-----------------------------------------------------------------------------
--
-- Code generation for foreign calls.
--
-- (c) The University of Glasgow 2004-2006
--
-----------------------------------------------------------------------------

module GHC.StgToCmm.Foreign (
  cgForeignCall,
  emitPrimCall, emitCCall,
  emitForeignCall,
  emitSaveThreadState,
  saveThreadState,
  emitLoadThreadState,
  emitSaveRegs,
  emitRestoreRegs,
  loadThreadState,
  emitOpenNursery,
  emitCloseNursery,
 ) where

import GHC.Prelude hiding( succ, (<*>) )

import GHC.Stg.Syntax
import GHC.StgToCmm.Prof (storeCurCCS, ccsType)
import GHC.StgToCmm.Env
import GHC.StgToCmm.Monad
import GHC.StgToCmm.Utils
import GHC.StgToCmm.Closure
import GHC.StgToCmm.Layout

import GHC.Cmm.BlockId (newBlockId)
import GHC.Cmm
import GHC.Cmm.Utils
import GHC.Cmm.Graph
import GHC.Cmm.CallConv
import GHC.Core.Type
import GHC.Types.RepType
import GHC.Cmm.CLabel
import GHC.Runtime.Heap.Layout
import GHC.Types.ForeignCall
import GHC.Driver.Session
import GHC.Platform
import GHC.Data.Maybe
import GHC.Utils.Outputable
import GHC.Types.Unique.Supply
import GHC.Types.Basic

import GHC.Core.TyCo.Rep
import GHC.Builtin.Types.Prim
import GHC.Utils.Misc (zipEqual)

import Control.Monad

-----------------------------------------------------------------------------
-- Code generation for Foreign Calls
-----------------------------------------------------------------------------

-- | Emit code for a foreign call, and return the results to the sequel.
-- Precondition: the length of the arguments list is the same as the
-- arity of the foreign function.
cgForeignCall :: ForeignCall            -- the op
              -> Type                   -- type of foreign function
              -> [StgArg]               -- x,y    arguments
              -> Type                   -- result type
              -> FCode ReturnKind

cgForeignCall :: ForeignCall -> Type -> [StgArg] -> Type -> FCode ReturnKind
cgForeignCall (CCall (CCallSpec CCallTarget
target CCallConv
cconv Safety
safety)) Type
typ [StgArg]
stg_args Type
res_ty
  = do  { Platform
platform <- FCode Platform
getPlatform
        ; let -- in the stdcall calling convention, the symbol needs @size appended
              -- to it, where size is the total number of bytes of arguments.  We
              -- attach this info to the CLabel here, and the CLabel pretty printer
              -- will generate the suffix when the label is printed.
            call_size :: [(CmmExpr, b)] -> Maybe ByteOff
call_size [(CmmExpr, b)]
args
              | CCallConv
StdCallConv <- CCallConv
cconv = ByteOff -> Maybe ByteOff
forall a. a -> Maybe a
Just ([ByteOff] -> ByteOff
forall (t :: * -> *) a. (Foldable t, Num a) => t a -> a
sum (((CmmExpr, b) -> ByteOff) -> [(CmmExpr, b)] -> [ByteOff]
forall a b. (a -> b) -> [a] -> [b]
map (CmmExpr, b) -> ByteOff
forall {b}. (CmmExpr, b) -> ByteOff
arg_size [(CmmExpr, b)]
args))
              | Bool
otherwise            = Maybe ByteOff
forall a. Maybe a
Nothing

              -- ToDo: this might not be correct for 64-bit API
              -- This is correct for the PowerPC ELF ABI version 1 and 2.
            arg_size :: (CmmExpr, b) -> ByteOff
arg_size (CmmExpr
arg, b
_) = ByteOff -> ByteOff -> ByteOff
forall a. Ord a => a -> a -> a
max (Width -> ByteOff
widthInBytes (Width -> ByteOff) -> Width -> ByteOff
forall a b. (a -> b) -> a -> b
$ CmmType -> Width
typeWidth (CmmType -> Width) -> CmmType -> Width
forall a b. (a -> b) -> a -> b
$ Platform -> CmmExpr -> CmmType
cmmExprType Platform
platform CmmExpr
arg)
                                     (Platform -> ByteOff
platformWordSizeInBytes Platform
platform)
        ; [(CmmExpr, ForeignHint)]
cmm_args <- [StgArg] -> Type -> FCode [(CmmExpr, ForeignHint)]
getFCallArgs [StgArg]
stg_args Type
typ
        ; ([LocalReg]
res_regs, [ForeignHint]
res_hints) <- Type -> FCode ([LocalReg], [ForeignHint])
newUnboxedTupleRegs Type
res_ty
        ; let (([CmmExpr]
call_args, [ForeignHint]
arg_hints), CmmExpr
cmm_target)
                = case CCallTarget
target of
                   StaticTarget SourceText
_ CLabelString
_   Maybe Unit
_      Bool
False ->
                       String -> (([CmmExpr], [ForeignHint]), CmmExpr)
forall a. String -> a
panic String
"cgForeignCall: unexpected FFI value import"
                   StaticTarget SourceText
_ CLabelString
lbl Maybe Unit
mPkgId Bool
True
                     -> let labelSource :: ForeignLabelSource
labelSource
                                = case Maybe Unit
mPkgId of
                                        Maybe Unit
Nothing         -> ForeignLabelSource
ForeignLabelInThisPackage
                                        Just Unit
pkgId      -> Unit -> ForeignLabelSource
ForeignLabelInPackage Unit
pkgId
                            size :: Maybe ByteOff
size = [(CmmExpr, ForeignHint)] -> Maybe ByteOff
forall {b}. [(CmmExpr, b)] -> Maybe ByteOff
call_size [(CmmExpr, ForeignHint)]
cmm_args
                        in  ( [(CmmExpr, ForeignHint)] -> ([CmmExpr], [ForeignHint])
forall a b. [(a, b)] -> ([a], [b])
unzip [(CmmExpr, ForeignHint)]
cmm_args
                            , CmmLit -> CmmExpr
CmmLit (CLabel -> CmmLit
CmmLabel
                                        (CLabelString
-> Maybe ByteOff -> ForeignLabelSource -> FunctionOrData -> CLabel
mkForeignLabel CLabelString
lbl Maybe ByteOff
size ForeignLabelSource
labelSource FunctionOrData
IsFunction)))

