the introduction of keepAlive#.



Other related tickets:

 - #15544
 - #17760
 - #14375
 - #15260
 - #18061

************************************************************************
*                                                                      *
                The main code
*                                                                      *
************************************************************************
-}

cpeBind :: TopLevelFlag -> CorePrepEnv -> CoreBind
        -> UniqSM (CorePrepEnv,
                   Floats,         -- Floating value bindings
                   Maybe CoreBind) -- Just bind' <=> returned new bind; no float
                                   -- Nothing <=> added bind' to floats instead
cpeBind :: TopLevelFlag
-> CorePrepEnv
-> CoreBind
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
cpeBind TopLevelFlag
top_lvl CorePrepEnv
env (NonRec Id
bndr CpeBody
rhs)
  | Bool -> Bool
not (Id -> Bool
isJoinId Id
bndr)
  = do { (CorePrepEnv
env1, Id
bndr1) <- CorePrepEnv -> Id -> UniqSM (CorePrepEnv, Id)
cpCloneBndr CorePrepEnv
env Id
bndr
       ; let dmd :: Demand
dmd         = Id -> Demand
idDemandInfo Id
bndr
             is_unlifted :: Bool
is_unlifted = HasDebugCallStack => Type -> Bool
Type -> Bool
isUnliftedType (Id -> Type
idType Id
bndr)
       ; (Floats
floats, CpeBody
rhs1) <- TopLevelFlag
-> RecFlag
-> Demand
-> Bool
-> CorePrepEnv
-> Id
-> CpeBody
-> UniqSM (Floats, CpeBody)
cpePair TopLevelFlag
top_lvl RecFlag
NonRecursive
                                   Demand
dmd Bool
is_unlifted
                                   CorePrepEnv
env Id
bndr1 CpeBody
rhs
       -- See Note [Inlining in CorePrep]
       ; let triv_rhs :: Bool
triv_rhs = CpeBody -> Bool
exprIsTrivial CpeBody
rhs1
             env2 :: CorePrepEnv
env2    | Bool
triv_rhs  = CorePrepEnv -> Id -> CpeBody -> CorePrepEnv
extendCorePrepEnvExpr CorePrepEnv
env1 Id
bndr CpeBody
rhs1
                     | Bool
otherwise = CorePrepEnv
env1
             floats1 :: Floats
floats1 | Bool
triv_rhs, Name -> Bool
isInternalName (Id -> Name
idName Id
bndr)
                     = Floats
floats
                     | Bool
otherwise
                     = Floats -> FloatingBind -> Floats
addFloat Floats
floats FloatingBind
new_float

             new_float :: FloatingBind
new_float = Demand -> Bool -> Id -> CpeBody -> FloatingBind
mkFloat Demand
dmd Bool
is_unlifted Id
bndr1 CpeBody
rhs1

       ; (CorePrepEnv, Floats, Maybe CoreBind)
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv
env2, Floats
floats1, Maybe CoreBind
forall a. Maybe a
Nothing) }

  | Bool
otherwise -- A join point; see Note [Join points and floating]
  = ASSERT(not (isTopLevel top_lvl)) -- can't have top-level join point
    do { (CorePrepEnv
_, Id
bndr1) <- CorePrepEnv -> Id -> UniqSM (CorePrepEnv, Id)
cpCloneBndr CorePrepEnv
env Id
bndr
       ; (Id
bndr2, CpeBody
rhs1) <- CorePrepEnv -> Id -> CpeBody -> UniqSM (Id, CpeBody)
cpeJoinPair CorePrepEnv
env Id
bndr1 CpeBody
rhs
       ; (CorePrepEnv, Floats, Maybe CoreBind)
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> Id -> Id -> CorePrepEnv
extendCorePrepEnv CorePrepEnv
env Id
bndr Id
bndr2,
                 Floats
emptyFloats,
                 CoreBind -> Maybe CoreBind
forall a. a -> Maybe a
Just (Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr2 CpeBody
rhs1)) }

cpeBind TopLevelFlag
top_lvl CorePrepEnv
env (Rec [(Id, CpeBody)]
pairs)
  | Bool -> Bool
not (Id -> Bool
isJoinId ([Id] -> Id
forall a. [a] -> a
head [Id]
bndrs))
  = do { (CorePrepEnv
env', [Id]
bndrs1) <- CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
cpCloneBndrs CorePrepEnv
env [Id]
bndrs
       ; [(Floats, CpeBody)]
stuff <- (Id -> CpeBody -> UniqSM (Floats, CpeBody))
-> [Id] -> [CpeBody] -> UniqSM [(Floats, CpeBody)]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (TopLevelFlag
-> RecFlag
-> Demand
-> Bool
-> CorePrepEnv
-> Id
-> CpeBody
-> UniqSM (Floats, CpeBody)
cpePair TopLevelFlag
top_lvl RecFlag
Recursive Demand
topDmd Bool
False CorePrepEnv
env')
                           [Id]
bndrs1 [CpeBody]
rhss

       ; let ([Floats]
floats_s, [CpeBody]
rhss1) = [(Floats, CpeBody)] -> ([Floats], [CpeBody])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Floats, CpeBody)]
stuff
             all_pairs :: [(Id, CpeBody)]
all_pairs = (FloatingBind -> [(Id, CpeBody)] -> [(Id, CpeBody)])
-> [(Id, CpeBody)] -> OrdList FloatingBind -> [(Id, CpeBody)]
forall a b. (a -> b -> b) -> b -> OrdList a -> b
foldrOL FloatingBind -> [(Id, CpeBody)] -> [(Id, CpeBody)]
add_float ([Id]
bndrs1 [Id] -> [CpeBody] -> [(Id, CpeBody)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [CpeBody]
rhss1)
                                           ([Floats] -> OrdList FloatingBind
concatFloats [Floats]
floats_s)

       ; (CorePrepEnv, Floats, Maybe CoreBind)
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> [(Id, Id)] -> CorePrepEnv
extendCorePrepEnvList CorePrepEnv
env ([Id]
bndrs [Id] -> [Id] -> [(Id, Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
bndrs1),
                 FloatingBind -> Floats
unitFloat (CoreBind -> FloatingBind
FloatLet ([(Id, CpeBody)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec [(Id, CpeBody)]
all_pairs)),
                 Maybe CoreBind
forall a. Maybe a
Nothing) }

  | Bool
otherwise -- See Note [Join points and floating]
  = do { (CorePrepEnv
env', [Id]
bndrs1) <- CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
cpCloneBndrs CorePrepEnv
env [Id]
bndrs
       ; [(Id, CpeBody)]
pairs1 <- (Id -> CpeBody -> UniqSM (Id, CpeBody))
-> [Id] -> [CpeBody] -> UniqSM [(Id, CpeBody)]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (CorePrepEnv -> Id -> CpeBody -> UniqSM (Id, CpeBody)
cpeJoinPair CorePrepEnv
env') [Id]
bndrs1 [CpeBody]
rhss

       ; let bndrs2 :: [Id]
bndrs2 = ((Id, CpeBody) -> Id) -> [(Id, CpeBody)] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map (Id, CpeBody) -> Id
forall a b. (a, b) -> a
fst [(Id, CpeBody)]
pairs1
       ; (CorePrepEnv, Floats, Maybe CoreBind)
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> [(Id, Id)] -> CorePrepEnv
extendCorePrepEnvList CorePrepEnv
env' ([Id]
bndrs [Id] -> [Id] -> [(Id, Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
bndrs2),
                 Floats
emptyFloats,
                 CoreBind -> Maybe CoreBind
forall a. a -> Maybe a
Just ([(Id, CpeBody)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec [(Id, CpeBody)]
pairs1)) }
  where
    ([Id]
bndrs, [CpeBody]
rhss) = [(Id, CpeBody)] -> ([Id], [CpeBody])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, CpeBody)]
pairs

        -- Flatten all the floats, and the current
        -- group into a single giant Rec
    add_float :: FloatingBind -> [(Id, CpeBody)] -> [(Id, CpeBody)]
add_float (FloatLet (NonRec Id
b CpeBody
r)) [(Id, CpeBody)]
prs2 = (Id
b,CpeBody
r) (Id, CpeBody) -> [(Id, CpeBody)] -> [(Id, CpeBody)]
forall a. a -> [a] -> [a]
: [(Id, CpeBody)]
prs2
    add_float (FloatLet (Rec [(Id, CpeBody)]
prs1))   [(Id, CpeBody)]
prs2 = [(Id, CpeBody)]
prs1 [(Id, CpeBody)] -> [(Id, CpeBody)] -> [(Id, CpeBody)]
forall a. [a] -> [a] -> [a]
++ [(Id, CpeBody)]
prs2
    add_float FloatingBind
b                       [(Id, CpeBody)]
_    = String -> SDoc -> [(Id, CpeBody)]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"cpeBind" (FloatingBind -> SDoc
forall a. Outputable a => a -> SDoc
ppr FloatingBind
b)

---------------
cpePair :: TopLevelFlag -> RecFlag -> Demand -> Bool
        -> CorePrepEnv -> OutId -> CoreExpr
        -> UniqSM (Floats, CpeRhs)
-- Used for all bindings
-- The binder is already cloned, hence an OutId
cpePair :: TopLevelFlag
-> RecFlag
-> Demand
-> Bool
-> CorePrepEnv
-> Id
-> CpeBody
-> UniqSM (Floats, CpeBody)
cpePair TopLevelFlag
top_lvl RecFlag
is_rec Demand
dmd Bool
is_unlifted CorePrepEnv
env Id
bndr CpeBody
rhs
  = ASSERT(not (isJoinId bndr)) -- those should use cpeJoinPair
    do { (Floats
floats1, CpeBody
rhs1) <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
rhs

       -- See if we are allowed to float this stuff out of the RHS
       ; (Floats
floats2, CpeBody
rhs2) <- Floats -> CpeBody -> UniqSM (Floats, CpeBody)
float_from_rhs Floats
floats1 CpeBody
rhs1

       -- Make the arity match up
       ; (Floats
floats3, CpeBody
rhs3)
            <- if CpeBody -> Int
manifestArity CpeBody
rhs1 Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
<= Int
arity
               then (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats2, Int -> CpeBody -> CpeBody
cpeEtaExpand Int
arity CpeBody
rhs2)
               else WARN(True, text "CorePrep: silly extra arguments:" <+> ppr bndr)
                               -- Note [Silly extra arguments]
                    (do { Id
v <- Type -> UniqSM Id
newVar (Id -> Type
idType Id
bndr)
                        ; let float :: FloatingBind
float = Demand -> Bool -> Id -> CpeBody -> FloatingBind
mkFloat Demand
topDmd Bool
False Id
v CpeBody
rhs2
                        ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return ( Floats -> FloatingBind -> Floats
addFloat Floats
floats2 FloatingBind
float
                                 , Int -> CpeBody -> CpeBody
cpeEtaExpand Int
arity (Id -> CpeBody
forall b. Id -> Expr b
Var Id
v)) })

        -- Wrap floating ticks
       ; let (Floats
floats4, CpeBody
rhs4) = Floats -> CpeBody -> (Floats, CpeBody)
wrapTicks Floats
floats3 CpeBody
rhs3

       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats4, CpeBody
rhs4) }
  where
    arity :: Int
arity = Id -> Int
idArity Id
bndr        -- We must match this arity

    ---------------------
    float_from_rhs :: Floats -> CpeBody -> UniqSM (Floats, CpeBody)
float_from_rhs Floats
floats CpeBody
rhs
      | Floats -> Bool
isEmptyFloats Floats
floats = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CpeBody
rhs)
      | TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl   = Floats -> CpeBody -> UniqSM (Floats, CpeBody)
float_top    Floats
floats CpeBody
rhs
      | Bool
otherwise            = Floats -> CpeBody -> UniqSM (Floats, CpeBody)
float_nested Floats
floats CpeBody
rhs

    ---------------------
    float_nested :: Floats -> CpeBody -> UniqSM (Floats, CpeBody)
float_nested Floats
floats CpeBody
rhs
      | RecFlag -> Demand -> Bool -> Floats -> CpeBody -> Bool
wantFloatNested RecFlag
is_rec Demand
dmd Bool
is_unlifted Floats
floats CpeBody
rhs
                  = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CpeBody
rhs)
      | Bool
otherwise = Floats -> CpeBody -> UniqSM (Floats, CpeBody)
dontFloat Floats
floats CpeBody
rhs

    ---------------------
    float_top :: Floats -> CpeBody -> UniqSM (Floats, CpeBody)
float_top Floats
floats CpeBody
rhs
      | Floats -> Bool
allLazyTop Floats
floats
      = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CpeBody
rhs)

      | Just (Floats, CpeBody)
floats <- Floats -> CpeBody -> Maybe (Floats, CpeBody)
canFloat Floats
floats CpeBody
rhs
      = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats, CpeBody)
floats

      | Bool
otherwise
      = Floats -> CpeBody -> UniqSM (Floats, CpeBody)
dontFloat Floats
floats CpeBody
rhs

dontFloat :: Floats -> CpeRhs -> UniqSM (Floats, CpeBody)
-- Non-empty floats, but do not want to float from rhs
-- So wrap the rhs in the floats
-- But: rhs1 might have lambdas, and we can't
--      put them inside a wrapBinds
dontFloat :: Floats -> CpeBody -> UniqSM (Floats, CpeBody)
dontFloat Floats
floats1 CpeBody
rhs
  = do { (Floats
floats2, CpeBody
body) <- CpeBody -> UniqSM (Floats, CpeBody)
rhsToBody CpeBody
rhs
        ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, Floats -> CpeBody -> CpeBody
wrapBinds Floats
floats1 (CpeBody -> CpeBody) -> CpeBody -> CpeBody
forall a b. (a -> b) -> a -> b
$
                               Floats -> CpeBody -> CpeBody
wrapBinds Floats
floats2 CpeBody
body) }

{- Note [Silly extra arguments]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we had this
        f{arity=1} = \x\y. e
We *must* match the arity on the Id, so we have to generate
        f' = \x\y. e
        f  = \x. f' x

It's a bizarre case: why is the arity on the Id wrong?  Reason
(in the days of __inline_me__):
        f{arity=0} = __inline_me__ (let v = expensive in \xy. e)
When InlineMe notes go away this won't happen any more.  But
it seems good for CorePrep to be robust.
-}

---------------
cpeJoinPair :: CorePrepEnv -> JoinId -> CoreExpr
            -> UniqSM (JoinId, CpeRhs)
-- Used for all join bindings
-- No eta-expansion: see Note [Do not eta-expand join points] in GHC.Core.Opt.Simplify.Utils
cpeJoinPair :: CorePrepEnv -> Id -> CpeBody -> UniqSM (Id, CpeBody)
cpeJoinPair CorePrepEnv
env Id
bndr CpeBody
rhs
  = ASSERT(isJoinId bndr)
    do { let Just Int
join_arity = Id -> Maybe Int
isJoinId_maybe Id
bndr
             ([Id]
bndrs, CpeBody
body)   = Int -> CpeBody -> ([Id], CpeBody)
forall b. Int -> Expr b -> ([b], Expr b)
collectNBinders Int
join_arity CpeBody
rhs

       ; (CorePrepEnv
env', [Id]
bndrs') <- CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
cpCloneBndrs CorePrepEnv
env [Id]
bndrs

       ; CpeBody
body' <- CorePrepEnv -> CpeBody -> UniqSM CpeBody
cpeBodyNF CorePrepEnv
env' CpeBody
body -- Will let-bind the body if it starts
                                      -- with a lambda

       ; let rhs' :: CpeBody
rhs'  = [Id] -> CpeBody -> CpeBody
mkCoreLams [Id]
bndrs' CpeBody
body'
             bndr' :: Id
bndr' = Id
bndr Id -> Unfolding -> Id
`setIdUnfolding` Unfolding
evaldUnfolding
                          Id -> Int -> Id
`setIdArity` (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
bndrs
                            -- See Note [Arity and join points]

       ; (Id, CpeBody) -> UniqSM (Id, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Id
bndr', CpeBody
rhs') }

{-
Note [Arity and join points]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Up to now, we've allowed a join point to have an arity greater than its join
arity (minus type arguments), since this is what's useful for eta expansion.
However, for code gen purposes, its arity must be exactly the number of value
arguments it will be called with, and it must have exactly that many value
lambdas. Hence if there are extra lambdas we must let-bind the body of the RHS:

  join j x y z = \w -> ... in ...
    =>
  join j x y z = (let f = \w -> ... in f) in ...

