{-# LANGUAGE QuasiQuotes, GeneralizedNewtypeDeriving, FlexibleInstances #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TupleSections #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
-- | C code generator framework.
module Futhark.CodeGen.Backends.GenericC
  ( compileProg
  , CParts(..)
  , asLibrary
  , asExecutable

  -- * Pluggable compiler
  , Operations (..)
  , defaultOperations
  , OpCompiler
  , ErrorCompiler

  , PointerQuals
  , MemoryType
  , WriteScalar
  , writeScalarPointerWithQuals
  , ReadScalar
  , readScalarPointerWithQuals
  , Allocate
  , Deallocate
  , Copy
  , StaticArray

  -- * Monadic compiler interface
  , CompilerM
  , CompilerState (compUserState)
  , getUserState
  , modifyUserState
  , contextContents
  , contextFinalInits
  , runCompilerM
  , blockScope
  , compileFun
  , compileCode
  , compileExp
  , compilePrimExp
  , compilePrimValue
  , compileExpToName
  , rawMem
  , item
  , stm
  , stms
  , decl
  , atInit
  , headerDecl
  , publicDef
  , publicDef_
  , profileReport
  , HeaderSection(..)
  , libDecl
  , earlyDecls
  , publicName
  , contextType
  , contextField

  -- * Building Blocks
  , primTypeToCType
  , copyMemoryDefaultSpace
  ) where

import Control.Monad.Identity
import Control.Monad.State
import Control.Monad.Reader
import Control.Monad.Writer
import Control.Monad.RWS
import Data.Bits (xor, shiftR)
import Data.Char (ord, isDigit, isAlphaNum)
import qualified Data.Map.Strict as M
import qualified Data.DList as DL
import Data.List (unzip4)
import Data.Loc
import Data.Maybe
import Data.FileEmbed
import Text.Printf

import qualified Language.C.Syntax as C
import qualified Language.C.Quote.OpenCL as C

import Futhark.CodeGen.ImpCode
import Futhark.MonadFreshNames
import Futhark.CodeGen.Backends.SimpleRepresentation
import Futhark.CodeGen.Backends.GenericC.Options
import Futhark.Util (zEncodeString)
import Futhark.Representation.AST.Attributes (isBuiltInFunction, builtInFunctions)


data CompilerState s = CompilerState {
    compTypeStructs :: [([Type], (C.Type, C.Definition))]
  , compArrayStructs :: [((C.Type, Int), (C.Type, [C.Definition]))]
  , compOpaqueStructs :: [(String, (C.Type, [C.Definition]))]
  , compEarlyDecls :: DL.DList C.Definition
  , compInit :: [C.Stm]
  , compNameSrc :: VNameSource
  , compUserState :: s
  , compHeaderDecls :: M.Map HeaderSection (DL.DList C.Definition)
  , compLibDecls :: DL.DList C.Definition
  , compCtxFields :: DL.DList (String, C.Type, Maybe C.Exp)
  , compProfileItems :: DL.DList C.BlockItem
  , compDeclaredMem :: [(VName,Space)]
  }

newCompilerState :: VNameSource -> s -> CompilerState s
newCompilerState src s = CompilerState { compTypeStructs = []
                                       , compArrayStructs = []
                                       , compOpaqueStructs = []
                                       , compEarlyDecls = mempty
                                       , compInit = []
                                       , compNameSrc = src
                                       , compUserState = s
                                       , compHeaderDecls = mempty
                                       , compLibDecls = mempty
                                       , compCtxFields = mempty
                                       , compProfileItems = mempty
                                       , compDeclaredMem = mempty
                                       }

-- | In which part of the header file we put the declaration.  This is
-- to ensure that the header file remains structured and readable.
data HeaderSection = ArrayDecl String
                   | OpaqueDecl String
                   | EntryDecl
                   | MiscDecl
                   | InitDecl
                   deriving (Eq, Ord)

-- | A substitute expression compiler, tried before the main
-- compilation function.
type OpCompiler op s = op -> CompilerM op s ()

type ErrorCompiler op s = ErrorMsg Exp -> String -> CompilerM op s ()