                   CCallTarget
DynamicTarget    ->  case [(CmmExpr, ForeignHint)]
cmm_args of
                                           (CmmExpr
fn,ForeignHint
_):[(CmmExpr, ForeignHint)]
rest -> ([(CmmExpr, ForeignHint)] -> ([CmmExpr], [ForeignHint])
forall a b. [(a, b)] -> ([a], [b])
unzip [(CmmExpr, ForeignHint)]
rest, CmmExpr
fn)
                                           [] -> String -> (([CmmExpr], [ForeignHint]), CmmExpr)
forall a. String -> a
panic String
"cgForeignCall []"
              fc :: ForeignConvention
fc = CCallConv
-> [ForeignHint]
-> [ForeignHint]
-> CmmReturnInfo
-> ForeignConvention
ForeignConvention CCallConv
cconv [ForeignHint]
arg_hints [ForeignHint]
res_hints CmmReturnInfo
CmmMayReturn
              call_target :: ForeignTarget
call_target = CmmExpr -> ForeignConvention -> ForeignTarget
ForeignTarget CmmExpr
cmm_target ForeignConvention
fc

        -- we want to emit code for the call, and then emitReturn.
        -- However, if the sequel is AssignTo, we shortcut a little
        -- and generate a foreign call that assigns the results
        -- directly.  Otherwise we end up generating a bunch of
        -- useless "r = r" assignments, which are not merely annoying:
        -- they prevent the common block elimination from working correctly
        -- in the case of a safe foreign call.
        -- See Note [safe foreign call convention]
        --
        ; Sequel
sequel <- FCode Sequel
getSequel
        ; case Sequel
sequel of
            AssignTo [LocalReg]
assign_to_these Bool
_ ->
                Safety
-> [LocalReg] -> ForeignTarget -> [CmmExpr] -> FCode ReturnKind
emitForeignCall Safety
safety [LocalReg]
assign_to_these ForeignTarget
call_target [CmmExpr]
call_args

            Sequel
_something_else ->
                do { ReturnKind
_ <- Safety
-> [LocalReg] -> ForeignTarget -> [CmmExpr] -> FCode ReturnKind
emitForeignCall Safety
safety [LocalReg]
res_regs ForeignTarget
call_target [CmmExpr]
call_args
                   ; [CmmExpr] -> FCode ReturnKind
emitReturn ((LocalReg -> CmmExpr) -> [LocalReg] -> [CmmExpr]
forall a b. (a -> b) -> [a] -> [b]
map (CmmReg -> CmmExpr
CmmReg (CmmReg -> CmmExpr) -> (LocalReg -> CmmReg) -> LocalReg -> CmmExpr
forall b c a. (b -> c) -> (a -> b) -> a -> c
. LocalReg -> CmmReg
CmmLocal) [LocalReg]
res_regs)
                   }
         }

{- Note [safe foreign call convention]

The simple thing to do for a safe foreign call would be the same as an
unsafe one: just

    emitForeignCall ...
    emitReturn ...

but consider what happens in this case

   case foo x y z of
     (# s, r #) -> ...

The sequel is AssignTo [r].  The call to newUnboxedTupleRegs picks [r]
as the result reg, and we generate

  r = foo(x,y,z) returns to L1  -- emitForeignCall
 L1:
  r = r  -- emitReturn
  goto L2
L2:
  ...

Now L1 is a proc point (by definition, it is the continuation of the
safe foreign call).  If L2 does a heap check, then L2 will also be a
proc point.

Furthermore, the stack layout algorithm has to arrange to save r
somewhere between the call and the jump to L1, which is annoying: we
would have to treat r differently from the other live variables, which
have to be saved *before* the call.

So we adopt a special convention for safe foreign calls: the results
are copied out according to the NativeReturn convention by the call,
and the continuation of the call should copyIn the results.  (The
copyOut code is actually inserted when the safe foreign call is
lowered later).  The result regs attached to the safe foreign call are
only used temporarily to hold the results before they are copied out.

We will now generate this:

  r = foo(x,y,z) returns to L1
 L1:
  r = R1  -- copyIn, inserted by mkSafeCall
  goto L2
 L2:
  ... r ...

And when the safe foreign call is lowered later (see Note [lower safe
foreign calls]) we get this:

  suspendThread()
  r = foo(x,y,z)
  resumeThread()
  R1 = r  -- copyOut, inserted by lowerSafeForeignCall
  jump L1
 L1:
  r = R1  -- copyIn, inserted by mkSafeCall
  goto L2
 L2:
  ... r ...

Now consider what happens if L2 does a heap check: the Adams
optimisation kicks in and commons up L1 with the heap-check
continuation, resulting in just one proc point instead of two. Yay!
-}


emitCCall :: [(CmmFormal,ForeignHint)]
          -> CmmExpr
          -> [(CmmActual,ForeignHint)]
          -> FCode ()
emitCCall :: [(LocalReg, ForeignHint)]
-> CmmExpr -> [(CmmExpr, ForeignHint)] -> FCode ()
emitCCall [(LocalReg, ForeignHint)]
hinted_results CmmExpr
fn [(CmmExpr, ForeignHint)]
hinted_args
  = FCode ReturnKind -> FCode ()
forall (f :: * -> *) a. Functor f => f a -> f ()
void (FCode ReturnKind -> FCode ()) -> FCode ReturnKind -> FCode ()
forall a b. (a -> b) -> a -> b
$ Safety
-> [LocalReg] -> ForeignTarget -> [CmmExpr] -> FCode ReturnKind
emitForeignCall Safety
PlayRisky [LocalReg]
results ForeignTarget
target [CmmExpr]
args
  where
    ([CmmExpr]
args, [ForeignHint]
arg_hints) = [(CmmExpr, ForeignHint)] -> ([CmmExpr], [ForeignHint])
forall a b. [(a, b)] -> ([a], [b])
unzip [(CmmExpr, ForeignHint)]
hinted_args
    ([LocalReg]
results, [ForeignHint]
result_hints) = [(LocalReg, ForeignHint)] -> ([LocalReg], [ForeignHint])
forall a b. [(a, b)] -> ([a], [b])
unzip [(LocalReg, ForeignHint)]
hinted_results
    target :: ForeignTarget
target = CmmExpr -> ForeignConvention -> ForeignTarget
ForeignTarget CmmExpr
fn ForeignConvention
fc
    fc :: ForeignConvention
fc = CCallConv
-> [ForeignHint]
-> [ForeignHint]
-> CmmReturnInfo
-> ForeignConvention
ForeignConvention CCallConv
CCallConv [ForeignHint]
arg_hints [ForeignHint]
result_hints CmmReturnInfo
CmmMayReturn


emitPrimCall :: [CmmFormal] -> CallishMachOp -> [CmmActual] -> FCode ()
emitPrimCall :: [LocalReg] -> CallishMachOp -> [CmmExpr] -> FCode ()
emitPrimCall [LocalReg]
res CallishMachOp
op [CmmExpr]
args
  = FCode ReturnKind -> FCode ()
forall (f :: * -> *) a. Functor f => f a -> f ()
void (FCode ReturnKind -> FCode ()) -> FCode ReturnKind -> FCode ()
forall a b. (a -> b) -> a -> b
$ Safety
-> [LocalReg] -> ForeignTarget -> [CmmExpr] -> FCode ReturnKind
emitForeignCall Safety
PlayRisky [LocalReg]
res (CallishMachOp -> ForeignTarget
PrimTarget CallishMachOp
op) [CmmExpr]
args