This is also what happens with Note [Silly extra arguments]. Note that it's okay
for us to mess with the arity because a join point is never exported.
-}

-- ---------------------------------------------------------------------------
--              CpeRhs: produces a result satisfying CpeRhs
-- ---------------------------------------------------------------------------

cpeRhsE :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CpeRhs)
-- If
--      e  ===>  (bs, e')
-- then
--      e = let bs in e'        (semantically, that is!)
--
-- For example
--      f (g x)   ===>   ([v = g x], f v)

cpeRhsE :: CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env (Type Type
ty)
  = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, Type -> CpeBody
forall b. Type -> Expr b
Type (CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env Type
ty))
cpeRhsE CorePrepEnv
env (Coercion Coercion
co)
  = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, Coercion -> CpeBody
forall b. Coercion -> Expr b
Coercion (CorePrepEnv -> Coercion -> Coercion
cpSubstCo CorePrepEnv
env Coercion
co))
cpeRhsE CorePrepEnv
env expr :: CpeBody
expr@(Lit (LitNumber LitNumType
nt Integer
i))
   = case CorePrepEnv -> LitNumType -> Integer -> Maybe CpeBody
cpe_convertNumLit CorePrepEnv
env LitNumType
nt Integer
i of
      Maybe CpeBody
Nothing -> (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CpeBody
expr)
      Just CpeBody
e  -> CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
e
cpeRhsE CorePrepEnv
_env expr :: CpeBody
expr@(Lit {}) = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CpeBody
expr)
cpeRhsE CorePrepEnv
env expr :: CpeBody
expr@(Var {})  = CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeApp CorePrepEnv
env CpeBody
expr
cpeRhsE CorePrepEnv
env expr :: CpeBody
expr@(App {}) = CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeApp CorePrepEnv
env CpeBody
expr

cpeRhsE CorePrepEnv
env (Let CoreBind
bind CpeBody
body)
  = do { (CorePrepEnv
env', Floats
bind_floats, Maybe CoreBind
maybe_bind') <- TopLevelFlag
-> CorePrepEnv
-> CoreBind
-> UniqSM (CorePrepEnv, Floats, Maybe CoreBind)
cpeBind TopLevelFlag
NotTopLevel CorePrepEnv
env CoreBind
bind
       ; (Floats
body_floats, CpeBody
body') <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env' CpeBody
body
       ; let expr' :: CpeBody
expr' = case Maybe CoreBind
maybe_bind' of Just CoreBind
bind' -> CoreBind -> CpeBody -> CpeBody
forall b. Bind b -> Expr b -> Expr b
Let CoreBind
bind' CpeBody
body'
                                         Maybe CoreBind
Nothing    -> CpeBody
body'
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
bind_floats Floats -> Floats -> Floats
`appendFloats` Floats
body_floats, CpeBody
expr') }

cpeRhsE CorePrepEnv
env (Tick CoreTickish
tickish CpeBody
expr)
  | CoreTickish -> TickishPlacement
forall (pass :: TickishPass). GenTickish pass -> TickishPlacement
tickishPlace CoreTickish
tickish TickishPlacement -> TickishPlacement -> Bool
forall a. Eq a => a -> a -> Bool
== TickishPlacement
PlaceNonLam Bool -> Bool -> Bool
&& CoreTickish
tickish CoreTickish -> TickishScoping -> Bool
forall (pass :: TickishPass).
GenTickish pass -> TickishScoping -> Bool
`tickishScopesLike` TickishScoping
SoftScope
  = do { (Floats
floats, CpeBody
body) <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
expr
         -- See [Floating Ticks in CorePrep]
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (FloatingBind -> Floats
unitFloat (CoreTickish -> FloatingBind
FloatTick CoreTickish
tickish) Floats -> Floats -> Floats
`appendFloats` Floats
floats, CpeBody
body) }
  | Bool
otherwise
  = do { CpeBody
body <- CorePrepEnv -> CpeBody -> UniqSM CpeBody
cpeBodyNF CorePrepEnv
env CpeBody
expr
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
tickish' CpeBody
body) }
  where
    tickish' :: CoreTickish
tickish' | Breakpoint XBreakpoint 'TickishPassCore
ext Int
n [XTickishId 'TickishPassCore]
fvs <- CoreTickish
tickish
             -- See also 'substTickish'
             = XBreakpoint 'TickishPassCore
-> Int -> [XTickishId 'TickishPassCore] -> CoreTickish
forall (pass :: TickishPass).
XBreakpoint pass -> Int -> [XTickishId pass] -> GenTickish pass
Breakpoint XBreakpoint 'TickishPassCore
ext Int
n ((Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map (HasDebugCallStack => CpeBody -> Id
CpeBody -> Id
getIdFromTrivialExpr (CpeBody -> Id) -> (Id -> CpeBody) -> Id -> Id
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CorePrepEnv -> Id -> CpeBody
lookupCorePrepEnv CorePrepEnv
env) [Id]
[XTickishId 'TickishPassCore]
fvs)
             | Bool
otherwise
             = CoreTickish
tickish

cpeRhsE CorePrepEnv
env (Cast CpeBody
expr Coercion
co)
   = do { (Floats
floats, CpeBody
expr') <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
expr
        ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CpeBody -> Coercion -> CpeBody
forall b. Expr b -> Coercion -> Expr b
Cast CpeBody
expr' (CorePrepEnv -> Coercion -> Coercion
cpSubstCo CorePrepEnv
env Coercion
co)) }

cpeRhsE CorePrepEnv
env expr :: CpeBody
expr@(Lam {})
   = do { let ([Id]
bndrs,CpeBody
body) = CpeBody -> ([Id], CpeBody)
forall b. Expr b -> ([b], Expr b)
collectBinders CpeBody
expr
        ; (CorePrepEnv
env', [Id]
bndrs') <- CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
cpCloneBndrs CorePrepEnv
env [Id]
bndrs
        ; CpeBody
body' <- CorePrepEnv -> CpeBody -> UniqSM CpeBody
cpeBodyNF CorePrepEnv
env' CpeBody
body
        ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, [Id] -> CpeBody -> CpeBody
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
bndrs' CpeBody
body') }

-- Eliminate empty case
-- See Note [Unsafe coercions]
cpeRhsE CorePrepEnv
env (Case CpeBody
scrut Id
_ Type
ty [])
  = do { (Floats
floats, CpeBody
scrut') <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
scrut
       ; let ty' :: Type
ty' = CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env Type
ty
             co' :: Coercion
co' = Role -> Type -> Type -> Coercion
mkUnsafeCo Role
Representational (CpeBody -> Type
exprType CpeBody
scrut') Type
ty'
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CpeBody -> Coercion -> CpeBody
forall b. Expr b -> Coercion -> Expr b
Cast CpeBody
scrut' Coercion
co') }
   -- This can give rise to
   --   Warning: Unsafe coercion: between unboxed and boxed value
   -- but it's fine because 'scrut' diverges

-- Eliminate unsafeEqualityProof
-- See Note [Unsafe coercions]
cpeRhsE CorePrepEnv
env (Case CpeBody
scrut Id
bndr Type
_ [Alt Id]
alts)
  | CpeBody -> Bool
isUnsafeEqualityProof CpeBody
scrut
  , Id -> Bool
isDeadBinder Id
bndr -- We can only discard the case if the case-binder
                      -- is dead.  It usually is, but see #18227
  , [Alt AltCon
_ [Id
co_var] CpeBody
rhs] <- [Alt Id]
alts
  , let Pair Type
ty1 Type
ty2 = HasDebugCallStack => Id -> Pair Type
Id -> Pair Type
coVarTypes Id
co_var
        the_co :: Coercion
the_co = Role -> Type -> Type -> Coercion
mkUnsafeCo Role
Nominal (CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env Type
ty1) (CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env Type
ty2)
        env' :: CorePrepEnv
env'   = CorePrepEnv -> Id -> Coercion -> CorePrepEnv
extendCoVarEnv CorePrepEnv
env Id
co_var Coercion
the_co
  = CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env' CpeBody
rhs

cpeRhsE CorePrepEnv
env (Case CpeBody
scrut Id
bndr Type
ty [Alt Id]
alts)
  = do { (Floats
floats, CpeBody
scrut') <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeBody CorePrepEnv
env CpeBody
scrut
       ; (CorePrepEnv
env', Id
bndr2) <- CorePrepEnv -> Id -> UniqSM (CorePrepEnv, Id)
cpCloneBndr CorePrepEnv
env Id
bndr
       ; let alts' :: [Alt Id]
alts'
                 -- This flag is intended to aid in debugging strictness
                 -- analysis bugs. These are particularly nasty to chase down as
                 -- they may manifest as segmentation faults. When this flag is
                 -- enabled we instead produce an 'error' expression to catch
                 -- the case where a function we think should bottom
                 -- unexpectedly returns.
               | GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_CatchBottoms (CorePrepEnv -> DynFlags
cpe_dynFlags CorePrepEnv
env)
               , Bool -> Bool
not ([Alt Id] -> Bool
forall b. [Alt b] -> Bool
altsAreExhaustive [Alt Id]
alts)
               = [Alt Id] -> Maybe CpeBody -> [Alt Id]
forall b. [Alt b] -> Maybe (Expr b) -> [Alt b]
addDefault [Alt Id]
alts (CpeBody -> Maybe CpeBody
forall a. a -> Maybe a
Just CpeBody
err)
               | Bool
otherwise = [Alt Id]
alts
               where err :: CpeBody
err = Id -> Type -> String -> CpeBody
mkRuntimeErrorApp Id
rUNTIME_ERROR_ID Type
ty
                                             String
"Bottoming expression returned"
       ; [Alt Id]
alts'' <- (Alt Id -> UniqSM (Alt Id)) -> [Alt Id] -> UniqSM [Alt Id]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (CorePrepEnv -> Alt Id -> UniqSM (Alt Id)
sat_alt CorePrepEnv
env') [Alt Id]
alts'

       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CpeBody -> Id -> Type -> [Alt Id] -> CpeBody
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case CpeBody
scrut' Id
bndr2 Type
ty [Alt Id]
alts'') }
  where
    sat_alt :: CorePrepEnv -> Alt Id -> UniqSM (Alt Id)
sat_alt CorePrepEnv
env (Alt AltCon
con [Id]
bs CpeBody
rhs)
       = do { (CorePrepEnv
env2, [Id]
bs') <- CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
cpCloneBndrs CorePrepEnv
env [Id]
bs
            ; CpeBody
rhs' <- CorePrepEnv -> CpeBody -> UniqSM CpeBody
cpeBodyNF CorePrepEnv
env2 CpeBody
rhs
            ; Alt Id -> UniqSM (Alt Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (AltCon -> [Id] -> CpeBody -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
con [Id]
bs' CpeBody
rhs') }

-- ---------------------------------------------------------------------------
--              CpeBody: produces a result satisfying CpeBody
-- ---------------------------------------------------------------------------

-- | Convert a 'CoreExpr' so it satisfies 'CpeBody', without
-- producing any floats (any generated floats are immediately
-- let-bound using 'wrapBinds').  Generally you want this, esp.
-- when you've reached a binding form (e.g., a lambda) and
-- floating any further would be incorrect.
cpeBodyNF :: CorePrepEnv -> CoreExpr -> UniqSM CpeBody
cpeBodyNF :: CorePrepEnv -> CpeBody -> UniqSM CpeBody
cpeBodyNF CorePrepEnv
env CpeBody
expr
  = do { (Floats
floats, CpeBody
body) <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeBody CorePrepEnv
env CpeBody
expr
       ; CpeBody -> UniqSM CpeBody
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats -> CpeBody -> CpeBody
wrapBinds Floats
floats CpeBody
body) }

-- | Convert a 'CoreExpr' so it satisfies 'CpeBody'; also produce
-- a list of 'Floats' which are being propagated upwards.  In
-- fact, this function is used in only two cases: to
-- implement 'cpeBodyNF' (which is what you usually want),
-- and in the case when a let-binding is in a case scrutinee--here,
-- we can always float out:
--
--      case (let x = y in z) of ...
--      ==> let x = y in case z of ...
--
cpeBody :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CpeBody)
cpeBody :: CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeBody CorePrepEnv
env CpeBody
expr
  = do { (Floats
floats1, CpeBody
rhs) <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
expr
       ; (Floats
floats2, CpeBody
body) <- CpeBody -> UniqSM (Floats, CpeBody)
rhsToBody CpeBody
rhs
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats1 Floats -> Floats -> Floats
`appendFloats` Floats
floats2, CpeBody
body) }

--------
rhsToBody :: CpeRhs -> UniqSM (Floats, CpeBody)
-- Remove top level lambdas by let-binding

rhsToBody :: CpeBody -> UniqSM (Floats, CpeBody)
rhsToBody (Tick CoreTickish
t CpeBody
expr)
  | CoreTickish -> TickishScoping
forall (pass :: TickishPass). GenTickish pass -> TickishScoping
tickishScoped CoreTickish
t TickishScoping -> TickishScoping -> Bool
forall a. Eq a => a -> a -> Bool
== TickishScoping
NoScope  -- only float out of non-scoped annotations
  = do { (Floats
floats, CpeBody
expr') <- CpeBody -> UniqSM (Floats, CpeBody)
rhsToBody CpeBody
expr
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
t CpeBody
expr') }

rhsToBody (Cast CpeBody
e Coercion
co)
        -- You can get things like
        --      case e of { p -> coerce t (\s -> ...) }
  = do { (Floats
floats, CpeBody
e') <- CpeBody -> UniqSM (Floats, CpeBody)
rhsToBody CpeBody
e
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats, CpeBody -> Coercion -> CpeBody
forall b. Expr b -> Coercion -> Expr b
Cast CpeBody
e' Coercion
co) }

rhsToBody expr :: CpeBody
expr@(Lam {})
  | Just CpeBody
no_lam_result <- [Id] -> CpeBody -> Maybe CpeBody
tryEtaReducePrep [Id]
bndrs CpeBody
body
  = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CpeBody
no_lam_result)
  | (Id -> Bool) -> [Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Id -> Bool
isTyVar [Id]
bndrs           -- Type lambdas are ok
  = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CpeBody
expr)
  | Bool
otherwise                   -- Some value lambdas
  = do { let rhs :: CpeBody
rhs = Int -> CpeBody -> CpeBody
cpeEtaExpand (CpeBody -> Int
exprArity CpeBody
expr) CpeBody
expr
       ; Id
fn <- Type -> UniqSM Id
newVar (CpeBody -> Type
exprType CpeBody
rhs)
       ; let float :: FloatingBind
float = CoreBind -> FloatingBind
FloatLet (Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
fn CpeBody
rhs)
       ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (FloatingBind -> Floats
unitFloat FloatingBind
float, Id -> CpeBody
forall b. Id -> Expr b
Var Id
fn) }
  where
    ([Id]
bndrs,CpeBody
body) = CpeBody -> ([Id], CpeBody)
forall b. Expr b -> ([b], Expr b)
collectBinders CpeBody
expr

rhsToBody CpeBody
expr = (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
emptyFloats, CpeBody
expr)