-- | The address space qualifiers for a pointer of the given type with
-- the given annotation.
type PointerQuals op s = String -> CompilerM op s [C.TypeQual]

-- | The type of a memory block in the given memory space.
type MemoryType op s = SpaceId -> CompilerM op s C.Type

-- | Write a scalar to the given memory block with the given element
-- index and in the given memory space.
type WriteScalar op s =
  C.Exp -> C.Exp -> C.Type -> SpaceId -> Volatility -> C.Exp -> CompilerM op s ()

-- | Read a scalar from the given memory block with the given element
-- index and in the given memory space.
type ReadScalar op s =
  C.Exp -> C.Exp -> C.Type -> SpaceId -> Volatility -> CompilerM op s C.Exp

-- | Allocate a memory block of the given size and with the given tag
-- in the given memory space, saving a reference in the given variable
-- name.
type Allocate op s = C.Exp -> C.Exp -> C.Exp -> SpaceId
                     -> CompilerM op s ()

-- | De-allocate the given memory block with the given tag, which is
-- in the given memory space.
type Deallocate op s = C.Exp -> C.Exp -> SpaceId -> CompilerM op s ()

-- | Create a static array of values - initialised at load time.
type StaticArray op s = VName -> SpaceId -> PrimType -> ArrayContents -> CompilerM op s ()

-- | Copy from one memory block to another.
type Copy op s = C.Exp -> C.Exp -> Space ->
                 C.Exp -> C.Exp -> Space ->
                 C.Exp ->
                 CompilerM op s ()

data Operations op s =
  Operations { opsWriteScalar :: WriteScalar op s
             , opsReadScalar :: ReadScalar op s
             , opsAllocate :: Allocate op s
             , opsDeallocate :: Deallocate op s
             , opsCopy :: Copy op s
             , opsStaticArray :: StaticArray op s

             , opsMemoryType :: MemoryType op s
             , opsCompiler :: OpCompiler op s
             , opsError :: ErrorCompiler op s

             , opsFatMemory :: Bool
               -- ^ If true, use reference counting.  Otherwise, bare
               -- pointers.
             }

defError :: ErrorCompiler op s
defError (ErrorMsg parts) stacktrace = do
  free_all_mem <- collect $ mapM_ (uncurry unRefMem) =<< gets compDeclaredMem
  let onPart (ErrorString s) = return ("%s", [C.cexp|$string:s|])
      onPart (ErrorInt32 x) = ("%d",) <$> compileExp x
  (formatstrs, formatargs) <- unzip <$> mapM onPart parts
  let formatstr = "Error: " ++ concat formatstrs ++ "\n\nBacktrace:\n%s"
  stm [C.cstm|{ ctx->error = msgprintf($string:formatstr, $args:formatargs, $string:stacktrace);
                $items:free_all_mem
                return 1;
              }|]

-- | A set of operations that fail for every operation involving
-- non-default memory spaces.  Uses plain pointers and @malloc@ for
-- memory management.
defaultOperations :: Operations op s
defaultOperations = Operations { opsWriteScalar = defWriteScalar
                               , opsReadScalar = defReadScalar
                               , opsAllocate  = defAllocate
                               , opsDeallocate  = defDeallocate
                               , opsCopy = defCopy
                               , opsStaticArray = defStaticArray
                               , opsMemoryType = defMemoryType
                               , opsCompiler = defCompiler
                               , opsFatMemory = True
                               , opsError = defError
                               }
  where defWriteScalar _ _ _ _ _ =
          error "Cannot write to non-default memory space because I am dumb"
        defReadScalar _ _ _ _ =
          error "Cannot read from non-default memory space"
        defAllocate _ _ _ =
          error "Cannot allocate in non-default memory space"
        defDeallocate _ _ =
          error "Cannot deallocate in non-default memory space"
        defCopy destmem destoffset DefaultSpace srcmem srcoffset DefaultSpace size =
          copyMemoryDefaultSpace destmem destoffset srcmem srcoffset size
        defCopy _ _ _ _ _ _ _ =
          error "Cannot copy to or from non-default memory space"
        defStaticArray _ _ _ _ =
          error "Cannot create static array in non-default memory space"
        defMemoryType _ =
          error "Has no type for non-default memory space"
        defCompiler _ =
          error "The default compiler cannot compile extended operations"