-- alternative entry point, used by GHC.Cmm.Parser
emitForeignCall
        :: Safety
        -> [CmmFormal]          -- where to put the results
        -> ForeignTarget        -- the op
        -> [CmmActual]          -- arguments
        -> FCode ReturnKind
emitForeignCall :: Safety
-> [LocalReg] -> ForeignTarget -> [CmmExpr] -> FCode ReturnKind
emitForeignCall Safety
safety [LocalReg]
results ForeignTarget
target [CmmExpr]
args
  | Bool -> Bool
not (Safety -> Bool
playSafe Safety
safety) = do
    DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
    let (CmmAGraph
caller_save, CmmAGraph
caller_load) = DynFlags -> (CmmAGraph, CmmAGraph)
callerSaveVolatileRegs DynFlags
dflags
    CmmAGraph -> FCode ()
emit CmmAGraph
caller_save
    ForeignTarget
target' <- ForeignTarget -> FCode ForeignTarget
load_target_into_temp ForeignTarget
target
    [CmmExpr]
args' <- (CmmExpr -> FCode CmmExpr) -> [CmmExpr] -> FCode [CmmExpr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM CmmExpr -> FCode CmmExpr
maybe_assign_temp [CmmExpr]
args
    CmmAGraph -> FCode ()
emit (CmmAGraph -> FCode ()) -> CmmAGraph -> FCode ()
forall a b. (a -> b) -> a -> b
$ ForeignTarget -> [LocalReg] -> [CmmExpr] -> CmmAGraph
mkUnsafeCall ForeignTarget
target' [LocalReg]
results [CmmExpr]
args'
    CmmAGraph -> FCode ()
emit CmmAGraph
caller_load
    ReturnKind -> FCode ReturnKind
forall (m :: * -> *) a. Monad m => a -> m a
return ReturnKind
AssignedDirectly

  | Bool
otherwise = do
    DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
    Platform
platform <- FCode Platform
getPlatform
    ByteOff
updfr_off <- FCode ByteOff
getUpdFrameOff
    ForeignTarget
target' <- ForeignTarget -> FCode ForeignTarget
load_target_into_temp ForeignTarget
target
    [CmmExpr]
args' <- (CmmExpr -> FCode CmmExpr) -> [CmmExpr] -> FCode [CmmExpr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM CmmExpr -> FCode CmmExpr
maybe_assign_temp [CmmExpr]
args
    BlockId
k <- FCode BlockId
forall (m :: * -> *). MonadUnique m => m BlockId
newBlockId
    let (ByteOff
off, [GlobalReg]
_, CmmAGraph
copyout) = DynFlags
-> Convention
-> Area
-> [LocalReg]
-> [LocalReg]
-> (ByteOff, [GlobalReg], CmmAGraph)
copyInOflow DynFlags
dflags Convention
NativeReturn (BlockId -> Area
Young BlockId
k) [LocalReg]
results []
       -- see Note [safe foreign call convention]
    CmmTickScope
tscope <- FCode CmmTickScope
getTickScope
    CmmAGraph -> FCode ()
emit (CmmAGraph -> FCode ()) -> CmmAGraph -> FCode ()
forall a b. (a -> b) -> a -> b
$
           (    CmmExpr -> CmmExpr -> CmmAGraph
mkStore (Area -> ByteOff -> CmmExpr
CmmStackSlot (BlockId -> Area
Young BlockId
k) (Width -> ByteOff
widthInBytes (Platform -> Width
wordWidth Platform
platform)))
                        (CmmLit -> CmmExpr
CmmLit (BlockId -> CmmLit
CmmBlock BlockId
k))
            CmmAGraph -> CmmAGraph -> CmmAGraph
<*> CmmNode O C -> CmmAGraph
mkLast (CmmForeignCall :: ForeignTarget
-> [LocalReg]
-> [CmmExpr]
-> BlockId
-> ByteOff
-> ByteOff
-> Bool
-> CmmNode O C
CmmForeignCall { tgt :: ForeignTarget
tgt  = ForeignTarget
target'
                                       , res :: [LocalReg]
res  = [LocalReg]
results
                                       , args :: [CmmExpr]
args = [CmmExpr]
args'
                                       , succ :: BlockId
succ = BlockId
k
                                       , ret_args :: ByteOff
ret_args = ByteOff
off
                                       , ret_off :: ByteOff
ret_off = ByteOff
updfr_off
                                       , intrbl :: Bool
intrbl = Safety -> Bool
playInterruptible Safety
safety })
            CmmAGraph -> CmmAGraph -> CmmAGraph
<*> BlockId -> CmmTickScope -> CmmAGraph
mkLabel BlockId
k CmmTickScope
tscope
            CmmAGraph -> CmmAGraph -> CmmAGraph
<*> CmmAGraph
copyout
           )
    ReturnKind -> FCode ReturnKind
forall (m :: * -> *) a. Monad m => a -> m a
return (BlockId -> ByteOff -> ReturnKind
ReturnedTo BlockId
k ByteOff
off)

load_target_into_temp :: ForeignTarget -> FCode ForeignTarget
load_target_into_temp :: ForeignTarget -> FCode ForeignTarget
load_target_into_temp (ForeignTarget CmmExpr
expr ForeignConvention
conv) = do
  CmmExpr
tmp <- CmmExpr -> FCode CmmExpr
maybe_assign_temp CmmExpr
expr
  ForeignTarget -> FCode ForeignTarget
forall (m :: * -> *) a. Monad m => a -> m a
return (CmmExpr -> ForeignConvention -> ForeignTarget
ForeignTarget CmmExpr
tmp ForeignConvention
conv)
load_target_into_temp other_target :: ForeignTarget
other_target@(PrimTarget CallishMachOp
_) =
  ForeignTarget -> FCode ForeignTarget
forall (m :: * -> *) a. Monad m => a -> m a
return ForeignTarget
other_target