-- ---------------------------------------------------------------------------
--              CpeApp: produces a result satisfying CpeApp
-- ---------------------------------------------------------------------------

data ArgInfo = CpeApp  CoreArg
             | CpeCast Coercion
             | CpeTick CoreTickish

instance Outputable ArgInfo where
  ppr :: ArgInfo -> SDoc
ppr (CpeApp CpeBody
arg) = String -> SDoc
text String
"app" SDoc -> SDoc -> SDoc
<+> CpeBody -> SDoc
forall a. Outputable a => a -> SDoc
ppr CpeBody
arg
  ppr (CpeCast Coercion
co) = String -> SDoc
text String
"cast" SDoc -> SDoc -> SDoc
<+> Coercion -> SDoc
forall a. Outputable a => a -> SDoc
ppr Coercion
co
  ppr (CpeTick CoreTickish
tick) = String -> SDoc
text String
"tick" SDoc -> SDoc -> SDoc
<+> CoreTickish -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreTickish
tick

cpeApp :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CpeRhs)
-- May return a CpeRhs because of saturating primops
cpeApp :: CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeApp CorePrepEnv
top_env CpeBody
expr
  = do { let (CpeBody
terminal, [ArgInfo]
args, Int
depth) = CpeBody -> (CpeBody, [ArgInfo], Int)
collect_args CpeBody
expr
       ; CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app CorePrepEnv
top_env CpeBody
terminal [ArgInfo]
args Int
depth
       }

  where
    -- We have a nested data structure of the form
    -- e `App` a1 `App` a2 ... `App` an, convert it into
    -- (e, [CpeApp a1, CpeApp a2, ..., CpeApp an], depth)
    -- We use 'ArgInfo' because we may also need to
    -- record casts and ticks.  Depth counts the number
    -- of arguments that would consume strictness information
    -- (so, no type or coercion arguments.)
    collect_args :: CoreExpr -> (CoreExpr, [ArgInfo], Int)
    collect_args :: CpeBody -> (CpeBody, [ArgInfo], Int)
collect_args CpeBody
e = CpeBody -> [ArgInfo] -> Int -> (CpeBody, [ArgInfo], Int)
forall {c}.
Num c =>
CpeBody -> [ArgInfo] -> c -> (CpeBody, [ArgInfo], c)
go CpeBody
e [] Int
0
      where
        go :: CpeBody -> [ArgInfo] -> c -> (CpeBody, [ArgInfo], c)
go (App CpeBody
fun CpeBody
arg)      [ArgInfo]
as !c
depth
            = CpeBody -> [ArgInfo] -> c -> (CpeBody, [ArgInfo], c)
go CpeBody
fun (CpeBody -> ArgInfo
CpeApp CpeBody
arg ArgInfo -> [ArgInfo] -> [ArgInfo]
forall a. a -> [a] -> [a]
: [ArgInfo]
as)
                (if CpeBody -> Bool
forall b. Expr b -> Bool
isTyCoArg CpeBody
arg then c
depth else c
depth c -> c -> c
forall a. Num a => a -> a -> a
+ c
1)
        go (Cast CpeBody
fun Coercion
co)      [ArgInfo]
as c
depth
            = CpeBody -> [ArgInfo] -> c -> (CpeBody, [ArgInfo], c)
go CpeBody
fun (Coercion -> ArgInfo
CpeCast Coercion
co ArgInfo -> [ArgInfo] -> [ArgInfo]
forall a. a -> [a] -> [a]
: [ArgInfo]
as) c
depth
        go (Tick CoreTickish
tickish CpeBody
fun) [ArgInfo]
as c
depth
            | CoreTickish -> TickishPlacement
forall (pass :: TickishPass). GenTickish pass -> TickishPlacement
tickishPlace CoreTickish
tickish TickishPlacement -> TickishPlacement -> Bool
forall a. Eq a => a -> a -> Bool
== TickishPlacement
PlaceNonLam
            Bool -> Bool -> Bool
&& CoreTickish
tickish CoreTickish -> TickishScoping -> Bool
forall (pass :: TickishPass).
GenTickish pass -> TickishScoping -> Bool
`tickishScopesLike` TickishScoping
SoftScope
            = CpeBody -> [ArgInfo] -> c -> (CpeBody, [ArgInfo], c)
go CpeBody
fun (CoreTickish -> ArgInfo
CpeTick CoreTickish
tickish ArgInfo -> [ArgInfo] -> [ArgInfo]
forall a. a -> [a] -> [a]
: [ArgInfo]
as) c
depth
        go CpeBody
terminal [ArgInfo]
as c
depth = (CpeBody
terminal, [ArgInfo]
as, c
depth)

    cpe_app :: CorePrepEnv
            -> CoreExpr
            -> [ArgInfo]
            -> Int
            -> UniqSM (Floats, CpeRhs)
    cpe_app :: CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app CorePrepEnv
env (Var Id
f) (CpeApp Type{} : CpeApp CpeBody
arg : [ArgInfo]
args) Int
depth
        | Id
f Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
lazyIdKey          -- Replace (lazy a) with a, and
            -- See Note [lazyId magic] in GHC.Types.Id.Make
       Bool -> Bool -> Bool
|| Id
f Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
noinlineIdKey      -- Replace (noinline a) with a
            -- See Note [noinlineId magic] in GHC.Types.Id.Make

        -- Consider the code:
        --
        --      lazy (f x) y
        --
        -- We need to make sure that we need to recursively collect arguments on
        -- "f x", otherwise we'll float "f x" out (it's not a variable) and
        -- end up with this awful -ddump-prep:
        --
        --      case f x of f_x {
        --        __DEFAULT -> f_x y
        --      }
        --
        -- rather than the far superior "f x y".  Test case is par01.
        = let (CpeBody
terminal, [ArgInfo]
args', Int
depth') = CpeBody -> (CpeBody, [ArgInfo], Int)
collect_args CpeBody
arg
          in CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app CorePrepEnv
env CpeBody
terminal ([ArgInfo]
args' [ArgInfo] -> [ArgInfo] -> [ArgInfo]
forall a. [a] -> [a] -> [a]
++ [ArgInfo]
args) (Int
depth Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
depth' Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)

    -- See Note [keepAlive# magic].
    cpe_app CorePrepEnv
env
            (Var Id
f)
            [ArgInfo]
args
            Int
n
        | Just PrimOp
KeepAliveOp <- Id -> Maybe PrimOp
isPrimOpId_maybe Id
f
        , CpeApp (Type Type
arg_rep)
          : CpeApp (Type Type
arg_ty)
          : CpeApp (Type Type
_result_rep)
          : CpeApp (Type Type
result_ty)
          : CpeApp CpeBody
arg
          : CpeApp CpeBody
s0
          : CpeApp CpeBody
k
          : [ArgInfo]
rest <- [ArgInfo]
args
        = do { Id
y  <- Type -> UniqSM Id
newVar (CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env Type
result_ty)
             ; Id
s2 <- Type -> UniqSM Id
newVar Type
realWorldStatePrimTy
             ; -- beta reduce if possible
             ; (Floats
floats, CpeBody
k') <- case CpeBody
k of
                  Lam Id
s CpeBody
body -> CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app (CorePrepEnv -> Id -> CpeBody -> CorePrepEnv
extendCorePrepEnvExpr CorePrepEnv
env Id
s CpeBody
s0) CpeBody
body [ArgInfo]
rest (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
2)
                  CpeBody
_          -> CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app CorePrepEnv
env CpeBody
k (CpeBody -> ArgInfo
CpeApp CpeBody
s0 ArgInfo -> [ArgInfo] -> [ArgInfo]
forall a. a -> [a] -> [a]
: [ArgInfo]
rest) (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1)
             ; let touchId :: Id
touchId = PrimOp -> Id
mkPrimOpId PrimOp
TouchOp
                   expr :: CpeBody
expr = CpeBody -> Id -> Type -> [Alt Id] -> CpeBody
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case CpeBody
k' Id
y Type
result_ty [AltCon -> [Id] -> CpeBody -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
DEFAULT [] CpeBody
rhs]
                   rhs :: CpeBody
rhs = let scrut :: CpeBody
scrut = CpeBody -> [CpeBody] -> CpeBody
forall b. Expr b -> [Expr b] -> Expr b
mkApps (Id -> CpeBody
forall b. Id -> Expr b
Var Id
touchId) [Type -> CpeBody
forall b. Type -> Expr b
Type Type
arg_rep, Type -> CpeBody
forall b. Type -> Expr b
Type Type
arg_ty, CpeBody
arg, Id -> CpeBody
forall b. Id -> Expr b
Var Id
realWorldPrimId]
                         in CpeBody -> Id -> Type -> [Alt Id] -> CpeBody
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case CpeBody
scrut Id
s2 Type
result_ty [AltCon -> [Id] -> CpeBody -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
DEFAULT [] (Id -> CpeBody
forall b. Id -> Expr b
Var Id
y)]
             ; (Floats
floats', CpeBody
expr') <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeBody CorePrepEnv
env CpeBody
expr
             ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats Floats -> Floats -> Floats
`appendFloats` Floats
floats', CpeBody
expr')
             }
        | Just PrimOp
KeepAliveOp <- Id -> Maybe PrimOp
isPrimOpId_maybe Id
f
        = String -> UniqSM (Floats, CpeBody)
forall a. String -> a
panic String
"invalid keepAlive# application"

    cpe_app CorePrepEnv
env (Var Id
f) (CpeApp _runtimeRep :: CpeBody
_runtimeRep@Type{} : CpeApp _type :: CpeBody
_type@Type{} : CpeApp CpeBody
arg : [ArgInfo]
rest) Int
n
        | Id
f Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
runRWKey
        -- N.B. While it may appear that n == 1 in the case of runRW#
        -- applications, keep in mind that we may have applications that return
        , Int
n Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int
1
        -- See Note [runRW magic]
        -- Replace (runRW# f) by (f realWorld#), beta reducing if possible (this
        -- is why we return a CorePrepEnv as well)
        = case CpeBody
arg of
            Lam Id
s CpeBody
body -> CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app (CorePrepEnv -> Id -> Id -> CorePrepEnv
extendCorePrepEnv CorePrepEnv
env Id
s Id
realWorldPrimId) CpeBody
body [ArgInfo]
rest (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
2)
            CpeBody
_          -> CorePrepEnv
-> CpeBody -> [ArgInfo] -> Int -> UniqSM (Floats, CpeBody)
cpe_app CorePrepEnv
env CpeBody
arg (CpeBody -> ArgInfo
CpeApp (Id -> CpeBody
forall b. Id -> Expr b
Var Id
realWorldPrimId) ArgInfo -> [ArgInfo] -> [ArgInfo]
forall a. a -> [a] -> [a]
: [ArgInfo]
rest) (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1)
             -- TODO: What about casts?

    cpe_app CorePrepEnv
env (Var Id
v) [ArgInfo]
args Int
depth
      = do { Id
v1 <- Id -> UniqSM Id
fiddleCCall Id
v
           ; let e2 :: CpeBody
e2 = CorePrepEnv -> Id -> CpeBody
lookupCorePrepEnv CorePrepEnv
env Id
v1
                 hd :: Maybe Id
hd = CpeBody -> Maybe Id
getIdFromTrivialExpr_maybe CpeBody
e2
           -- NB: depth from collect_args is right, because e2 is a trivial expression
           -- and thus its embedded Id *must* be at the same depth as any
           -- Apps it is under are type applications only (c.f.
           -- exprIsTrivial).  But note that we need the type of the
           -- expression, not the id.
           ; (CpeBody
app, Floats
floats) <- CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
args CpeBody
e2 Floats
emptyFloats [Demand]
stricts
           ; Maybe Id -> CpeBody -> Floats -> Int -> UniqSM (Floats, CpeBody)
forall {a}. Maybe Id -> CpeBody -> a -> Int -> UniqSM (a, CpeBody)
mb_saturate Maybe Id
hd CpeBody
app Floats
floats Int
depth }
        where
          stricts :: [Demand]
stricts = case Id -> StrictSig
idStrictness Id
v of
                            StrictSig (DmdType DmdEnv
_ [Demand]
demands Divergence
_)
                              | [Demand] -> Int -> Ordering
forall a. [a] -> Int -> Ordering
listLengthCmp [Demand]
demands Int
depth Ordering -> Ordering -> Bool
forall a. Eq a => a -> a -> Bool
/= Ordering
GT -> [Demand]
demands
                                    -- length demands <= depth
                              | Bool
otherwise                         -> []
                -- If depth < length demands, then we have too few args to
                -- satisfy strictness  info so we have to  ignore all the
                -- strictness info, e.g. + (error "urk")
                -- Here, we can't evaluate the arg strictly, because this
                -- partial application might be seq'd

        -- We inlined into something that's not a var and has no args.
        -- Bounce it back up to cpeRhsE.
    cpe_app CorePrepEnv
env CpeBody
fun [] Int
_ = CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
fun

        -- N-variable fun, better let-bind it
    cpe_app CorePrepEnv
env CpeBody
fun [ArgInfo]
args Int
depth
      = do { (Floats
fun_floats, CpeBody
fun') <- CorePrepEnv -> Demand -> CpeBody -> UniqSM (Floats, CpeBody)
cpeArg CorePrepEnv
env Demand
evalDmd CpeBody
fun
                          -- The evalDmd says that it's sure to be evaluated,
                          -- so we'll end up case-binding it
           ; (CpeBody
app, Floats
floats) <- CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
args CpeBody
fun' Floats
fun_floats []
           ; Maybe Id -> CpeBody -> Floats -> Int -> UniqSM (Floats, CpeBody)
forall {a}. Maybe Id -> CpeBody -> a -> Int -> UniqSM (a, CpeBody)
mb_saturate Maybe Id
forall a. Maybe a
Nothing CpeBody
app Floats
floats Int
depth }

    -- Saturate if necessary
    mb_saturate :: Maybe Id -> CpeBody -> a -> Int -> UniqSM (a, CpeBody)
mb_saturate Maybe Id
head CpeBody
app a
floats Int
depth =
       case Maybe Id
head of
         Just Id
fn_id -> do { CpeBody
sat_app <- Id -> CpeBody -> Int -> UniqSM CpeBody
maybeSaturate Id
fn_id CpeBody
app Int
depth
                          ; (a, CpeBody) -> UniqSM (a, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (a
floats, CpeBody
sat_app) }
         Maybe Id
_other              -> (a, CpeBody) -> UniqSM (a, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (a
floats, CpeBody
app)

    -- Deconstruct and rebuild the application, floating any non-atomic
    -- arguments to the outside.  We collect the type of the expression,
    -- the head of the application, and the number of actual value arguments,
    -- all of which are used to possibly saturate this application if it
    -- has a constructor or primop at the head.
    rebuild_app
        :: CorePrepEnv
        -> [ArgInfo]                  -- The arguments (inner to outer)
        -> CpeApp
        -> Floats
        -> [Demand]
        -> UniqSM (CpeApp, Floats)
    rebuild_app :: CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
_ [] CpeBody
app Floats
floats [Demand]
ss
      = ASSERT(null ss) -- make sure we used all the strictness info
        (CpeBody, Floats) -> UniqSM (CpeBody, Floats)
forall (m :: * -> *) a. Monad m => a -> m a
return (CpeBody
app, Floats
floats)

    rebuild_app CorePrepEnv
env (ArgInfo
a : [ArgInfo]
as) CpeBody
fun' Floats
floats [Demand]
ss = case ArgInfo
a of

      CpeApp (Type Type
arg_ty)
        -> CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
as (CpeBody -> CpeBody -> CpeBody
forall b. Expr b -> Expr b -> Expr b
App CpeBody
fun' (Type -> CpeBody
forall b. Type -> Expr b
Type Type
arg_ty')) Floats
floats [Demand]
ss
        where
          arg_ty' :: Type
arg_ty' = CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env Type
arg_ty

      CpeApp (Coercion Coercion
co)
        -> CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
as (CpeBody -> CpeBody -> CpeBody
forall b. Expr b -> Expr b -> Expr b
App CpeBody
fun' (Coercion -> CpeBody
forall b. Coercion -> Expr b
Coercion Coercion
co')) Floats
floats [Demand]
ss
        where
            co' :: Coercion
co' = CorePrepEnv -> Coercion -> Coercion
cpSubstCo CorePrepEnv
env Coercion
co

      CpeApp CpeBody
arg -> do
        let (Demand
ss1, [Demand]
ss_rest)  -- See Note [lazyId magic] in GHC.Types.Id.Make
               = case ([Demand]
ss, CpeBody -> Bool
isLazyExpr CpeBody
arg) of
                   (Demand
_   : [Demand]
ss_rest, Bool
True)  -> (Demand
topDmd, [Demand]
ss_rest)
                   (Demand
ss1 : [Demand]
ss_rest, Bool
False) -> (Demand
ss1,    [Demand]
ss_rest)
                   ([],            Bool
_)     -> (Demand
topDmd, [])
        (Floats
fs, CpeBody
arg') <- CorePrepEnv -> Demand -> CpeBody -> UniqSM (Floats, CpeBody)
cpeArg CorePrepEnv
top_env Demand
ss1 CpeBody
arg
        CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
as (CpeBody -> CpeBody -> CpeBody
forall b. Expr b -> Expr b -> Expr b
App CpeBody
fun' CpeBody
arg') (Floats
fs Floats -> Floats -> Floats
`appendFloats` Floats
floats) [Demand]
ss_rest

      CpeCast Coercion
co
        -> CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
as (CpeBody -> Coercion -> CpeBody
forall b. Expr b -> Coercion -> Expr b
Cast CpeBody
fun' Coercion
co') Floats
floats [Demand]
ss
        where
           co' :: Coercion
co' = CorePrepEnv -> Coercion -> Coercion
cpSubstCo CorePrepEnv
env Coercion
co