data CompilerEnv op s = CompilerEnv {
    envOperations :: Operations op s
  , envFtable     :: M.Map Name [Type]
  }

newtype CompilerAcc op s = CompilerAcc {
    accItems :: DL.DList C.BlockItem
  }

instance Semigroup (CompilerAcc op s) where
  CompilerAcc items1 <> CompilerAcc items2 =
    CompilerAcc (items1<>items2)

instance Monoid (CompilerAcc op s) where
  mempty = CompilerAcc mempty

envOpCompiler :: CompilerEnv op s -> OpCompiler op s
envOpCompiler = opsCompiler . envOperations

envMemoryType :: CompilerEnv op s -> MemoryType op s
envMemoryType = opsMemoryType . envOperations

envReadScalar :: CompilerEnv op s -> ReadScalar op s
envReadScalar = opsReadScalar . envOperations

envWriteScalar :: CompilerEnv op s -> WriteScalar op s
envWriteScalar = opsWriteScalar . envOperations

envAllocate :: CompilerEnv op s -> Allocate op s
envAllocate = opsAllocate . envOperations

envDeallocate :: CompilerEnv op s -> Deallocate op s
envDeallocate = opsDeallocate . envOperations

envCopy :: CompilerEnv op s -> Copy op s
envCopy = opsCopy . envOperations

envStaticArray :: CompilerEnv op s -> StaticArray op s
envStaticArray = opsStaticArray . envOperations

envFatMemory :: CompilerEnv op s -> Bool
envFatMemory = opsFatMemory . envOperations

newCompilerEnv :: Functions op -> Operations op s
               -> CompilerEnv op s
newCompilerEnv (Functions funs) ops =
  CompilerEnv { envOperations = ops
              , envFtable = ftable <> builtinFtable
              }
  where ftable = M.fromList $ map funReturn funs
        funReturn (name, fun) =
          (name, paramsTypes $ functionOutput fun)
        builtinFtable =
          M.map (map Scalar . snd) builtInFunctions

tupleDefinitions, arrayDefinitions, opaqueDefinitions :: CompilerState s -> [C.Definition]
tupleDefinitions = map (snd . snd) . compTypeStructs
arrayDefinitions = concatMap (snd . snd) . compArrayStructs
opaqueDefinitions = concatMap (snd . snd) . compOpaqueStructs

initDecls, arrayDecls, opaqueDecls, entryDecls, miscDecls :: CompilerState s -> [C.Definition]
initDecls = concatMap (DL.toList . snd) . filter ((==InitDecl) . fst) . M.toList . compHeaderDecls
arrayDecls = concatMap (DL.toList . snd) . filter (isArrayDecl . fst) . M.toList . compHeaderDecls
  where isArrayDecl ArrayDecl{} = True
        isArrayDecl _           = False
opaqueDecls = concatMap (DL.toList . snd) . filter (isOpaqueDecl . fst) . M.toList . compHeaderDecls
  where isOpaqueDecl OpaqueDecl{} = True
        isOpaqueDecl _           = False
entryDecls = concatMap (DL.toList . snd) . filter ((==EntryDecl) . fst) . M.toList . compHeaderDecls
miscDecls = concatMap (DL.toList . snd) . filter ((==MiscDecl) . fst) . M.toList . compHeaderDecls

contextContents :: CompilerM op s ([C.FieldGroup], [C.Stm])
contextContents = do
  (field_names, field_types, field_values) <- gets $ unzip3 . DL.toList . compCtxFields
  let fields = [ [C.csdecl|$ty:ty $id:name;|]
               | (name, ty) <- zip field_names field_types ]
      init_fields = [ [C.cstm|ctx->$id:name = $exp:e;|]
                    | (name, Just e) <- zip field_names field_values ]
  return (fields, init_fields)

contextFinalInits :: CompilerM op s [C.Stm]
contextFinalInits = gets compInit

newtype CompilerM op s a = CompilerM (RWS
                                      (CompilerEnv op s)
                                      (CompilerAcc op s)
                                      (CompilerState s) a)
  deriving (Functor, Applicative, Monad,
            MonadState (CompilerState s),
            MonadReader (CompilerEnv op s),
            MonadWriter (CompilerAcc op s))