-- What we want to do here is create a new temporary for the foreign
-- call argument if it is not safe to use the expression directly,
-- because the expression mentions caller-saves GlobalRegs (see
-- Note [Register parameter passing]).
--
-- However, we can't pattern-match on the expression here, because
-- this is used in a loop by GHC.Cmm.Parser, and testing the expression
-- results in a black hole.  So we always create a temporary, and rely
-- on GHC.Cmm.Sink to clean it up later.  (Yuck, ToDo).  The generated code
-- ends up being the same, at least for the RTS .cmm code.
--
maybe_assign_temp :: CmmExpr -> FCode CmmExpr
maybe_assign_temp :: CmmExpr -> FCode CmmExpr
maybe_assign_temp CmmExpr
e = do
  Platform
platform <- FCode Platform
getPlatform
  LocalReg
reg <- CmmType -> FCode LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmExpr -> CmmType
cmmExprType Platform
platform CmmExpr
e)
  CmmReg -> CmmExpr -> FCode ()
emitAssign (LocalReg -> CmmReg
CmmLocal LocalReg
reg) CmmExpr
e
  CmmExpr -> FCode CmmExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
reg))

-- -----------------------------------------------------------------------------
-- Save/restore the thread state in the TSO

-- This stuff can't be done in suspendThread/resumeThread, because it
-- refers to global registers which aren't available in the C world.

emitSaveThreadState :: FCode ()
emitSaveThreadState :: FCode ()
emitSaveThreadState = do
  DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
  CmmAGraph
code <- DynFlags -> FCode CmmAGraph
forall (m :: * -> *). MonadUnique m => DynFlags -> m CmmAGraph
saveThreadState DynFlags
dflags
  CmmAGraph -> FCode ()
emit CmmAGraph
code

-- | Produce code to save the current thread state to @CurrentTSO@
saveThreadState :: MonadUnique m => DynFlags -> m CmmAGraph
saveThreadState :: forall (m :: * -> *). MonadUnique m => DynFlags -> m CmmAGraph
saveThreadState DynFlags
dflags = do
  let platform :: Platform
platform = DynFlags -> Platform
targetPlatform DynFlags
dflags
  LocalReg
tso <- CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
gcWord Platform
platform)
  CmmAGraph
close_nursery <- DynFlags -> LocalReg -> m CmmAGraph
forall (m :: * -> *).
MonadUnique m =>
DynFlags -> LocalReg -> m CmmAGraph
closeNursery DynFlags
dflags LocalReg
tso
  CmmAGraph -> m CmmAGraph
forall (f :: * -> *) a. Applicative f => a -> f a
pure (CmmAGraph -> m CmmAGraph) -> CmmAGraph -> m CmmAGraph
forall a b. (a -> b) -> a -> b
$ [CmmAGraph] -> CmmAGraph
catAGraphs [
    -- tso = CurrentTSO;
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign (LocalReg -> CmmReg
CmmLocal LocalReg
tso) CmmExpr
currentTSOExpr,
    -- tso->stackobj->sp = Sp;
    CmmExpr -> CmmExpr -> CmmAGraph
mkStore (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform
                       (CmmExpr -> CmmType -> CmmExpr
CmmLoad (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform
                                           (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
tso))
                                           (DynFlags -> ByteOff
tso_stackobj DynFlags
dflags))
                                (Platform -> CmmType
bWord Platform
platform))
                       (DynFlags -> ByteOff
stack_SP DynFlags
dflags))
            CmmExpr
spExpr,
    CmmAGraph
close_nursery,
    -- and save the current cost centre stack in the TSO when profiling:
    if DynFlags -> Bool
sccProfilingEnabled DynFlags
dflags then
        CmmExpr -> CmmExpr -> CmmAGraph
mkStore (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
tso)) (DynFlags -> ByteOff
tso_CCCS DynFlags
dflags)) CmmExpr
cccsExpr
      else CmmAGraph
mkNop
    ]



-- | Save STG registers
--
-- STG registers must be saved around a C call, just in case the STG
-- register is mapped to a caller-saves machine register.  Normally we
-- don't need to worry about this the code generator has already
-- loaded any live STG registers into variables for us, but in
-- hand-written low-level Cmm code where we don't know which registers
-- are live, we might have to save them all.
emitSaveRegs :: FCode ()
emitSaveRegs :: FCode ()
emitSaveRegs = do
   DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
   let regs :: [GlobalReg]
regs = DynFlags -> [GlobalReg]
realArgRegsCover DynFlags
dflags
       save :: CmmAGraph
save = [CmmAGraph] -> CmmAGraph
catAGraphs ((GlobalReg -> CmmAGraph) -> [GlobalReg] -> [CmmAGraph]
forall a b. (a -> b) -> [a] -> [b]
map (DynFlags -> GlobalReg -> CmmAGraph
callerSaveGlobalReg DynFlags
dflags) [GlobalReg]
regs)
   CmmAGraph -> FCode ()
emit CmmAGraph
save

-- | Restore STG registers (see 'emitSaveRegs')
emitRestoreRegs :: FCode ()
emitRestoreRegs :: FCode ()
emitRestoreRegs = do
   DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
   let regs :: [GlobalReg]
regs = DynFlags -> [GlobalReg]
realArgRegsCover DynFlags
dflags
       save :: CmmAGraph
save = [CmmAGraph] -> CmmAGraph
catAGraphs ((GlobalReg -> CmmAGraph) -> [GlobalReg] -> [CmmAGraph]
forall a b. (a -> b) -> [a] -> [b]
map (DynFlags -> GlobalReg -> CmmAGraph
callerRestoreGlobalReg DynFlags
dflags) [GlobalReg]
regs)
   CmmAGraph -> FCode ()
emit CmmAGraph
save


emitCloseNursery :: FCode ()
emitCloseNursery :: FCode ()
emitCloseNursery = do
  DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
  Platform
platform <- FCode Platform
getPlatform
  LocalReg
tso <- CmmType -> FCode LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
bWord Platform
platform)
  CmmAGraph
code <- DynFlags -> LocalReg -> FCode CmmAGraph
forall (m :: * -> *).
MonadUnique m =>
DynFlags -> LocalReg -> m CmmAGraph
closeNursery DynFlags
dflags LocalReg
tso
  CmmAGraph -> FCode ()
emit (CmmAGraph -> FCode ()) -> CmmAGraph -> FCode ()
forall a b. (a -> b) -> a -> b
$ CmmReg -> CmmExpr -> CmmAGraph
mkAssign (LocalReg -> CmmReg
CmmLocal LocalReg
tso) CmmExpr
currentTSOExpr CmmAGraph -> CmmAGraph -> CmmAGraph
<*> CmmAGraph
code

{- |
@closeNursery dflags tso@ produces code to close the nursery.
A local register holding the value of @CurrentTSO@ is expected for
efficiency.