      CpeTick CoreTickish
tickish
        -- See [Floating Ticks in CorePrep]
        -> CorePrepEnv
-> [ArgInfo]
-> CpeBody
-> Floats
-> [Demand]
-> UniqSM (CpeBody, Floats)
rebuild_app CorePrepEnv
env [ArgInfo]
as CpeBody
fun' (Floats -> FloatingBind -> Floats
addFloat Floats
floats (CoreTickish -> FloatingBind
FloatTick CoreTickish
tickish)) [Demand]
ss

isLazyExpr :: CoreExpr -> Bool
-- See Note [lazyId magic] in GHC.Types.Id.Make
isLazyExpr :: CpeBody -> Bool
isLazyExpr (Cast CpeBody
e Coercion
_)              = CpeBody -> Bool
isLazyExpr CpeBody
e
isLazyExpr (Tick CoreTickish
_ CpeBody
e)              = CpeBody -> Bool
isLazyExpr CpeBody
e
isLazyExpr (Var Id
f `App` CpeBody
_ `App` CpeBody
_) = Id
f Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
lazyIdKey
isLazyExpr CpeBody
_                       = Bool
False

{- Note [runRW magic]
~~~~~~~~~~~~~~~~~~~~~
Some definitions, for instance @runST@, must have careful control over float out
of the bindings in their body. Consider this use of @runST@,

    f x = runST ( \ s -> let (a, s')  = newArray# 100 [] s
                             (_, s'') = fill_in_array_or_something a x s'
                         in freezeArray# a s'' )

If we inline @runST@, we'll get:

    f x = let (a, s')  = newArray# 100 [] realWorld#{-NB-}
              (_, s'') = fill_in_array_or_something a x s'
          in freezeArray# a s''

And now if we allow the @newArray#@ binding to float out to become a CAF,
we end up with a result that is totally and utterly wrong:

    f = let (a, s')  = newArray# 100 [] realWorld#{-NB-} -- YIKES!!!
        in \ x ->
            let (_, s'') = fill_in_array_or_something a x s'
            in freezeArray# a s''

All calls to @f@ will share a {\em single} array! Clearly this is nonsense and
must be prevented.

This is what @runRW#@ gives us: by being inlined extremely late in the
optimization (right before lowering to STG, in CorePrep), we can ensure that
no further floating will occur. This allows us to safely inline things like
@runST@, which are otherwise needlessly expensive (see #10678 and #5916).

'runRW' has a variety of quirks:

 * 'runRW' is known-key with a NOINLINE definition in
   GHC.Magic. This definition is used in cases where runRW is curried.

 * In addition to its normal Haskell definition in GHC.Magic, we give it
   a special late inlining here in CorePrep and GHC.StgToByteCode, avoiding
   the incorrect sharing due to float-out noted above.

 * It is levity-polymorphic:

    runRW# :: forall (r1 :: RuntimeRep). (o :: TYPE r)
           => (State# RealWorld -> (# State# RealWorld, o #))
           -> (# State# RealWorld, o #)

 * It has some special simplification logic to allow unboxing of results when
   runRW# appears in a strict context. See Note [Simplification of runRW#]
   below.

 * Since its body is inlined, we allow runRW#'s argument to contain jumps to
   join points. That is, the following is allowed:

    join j x = ...
    in runRW# @_ @_ (\s -> ... jump j 42 ...)

   The Core Linter knows about this. See Note [Linting of runRW#] in
   GHC.Core.Lint for details.

   The occurrence analyser and SetLevels also know about this, as described in
   Note [Simplification of runRW#].

Other relevant Notes:

 * Note [Simplification of runRW#] below, describing a transformation of runRW
   applications in strict contexts performed by the simplifier.
 * Note [Linting of runRW#] in GHC.Core.Lint
 * Note [runRW arg] below, describing a non-obvious case where the
   late-inlining could go wrong.


 Note [runRW arg]
~~~~~~~~~~~~~~~~~~~
Consider the Core program (from #11291),

   runRW# (case bot of {})

The late inlining logic in cpe_app would transform this into:

   (case bot of {}) realWorldPrimId#

Which would rise to a panic in CoreToStg.myCollectArgs, which expects only
variables in function position.

However, as runRW#'s strictness signature captures the fact that it will call
its argument this can't happen: the simplifier will transform the bottoming
application into simply (case bot of {}).

Note that this reasoning does *not* apply to non-bottoming continuations like:

    hello :: Bool -> Int
    hello n =
      runRW# (
          case n of
            True -> \s -> 23
            _    -> \s -> 10)

Why? The difference is that (case bot of {}) is considered by okCpeArg to be
trivial, consequently cpeArg (which the catch-all case of cpe_app calls on both
the function and the arguments) will forgo binding it to a variable. By
contrast, in the non-bottoming case of `hello` above  the function will be
deemed non-trivial and consequently will be case-bound.


Note [Simplification of runRW#]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider the program,

    case runRW# (\s -> I# 42#) of
      I# n# -> f n#

There is no reason why we should allocate an I# constructor given that we
immediately destructure it.

To avoid this the simplifier has a special transformation rule, specific to
runRW#, that pushes a strict context into runRW#'s continuation.  See the
`runRW#` guard in `GHC.Core.Opt.Simplify.rebuildCall`.  That is, it transforms

    K[ runRW# @r @ty cont ]
              ~>
    runRW# @r @ty (\s -> K[cont s])

This has a few interesting implications. Consider, for instance, this program:

    join j = ...
    in case runRW# @r @ty cont of
         result -> jump j result

Performing the transform described above would result in:

    join j x = ...
    in runRW# @r @ty (\s ->
         case cont of in
           result -> jump j result
       )

If runRW# were a "normal" function this call to join point j would not be
allowed in its continuation argument. However, since runRW# is inlined (as
described in Note [runRW magic] above), such join point occurrences are
completely fine. Both occurrence analysis (see the runRW guard in occAnalApp)
and Core Lint (see the App case of lintCoreExpr) have special treatment for
runRW# applications. See Note [Linting of runRW#] for details on the latter.

Moreover, it's helpful to ensure that runRW's continuation isn't floated out
For instance, if we have

    runRW# (\s -> do_something)

where do_something contains only top-level free variables, we may be tempted to
float the argument to the top-level. However, we must resist this urge as since
doing so would then require that runRW# produce an allocation and call, e.g.:

    let lvl = \s -> do_somethign
    in
    ....(runRW# lvl)....

whereas without floating the inlining of the definition of runRW would result
in straight-line code. Consequently, GHC.Core.Opt.SetLevels.lvlApp has special
treatment for runRW# applications, ensure the arguments are not floated as
MFEs.

Now that we float evaluation context into runRW#, we also have to give runRW# a
special higher-order CPR transformer lest we risk #19822. E.g.,

  case runRW# (\s -> doThings) of x -> Data.Text.Text x something something'
      ~>
  runRW# (\s -> case doThings s of x -> Data.Text.Text x something something')

The former had the CPR property, and so should the latter.

Other considered designs
------------------------

One design that was rejected was to *require* that runRW#'s continuation be
headed by a lambda. However, this proved to be quite fragile. For instance,
SetLevels is very eager to float bottoming expressions. For instance given
something of the form,

    runRW# @r @ty (\s -> case expr of x -> undefined)

SetLevels will see that the body the lambda is bottoming and will consequently
float it to the top-level (assuming expr has no free coercion variables which
prevent this). We therefore end up with

    runRW# @r @ty (\s -> lvl s)

Which the simplifier will beta reduce, leaving us with

    runRW# @r @ty lvl

Breaking our desired invariant. Ultimately we decided to simply accept that
the continuation may not be a manifest lambda.


-- ---------------------------------------------------------------------------
--      CpeArg: produces a result satisfying CpeArg
-- ---------------------------------------------------------------------------

Note [ANF-ising literal string arguments]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Consider a program like,

    data Foo = Foo Addr#

    foo = Foo "turtle"#

When we go to ANFise this we might think that we want to float the string
literal like we do any other non-trivial argument. This would look like,

    foo = u\ [] case "turtle"# of s { __DEFAULT__ -> Foo s }

However, this 1) isn't necessary since strings are in a sense "trivial"; and 2)
wreaks havoc on the CAF annotations that we produce here since we the result
above is caffy since it is updateable. Ideally at some point in the future we
would like to just float the literal to the top level as suggested in #11312,

    s = "turtle"#
    foo = Foo s

However, until then we simply add a special case excluding literals from the
floating done by cpeArg.
-}

mkUnsafeCo :: Role -> Type -> Type -> Coercion
mkUnsafeCo :: Role -> Type -> Type -> Coercion
mkUnsafeCo Role
role Type
ty1 Type
ty2 = UnivCoProvenance -> Role -> Type -> Type -> Coercion
mkUnivCo UnivCoProvenance
CorePrepProv Role
role Type
ty1 Type
ty2

-- | Is an argument okay to CPE?
okCpeArg :: CoreExpr -> Bool
-- Don't float literals. See Note [ANF-ising literal string arguments].
okCpeArg :: CpeBody -> Bool
okCpeArg (Lit Literal
_) = Bool
False
-- Do not eta expand a trivial argument
okCpeArg CpeBody
expr    = Bool -> Bool
not (CpeBody -> Bool
exprIsTrivial CpeBody
expr)

-- This is where we arrange that a non-trivial argument is let-bound
cpeArg :: CorePrepEnv -> Demand
       -> CoreArg -> UniqSM (Floats, CpeArg)
cpeArg :: CorePrepEnv -> Demand -> CpeBody -> UniqSM (Floats, CpeBody)
cpeArg CorePrepEnv
env Demand
dmd CpeBody
arg
  = do { (Floats
floats1, CpeBody
arg1) <- CorePrepEnv -> CpeBody -> UniqSM (Floats, CpeBody)
cpeRhsE CorePrepEnv
env CpeBody
arg     -- arg1 can be a lambda
       ; let arg_ty :: Type
arg_ty      = CpeBody -> Type
exprType CpeBody
arg1
             is_unlifted :: Bool
is_unlifted = HasDebugCallStack => Type -> Bool
Type -> Bool
isUnliftedType Type
arg_ty
             want_float :: Floats -> CpeBody -> Bool
want_float  = RecFlag -> Demand -> Bool -> Floats -> CpeBody -> Bool
wantFloatNested RecFlag
NonRecursive Demand
dmd Bool
is_unlifted
       ; (Floats
floats2, CpeBody
arg2) <- if Floats -> CpeBody -> Bool
want_float Floats
floats1 CpeBody
arg1
                            then (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats1, CpeBody
arg1)
                            else Floats -> CpeBody -> UniqSM (Floats, CpeBody)
dontFloat Floats
floats1 CpeBody
arg1
                -- Else case: arg1 might have lambdas, and we can't
                --            put them inside a wrapBinds

       ; if CpeBody -> Bool
okCpeArg CpeBody
arg2
         then do { Id
v <- Type -> UniqSM Id
newVar Type
arg_ty
                 ; let arg3 :: CpeBody
arg3      = Int -> CpeBody -> CpeBody
cpeEtaExpand (CpeBody -> Int
exprArity CpeBody
arg2) CpeBody
arg2
                       arg_float :: FloatingBind
arg_float = Demand -> Bool -> Id -> CpeBody -> FloatingBind
mkFloat Demand
dmd Bool
is_unlifted Id
v CpeBody
arg3
                 ; (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats -> FloatingBind -> Floats
addFloat Floats
floats2 FloatingBind
arg_float, Id -> CpeBody
forall b. Id -> Expr b
varToCoreExpr Id
v) }
         else (Floats, CpeBody) -> UniqSM (Floats, CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return (Floats
floats2, CpeBody
arg2)
       }

{-
Note [Floating unlifted arguments]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider    C (let v* = expensive in v)

where the "*" indicates "will be demanded".  Usually v will have been
inlined by now, but let's suppose it hasn't (see #2756).  Then we
do *not* want to get

     let v* = expensive in C v

because that has different strictness.  Hence the use of 'allLazy'.
(NB: the let v* turns into a FloatCase, in mkLocalNonRec.)


------------------------------------------------------------------------------
-- Building the saturated syntax
-- ---------------------------------------------------------------------------

Note [Eta expansion of hasNoBinding things in CorePrep]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
maybeSaturate deals with eta expanding to saturate things that can't deal with
unsaturated applications (identified by 'hasNoBinding', currently just
foreign calls and unboxed tuple/sum constructors).

Historical Note: Note that eta expansion in CorePrep used to be very fragile
due to the "prediction" of CAFfyness that we used to make during tidying.
We previously saturated primop
applications here as well but due to this fragility (see #16846) we now deal
with this another way, as described in Note [Primop wrappers] in GHC.Builtin.PrimOps.
-}

maybeSaturate :: Id -> CpeApp -> Int -> UniqSM CpeRhs
maybeSaturate :: Id -> CpeBody -> Int -> UniqSM CpeBody
maybeSaturate Id
fn CpeBody
expr Int
n_args
  | Id -> Bool
hasNoBinding Id
fn        -- There's no binding
  = CpeBody -> UniqSM CpeBody
forall (m :: * -> *) a. Monad m => a -> m a
return CpeBody
sat_expr

  | Bool
otherwise
  = CpeBody -> UniqSM CpeBody
forall (m :: * -> *) a. Monad m => a -> m a
return CpeBody
expr
  where
    fn_arity :: Int
fn_arity     = Id -> Int
idArity Id
fn
    excess_arity :: Int
excess_arity = Int
fn_arity Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
n_args
    sat_expr :: CpeBody
sat_expr     = Int -> CpeBody -> CpeBody
cpeEtaExpand Int
excess_arity CpeBody
expr

{-
************************************************************************
*                                                                      *
                Simple GHC.Core operations
*                                                                      *
************************************************************************
-}

{-
-- -----------------------------------------------------------------------------
--      Eta reduction
-- -----------------------------------------------------------------------------