instance MonadFreshNames (CompilerM op s) where
  getNameSource = gets compNameSrc
  putNameSource src = modify $ \s -> s { compNameSrc = src }

runCompilerM :: Functions op -> Operations op s -> VNameSource -> s
             -> CompilerM op s a
             -> (a, CompilerState s)
runCompilerM prog ops src userstate (CompilerM m) =
  let (x, s, _) = runRWS m (newCompilerEnv prog ops) (newCompilerState src userstate)
  in (x, s)

getUserState :: CompilerM op s s
getUserState = gets compUserState

modifyUserState :: (s -> s) -> CompilerM op s ()
modifyUserState f = modify $ \compstate ->
  compstate { compUserState = f $ compUserState compstate }

atInit :: C.Stm -> CompilerM op s ()
atInit x = modify $ \s ->
  s { compInit = compInit s ++ [x] }

collect :: CompilerM op s () -> CompilerM op s [C.BlockItem]
collect m = snd <$> collect' m

collect' :: CompilerM op s a -> CompilerM op s (a, [C.BlockItem])
collect' m = pass $ do
  (x, w) <- listen m
  return ((x, DL.toList $ accItems w),
          const w { accItems = mempty})

item :: C.BlockItem -> CompilerM op s ()
item x = tell $ mempty { accItems = DL.singleton x }

fatMemory :: Space -> CompilerM op s Bool
fatMemory ScalarSpace{} = return False
fatMemory _ = asks envFatMemory

instance C.ToIdent Name where
  toIdent = C.toIdent . zEncodeString . nameToString

instance C.ToIdent VName where
  toIdent = C.toIdent . zEncodeString . pretty

instance C.ToExp VName where
  toExp v _ = [C.cexp|$id:v|]

instance C.ToExp IntValue where
  toExp (Int8Value v) = C.toExp v
  toExp (Int16Value v) = C.toExp v
  toExp (Int32Value v) = C.toExp v
  toExp (Int64Value v) = C.toExp v

instance C.ToExp FloatValue where
  toExp (Float32Value v) = C.toExp v
  toExp (Float64Value v) = C.toExp v

instance C.ToExp PrimValue where
  toExp (IntValue v) = C.toExp v
  toExp (FloatValue v) = C.toExp v
  toExp (BoolValue True) = C.toExp (1::Int8)
  toExp (BoolValue False) = C.toExp (0::Int8)
  toExp Checked = C.toExp (1::Int8)

instance C.ToExp SubExp where
  toExp (Var v) = C.toExp v
  toExp (Constant c) = C.toExp c

-- | Construct a publicly visible definition using the specified name
-- as the template.  The first returned definition is put in the
-- header file, and the second is the implementation.  Returns the public
-- name.
publicDef :: String -> HeaderSection -> (String -> (C.Definition, C.Definition))
          -> CompilerM op s String
publicDef s h f = do
  s' <- publicName s
  let (pub, priv) = f s'
  headerDecl h pub
  libDecl priv
  return s'

-- | As 'publicDef', but ignores the public name.
publicDef_ :: String -> HeaderSection -> (String -> (C.Definition, C.Definition))
           -> CompilerM op s ()
publicDef_ s h f = void $ publicDef s h f

headerDecl :: HeaderSection -> C.Definition -> CompilerM op s ()
headerDecl sec def = modify $ \s ->
  s { compHeaderDecls = M.unionWith (<>) (compHeaderDecls s)
                              (M.singleton sec (DL.singleton def)) }

libDecl :: C.Definition -> CompilerM op s ()
libDecl def = modify $ \s ->
  s { compLibDecls = compLibDecls s <> DL.singleton def }

earlyDecls :: [C.Definition] -> CompilerM op s ()
earlyDecls def = modify $ \s ->
  s { compEarlyDecls = compEarlyDecls s <> DL.fromList def }

contextField :: String -> C.Type -> Maybe C.Exp -> CompilerM op s ()
contextField name ty initial = modify $ \s ->
  s { compCtxFields = compCtxFields s <> DL.singleton (name,ty,initial) }