Closing the nursery corresponds to the following code:

@
  tso = CurrentTSO;
  cn = CurrentNuresry;

  // Update the allocation limit for the current thread.  We don't
  // check to see whether it has overflowed at this point, that check is
  // made when we run out of space in the current heap block (stg_gc_noregs)
  // and in the scheduler when context switching (schedulePostRunThread).
  tso->alloc_limit -= Hp + WDS(1) - cn->start;

  // Set cn->free to the next unoccupied word in the block
  cn->free = Hp + WDS(1);
@
-}
closeNursery :: MonadUnique m => DynFlags -> LocalReg -> m CmmAGraph
closeNursery :: forall (m :: * -> *).
MonadUnique m =>
DynFlags -> LocalReg -> m CmmAGraph
closeNursery DynFlags
df LocalReg
tso = do
  let tsoreg :: CmmReg
tsoreg  = LocalReg -> CmmReg
CmmLocal LocalReg
tso
      platform :: Platform
platform = DynFlags -> Platform
targetPlatform DynFlags
df
  CmmReg
cnreg      <- LocalReg -> CmmReg
CmmLocal (LocalReg -> CmmReg) -> m LocalReg -> m CmmReg
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
bWord Platform
platform)
  CmmAGraph -> m CmmAGraph
forall (f :: * -> *) a. Applicative f => a -> f a
pure (CmmAGraph -> m CmmAGraph) -> CmmAGraph -> m CmmAGraph
forall a b. (a -> b) -> a -> b
$ [CmmAGraph] -> CmmAGraph
catAGraphs [
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
cnreg CmmExpr
currentNurseryExpr,

    -- CurrentNursery->free = Hp+1;
    CmmExpr -> CmmExpr -> CmmAGraph
mkStore (DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_free DynFlags
df CmmReg
cnreg) (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetW Platform
platform CmmExpr
hpExpr ByteOff
1),

    let alloc :: CmmExpr
alloc =
           MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Platform -> MachOp
mo_wordSub Platform
platform)
              [ Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetW Platform
platform CmmExpr
hpExpr ByteOff
1
              , CmmExpr -> CmmType -> CmmExpr
CmmLoad (DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_start DynFlags
df CmmReg
cnreg) (Platform -> CmmType
bWord Platform
platform)
              ]

        alloc_limit :: CmmExpr
alloc_limit = Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg CmmReg
tsoreg) (DynFlags -> ByteOff
tso_alloc_limit DynFlags
df)
    in

    -- tso->alloc_limit += alloc
    CmmExpr -> CmmExpr -> CmmAGraph
mkStore CmmExpr
alloc_limit (MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Width -> MachOp
MO_Sub Width
W64)
                               [ CmmExpr -> CmmType -> CmmExpr
CmmLoad CmmExpr
alloc_limit CmmType
b64
                               , MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Platform -> MachOp
mo_WordTo64 Platform
platform) [CmmExpr
alloc] ])
   ]

emitLoadThreadState :: FCode ()
emitLoadThreadState :: FCode ()
emitLoadThreadState = do
  DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
  CmmAGraph
code <- DynFlags -> FCode CmmAGraph
forall (m :: * -> *). MonadUnique m => DynFlags -> m CmmAGraph
loadThreadState DynFlags
dflags
  CmmAGraph -> FCode ()
emit CmmAGraph
code

-- | Produce code to load the current thread state from @CurrentTSO@
loadThreadState :: MonadUnique m => DynFlags -> m CmmAGraph
loadThreadState :: forall (m :: * -> *). MonadUnique m => DynFlags -> m CmmAGraph
loadThreadState DynFlags
dflags = do
  let platform :: Platform
platform = DynFlags -> Platform
targetPlatform DynFlags
dflags
  LocalReg
tso <- CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
gcWord Platform
platform)
  LocalReg
stack <- CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
gcWord Platform
platform)
  CmmAGraph
open_nursery <- DynFlags -> LocalReg -> m CmmAGraph
forall (m :: * -> *).
MonadUnique m =>
DynFlags -> LocalReg -> m CmmAGraph
openNursery DynFlags
dflags LocalReg
tso
  CmmAGraph -> m CmmAGraph
forall (f :: * -> *) a. Applicative f => a -> f a
pure (CmmAGraph -> m CmmAGraph) -> CmmAGraph -> m CmmAGraph
forall a b. (a -> b) -> a -> b
$ [CmmAGraph] -> CmmAGraph
catAGraphs [
    -- tso = CurrentTSO;
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign (LocalReg -> CmmReg
CmmLocal LocalReg
tso) CmmExpr
currentTSOExpr,
    -- stack = tso->stackobj;
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign (LocalReg -> CmmReg
CmmLocal LocalReg
stack) (CmmExpr -> CmmType -> CmmExpr
CmmLoad (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
tso)) (DynFlags -> ByteOff
tso_stackobj DynFlags
dflags)) (Platform -> CmmType
bWord Platform
platform)),
    -- Sp = stack->sp;
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
spReg (CmmExpr -> CmmType -> CmmExpr
CmmLoad (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
stack)) (DynFlags -> ByteOff
stack_SP DynFlags
dflags)) (Platform -> CmmType
bWord Platform
platform)),
    -- SpLim = stack->stack + RESERVED_STACK_WORDS;
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
spLimReg (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetW Platform
platform (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
stack)) (DynFlags -> ByteOff
stack_STACK DynFlags
dflags))
                                (DynFlags -> ByteOff
rESERVED_STACK_WORDS DynFlags
dflags)),
    -- HpAlloc = 0;
    --   HpAlloc is assumed to be set to non-zero only by a failed
    --   a heap check, see HeapStackCheck.cmm:GC_GENERIC
    CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
hpAllocReg (Platform -> CmmExpr
zeroExpr Platform
platform),
    CmmAGraph
open_nursery,
    -- and load the current cost centre stack from the TSO when profiling:
    if DynFlags -> Bool
sccProfilingEnabled DynFlags
dflags
       then CmmExpr -> CmmAGraph
storeCurCCS
              (CmmExpr -> CmmType -> CmmExpr
CmmLoad (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg (LocalReg -> CmmReg
CmmLocal LocalReg
tso))
                 (DynFlags -> ByteOff
tso_CCCS DynFlags
dflags)) (Platform -> CmmType
ccsType Platform
platform))
       else CmmAGraph
mkNop
   ]


emitOpenNursery :: FCode ()
emitOpenNursery :: FCode ()
emitOpenNursery = do
  DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
  Platform
platform <- FCode Platform
getPlatform
  LocalReg
tso <- CmmType -> FCode LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
bWord Platform
platform)
  CmmAGraph
code <- DynFlags -> LocalReg -> FCode CmmAGraph
forall (m :: * -> *).
MonadUnique m =>
DynFlags -> LocalReg -> m CmmAGraph
openNursery DynFlags
dflags LocalReg
tso
  CmmAGraph -> FCode ()
emit (CmmAGraph -> FCode ()) -> CmmAGraph -> FCode ()
forall a b. (a -> b) -> a -> b
$ CmmReg -> CmmExpr -> CmmAGraph
mkAssign (LocalReg -> CmmReg
CmmLocal LocalReg
tso) CmmExpr
currentTSOExpr CmmAGraph -> CmmAGraph -> CmmAGraph
<*> CmmAGraph
code

{- |
@openNursery dflags tso@ produces code to open the nursery. A local register
holding the value of @CurrentTSO@ is expected for efficiency.