Note [Eta expansion]
~~~~~~~~~~~~~~~~~~~~~
Eta expand to match the arity claimed by the binder Remember,
CorePrep must not change arity

Eta expansion might not have happened already, because it is done by
the simplifier only when there at least one lambda already.

NB1:we could refrain when the RHS is trivial (which can happen
    for exported things).  This would reduce the amount of code
    generated (a little) and make things a little words for
    code compiled without -O.  The case in point is data constructor
    wrappers.

NB2: we have to be careful that the result of etaExpand doesn't
   invalidate any of the assumptions that CorePrep is attempting
   to establish.  One possible cause is eta expanding inside of
   an SCC note - we're now careful in etaExpand to make sure the
   SCC is pushed inside any new lambdas that are generated.

Note [Eta expansion and the CorePrep invariants]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It turns out to be much much easier to do eta expansion
*after* the main CorePrep stuff.  But that places constraints
on the eta expander: given a CpeRhs, it must return a CpeRhs.

For example here is what we do not want:
                f = /\a -> g (h 3)      -- h has arity 2
After ANFing we get
                f = /\a -> let s = h 3 in g s
and now we do NOT want eta expansion to give
                f = /\a -> \ y -> (let s = h 3 in g s) y

Instead GHC.Core.Opt.Arity.etaExpand gives
                f = /\a -> \y -> let s = h 3 in g s y

-}

cpeEtaExpand :: Arity -> CpeRhs -> CpeRhs
cpeEtaExpand :: Int -> CpeBody -> CpeBody
cpeEtaExpand Int
arity CpeBody
expr
  | Int
arity Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0 = CpeBody
expr
  | Bool
otherwise  = Int -> CpeBody -> CpeBody
etaExpand Int
arity CpeBody
expr

{-
-- -----------------------------------------------------------------------------
--      Eta reduction
-- -----------------------------------------------------------------------------

Why try eta reduction?  Hasn't the simplifier already done eta?
But the simplifier only eta reduces if that leaves something
trivial (like f, or f Int).  But for deLam it would be enough to
get to a partial application:
        case x of { p -> \xs. map f xs }
    ==> case x of { p -> map f }
-}

-- When updating this function, make sure it lines up with
-- GHC.Core.Utils.tryEtaReduce!
tryEtaReducePrep :: [CoreBndr] -> CoreExpr -> Maybe CoreExpr
tryEtaReducePrep :: [Id] -> CpeBody -> Maybe CpeBody
tryEtaReducePrep [Id]
bndrs expr :: CpeBody
expr@(App CpeBody
_ CpeBody
_)
  | CpeBody -> Bool
forall b. Expr b -> Bool
ok_to_eta_reduce CpeBody
f
  , Int
n_remaining Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int
0
  , [Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
and ((Id -> CpeBody -> Bool) -> [Id] -> [CpeBody] -> [Bool]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith Id -> CpeBody -> Bool
forall {b}. Id -> Expr b -> Bool
ok [Id]
bndrs [CpeBody]
last_args)
  , Bool -> Bool
not ((Id -> Bool) -> [Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (Id -> VarSet -> Bool
`elemVarSet` VarSet
fvs_remaining) [Id]
bndrs)
  , CpeBody -> Bool
exprIsHNF CpeBody
remaining_expr   -- Don't turn value into a non-value
                               -- else the behaviour with 'seq' changes
  = CpeBody -> Maybe CpeBody
forall a. a -> Maybe a
Just CpeBody
remaining_expr
  where
    (CpeBody
f, [CpeBody]
args) = CpeBody -> (CpeBody, [CpeBody])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs CpeBody
expr
    remaining_expr :: CpeBody
remaining_expr = CpeBody -> [CpeBody] -> CpeBody
forall b. Expr b -> [Expr b] -> Expr b
mkApps CpeBody
f [CpeBody]
remaining_args
    fvs_remaining :: VarSet
fvs_remaining = CpeBody -> VarSet
exprFreeVars CpeBody
remaining_expr
    ([CpeBody]
remaining_args, [CpeBody]
last_args) = Int -> [CpeBody] -> ([CpeBody], [CpeBody])
forall a. Int -> [a] -> ([a], [a])
splitAt Int
n_remaining [CpeBody]
args
    n_remaining :: Int
n_remaining = [CpeBody] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [CpeBody]
args Int -> Int -> Int
forall a. Num a => a -> a -> a
- [Id] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Id]
bndrs

    ok :: Id -> Expr b -> Bool
ok Id
bndr (Var Id
arg) = Id
bndr Id -> Id -> Bool
forall a. Eq a => a -> a -> Bool
== Id
arg
    ok Id
_    Expr b
_         = Bool
False

    -- We can't eta reduce something which must be saturated.
    ok_to_eta_reduce :: Expr b -> Bool
ok_to_eta_reduce (Var Id
f) = Bool -> Bool
not (Id -> Bool
hasNoBinding Id
f) Bool -> Bool -> Bool
&& Bool -> Bool
not (Type -> Bool
isLinearType (Id -> Type
idType Id
f))
    ok_to_eta_reduce Expr b
_       = Bool
False -- Safe. ToDo: generalise


tryEtaReducePrep [Id]
bndrs (Tick CoreTickish
tickish CpeBody
e)
  | CoreTickish -> Bool
forall (pass :: TickishPass). GenTickish pass -> Bool
tickishFloatable CoreTickish
tickish
  = (CpeBody -> CpeBody) -> Maybe CpeBody -> Maybe CpeBody
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
tickish) (Maybe CpeBody -> Maybe CpeBody) -> Maybe CpeBody -> Maybe CpeBody
forall a b. (a -> b) -> a -> b
$ [Id] -> CpeBody -> Maybe CpeBody
tryEtaReducePrep [Id]
bndrs CpeBody
e

tryEtaReducePrep [Id]
_ CpeBody
_ = Maybe CpeBody
forall a. Maybe a
Nothing

{-
************************************************************************
*                                                                      *
                Floats
*                                                                      *
************************************************************************

Note [Pin demand info on floats]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We pin demand info on floated lets, so that we can see the one-shot thunks.

Note [Speculative evaluation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Since call-by-value is much cheaper than call-by-need, we case-bind arguments
that are either

  1. Strictly evaluated anyway, according to the DmdSig of the callee, or
  2. ok-for-spec, according to 'exprOkForSpeculation'

While (1) is a no-brainer and always beneficial, (2) is a bit
more subtle, as the careful haddock for 'exprOkForSpeculation'
points out. Still, by case-binding the argument we don't need
to allocate a thunk for it, whose closure must be retained as
long as the callee might evaluate it. And if it is evaluated on
most code paths anyway, we get to turn the unknown eval in the
callee into a known call at the call site.
-}

data FloatingBind
  = FloatLet CoreBind    -- Rhs of bindings are CpeRhss
                         -- They are always of lifted type;
                         -- unlifted ones are done with FloatCase

 | FloatCase
      CpeBody         -- Always ok-for-speculation
      Id              -- Case binder
      AltCon [Var]    -- Single alternative
      Bool            -- Ok-for-speculation; False of a strict,
                      -- but lifted binding

 -- | See Note [Floating Ticks in CorePrep]
 | FloatTick CoreTickish

data Floats = Floats OkToSpec (OrdList FloatingBind)

instance Outputable FloatingBind where
  ppr :: FloatingBind -> SDoc
ppr (FloatLet CoreBind
b) = CoreBind -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreBind
b
  ppr (FloatCase CpeBody
r Id
b AltCon
k [Id]
bs Bool
ok) = String -> SDoc
text String
"case" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
braces (Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bool
ok) SDoc -> SDoc -> SDoc
<+> CpeBody -> SDoc
forall a. Outputable a => a -> SDoc
ppr CpeBody
r
                                SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"of"SDoc -> SDoc -> SDoc
<+> Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
b SDoc -> SDoc -> SDoc
<> String -> SDoc
text String
"@"
                                SDoc -> SDoc -> SDoc
<> case [Id]
bs of
                                   [] -> AltCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr AltCon
k
                                   [Id]
_  -> SDoc -> SDoc
parens (AltCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr AltCon
k SDoc -> SDoc -> SDoc
<+> [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
bs)
  ppr (FloatTick CoreTickish
t) = CoreTickish -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreTickish
t

instance Outputable Floats where
  ppr :: Floats -> SDoc
ppr (Floats OkToSpec
flag OrdList FloatingBind
fs) = String -> SDoc
text String
"Floats" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
brackets (OkToSpec -> SDoc
forall a. Outputable a => a -> SDoc
ppr OkToSpec
flag) SDoc -> SDoc -> SDoc
<+>
                         SDoc -> SDoc
braces ([SDoc] -> SDoc
vcat ((FloatingBind -> SDoc) -> [FloatingBind] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map FloatingBind -> SDoc
forall a. Outputable a => a -> SDoc
ppr (OrdList FloatingBind -> [FloatingBind]
forall a. OrdList a -> [a]
fromOL OrdList FloatingBind
fs)))

instance Outputable OkToSpec where
  ppr :: OkToSpec -> SDoc
ppr OkToSpec
OkToSpec    = String -> SDoc
text String
"OkToSpec"
  ppr OkToSpec
IfUnboxedOk = String -> SDoc
text String
"IfUnboxedOk"
  ppr OkToSpec
NotOkToSpec = String -> SDoc
text String
"NotOkToSpec"

-- Can we float these binds out of the rhs of a let?  We cache this decision
-- to avoid having to recompute it in a non-linear way when there are
-- deeply nested lets.
data OkToSpec
   = OkToSpec           -- Lazy bindings of lifted type
   | IfUnboxedOk        -- A mixture of lazy lifted bindings and n
                        -- ok-to-speculate unlifted bindings
   | NotOkToSpec        -- Some not-ok-to-speculate unlifted bindings

mkFloat :: Demand -> Bool -> Id -> CpeRhs -> FloatingBind
mkFloat :: Demand -> Bool -> Id -> CpeBody -> FloatingBind
mkFloat Demand
dmd Bool
is_unlifted Id
bndr CpeBody
rhs
  | Bool
is_strict Bool -> Bool -> Bool
|| Bool
ok_for_spec -- See Note [Speculative evaluation]
  , Bool -> Bool
not Bool
is_hnf  = CpeBody -> Id -> AltCon -> [Id] -> Bool -> FloatingBind
FloatCase CpeBody
rhs Id
bndr AltCon
DEFAULT [] Bool
ok_for_spec
    -- Don't make a case for a HNF binding, even if it's strict
    -- Otherwise we get  case (\x -> e) of ...!

  | Bool
is_unlifted = CpeBody -> Id -> AltCon -> [Id] -> Bool -> FloatingBind
FloatCase CpeBody
rhs Id
bndr AltCon
DEFAULT [] Bool
True
      -- we used to ASSERT2(ok_for_spec, ppr rhs) here, but it is now disabled
      -- because exprOkForSpeculation isn't stable under ANF-ing. See for
      -- example #19489 where the following unlifted expression:
      --
      --    GHC.Prim.(#|_#) @LiftedRep @LiftedRep @[a_ax0] @[a_ax0]
      --                    (GHC.Types.: @a_ax0 a2_agq a3_agl)
      --
      -- is ok-for-spec but is ANF-ised into:
      --
      --    let sat = GHC.Types.: @a_ax0 a2_agq a3_agl
      --    in GHC.Prim.(#|_#) @LiftedRep @LiftedRep @[a_ax0] @[a_ax0] sat
      --
      -- which isn't ok-for-spec because of the let-expression.

  | Bool
is_hnf      = CoreBind -> FloatingBind
FloatLet (Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr                       CpeBody
rhs)
  | Bool
otherwise   = CoreBind -> FloatingBind
FloatLet (Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec (Id -> Demand -> Id
setIdDemandInfo Id
bndr Demand
dmd) CpeBody
rhs)
                   -- See Note [Pin demand info on floats]
  where
    is_hnf :: Bool
is_hnf      = CpeBody -> Bool
exprIsHNF CpeBody
rhs
    is_strict :: Bool
is_strict   = Demand -> Bool
isStrUsedDmd Demand
dmd
    ok_for_spec :: Bool
ok_for_spec = CpeBody -> Bool
exprOkForSpeculation CpeBody
rhs

emptyFloats :: Floats
emptyFloats :: Floats
emptyFloats = OkToSpec -> OrdList FloatingBind -> Floats
Floats OkToSpec
OkToSpec OrdList FloatingBind
forall a. OrdList a
nilOL

isEmptyFloats :: Floats -> Bool
isEmptyFloats :: Floats -> Bool
isEmptyFloats (Floats OkToSpec
_ OrdList FloatingBind
bs) = OrdList FloatingBind -> Bool
forall a. OrdList a -> Bool
isNilOL OrdList FloatingBind
bs

wrapBinds :: Floats -> CpeBody -> CpeBody
wrapBinds :: Floats -> CpeBody -> CpeBody
wrapBinds (Floats OkToSpec
_ OrdList FloatingBind
binds) CpeBody
body
  = (FloatingBind -> CpeBody -> CpeBody)
-> CpeBody -> OrdList FloatingBind -> CpeBody
forall a b. (a -> b -> b) -> b -> OrdList a -> b
foldrOL FloatingBind -> CpeBody -> CpeBody
mk_bind CpeBody
body OrdList FloatingBind
binds
  where
    mk_bind :: FloatingBind -> CpeBody -> CpeBody
mk_bind (FloatCase CpeBody
rhs Id
bndr AltCon
con [Id]
bs Bool
_) CpeBody
body = CpeBody -> Id -> Type -> [Alt Id] -> CpeBody
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case CpeBody
rhs Id
bndr (CpeBody -> Type
exprType CpeBody
body) [AltCon -> [Id] -> CpeBody -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
con [Id]
bs CpeBody
body]
    mk_bind (FloatLet CoreBind
bind)               CpeBody
body = CoreBind -> CpeBody -> CpeBody
forall b. Bind b -> Expr b -> Expr b
Let CoreBind
bind CpeBody
body
    mk_bind (FloatTick CoreTickish
tickish)           CpeBody
body = CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
tickish CpeBody
body

addFloat :: Floats -> FloatingBind -> Floats
addFloat :: Floats -> FloatingBind -> Floats
addFloat (Floats OkToSpec
ok_to_spec OrdList FloatingBind
floats) FloatingBind
new_float
  = OkToSpec -> OrdList FloatingBind -> Floats
Floats (OkToSpec -> OkToSpec -> OkToSpec
combine OkToSpec
ok_to_spec (FloatingBind -> OkToSpec
check FloatingBind
new_float)) (OrdList FloatingBind
floats OrdList FloatingBind -> FloatingBind -> OrdList FloatingBind
forall a. OrdList a -> a -> OrdList a
`snocOL` FloatingBind
new_float)
  where
    check :: FloatingBind -> OkToSpec
check (FloatLet {})  = OkToSpec
OkToSpec
    check (FloatCase CpeBody
_ Id
_ AltCon
_ [Id]
_ Bool
ok_for_spec)
      | Bool
ok_for_spec = OkToSpec
IfUnboxedOk
      | Bool
otherwise   = OkToSpec
NotOkToSpec
    check FloatTick{}    = OkToSpec
OkToSpec
        -- The ok-for-speculation flag says that it's safe to
        -- float this Case out of a let, and thereby do it more eagerly
        -- We need the top-level flag because it's never ok to float
        -- an unboxed binding to the top level

unitFloat :: FloatingBind -> Floats
unitFloat :: FloatingBind -> Floats
unitFloat = Floats -> FloatingBind -> Floats
addFloat Floats
emptyFloats

appendFloats :: Floats -> Floats -> Floats
appendFloats :: Floats -> Floats -> Floats
appendFloats (Floats OkToSpec
spec1 OrdList FloatingBind
floats1) (Floats OkToSpec
spec2 OrdList FloatingBind
floats2)
  = OkToSpec -> OrdList FloatingBind -> Floats
Floats (OkToSpec -> OkToSpec -> OkToSpec
combine OkToSpec
spec1 OkToSpec
spec2) (OrdList FloatingBind
floats1 OrdList FloatingBind
-> OrdList FloatingBind -> OrdList FloatingBind
forall a. OrdList a -> OrdList a -> OrdList a
`appOL` OrdList FloatingBind
floats2)

concatFloats :: [Floats] -> OrdList FloatingBind
concatFloats :: [Floats] -> OrdList FloatingBind
concatFloats = (Floats -> OrdList FloatingBind -> OrdList FloatingBind)
-> OrdList FloatingBind -> [Floats] -> OrdList FloatingBind
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (\ (Floats OkToSpec
_ OrdList FloatingBind
bs1) OrdList FloatingBind
bs2 -> OrdList FloatingBind
-> OrdList FloatingBind -> OrdList FloatingBind
forall a. OrdList a -> OrdList a -> OrdList a
appOL OrdList FloatingBind
bs1 OrdList FloatingBind
bs2) OrdList FloatingBind
forall a. OrdList a
nilOL

combine :: OkToSpec -> OkToSpec -> OkToSpec
combine :: OkToSpec -> OkToSpec -> OkToSpec
combine OkToSpec
NotOkToSpec OkToSpec
_ = OkToSpec
NotOkToSpec
combine OkToSpec
_ OkToSpec
NotOkToSpec = OkToSpec
NotOkToSpec
combine OkToSpec
IfUnboxedOk OkToSpec
_ = OkToSpec
IfUnboxedOk
combine OkToSpec
_ OkToSpec
IfUnboxedOk = OkToSpec
IfUnboxedOk
combine OkToSpec
_ OkToSpec
_           = OkToSpec
OkToSpec

deFloatTop :: Floats -> [CoreBind]
-- For top level only; we don't expect any FloatCases
deFloatTop :: Floats -> CoreProgram
deFloatTop (Floats OkToSpec
_ OrdList FloatingBind
floats)
  = (FloatingBind -> CoreProgram -> CoreProgram)
-> CoreProgram -> OrdList FloatingBind -> CoreProgram
forall a b. (a -> b -> b) -> b -> OrdList a -> b
foldrOL FloatingBind -> CoreProgram -> CoreProgram
get [] OrdList FloatingBind
floats
  where
    get :: FloatingBind -> CoreProgram -> CoreProgram
get (FloatLet CoreBind
b)               CoreProgram
bs = CoreBind -> CoreBind
get_bind CoreBind
b                 CoreBind -> CoreProgram -> CoreProgram
forall a. a -> [a] -> [a]
: CoreProgram
bs
    get (FloatCase CpeBody
body Id
var AltCon
_ [Id]
_ Bool
_) CoreProgram
bs = CoreBind -> CoreBind
get_bind (Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
var CpeBody
body) CoreBind -> CoreProgram -> CoreProgram
forall a. a -> [a] -> [a]
: CoreProgram
bs
    get FloatingBind
b CoreProgram
_ = String -> SDoc -> CoreProgram
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"corePrepPgm" (FloatingBind -> SDoc
forall a. Outputable a => a -> SDoc
ppr FloatingBind
b)

    -- See Note [Dead code in CorePrep]
    get_bind :: CoreBind -> CoreBind
get_bind (NonRec Id
x CpeBody
e) = Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
x (CpeBody -> CpeBody
occurAnalyseExpr CpeBody
e)
    get_bind (Rec [(Id, CpeBody)]
xes)    = [(Id, CpeBody)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec [(Id
x, CpeBody -> CpeBody
occurAnalyseExpr CpeBody
e) | (Id
x, CpeBody
e) <- [(Id, CpeBody)]
xes]

---------------------------------------------------------------------------

canFloat :: Floats -> CpeRhs -> Maybe (Floats, CpeRhs)
canFloat :: Floats -> CpeBody -> Maybe (Floats, CpeBody)
canFloat (Floats OkToSpec
ok_to_spec OrdList FloatingBind
fs) CpeBody
rhs
  | OkToSpec
OkToSpec <- OkToSpec
ok_to_spec           -- Worth trying
  , Just OrdList FloatingBind
fs' <- OrdList FloatingBind
-> [FloatingBind] -> Maybe (OrdList FloatingBind)
go OrdList FloatingBind
forall a. OrdList a
nilOL (OrdList FloatingBind -> [FloatingBind]
forall a. OrdList a -> [a]
fromOL OrdList FloatingBind
fs)
  = (Floats, CpeBody) -> Maybe (Floats, CpeBody)
forall a. a -> Maybe a
Just (OkToSpec -> OrdList FloatingBind -> Floats
Floats OkToSpec
OkToSpec OrdList FloatingBind
fs', CpeBody
rhs)
  | Bool
otherwise
  = Maybe (Floats, CpeBody)
forall a. Maybe a
Nothing
  where
    go :: OrdList FloatingBind -> [FloatingBind]
       -> Maybe (OrdList FloatingBind)

    go :: OrdList FloatingBind
-> [FloatingBind] -> Maybe (OrdList FloatingBind)
go (OrdList FloatingBind
fbs_out) [] = OrdList FloatingBind -> Maybe (OrdList FloatingBind)
forall a. a -> Maybe a
Just OrdList FloatingBind
fbs_out

    go OrdList FloatingBind
fbs_out (fb :: FloatingBind
fb@(FloatLet CoreBind
_) : [FloatingBind]
fbs_in)
      = OrdList FloatingBind
-> [FloatingBind] -> Maybe (OrdList FloatingBind)
go (OrdList FloatingBind
fbs_out OrdList FloatingBind -> FloatingBind -> OrdList FloatingBind
forall a. OrdList a -> a -> OrdList a
`snocOL` FloatingBind
fb) [FloatingBind]
fbs_in

    go OrdList FloatingBind
fbs_out (ft :: FloatingBind
ft@FloatTick{} : [FloatingBind]
fbs_in)
      = OrdList FloatingBind
-> [FloatingBind] -> Maybe (OrdList FloatingBind)
go (OrdList FloatingBind
fbs_out OrdList FloatingBind -> FloatingBind -> OrdList FloatingBind
forall a. OrdList a -> a -> OrdList a
`snocOL` FloatingBind
ft) [FloatingBind]
fbs_in

    go OrdList FloatingBind
_ (FloatCase{} : [FloatingBind]
_) = Maybe (OrdList FloatingBind)
forall a. Maybe a
Nothing


wantFloatNested :: RecFlag -> Demand -> Bool -> Floats -> CpeRhs -> Bool
wantFloatNested :: RecFlag -> Demand -> Bool -> Floats -> CpeBody -> Bool
wantFloatNested RecFlag
is_rec Demand
dmd Bool
is_unlifted Floats
floats CpeBody
rhs
  =  Floats -> Bool
isEmptyFloats Floats
floats
  Bool -> Bool -> Bool
|| Demand -> Bool
isStrUsedDmd Demand
dmd
  Bool -> Bool -> Bool
|| Bool
is_unlifted
  Bool -> Bool -> Bool
|| (RecFlag -> Floats -> Bool
allLazyNested RecFlag
is_rec Floats
floats Bool -> Bool -> Bool
&& CpeBody -> Bool
exprIsHNF CpeBody
rhs)
        -- Why the test for allLazyNested?
        --      v = f (x `divInt#` y)
        -- we don't want to float the case, even if f has arity 2,
        -- because floating the case would make it evaluated too early

allLazyTop :: Floats -> Bool
allLazyTop :: Floats -> Bool
allLazyTop (Floats OkToSpec
OkToSpec OrdList FloatingBind
_) = Bool
True
allLazyTop Floats
_                   = Bool
False

allLazyNested :: RecFlag -> Floats -> Bool
allLazyNested :: RecFlag -> Floats -> Bool
allLazyNested RecFlag
_      (Floats OkToSpec
OkToSpec    OrdList FloatingBind
_) = Bool
True
allLazyNested RecFlag
_      (Floats OkToSpec
NotOkToSpec OrdList FloatingBind
_) = Bool
False
allLazyNested RecFlag
is_rec (Floats OkToSpec
IfUnboxedOk OrdList FloatingBind
_) = RecFlag -> Bool
isNonRec RecFlag
is_rec

{-
************************************************************************
*                                                                      *
                Cloning
*                                                                      *
************************************************************************
-}

-- ---------------------------------------------------------------------------
--                      The environment
-- ---------------------------------------------------------------------------

{- Note [Inlining in CorePrep]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
There is a subtle but important invariant that must be upheld in the output
of CorePrep: there are no "trivial" updatable thunks.  Thus, this Core
is impermissible:

     let x :: ()
         x = y

(where y is a reference to a GLOBAL variable).  Thunks like this are silly:
they can always be profitably replaced by inlining x with y. Consequently,
the code generator/runtime does not bother implementing this properly
(specifically, there is no implementation of stg_ap_0_upd_info, which is the
stack frame that would be used to update this thunk.  The "0" means it has
zero free variables.)

In general, the inliner is good at eliminating these let-bindings.  However,
there is one case where these trivial updatable thunks can arise: when
we are optimizing away 'lazy' (see Note [lazyId magic], and also
'cpeRhsE'.)  Then, we could have started with:

     let x :: ()
         x = lazy @ () y

which is a perfectly fine, non-trivial thunk, but then CorePrep will
drop 'lazy', giving us 'x = y' which is trivial and impermissible.
The solution is CorePrep to have a miniature inlining pass which deals
with cases like this.  We can then drop the let-binding altogether.

Why does the removal of 'lazy' have to occur in CorePrep?
The gory details are in Note [lazyId magic] in GHC.Types.Id.Make, but the
main reason is that lazy must appear in unfoldings (optimizer
output) and it must prevent call-by-value for catch# (which
is implemented by CorePrep.)

An alternate strategy for solving this problem is to have the
inliner treat 'lazy e' as a trivial expression if 'e' is trivial.
We decided not to adopt this solution to keep the definition
of 'exprIsTrivial' simple.

There is ONE caveat however: for top-level bindings we have
to preserve the binding so that we float the (hacky) non-recursive
binding for data constructors; see Note [Data constructor workers].

Note [CorePrep inlines trivial CoreExpr not Id]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Why does cpe_env need to be an IdEnv CoreExpr, as opposed to an
IdEnv Id?  Naively, we might conjecture that trivial updatable thunks
as per Note [Inlining in CorePrep] always have the form
'lazy @ SomeType gbl_id'.  But this is not true: the following is
perfectly reasonable Core:

     let x :: ()
         x = lazy @ (forall a. a) y @ Bool

When we inline 'x' after eliminating 'lazy', we need to replace
occurrences of 'x' with 'y @ bool', not just 'y'.  Situations like
this can easily arise with higher-rank types; thus, cpe_env must
map to CoreExprs, not Ids.

-}

data CorePrepEnv
  = CPE { CorePrepEnv -> DynFlags
cpe_dynFlags        :: DynFlags
        , CorePrepEnv -> IdEnv CpeBody
cpe_env             :: IdEnv CoreExpr   -- Clone local Ids
        -- ^ This environment is used for three operations:
        --
        --      1. To support cloning of local Ids so that they are
        --      all unique (see item (6) of CorePrep overview).
        --
        --      2. To support beta-reduction of runRW, see
        --      Note [runRW magic] and Note [runRW arg].
        --
        --      3. To let us inline trivial RHSs of non top-level let-bindings,
        --      see Note [lazyId magic], Note [Inlining in CorePrep]
        --      and Note [CorePrep inlines trivial CoreExpr not Id] (#12076)

        , CorePrepEnv -> Maybe CpeTyCoEnv
cpe_tyco_env :: Maybe CpeTyCoEnv -- See Note [CpeTyCoEnv]

        , CorePrepEnv -> LitNumType -> Integer -> Maybe CpeBody
cpe_convertNumLit   :: LitNumType -> Integer -> Maybe CoreExpr
        -- ^ Convert some numeric literals (Integer, Natural) into their
        -- final Core form
    }

mkInitialCorePrepEnv :: HscEnv -> IO CorePrepEnv
mkInitialCorePrepEnv :: HscEnv -> IO CorePrepEnv
mkInitialCorePrepEnv HscEnv
hsc_env = do
   LitNumType -> Integer -> Maybe CpeBody
convertNumLit <- HscEnv -> IO (LitNumType -> Integer -> Maybe CpeBody)
mkConvertNumLiteral HscEnv
hsc_env
   CorePrepEnv -> IO CorePrepEnv
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> IO CorePrepEnv) -> CorePrepEnv -> IO CorePrepEnv
forall a b. (a -> b) -> a -> b
$ CPE
      { cpe_dynFlags :: DynFlags
cpe_dynFlags      = HscEnv -> DynFlags
hsc_dflags HscEnv
hsc_env
      , cpe_env :: IdEnv CpeBody
cpe_env           = IdEnv CpeBody
forall a. VarEnv a
emptyVarEnv
      , cpe_tyco_env :: Maybe CpeTyCoEnv
cpe_tyco_env      = Maybe CpeTyCoEnv
forall a. Maybe a
Nothing
      , cpe_convertNumLit :: LitNumType -> Integer -> Maybe CpeBody
cpe_convertNumLit = LitNumType -> Integer -> Maybe CpeBody
convertNumLit
      }

extendCorePrepEnv :: CorePrepEnv -> Id -> Id -> CorePrepEnv
extendCorePrepEnv :: CorePrepEnv -> Id -> Id -> CorePrepEnv
extendCorePrepEnv CorePrepEnv
cpe Id
id Id
id'
    = CorePrepEnv
cpe { cpe_env :: IdEnv CpeBody
cpe_env = IdEnv CpeBody -> Id -> CpeBody -> IdEnv CpeBody
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv (CorePrepEnv -> IdEnv CpeBody
cpe_env CorePrepEnv
cpe) Id
id (Id -> CpeBody
forall b. Id -> Expr b
Var Id
id') }

extendCorePrepEnvExpr :: CorePrepEnv -> Id -> CoreExpr -> CorePrepEnv
extendCorePrepEnvExpr :: CorePrepEnv -> Id -> CpeBody -> CorePrepEnv
extendCorePrepEnvExpr CorePrepEnv
cpe Id
id CpeBody
expr
    = CorePrepEnv
cpe { cpe_env :: IdEnv CpeBody
cpe_env = IdEnv CpeBody -> Id -> CpeBody -> IdEnv CpeBody
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv (CorePrepEnv -> IdEnv CpeBody
cpe_env CorePrepEnv
cpe) Id
id CpeBody
expr }

extendCorePrepEnvList :: CorePrepEnv -> [(Id,Id)] -> CorePrepEnv
extendCorePrepEnvList :: CorePrepEnv -> [(Id, Id)] -> CorePrepEnv
extendCorePrepEnvList CorePrepEnv
cpe [(Id, Id)]
prs
    = CorePrepEnv
cpe { cpe_env :: IdEnv CpeBody
cpe_env = IdEnv CpeBody -> [(Id, CpeBody)] -> IdEnv CpeBody
forall a. VarEnv a -> [(Id, a)] -> VarEnv a
extendVarEnvList (CorePrepEnv -> IdEnv CpeBody
cpe_env CorePrepEnv
cpe)
                        (((Id, Id) -> (Id, CpeBody)) -> [(Id, Id)] -> [(Id, CpeBody)]
forall a b. (a -> b) -> [a] -> [b]
map (\(Id
id, Id
id') -> (Id
id, Id -> CpeBody
forall b. Id -> Expr b
Var Id
id')) [(Id, Id)]
prs) }

lookupCorePrepEnv :: CorePrepEnv -> Id -> CoreExpr
lookupCorePrepEnv :: CorePrepEnv -> Id -> CpeBody
lookupCorePrepEnv CorePrepEnv
cpe Id
id
  = case IdEnv CpeBody -> Id -> Maybe CpeBody
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv (CorePrepEnv -> IdEnv CpeBody
cpe_env CorePrepEnv
cpe) Id
id of
        Maybe CpeBody
Nothing  -> Id -> CpeBody
forall b. Id -> Expr b
Var Id
id
        Just CpeBody
exp -> CpeBody
exp

------------------------------------------------------------------------------
--           CpeTyCoEnv
-- ---------------------------------------------------------------------------

{- Note [CpeTyCoEnv]
~~~~~~~~~~~~~~~~~~~~
The cpe_tyco_env :: Maybe CpeTyCoEnv field carries a substitution
for type and coercion varibles