profileReport :: C.BlockItem -> CompilerM op s ()
profileReport x = modify $ \s ->
  s { compProfileItems = compProfileItems s <> DL.singleton x }

stm :: C.Stm -> CompilerM op s ()
stm (C.Block items _) = mapM_ item items
stm (C.Default s _) = stm s
stm s = item [C.citem|$stm:s|]

stms :: [C.Stm] -> CompilerM op s ()
stms = mapM_ stm

decl :: C.InitGroup -> CompilerM op s ()
decl x = item [C.citem|$decl:x;|]

addrOf :: C.Exp -> C.Exp
addrOf e = [C.cexp|&$exp:e|]

-- | Public names must have a consitent prefix.
publicName :: String -> CompilerM op s String
publicName s = return $ "futhark_" ++ s

-- | The generated code must define a struct with this name.
contextType :: CompilerM op s C.Type
contextType = do
  name <- publicName "context"
  return [C.cty|struct $id:name|]

memToCType :: Space -> CompilerM op s C.Type
memToCType space = do
  refcount <- fatMemory space
  if refcount
     then return $ fatMemType space
     else rawMemCType space

rawMemCType :: Space -> CompilerM op s C.Type
rawMemCType DefaultSpace = return defaultMemBlockType
rawMemCType (Space sid) = join $ asks envMemoryType <*> pure sid
rawMemCType (ScalarSpace [] t) =
  return [C.cty|$ty:(primTypeToCType t)[1]|]
rawMemCType (ScalarSpace ds t) =
  return [C.cty|$ty:(primTypeToCType t)[$exp:(cproduct ds')]|]
  where ds' = map (`C.toExp` noLoc) ds

fatMemType :: Space -> C.Type
fatMemType space =
  [C.cty|struct $id:name|]
  where name = case space of
          Space sid    -> "memblock_" ++ sid
          _            -> "memblock"

fatMemSet :: Space -> String
fatMemSet (Space sid) = "memblock_set_" ++ sid
fatMemSet _ = "memblock_set"

fatMemAlloc :: Space -> String
fatMemAlloc (Space sid) = "memblock_alloc_" ++ sid
fatMemAlloc _ = "memblock_alloc"

fatMemUnRef :: Space -> String
fatMemUnRef (Space sid) = "memblock_unref_" ++ sid
fatMemUnRef _ = "memblock_unref"

rawMem :: C.ToExp a => a -> CompilerM op s C.Exp
rawMem v = rawMem' <$> asks envFatMemory <*> pure v

rawMem' :: C.ToExp a => Bool -> a -> C.Exp
rawMem' True  e = [C.cexp|$exp:e.mem|]
rawMem' False e = [C.cexp|$exp:e|]

defineMemorySpace :: Space -> CompilerM op s (C.Definition, [C.Definition], C.BlockItem)
defineMemorySpace space = do
  rm <- rawMemCType space
  let structdef =
        [C.cedecl|struct $id:sname { int *references;
                                     $ty:rm mem;
                                     typename int64_t size;
                                     const char *desc; };|]

  contextField peakname [C.cty|typename int64_t|] $ Just [C.cexp|0|]
  contextField usagename [C.cty|typename int64_t|] $ Just [C.cexp|0|]

  -- Unreferencing a memory block consists of decreasing its reference
  -- count and freeing the corresponding memory if the count reaches
  -- zero.
  free <- case space of
    Space sid -> do free_mem <- asks envDeallocate
                    collect $ free_mem [C.cexp|block->mem|] [C.cexp|block->desc|] sid
    _ -> return [[C.citem|free(block->mem);|]]
  ctx_ty <- contextType
  let unrefdef = [C.cedecl|static int $id:(fatMemUnRef space) ($ty:ctx_ty *ctx, $ty:mty *block, const char *desc) {
  if (block->references != NULL) {
    *(block->references) -= 1;
    if (ctx->detail_memory) {
      fprintf(stderr, $string:("Unreferencing block %s (allocated as %s) in %s: %d references remaining.\n"),
                               desc, block->desc, $string:spacedesc, *(block->references));
    }
    if (*(block->references) == 0) {
      ctx->$id:usagename -= block->size;
      $items:free
      free(block->references);
      if (ctx->detail_memory) {
        fprintf(stderr, "%lld bytes freed (now allocated: %lld bytes)\n",
                (long long) block->size, (long long) ctx->$id:usagename);
      }
    }
    block->references = NULL;
  }
  return 0;
}|]