Opening the nursery corresponds to the following code:

@
   tso = CurrentTSO;
   cn = CurrentNursery;
   bdfree = CurrentNursery->free;
   bdstart = CurrentNursery->start;

   // We *add* the currently occupied portion of the nursery block to
   // the allocation limit, because we will subtract it again in
   // closeNursery.
   tso->alloc_limit += bdfree - bdstart;

   // Set Hp to the last occupied word of the heap block.  Why not the
   // next unocupied word?  Doing it this way means that we get to use
   // an offset of zero more often, which might lead to slightly smaller
   // code on some architectures.
   Hp = bdfree - WDS(1);

   // Set HpLim to the end of the current nursery block (note that this block
   // might be a block group, consisting of several adjacent blocks.
   HpLim = bdstart + CurrentNursery->blocks*BLOCK_SIZE_W - 1;
@
-}
openNursery :: MonadUnique m => DynFlags -> LocalReg -> m CmmAGraph
openNursery :: forall (m :: * -> *).
MonadUnique m =>
DynFlags -> LocalReg -> m CmmAGraph
openNursery DynFlags
dflags LocalReg
tso = do
  let tsoreg :: CmmReg
tsoreg =  LocalReg -> CmmReg
CmmLocal LocalReg
tso
      platform :: Platform
platform = DynFlags -> Platform
targetPlatform DynFlags
dflags
  CmmReg
cnreg      <- LocalReg -> CmmReg
CmmLocal (LocalReg -> CmmReg) -> m LocalReg -> m CmmReg
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
bWord Platform
platform)
  CmmReg
bdfreereg  <- LocalReg -> CmmReg
CmmLocal (LocalReg -> CmmReg) -> m LocalReg -> m CmmReg
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
bWord Platform
platform)
  CmmReg
bdstartreg <- LocalReg -> CmmReg
CmmLocal (LocalReg -> CmmReg) -> m LocalReg -> m CmmReg
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CmmType -> m LocalReg
forall (m :: * -> *). MonadUnique m => CmmType -> m LocalReg
newTemp (Platform -> CmmType
bWord Platform
platform)

  -- These assignments are carefully ordered to reduce register
  -- pressure and generate not completely awful code on x86.  To see
  -- what code we generate, look at the assembly for
  -- stg_returnToStackTop in rts/StgStartup.cmm.
  CmmAGraph -> m CmmAGraph
forall (f :: * -> *) a. Applicative f => a -> f a
pure (CmmAGraph -> m CmmAGraph) -> CmmAGraph -> m CmmAGraph
forall a b. (a -> b) -> a -> b
$ [CmmAGraph] -> CmmAGraph
catAGraphs [
     CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
cnreg CmmExpr
currentNurseryExpr,
     CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
bdfreereg  (CmmExpr -> CmmType -> CmmExpr
CmmLoad (DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_free DynFlags
dflags CmmReg
cnreg)  (Platform -> CmmType
bWord Platform
platform)),

     -- Hp = CurrentNursery->free - 1;
     CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
hpReg (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetW Platform
platform (CmmReg -> CmmExpr
CmmReg CmmReg
bdfreereg) (-ByteOff
1)),

     CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
bdstartreg (CmmExpr -> CmmType -> CmmExpr
CmmLoad (DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_start DynFlags
dflags CmmReg
cnreg) (Platform -> CmmType
bWord Platform
platform)),

     -- HpLim = CurrentNursery->start +
     --              CurrentNursery->blocks*BLOCK_SIZE_W - 1;
     CmmReg -> CmmExpr -> CmmAGraph
mkAssign CmmReg
hpLimReg
         (Platform -> CmmExpr -> CmmExpr -> CmmExpr
cmmOffsetExpr Platform
platform
             (CmmReg -> CmmExpr
CmmReg CmmReg
bdstartreg)
             (Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform
               (MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Platform -> MachOp
mo_wordMul Platform
platform) [
                 MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Width -> Width -> MachOp
MO_SS_Conv Width
W32 (Platform -> Width
wordWidth Platform
platform))
                   [CmmExpr -> CmmType -> CmmExpr
CmmLoad (DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_blocks DynFlags
dflags CmmReg
cnreg) CmmType
b32],
                 Platform -> ByteOff -> CmmExpr
mkIntExpr Platform
platform (DynFlags -> ByteOff
bLOCK_SIZE DynFlags
dflags)
                ])
               (-ByteOff
1)
             )
         ),

     -- alloc = bd->free - bd->start
     let alloc :: CmmExpr
alloc =
           MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Platform -> MachOp
mo_wordSub Platform
platform) [CmmReg -> CmmExpr
CmmReg CmmReg
bdfreereg, CmmReg -> CmmExpr
CmmReg CmmReg
bdstartreg]

         alloc_limit :: CmmExpr
alloc_limit = Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset Platform
platform (CmmReg -> CmmExpr
CmmReg CmmReg
tsoreg) (DynFlags -> ByteOff
tso_alloc_limit DynFlags
dflags)
     in

     -- tso->alloc_limit += alloc
     CmmExpr -> CmmExpr -> CmmAGraph
mkStore CmmExpr
alloc_limit (MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Width -> MachOp
MO_Add Width
W64)
                               [ CmmExpr -> CmmType -> CmmExpr
CmmLoad CmmExpr
alloc_limit CmmType
b64
                               , MachOp -> [CmmExpr] -> CmmExpr
CmmMachOp (Platform -> MachOp
mo_WordTo64 Platform
platform) [CmmExpr
alloc] ])