* We need the coercion substitution to support the elimination of
  unsafeEqualityProof (see Note [Unsafe coercions])

* We need the type substitution in case one of those unsafe
  coercions occurs in the kind of tyvar binder (sigh)

We don't need an in-scope set because we don't clone any of these
binders at all, so no new capture can take place.

The cpe_tyco_env is almost always empty -- it only gets populated
when we get under an usafeEqualityProof.  Hence the Maybe CpeTyCoEnv,
which makes everything into a no-op in the common case.
-}

data CpeTyCoEnv = TCE TvSubstEnv CvSubstEnv

emptyTCE :: CpeTyCoEnv
emptyTCE :: CpeTyCoEnv
emptyTCE = TvSubstEnv -> CvSubstEnv -> CpeTyCoEnv
TCE TvSubstEnv
emptyTvSubstEnv CvSubstEnv
emptyCvSubstEnv

extend_tce_cv :: CpeTyCoEnv -> CoVar -> Coercion -> CpeTyCoEnv
extend_tce_cv :: CpeTyCoEnv -> Id -> Coercion -> CpeTyCoEnv
extend_tce_cv (TCE TvSubstEnv
tv_env CvSubstEnv
cv_env) Id
cv Coercion
co
  = TvSubstEnv -> CvSubstEnv -> CpeTyCoEnv
TCE TvSubstEnv
tv_env (CvSubstEnv -> Id -> Coercion -> CvSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv CvSubstEnv
cv_env Id
cv Coercion
co)

extend_tce_tv :: CpeTyCoEnv -> TyVar -> Type -> CpeTyCoEnv
extend_tce_tv :: CpeTyCoEnv -> Id -> Type -> CpeTyCoEnv
extend_tce_tv (TCE TvSubstEnv
tv_env CvSubstEnv
cv_env) Id
tv Type
ty
  = TvSubstEnv -> CvSubstEnv -> CpeTyCoEnv
TCE (TvSubstEnv -> Id -> Type -> TvSubstEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv TvSubstEnv
tv_env Id
tv Type
ty) CvSubstEnv
cv_env

lookup_tce_cv :: CpeTyCoEnv -> CoVar -> Coercion
lookup_tce_cv :: CpeTyCoEnv -> Id -> Coercion
lookup_tce_cv (TCE TvSubstEnv
_ CvSubstEnv
cv_env) Id
cv
  = case CvSubstEnv -> Id -> Maybe Coercion
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv CvSubstEnv
cv_env Id
cv of
        Just Coercion
co -> Coercion
co
        Maybe Coercion
Nothing -> Id -> Coercion
mkCoVarCo Id
cv

lookup_tce_tv :: CpeTyCoEnv -> TyVar -> Type
lookup_tce_tv :: CpeTyCoEnv -> Id -> Type
lookup_tce_tv (TCE TvSubstEnv
tv_env CvSubstEnv
_) Id
tv
  = case TvSubstEnv -> Id -> Maybe Type
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv TvSubstEnv
tv_env Id
tv of
        Just Type
ty -> Type
ty
        Maybe Type
Nothing -> Id -> Type
mkTyVarTy Id
tv

extendCoVarEnv :: CorePrepEnv -> CoVar -> Coercion -> CorePrepEnv
extendCoVarEnv :: CorePrepEnv -> Id -> Coercion -> CorePrepEnv
extendCoVarEnv cpe :: CorePrepEnv
cpe@(CPE { cpe_tyco_env :: CorePrepEnv -> Maybe CpeTyCoEnv
cpe_tyco_env = Maybe CpeTyCoEnv
mb_tce }) Id
cv Coercion
co
  = CorePrepEnv
cpe { cpe_tyco_env :: Maybe CpeTyCoEnv
cpe_tyco_env = CpeTyCoEnv -> Maybe CpeTyCoEnv
forall a. a -> Maybe a
Just (CpeTyCoEnv -> Id -> Coercion -> CpeTyCoEnv
extend_tce_cv CpeTyCoEnv
tce Id
cv Coercion
co) }
  where
    tce :: CpeTyCoEnv
tce = Maybe CpeTyCoEnv
mb_tce Maybe CpeTyCoEnv -> CpeTyCoEnv -> CpeTyCoEnv
forall a. Maybe a -> a -> a
`orElse` CpeTyCoEnv
emptyTCE