  -- When allocating a memory block we initialise the reference count to 1.
  alloc <- collect $
    case space of
      Space sid ->
        join $ asks envAllocate <*> pure [C.cexp|block->mem|] <*>
        pure [C.cexp|size|] <*> pure [C.cexp|desc|] <*> pure sid
      _ ->
        stm [C.cstm|block->mem = (char*) malloc(size);|]
  let allocdef = [C.cedecl|static int $id:(fatMemAlloc space) ($ty:ctx_ty *ctx, $ty:mty *block, typename int64_t size, const char *desc) {
  if (size < 0) {
    panic(1, "Negative allocation of %lld bytes attempted for %s in %s.\n",
          (long long)size, desc, $string:spacedesc, ctx->$id:usagename);
  }
  int ret = $id:(fatMemUnRef space)(ctx, block, desc);

  ctx->$id:usagename += size;
  if (ctx->detail_memory) {
    fprintf(stderr, "Allocating %lld bytes for %s in %s (then allocated: %lld bytes)",
            (long long) size,
            desc, $string:spacedesc,
            (long long) ctx->$id:usagename);
  }
  if (ctx->$id:usagename > ctx->$id:peakname) {
    ctx->$id:peakname = ctx->$id:usagename;
    if (ctx->detail_memory) {
      fprintf(stderr, " (new peak).\n");
    }
  } else if (ctx->detail_memory) {
    fprintf(stderr, ".\n");
  }

  $items:alloc
  block->references = (int*) malloc(sizeof(int));
  *(block->references) = 1;
  block->size = size;
  block->desc = desc;
  return ret;
  }|]

  -- Memory setting - unreference the destination and increase the
  -- count of the source by one.
  let setdef = [C.cedecl|static int $id:(fatMemSet space) ($ty:ctx_ty *ctx, $ty:mty *lhs, $ty:mty *rhs, const char *lhs_desc) {
  int ret = $id:(fatMemUnRef space)(ctx, lhs, lhs_desc);
  (*(rhs->references))++;
  *lhs = *rhs;
  return ret;
}
|]

  let peakmsg = "Peak memory usage for " ++ spacedesc ++ ": %lld bytes.\n"
  return (structdef,
          [unrefdef, allocdef, setdef],
          [C.citem|fprintf(stderr, $string:peakmsg,
                           (long long) ctx->$id:peakname);|])
  where mty = fatMemType space
        (peakname, usagename, sname, spacedesc) = case space of
          Space sid    -> ("peak_mem_usage_" ++ sid,
                           "cur_mem_usage_" ++ sid,
                           "memblock_" ++ sid,
                           "space '" ++ sid ++ "'")
          _ -> ("peak_mem_usage_default",
                "cur_mem_usage_default",
                "memblock",
                "default space")

declMem :: VName -> Space -> CompilerM op s ()
declMem name space = do
  ty <- memToCType space
  decl [C.cdecl|$ty:ty $id:name;|]
  resetMem name space
  modify $ \s -> s { compDeclaredMem = (name, space) : compDeclaredMem s }

resetMem :: C.ToExp a => a -> Space -> CompilerM op s ()
resetMem mem space = do
  refcount <- fatMemory space
  when refcount $
    stm [C.cstm|$exp:mem.references = NULL;|]

setMem :: (C.ToExp a, C.ToExp b) => a -> b -> Space -> CompilerM op s ()
setMem dest src space = do
  refcount <- fatMemory space
  let src_s = pretty $ C.toExp src noLoc
  if refcount
    then stm [C.cstm|if ($id:(fatMemSet space)(ctx, &$exp:dest, &$exp:src,
                                               $string:src_s) != 0) {
                       return 1;
                     }|]
    else stm [C.cstm|$exp:dest = $exp:src;|]