   ]

nursery_bdescr_free, nursery_bdescr_start, nursery_bdescr_blocks
  :: DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_free :: DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_free   DynFlags
dflags CmmReg
cn =
  Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset (DynFlags -> Platform
targetPlatform DynFlags
dflags) (CmmReg -> CmmExpr
CmmReg CmmReg
cn) (DynFlags -> ByteOff
oFFSET_bdescr_free DynFlags
dflags)
nursery_bdescr_start :: DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_start  DynFlags
dflags CmmReg
cn =
  Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset (DynFlags -> Platform
targetPlatform DynFlags
dflags) (CmmReg -> CmmExpr
CmmReg CmmReg
cn) (DynFlags -> ByteOff
oFFSET_bdescr_start DynFlags
dflags)
nursery_bdescr_blocks :: DynFlags -> CmmReg -> CmmExpr
nursery_bdescr_blocks DynFlags
dflags CmmReg
cn =
  Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffset (DynFlags -> Platform
targetPlatform DynFlags
dflags) (CmmReg -> CmmExpr
CmmReg CmmReg
cn) (DynFlags -> ByteOff
oFFSET_bdescr_blocks DynFlags
dflags)

tso_stackobj, tso_CCCS, tso_alloc_limit, stack_STACK, stack_SP :: DynFlags -> ByteOff
tso_stackobj :: DynFlags -> ByteOff
tso_stackobj DynFlags
dflags = DynFlags -> ByteOff -> ByteOff
closureField DynFlags
dflags (DynFlags -> ByteOff
oFFSET_StgTSO_stackobj DynFlags
dflags)
tso_alloc_limit :: DynFlags -> ByteOff
tso_alloc_limit DynFlags
dflags = DynFlags -> ByteOff -> ByteOff
closureField DynFlags
dflags (DynFlags -> ByteOff
oFFSET_StgTSO_alloc_limit DynFlags
dflags)
tso_CCCS :: DynFlags -> ByteOff
tso_CCCS     DynFlags
dflags = DynFlags -> ByteOff -> ByteOff
closureField DynFlags
dflags (DynFlags -> ByteOff
oFFSET_StgTSO_cccs DynFlags
dflags)
stack_STACK :: DynFlags -> ByteOff
stack_STACK  DynFlags
dflags = DynFlags -> ByteOff -> ByteOff
closureField DynFlags
dflags (DynFlags -> ByteOff
oFFSET_StgStack_stack DynFlags
dflags)
stack_SP :: DynFlags -> ByteOff
stack_SP     DynFlags
dflags = DynFlags -> ByteOff -> ByteOff
closureField DynFlags
dflags (DynFlags -> ByteOff
oFFSET_StgStack_sp DynFlags
dflags)


closureField :: DynFlags -> ByteOff -> ByteOff
closureField :: DynFlags -> ByteOff -> ByteOff
closureField DynFlags
dflags ByteOff
off = ByteOff
off ByteOff -> ByteOff -> ByteOff
forall a. Num a => a -> a -> a
+ DynFlags -> ByteOff
fixedHdrSize DynFlags
dflags

-- Note [Unlifted boxed arguments to foreign calls]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
-- For certain types passed to foreign calls, we adjust the actual
-- value passed to the call.  For ByteArray#, Array#, SmallArray#,
-- and ArrayArray#, we pass the address of the array's payload, not
-- the address of the heap object. For example, consider
--   foreign import "c_foo" foo :: ByteArray# -> Int# -> IO ()
-- At a Haskell call like `foo x y`, we'll generate a C call that
-- is more like
--   c_foo( x+8, y )
-- where the "+8" takes the heap pointer (x :: ByteArray#) and moves
-- it past the header words of the ByteArray object to point directly
-- to the data inside the ByteArray#. (The exact offset depends
-- on the target architecture and on profiling) By contrast, (y :: Int#)
-- requires no such adjustment.
--
-- This adjustment is performed by 'add_shim'. The size of the
-- adjustment depends on the type of heap object. But
-- how can we determine that type? There are two available options.
-- We could use the types of the actual values that the foreign call
-- has been applied to, or we could use the types present in the
-- foreign function's type. Prior to GHC 8.10, we used the former
-- strategy since it's a little more simple. However, in issue #16650
-- and more compellingly in the comments of
-- https://gitlab.haskell.org/ghc/ghc/merge_requests/939, it was
-- demonstrated that this leads to bad behavior in the presence
-- of unsafeCoerce#. Returning to the above example, suppose the
-- Haskell call looked like
--   foo (unsafeCoerce# p)
-- where the types of expressions comprising the arguments are
--   p :: (Any :: TYPE 'UnliftedRep)
--   i :: Int#
-- so that the unsafe-coerce is between Any and ByteArray#.
-- These two types have the same kind (they are both represented by
-- a heap pointer) so no GC errors will occur if we do this unsafe coerce.
-- By the time this gets to the code generator the cast has been
-- discarded so we have
--   foo p y
-- But we *must* adjust the pointer to p by a ByteArray# shim,
-- *not* by an Any shim (the Any shim involves no offset at all).
--
-- To avoid this bad behavior, we adopt the second strategy: use
-- the types present in the foreign function's type.
-- In collectStgFArgTypes, we convert the foreign function's
-- type to a list of StgFArgType. Then, in add_shim, we interpret
-- these as numeric offsets.