cpSubstTy :: CorePrepEnv -> Type -> Type
cpSubstTy :: CorePrepEnv -> Type -> Type
cpSubstTy (CPE { cpe_tyco_env :: CorePrepEnv -> Maybe CpeTyCoEnv
cpe_tyco_env = Maybe CpeTyCoEnv
mb_env }) Type
ty
  = case Maybe CpeTyCoEnv
mb_env of
      Just CpeTyCoEnv
env -> Identity Type -> Type
forall a. Identity a -> a
runIdentity (CpeTyCoEnv -> Type -> Identity Type
subst_ty CpeTyCoEnv
env Type
ty)
      Maybe CpeTyCoEnv
Nothing  -> Type
ty

cpSubstCo :: CorePrepEnv -> Coercion -> Coercion
cpSubstCo :: CorePrepEnv -> Coercion -> Coercion
cpSubstCo (CPE { cpe_tyco_env :: CorePrepEnv -> Maybe CpeTyCoEnv
cpe_tyco_env = Maybe CpeTyCoEnv
mb_env }) Coercion
co
  = case Maybe CpeTyCoEnv
mb_env of
      Just CpeTyCoEnv
tce -> Identity Coercion -> Coercion
forall a. Identity a -> a
runIdentity (CpeTyCoEnv -> Coercion -> Identity Coercion
subst_co CpeTyCoEnv
tce Coercion
co)
      Maybe CpeTyCoEnv
Nothing  -> Coercion
co

subst_tyco_mapper :: TyCoMapper CpeTyCoEnv Identity
subst_tyco_mapper :: TyCoMapper CpeTyCoEnv Identity
subst_tyco_mapper = TyCoMapper
  { tcm_tyvar :: CpeTyCoEnv -> Id -> Identity Type
tcm_tyvar      = \CpeTyCoEnv
env Id
tv -> Type -> Identity Type
forall (m :: * -> *) a. Monad m => a -> m a
return (CpeTyCoEnv -> Id -> Type
lookup_tce_tv CpeTyCoEnv
env Id
tv)
  , tcm_covar :: CpeTyCoEnv -> Id -> Identity Coercion
tcm_covar      = \CpeTyCoEnv
env Id
cv -> Coercion -> Identity Coercion
forall (m :: * -> *) a. Monad m => a -> m a
return (CpeTyCoEnv -> Id -> Coercion
lookup_tce_cv CpeTyCoEnv
env Id
cv)
  , tcm_hole :: CpeTyCoEnv -> CoercionHole -> Identity Coercion
tcm_hole       = \CpeTyCoEnv
_ CoercionHole
hole -> String -> SDoc -> Identity Coercion
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"subst_co_mapper:hole" (CoercionHole -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoercionHole
hole)
  , tcm_tycobinder :: CpeTyCoEnv -> Id -> ArgFlag -> Identity (CpeTyCoEnv, Id)
tcm_tycobinder = \CpeTyCoEnv
env Id
tcv ArgFlag
_vis -> if Id -> Bool
isTyVar Id
tcv
                                      then (CpeTyCoEnv, Id) -> Identity (CpeTyCoEnv, Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (CpeTyCoEnv -> Id -> (CpeTyCoEnv, Id)
subst_tv_bndr CpeTyCoEnv
env Id
tcv)
                                      else (CpeTyCoEnv, Id) -> Identity (CpeTyCoEnv, Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (CpeTyCoEnv -> Id -> (CpeTyCoEnv, Id)
subst_cv_bndr CpeTyCoEnv
env Id
tcv)
  , tcm_tycon :: TyCon -> Identity TyCon
tcm_tycon      = \TyCon
tc -> TyCon -> Identity TyCon
forall (m :: * -> *) a. Monad m => a -> m a
return TyCon
tc }

subst_ty :: CpeTyCoEnv -> Type     -> Identity Type
subst_co :: CpeTyCoEnv -> Coercion -> Identity Coercion
(CpeTyCoEnv -> Type -> Identity Type
subst_ty, CpeTyCoEnv -> [Type] -> Identity [Type]
_, CpeTyCoEnv -> Coercion -> Identity Coercion
subst_co, CpeTyCoEnv -> [Coercion] -> Identity [Coercion]
_) = TyCoMapper CpeTyCoEnv Identity
-> (CpeTyCoEnv -> Type -> Identity Type,
    CpeTyCoEnv -> [Type] -> Identity [Type],
    CpeTyCoEnv -> Coercion -> Identity Coercion,
    CpeTyCoEnv -> [Coercion] -> Identity [Coercion])
forall (m :: * -> *) env.
Monad m =>
TyCoMapper env m
-> (env -> Type -> m Type, env -> [Type] -> m [Type],
    env -> Coercion -> m Coercion, env -> [Coercion] -> m [Coercion])
mapTyCoX TyCoMapper CpeTyCoEnv Identity
subst_tyco_mapper

cpSubstTyVarBndr :: CorePrepEnv -> TyVar -> (CorePrepEnv, TyVar)
cpSubstTyVarBndr :: CorePrepEnv -> Id -> (CorePrepEnv, Id)
cpSubstTyVarBndr env :: CorePrepEnv
env@(CPE { cpe_tyco_env :: CorePrepEnv -> Maybe CpeTyCoEnv
cpe_tyco_env = Maybe CpeTyCoEnv
mb_env }) Id
tv
  = case Maybe CpeTyCoEnv
mb_env of
      Maybe CpeTyCoEnv
Nothing  -> (CorePrepEnv
env, Id
tv)
      Just CpeTyCoEnv
tce -> (CorePrepEnv
env { cpe_tyco_env :: Maybe CpeTyCoEnv
cpe_tyco_env = CpeTyCoEnv -> Maybe CpeTyCoEnv
forall a. a -> Maybe a
Just CpeTyCoEnv
tce' }, Id
tv')
               where
                  (CpeTyCoEnv
tce', Id
tv') = CpeTyCoEnv -> Id -> (CpeTyCoEnv, Id)
subst_tv_bndr CpeTyCoEnv
tce Id
tv

subst_tv_bndr :: CpeTyCoEnv -> TyVar -> (CpeTyCoEnv, TyVar)
subst_tv_bndr :: CpeTyCoEnv -> Id -> (CpeTyCoEnv, Id)
subst_tv_bndr CpeTyCoEnv
tce Id
tv
  = (CpeTyCoEnv -> Id -> Type -> CpeTyCoEnv
extend_tce_tv CpeTyCoEnv
tce Id
tv (Id -> Type
mkTyVarTy Id
tv'), Id
tv')
  where
    tv' :: Id
tv'   = Name -> Type -> Id
mkTyVar (Id -> Name
tyVarName Id
tv) Type
kind'
    kind' :: Type
kind' = Identity Type -> Type
forall a. Identity a -> a
runIdentity (Identity Type -> Type) -> Identity Type -> Type
forall a b. (a -> b) -> a -> b
$ CpeTyCoEnv -> Type -> Identity Type
subst_ty CpeTyCoEnv
tce (Type -> Identity Type) -> Type -> Identity Type
forall a b. (a -> b) -> a -> b
$ Id -> Type
tyVarKind Id
tv

cpSubstCoVarBndr :: CorePrepEnv -> CoVar -> (CorePrepEnv, CoVar)
cpSubstCoVarBndr :: CorePrepEnv -> Id -> (CorePrepEnv, Id)
cpSubstCoVarBndr env :: CorePrepEnv
env@(CPE { cpe_tyco_env :: CorePrepEnv -> Maybe CpeTyCoEnv
cpe_tyco_env = Maybe CpeTyCoEnv
mb_env }) Id
cv
  = case Maybe CpeTyCoEnv
mb_env of
      Maybe CpeTyCoEnv
Nothing  -> (CorePrepEnv
env, Id
cv)
      Just CpeTyCoEnv
tce -> (CorePrepEnv
env { cpe_tyco_env :: Maybe CpeTyCoEnv
cpe_tyco_env = CpeTyCoEnv -> Maybe CpeTyCoEnv
forall a. a -> Maybe a
Just CpeTyCoEnv
tce' }, Id
cv')
               where
                  (CpeTyCoEnv
tce', Id
cv') = CpeTyCoEnv -> Id -> (CpeTyCoEnv, Id)
subst_cv_bndr CpeTyCoEnv
tce Id
cv

subst_cv_bndr :: CpeTyCoEnv -> CoVar -> (CpeTyCoEnv, CoVar)
subst_cv_bndr :: CpeTyCoEnv -> Id -> (CpeTyCoEnv, Id)
subst_cv_bndr CpeTyCoEnv
tce Id
cv
  = (CpeTyCoEnv -> Id -> Coercion -> CpeTyCoEnv
extend_tce_cv CpeTyCoEnv
tce Id
cv (Id -> Coercion
mkCoVarCo Id
cv'), Id
cv')
  where
    cv' :: Id
cv' = Name -> Type -> Id
mkCoVar (Id -> Name
varName Id
cv) Type
ty'
    ty' :: Type
ty' = Identity Type -> Type
forall a. Identity a -> a
runIdentity (CpeTyCoEnv -> Type -> Identity Type
subst_ty CpeTyCoEnv
tce (Type -> Identity Type) -> Type -> Identity Type
forall a b. (a -> b) -> a -> b
$ Id -> Type
varType Id
cv)

------------------------------------------------------------------------------
-- Cloning binders
-- ---------------------------------------------------------------------------

cpCloneBndrs :: CorePrepEnv -> [InVar] -> UniqSM (CorePrepEnv, [OutVar])
cpCloneBndrs :: CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
cpCloneBndrs CorePrepEnv
env [Id]
bs = (CorePrepEnv -> Id -> UniqSM (CorePrepEnv, Id))
-> CorePrepEnv -> [Id] -> UniqSM (CorePrepEnv, [Id])
forall (m :: * -> *) acc x y.
Monad m =>
(acc -> x -> m (acc, y)) -> acc -> [x] -> m (acc, [y])
mapAccumLM CorePrepEnv -> Id -> UniqSM (CorePrepEnv, Id)
cpCloneBndr CorePrepEnv
env [Id]
bs

cpCloneBndr  :: CorePrepEnv -> InVar -> UniqSM (CorePrepEnv, OutVar)
cpCloneBndr :: CorePrepEnv -> Id -> UniqSM (CorePrepEnv, Id)
cpCloneBndr CorePrepEnv
env Id
bndr
  | Id -> Bool
isTyVar Id
bndr
  = (CorePrepEnv, Id) -> UniqSM (CorePrepEnv, Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> Id -> (CorePrepEnv, Id)
cpSubstTyVarBndr CorePrepEnv
env Id
bndr)

  | Id -> Bool
isCoVar Id
bndr
  = (CorePrepEnv, Id) -> UniqSM (CorePrepEnv, Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> Id -> (CorePrepEnv, Id)
cpSubstCoVarBndr CorePrepEnv
env Id
bndr)

  | Bool
otherwise
  = do { Id
bndr' <- Id -> UniqSM Id
clone_it Id
bndr

       -- Drop (now-useless) rules/unfoldings
       -- See Note [Drop unfoldings and rules]
       -- and Note [Preserve evaluatedness] in GHC.Core.Tidy
       ; let unfolding' :: Unfolding
unfolding' = Unfolding -> Unfolding
zapUnfolding (Id -> Unfolding
realIdUnfolding Id
bndr)
                          -- Simplifier will set the Id's unfolding

             bndr'' :: Id
bndr'' = Id
bndr' Id -> Unfolding -> Id
`setIdUnfolding`      Unfolding
unfolding'
                            Id -> RuleInfo -> Id
`setIdSpecialisation` RuleInfo
emptyRuleInfo

       ; (CorePrepEnv, Id) -> UniqSM (CorePrepEnv, Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (CorePrepEnv -> Id -> Id -> CorePrepEnv
extendCorePrepEnv CorePrepEnv
env Id
bndr Id
bndr'', Id
bndr'') }
  where
    clone_it :: Id -> UniqSM Id
clone_it Id
bndr
      | Id -> Bool
isLocalId Id
bndr
      = do { Unique
uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
           ; let ty' :: Type
ty' = CorePrepEnv -> Type -> Type
cpSubstTy CorePrepEnv
env (Id -> Type
idType Id
bndr)
           ; Id -> UniqSM Id
forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> Unique -> Id
setVarUnique (Id -> Type -> Id
setIdType Id
bndr Type
ty') Unique
uniq) }

      | Bool
otherwise   -- Top level things, which we don't want
                    -- to clone, have become GlobalIds by now
      = Id -> UniqSM Id
forall (m :: * -> *) a. Monad m => a -> m a
return Id
bndr

{- Note [Drop unfoldings and rules]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We want to drop the unfolding/rules on every Id:

  - We are now past interface-file generation, and in the
    codegen pipeline, so we really don't need full unfoldings/rules

  - The unfolding/rule may be keeping stuff alive that we'd like
    to discard.  See  Note [Dead code in CorePrep]

  - Getting rid of unnecessary unfoldings reduces heap usage

  - We are changing uniques, so if we didn't discard unfoldings/rules
    we'd have to substitute in them

HOWEVER, we want to preserve evaluated-ness;
see Note [Preserve evaluatedness] in GHC.Core.Tidy.
-}

------------------------------------------------------------------------------
-- Cloning ccall Ids; each must have a unique name,
-- to give the code generator a handle to hang it on
-- ---------------------------------------------------------------------------

fiddleCCall :: Id -> UniqSM Id
fiddleCCall :: Id -> UniqSM Id
fiddleCCall Id
id
  | Id -> Bool
isFCallId Id
id = (Id
id Id -> Unique -> Id
`setVarUnique`) (Unique -> Id) -> UniqSM Unique -> UniqSM Id
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
  | Bool
otherwise    = Id -> UniqSM Id
forall (m :: * -> *) a. Monad m => a -> m a
return Id
id

------------------------------------------------------------------------------
-- Generating new binders
-- ---------------------------------------------------------------------------

newVar :: Type -> UniqSM Id
newVar :: Type -> UniqSM Id
newVar Type
ty
 = Type -> ()
seqType Type
ty () -> UniqSM Id -> UniqSM Id
`seq` do
     Unique
uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
     Id -> UniqSM Id
forall (m :: * -> *) a. Monad m => a -> m a
return (FastString -> Unique -> Type -> Type -> Id
mkSysLocalOrCoVar (String -> FastString
fsLit String
"sat") Unique
uniq Type
Many Type
ty)


------------------------------------------------------------------------------
-- Floating ticks
-- ---------------------------------------------------------------------------
--
-- Note [Floating Ticks in CorePrep]
--
-- It might seem counter-intuitive to float ticks by default, given
-- that we don't actually want to move them if we can help it. On the
-- other hand, nothing gets very far in CorePrep anyway, and we want
-- to preserve the order of let bindings and tick annotations in
-- relation to each other. For example, if we just wrapped let floats
-- when they pass through ticks, we might end up performing the
-- following transformation:
--
--   src<...> let foo = bar in baz
--   ==>  let foo = src<...> bar in src<...> baz
--
-- Because the let-binding would float through the tick, and then
-- immediately materialize, achieving nothing but decreasing tick
-- accuracy. The only special case is the following scenario:
--
--   let foo = src<...> (let a = b in bar) in baz
--   ==>  let foo = src<...> bar; a = src<...> b in baz
--
-- Here we would not want the source tick to end up covering "baz" and
-- therefore refrain from pushing ticks outside. Instead, we copy them
-- into the floating binds (here "a") in cpePair. Note that where "b"
-- or "bar" are (value) lambdas we have to push the annotations
-- further inside in order to uphold our rules.
--
-- All of this is implemented below in @wrapTicks@.