getFCallArgs ::
     [StgArg]
  -> Type -- the type of the foreign function
  -> FCode [(CmmExpr, ForeignHint)]
-- (a) Drop void args
-- (b) Add foreign-call shim code
-- It's (b) that makes this differ from getNonVoidArgAmodes
-- Precondition: args and typs have the same length
-- See Note [Unlifted boxed arguments to foreign calls]
getFCallArgs :: [StgArg] -> Type -> FCode [(CmmExpr, ForeignHint)]
getFCallArgs [StgArg]
args Type
typ
  = do  { [Maybe (CmmExpr, ForeignHint)]
mb_cmms <- ((StgArg, StgFArgType) -> FCode (Maybe (CmmExpr, ForeignHint)))
-> [(StgArg, StgFArgType)] -> FCode [Maybe (CmmExpr, ForeignHint)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (StgArg, StgFArgType) -> FCode (Maybe (CmmExpr, ForeignHint))
get (String -> [StgArg] -> [StgFArgType] -> [(StgArg, StgFArgType)]
forall a b. String -> [a] -> [b] -> [(a, b)]
zipEqual String
"getFCallArgs" [StgArg]
args (Type -> [StgFArgType]
collectStgFArgTypes Type
typ))
        ; [(CmmExpr, ForeignHint)] -> FCode [(CmmExpr, ForeignHint)]
forall (m :: * -> *) a. Monad m => a -> m a
return ([Maybe (CmmExpr, ForeignHint)] -> [(CmmExpr, ForeignHint)]
forall a. [Maybe a] -> [a]
catMaybes [Maybe (CmmExpr, ForeignHint)]
mb_cmms) }
  where
    get :: (StgArg, StgFArgType) -> FCode (Maybe (CmmExpr, ForeignHint))
get (StgArg
arg,StgFArgType
typ)
      | [PrimRep] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [PrimRep]
arg_reps
      = Maybe (CmmExpr, ForeignHint)
-> FCode (Maybe (CmmExpr, ForeignHint))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (CmmExpr, ForeignHint)
forall a. Maybe a
Nothing
      | Bool
otherwise
      = do { CmmExpr
cmm <- NonVoid StgArg -> FCode CmmExpr
getArgAmode (StgArg -> NonVoid StgArg
forall a. a -> NonVoid a
NonVoid StgArg
arg)
           ; DynFlags
dflags <- FCode DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
           ; Maybe (CmmExpr, ForeignHint)
-> FCode (Maybe (CmmExpr, ForeignHint))
forall (m :: * -> *) a. Monad m => a -> m a
return ((CmmExpr, ForeignHint) -> Maybe (CmmExpr, ForeignHint)
forall a. a -> Maybe a
Just (DynFlags -> StgFArgType -> CmmExpr -> CmmExpr
add_shim DynFlags
dflags StgFArgType
typ CmmExpr
cmm, ForeignHint
hint)) }
      where
        arg_ty :: Type
arg_ty   = StgArg -> Type
stgArgType StgArg
arg
        arg_reps :: [PrimRep]
arg_reps = HasDebugCallStack => Type -> [PrimRep]
Type -> [PrimRep]
typePrimRep Type
arg_ty
        hint :: ForeignHint
hint     = Type -> ForeignHint
typeForeignHint Type
arg_ty

-- The minimum amount of information needed to determine
-- the offset to apply to an argument to a foreign call.
-- See Note [Unlifted boxed arguments to foreign calls]
data StgFArgType
  = StgPlainType
  | StgArrayType
  | StgSmallArrayType
  | StgByteArrayType

-- See Note [Unlifted boxed arguments to foreign calls]
add_shim :: DynFlags -> StgFArgType -> CmmExpr -> CmmExpr
add_shim :: DynFlags -> StgFArgType -> CmmExpr -> CmmExpr
add_shim DynFlags
dflags StgFArgType
ty CmmExpr
expr = case StgFArgType
ty of
  StgFArgType
StgPlainType -> CmmExpr
expr
  StgFArgType
StgArrayType -> Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetB Platform
platform CmmExpr
expr (DynFlags -> ByteOff
arrPtrsHdrSize DynFlags
dflags)
  StgFArgType
StgSmallArrayType -> Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetB Platform
platform CmmExpr
expr (DynFlags -> ByteOff
smallArrPtrsHdrSize DynFlags
dflags)
  StgFArgType
StgByteArrayType -> Platform -> CmmExpr -> ByteOff -> CmmExpr
cmmOffsetB Platform
platform CmmExpr
expr (DynFlags -> ByteOff
arrWordsHdrSize DynFlags
dflags)
  where
    platform :: Platform
platform = DynFlags -> Platform
targetPlatform DynFlags
dflags

-- From a function, extract information needed to determine
-- the offset of each argument when used as a C FFI argument.
-- See Note [Unlifted boxed arguments to foreign calls]
collectStgFArgTypes :: Type -> [StgFArgType]
collectStgFArgTypes :: Type -> [StgFArgType]
collectStgFArgTypes = [StgFArgType] -> Type -> [StgFArgType]
go []
  where
    -- Skip foralls
    go :: [StgFArgType] -> Type -> [StgFArgType]
go [StgFArgType]
bs (ForAllTy TyCoVarBinder
_ Type
res) = [StgFArgType] -> Type -> [StgFArgType]
go [StgFArgType]
bs Type
res
    go [StgFArgType]
bs (AppTy{}) = [StgFArgType] -> [StgFArgType]
forall a. [a] -> [a]
reverse [StgFArgType]
bs
    go [StgFArgType]
bs (TyConApp{}) = [StgFArgType] -> [StgFArgType]
forall a. [a] -> [a]
reverse [StgFArgType]
bs
    go [StgFArgType]
bs (LitTy{}) = [StgFArgType] -> [StgFArgType]
forall a. [a] -> [a]
reverse [StgFArgType]
bs
    go [StgFArgType]
bs (TyVarTy{}) = [StgFArgType] -> [StgFArgType]
forall a. [a] -> [a]
reverse [StgFArgType]
bs
    go  [StgFArgType]
_ (CastTy{}) = String -> [StgFArgType]
forall a. String -> a
panic String
"myCollectTypeArgs: CastTy"
    go  [StgFArgType]
_ (CoercionTy{}) = String -> [StgFArgType]
forall a. String -> a
panic String
"myCollectTypeArgs: CoercionTy"
    go [StgFArgType]
bs (FunTy {ft_arg :: Type -> Type
ft_arg = Type
arg, ft_res :: Type -> Type
ft_res=Type
res}) =
      [StgFArgType] -> Type -> [StgFArgType]
go (Type -> StgFArgType
typeToStgFArgType Type
argStgFArgType -> [StgFArgType] -> [StgFArgType]
forall a. a -> [a] -> [a]
:[StgFArgType]
bs) Type
res

-- Choose the offset based on the type. For anything other
-- than an unlifted boxed type, there is no offset.
-- See Note [Unlifted boxed arguments to foreign calls]
typeToStgFArgType :: Type -> StgFArgType
typeToStgFArgType :: Type -> StgFArgType
typeToStgFArgType Type
typ
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
arrayPrimTyCon = StgFArgType
StgArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
mutableArrayPrimTyCon = StgFArgType
StgArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
arrayArrayPrimTyCon = StgFArgType
StgArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
mutableArrayArrayPrimTyCon = StgFArgType
StgArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
smallArrayPrimTyCon = StgFArgType
StgSmallArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
smallMutableArrayPrimTyCon = StgFArgType
StgSmallArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
byteArrayPrimTyCon = StgFArgType
StgByteArrayType
  | TyCon
tycon TyCon -> TyCon -> Bool
forall a. Eq a => a -> a -> Bool
== TyCon
mutableByteArrayPrimTyCon = StgFArgType
StgByteArrayType
  | Bool
otherwise = StgFArgType
StgPlainType
  where
  -- Should be a tycon app, since this is a foreign call. We look
  -- through newtypes so the offset does not change if a user replaces
  -- a type in a foreign function signature with a representationally
  -- equivalent newtype.
  tycon :: TyCon
tycon = Type -> TyCon
tyConAppTyCon (Type -> Type
unwrapType Type
typ)