-- | Like wrapFloats, but only wraps tick floats
wrapTicks :: Floats -> CoreExpr -> (Floats, CoreExpr)
wrapTicks :: Floats -> CpeBody -> (Floats, CpeBody)
wrapTicks (Floats OkToSpec
flag OrdList FloatingBind
floats0) CpeBody
expr =
    (OkToSpec -> OrdList FloatingBind -> Floats
Floats OkToSpec
flag ([FloatingBind] -> OrdList FloatingBind
forall a. [a] -> OrdList a
toOL ([FloatingBind] -> OrdList FloatingBind)
-> [FloatingBind] -> OrdList FloatingBind
forall a b. (a -> b) -> a -> b
$ [FloatingBind] -> [FloatingBind]
forall a. [a] -> [a]
reverse [FloatingBind]
floats1), (CoreTickish -> CpeBody -> CpeBody)
-> CpeBody -> [CoreTickish] -> CpeBody
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr CoreTickish -> CpeBody -> CpeBody
mkTick CpeBody
expr ([CoreTickish] -> [CoreTickish]
forall a. [a] -> [a]
reverse [CoreTickish]
ticks1))
  where ([FloatingBind]
floats1, [CoreTickish]
ticks1) = (([FloatingBind], [CoreTickish])
 -> FloatingBind -> ([FloatingBind], [CoreTickish]))
-> ([FloatingBind], [CoreTickish])
-> OrdList FloatingBind
-> ([FloatingBind], [CoreTickish])
forall b a. (b -> a -> b) -> b -> OrdList a -> b
foldlOL ([FloatingBind], [CoreTickish])
-> FloatingBind -> ([FloatingBind], [CoreTickish])
go ([], []) (OrdList FloatingBind -> ([FloatingBind], [CoreTickish]))
-> OrdList FloatingBind -> ([FloatingBind], [CoreTickish])
forall a b. (a -> b) -> a -> b
$ OrdList FloatingBind
floats0
        -- Deeply nested constructors will produce long lists of
        -- redundant source note floats here. We need to eliminate
        -- those early, as relying on mkTick to spot it after the fact
        -- can yield O(n^3) complexity [#11095]
        go :: ([FloatingBind], [CoreTickish])
-> FloatingBind -> ([FloatingBind], [CoreTickish])
go ([FloatingBind]
floats, [CoreTickish]
ticks) (FloatTick CoreTickish
t)
          = ASSERT(tickishPlace t == PlaceNonLam)
            ([FloatingBind]
floats, if (CoreTickish -> Bool) -> [CoreTickish] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any ((CoreTickish -> CoreTickish -> Bool)
-> CoreTickish -> CoreTickish -> Bool
forall a b c. (a -> b -> c) -> b -> a -> c
flip CoreTickish -> CoreTickish -> Bool
forall (pass :: TickishPass).
Eq (GenTickish pass) =>
GenTickish pass -> GenTickish pass -> Bool
tickishContains CoreTickish
t) [CoreTickish]
ticks
                     then [CoreTickish]
ticks else CoreTickish
tCoreTickish -> [CoreTickish] -> [CoreTickish]
forall a. a -> [a] -> [a]
:[CoreTickish]
ticks)
        go ([FloatingBind]
floats, [CoreTickish]
ticks) FloatingBind
f
          = ((CoreTickish -> FloatingBind -> FloatingBind)
-> FloatingBind -> [CoreTickish] -> FloatingBind
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr CoreTickish -> FloatingBind -> FloatingBind
wrap FloatingBind
f ([CoreTickish] -> [CoreTickish]
forall a. [a] -> [a]
reverse [CoreTickish]
ticks)FloatingBind -> [FloatingBind] -> [FloatingBind]
forall a. a -> [a] -> [a]
:[FloatingBind]
floats, [CoreTickish]
ticks)

        wrap :: CoreTickish -> FloatingBind -> FloatingBind
wrap CoreTickish
t (FloatLet CoreBind
bind)           = CoreBind -> FloatingBind
FloatLet (CoreTickish -> CoreBind -> CoreBind
wrapBind CoreTickish
t CoreBind
bind)
        wrap CoreTickish
t (FloatCase CpeBody
r Id
b AltCon
con [Id]
bs Bool
ok) = CpeBody -> Id -> AltCon -> [Id] -> Bool -> FloatingBind
FloatCase (CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
t CpeBody
r) Id
b AltCon
con [Id]
bs Bool
ok
        wrap CoreTickish
_ FloatingBind
other                     = String -> SDoc -> FloatingBind
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"wrapTicks: unexpected float!"
                                             (FloatingBind -> SDoc
forall a. Outputable a => a -> SDoc
ppr FloatingBind
other)
        wrapBind :: CoreTickish -> CoreBind -> CoreBind
wrapBind CoreTickish
t (NonRec Id
binder CpeBody
rhs) = Id -> CpeBody -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec Id
binder (CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
t CpeBody
rhs)
        wrapBind CoreTickish
t (Rec [(Id, CpeBody)]
pairs)         = [(Id, CpeBody)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec ((CpeBody -> CpeBody) -> [(Id, CpeBody)] -> [(Id, CpeBody)]
forall b c a. (b -> c) -> [(a, b)] -> [(a, c)]
mapSnd (CoreTickish -> CpeBody -> CpeBody
mkTick CoreTickish
t) [(Id, CpeBody)]
pairs)

------------------------------------------------------------------------------
-- Collecting cost centres
-- ---------------------------------------------------------------------------

-- | Collect cost centres defined in the current module, including those in
-- unfoldings.
collectCostCentres :: Module -> CoreProgram -> S.Set CostCentre
collectCostCentres :: Module -> CoreProgram -> Set CostCentre
collectCostCentres Module
mod_name
  = (Set CostCentre -> CoreBind -> Set CostCentre)
-> Set CostCentre -> CoreProgram -> Set CostCentre
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' Set CostCentre -> CoreBind -> Set CostCentre
go_bind Set CostCentre
forall a. Set a
S.empty
  where
    go :: Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
e = case CpeBody
e of
      Var{} -> Set CostCentre
cs
      Lit{} -> Set CostCentre
cs
      App CpeBody
e1 CpeBody
e2 -> Set CostCentre -> CpeBody -> Set CostCentre
go (Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
e1) CpeBody
e2
      Lam Id
_ CpeBody
e -> Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
e
      Let CoreBind
b CpeBody
e -> Set CostCentre -> CpeBody -> Set CostCentre
go (Set CostCentre -> CoreBind -> Set CostCentre
go_bind Set CostCentre
cs CoreBind
b) CpeBody
e
      Case CpeBody
scrt Id
_ Type
_ [Alt Id]
alts -> Set CostCentre -> [Alt Id] -> Set CostCentre
go_alts (Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
scrt) [Alt Id]
alts
      Cast CpeBody
e Coercion
_ -> Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
e
      Tick (ProfNote CostCentre
cc Bool
_ Bool
_) CpeBody
e ->
        Set CostCentre -> CpeBody -> Set CostCentre
go (if CostCentre -> Module -> Bool
ccFromThisModule CostCentre
cc Module
mod_name then CostCentre -> Set CostCentre -> Set CostCentre
forall a. Ord a => a -> Set a -> Set a
S.insert CostCentre
cc Set CostCentre
cs else Set CostCentre
cs) CpeBody
e
      Tick CoreTickish
_ CpeBody
e -> Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
e
      Type{} -> Set CostCentre
cs
      Coercion{} -> Set CostCentre
cs

    go_alts :: Set CostCentre -> [Alt Id] -> Set CostCentre
go_alts = (Set CostCentre -> Alt Id -> Set CostCentre)
-> Set CostCentre -> [Alt Id] -> Set CostCentre
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' (\Set CostCentre
cs (Alt AltCon
_con [Id]
_bndrs CpeBody
e) -> Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs CpeBody
e)

    go_bind :: S.Set CostCentre -> CoreBind -> S.Set CostCentre
    go_bind :: Set CostCentre -> CoreBind -> Set CostCentre
go_bind Set CostCentre
cs (NonRec Id
b CpeBody
e) =
      Set CostCentre -> CpeBody -> Set CostCentre
go (Set CostCentre
-> (CpeBody -> Set CostCentre) -> Maybe CpeBody -> Set CostCentre
forall b a. b -> (a -> b) -> Maybe a -> b
maybe Set CostCentre
cs (Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs) (Id -> Maybe CpeBody
get_unf Id
b)) CpeBody
e
    go_bind Set CostCentre
cs (Rec [(Id, CpeBody)]
bs) =
      (Set CostCentre -> (Id, CpeBody) -> Set CostCentre)
-> Set CostCentre -> [(Id, CpeBody)] -> Set CostCentre
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' (\Set CostCentre
cs' (Id
b, CpeBody
e) -> Set CostCentre -> CpeBody -> Set CostCentre
go (Set CostCentre
-> (CpeBody -> Set CostCentre) -> Maybe CpeBody -> Set CostCentre
forall b a. b -> (a -> b) -> Maybe a -> b
maybe Set CostCentre
cs' (Set CostCentre -> CpeBody -> Set CostCentre
go Set CostCentre
cs') (Id -> Maybe CpeBody
get_unf Id
b)) CpeBody
e) Set CostCentre
cs [(Id, CpeBody)]
bs

    -- Unfoldings may have cost centres that in the original definion are
    -- optimized away, see #5889.
    get_unf :: Id -> Maybe CpeBody
get_unf = Unfolding -> Maybe CpeBody
maybeUnfoldingTemplate (Unfolding -> Maybe CpeBody)
-> (Id -> Unfolding) -> Id -> Maybe CpeBody
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Id -> Unfolding
realIdUnfolding


------------------------------------------------------------------------------
-- Numeric literals
-- ---------------------------------------------------------------------------

-- | Create a function that converts Bignum literals into their final CoreExpr
mkConvertNumLiteral
   :: HscEnv
   -> IO (LitNumType -> Integer -> Maybe CoreExpr)
mkConvertNumLiteral :: HscEnv -> IO (LitNumType -> Integer -> Maybe CpeBody)
mkConvertNumLiteral HscEnv
hsc_env = do
   let
      dflags :: DynFlags
dflags   = HscEnv -> DynFlags
hsc_dflags HscEnv
hsc_env
      platform :: Platform
platform = DynFlags -> Platform
targetPlatform DynFlags
dflags
      home_unit :: HomeUnit
home_unit = HscEnv -> HomeUnit
hsc_home_unit HscEnv
hsc_env
      guardBignum :: IO Id -> IO Id
guardBignum IO Id
act
         | HomeUnit -> UnitId -> Bool
isHomeUnitInstanceOf HomeUnit
home_unit UnitId
primUnitId
         = Id -> IO Id
forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> IO Id) -> Id -> IO Id
forall a b. (a -> b) -> a -> b
$ String -> Id
forall a. String -> a
panic String
"Bignum literals are not supported in ghc-prim"
         | HomeUnit -> UnitId -> Bool
isHomeUnitInstanceOf HomeUnit
home_unit UnitId
bignumUnitId
         = Id -> IO Id
forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> IO Id) -> Id -> IO Id
forall a b. (a -> b) -> a -> b
$ String -> Id
forall a. String -> a
panic String
"Bignum literals are not supported in ghc-bignum"
         | Bool
otherwise = IO Id
act

      lookupBignumId :: Name -> IO Id
lookupBignumId Name
n      = IO Id -> IO Id
guardBignum (HasDebugCallStack => TyThing -> Id
TyThing -> Id
tyThingId (TyThing -> Id) -> IO TyThing -> IO Id
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> HscEnv -> Name -> IO TyThing
lookupGlobal HscEnv
hsc_env Name
n)

   -- The lookup is done here but the failure (panic) is reported lazily when we
   -- try to access the `bigNatFromWordList` function.
   --
   -- If we ever get built-in ByteArray# literals, we could avoid the lookup by
   -- directly using the Integer/Natural wired-in constructors for big numbers.

   Id
bignatFromWordListId <- Name -> IO Id
lookupBignumId Name
bignatFromWordListName

   let
      convertNumLit :: LitNumType -> Integer -> Maybe CpeBody
convertNumLit LitNumType
nt Integer
i = case LitNumType
nt of
         LitNumType
LitNumInteger -> CpeBody -> Maybe CpeBody
forall a. a -> Maybe a
Just (Integer -> CpeBody
convertInteger Integer
i)
         LitNumType
LitNumNatural -> CpeBody -> Maybe CpeBody
forall a. a -> Maybe a
Just (Integer -> CpeBody
convertNatural Integer
i)
         LitNumType
_             -> Maybe CpeBody
forall a. Maybe a
Nothing

      convertInteger :: Integer -> CpeBody
convertInteger Integer
i
         | Platform -> Integer -> Bool
platformInIntRange Platform
platform Integer
i -- fit in a Int#
         = DataCon -> [CpeBody] -> CpeBody
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
integerISDataCon [Literal -> CpeBody
forall b. Literal -> Expr b
Lit (Platform -> Integer -> Literal
mkLitInt Platform
platform Integer
i)]

         | Bool
otherwise -- build a BigNat and embed into IN or IP
         = let con :: DataCon
con = if Integer
i Integer -> Integer -> Bool
forall a. Ord a => a -> a -> Bool
> Integer
0 then DataCon
integerIPDataCon else DataCon
integerINDataCon
           in DataCon -> CpeBody -> CpeBody
mkBigNum DataCon
con (Integer -> CpeBody
convertBignatPrim (Integer -> Integer
forall a. Num a => a -> a
abs Integer
i))

      convertNatural :: Integer -> CpeBody
convertNatural Integer
i
         | Platform -> Integer -> Bool
platformInWordRange Platform
platform Integer
i -- fit in a Word#
         = DataCon -> [CpeBody] -> CpeBody
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
naturalNSDataCon [Literal -> CpeBody
forall b. Literal -> Expr b
Lit (Platform -> Integer -> Literal
mkLitWord Platform
platform Integer
i)]

         | Bool
otherwise --build a BigNat and embed into NB
         = DataCon -> CpeBody -> CpeBody
mkBigNum DataCon
naturalNBDataCon (Integer -> CpeBody
convertBignatPrim Integer
i)

      -- we can't simply generate:
      --
      --    NB (bigNatFromWordList# [W# 10, W# 20])
      --
      -- using `mkConApp` because it isn't in ANF form. Instead we generate:
      --
      --    case bigNatFromWordList# [W# 10, W# 20] of ba { DEFAULT -> NB ba }
      --
      -- via `mkCoreApps`

      mkBigNum :: DataCon -> CpeBody -> CpeBody
mkBigNum DataCon
con CpeBody
ba = CpeBody -> [CpeBody] -> CpeBody
mkCoreApps (Id -> CpeBody
forall b. Id -> Expr b
Var (DataCon -> Id
dataConWorkId DataCon
con)) [CpeBody
ba]

      convertBignatPrim :: Integer -> CpeBody
convertBignatPrim Integer
i =
         let
            target :: Platform
target    = DynFlags -> Platform
targetPlatform DynFlags
dflags

            -- ByteArray# literals aren't supported (yet). Were they supported,
            -- we would use them directly. We would need to handle
            -- wordSize/endianness conversion between host and target
            -- wordSize  = platformWordSize platform
            -- byteOrder = platformByteOrder platform

            -- For now we build a list of Words and we produce
            -- `bigNatFromWordList# list_of_words`

            words :: CpeBody
words = Type -> [CpeBody] -> CpeBody
mkListExpr Type
wordTy ([CpeBody] -> [CpeBody]
forall a. [a] -> [a]
reverse ((Integer -> Maybe (CpeBody, Integer)) -> Integer -> [CpeBody]
forall b a. (b -> Maybe (a, b)) -> b -> [a]
unfoldr Integer -> Maybe (CpeBody, Integer)
f Integer
i))
               where
                  f :: Integer -> Maybe (CpeBody, Integer)
f Integer
0 = Maybe (CpeBody, Integer)
forall a. Maybe a
Nothing
                  f Integer
x = let low :: Integer
low  = Integer
x Integer -> Integer -> Integer
forall a. Bits a => a -> a -> a
.&. Integer
mask
                            high :: Integer
high = Integer
x Integer -> Int -> Integer
forall a. Bits a => a -> Int -> a
`shiftR` Int
bits
                        in (CpeBody, Integer) -> Maybe (CpeBody, Integer)
forall a. a -> Maybe a
Just (DataCon -> [CpeBody] -> CpeBody
forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
wordDataCon [Literal -> CpeBody
forall b. Literal -> Expr b
Lit (Platform -> Integer -> Literal
mkLitWord Platform
platform Integer
low)], Integer
high)
                  bits :: Int
bits = Platform -> Int
platformWordSizeInBits Platform
target
                  mask :: Integer
mask = Integer
2 Integer -> Int -> Integer
forall a b. (Num a, Integral b) => a -> b -> a
^ Int
bits Integer -> Integer -> Integer
forall a. Num a => a -> a -> a
- Integer
1

         in CpeBody -> [CpeBody] -> CpeBody
forall b. Expr b -> [Expr b] -> Expr b
mkApps (Id -> CpeBody
forall b. Id -> Expr b
Var Id
bignatFromWordListId) [CpeBody
words]


   (LitNumType -> Integer -> Maybe CpeBody)
-> IO (LitNumType -> Integer -> Maybe CpeBody)
forall (m :: * -> *) a. Monad m => a -> m a
return LitNumType -> Integer -> Maybe CpeBody
convertNumLit