unRefMem :: C.ToExp a => a -> Space -> CompilerM op s ()
unRefMem mem space = do
  refcount <- fatMemory space
  let mem_s = pretty $ C.toExp mem noLoc
  when refcount $
    stm [C.cstm|if ($id:(fatMemUnRef space)(ctx, &$exp:mem, $string:mem_s) != 0) {
               return 1;
             }|]

allocMem :: (C.ToExp a, C.ToExp b) =>
            a -> b -> Space -> C.Stm -> CompilerM op s ()
allocMem name size space on_failure = do
  refcount <- fatMemory space
  let name_s = pretty $ C.toExp name noLoc
  if refcount
    then stm [C.cstm|if ($id:(fatMemAlloc space)(ctx, &$exp:name, $exp:size,
                                                 $string:name_s)) {
                       $stm:on_failure
                     }|]
    else alloc name
  where alloc dest = case space of
          Space sid ->
            join $ asks envAllocate <*> rawMem name <*>
            pure [C.cexp|$exp:size|] <*> pure [C.cexp|desc|] <*> pure sid
          _ ->
            stm [C.cstm|$exp:dest = (char*) malloc($exp:size);|]

primTypeInfo :: PrimType -> Signedness -> C.Exp
primTypeInfo (IntType it) t = case (it, t) of
  (Int8,  TypeUnsigned) -> [C.cexp|u8_info|]
  (Int16, TypeUnsigned) -> [C.cexp|u16_info|]
  (Int32, TypeUnsigned) -> [C.cexp|u32_info|]
  (Int64, TypeUnsigned) -> [C.cexp|u64_info|]
  (Int8,  _) -> [C.cexp|i8_info|]
  (Int16, _) -> [C.cexp|i16_info|]
  (Int32, _) -> [C.cexp|i32_info|]
  (Int64, _) -> [C.cexp|i64_info|]
primTypeInfo (FloatType Float32) _ = [C.cexp|f32_info|]
primTypeInfo (FloatType Float64) _ = [C.cexp|f64_info|]
primTypeInfo Bool _ = [C.cexp|bool_info|]
primTypeInfo Cert _ = [C.cexp|bool_info|]

copyMemoryDefaultSpace :: C.Exp -> C.Exp -> C.Exp -> C.Exp -> C.Exp ->
                          CompilerM op s ()
copyMemoryDefaultSpace destmem destidx srcmem srcidx nbytes =
  stm [C.cstm|memmove($exp:destmem + $exp:destidx,
                      $exp:srcmem + $exp:srcidx,
                      $exp:nbytes);|]

paramsTypes :: [Param] -> [Type]
paramsTypes = map paramType
  -- Let's hope we don't need the size for anything, because we are
  -- just making something up.
  where paramType (MemParam _ space) = Mem space
        paramType (ScalarParam _ t) = Scalar t

--- Entry points.

arrayName :: PrimType -> Signedness -> Int -> String
arrayName pt signed rank =
  prettySigned (signed==TypeUnsigned) pt ++ "_" ++ show rank ++ "d"

opaqueName :: String -> [ValueDesc] -> String
opaqueName s _
  | valid = "opaque_" ++ s
  where valid = head s /= '_' &&
                not (isDigit $ head s) &&
                all ok s
        ok c = isAlphaNum c || c == '_'
opaqueName s vds = "opaque_" ++ hash (zipWith xor [0..] $ map ord (s ++ concatMap p vds))
  where p (ScalarValue pt signed _) =
          show (pt, signed)
        p (ArrayValue _ space pt signed dims) =
          show (space, pt, signed, length dims)

        -- FIXME: a stupid hash algorithm; may have collisions.
        hash = printf "%x" . foldl xor 0 . map (iter . (*0x45d9f3b) .
                                                iter . (*0x45d9f3b) .
                                                iter . fromIntegral)
        iter x = ((x::Word32) `shiftR` 16) `xor` x

criticalSection :: [C.BlockItem] -> [C.BlockItem]
criticalSection items = [[C.citem|lock_lock(&ctx->lock);|]] <>
                        items <>
                        [[C.citem|lock_unlock(&ctx->lock);|]]

arrayLibraryFunctions :: Space -> PrimType -> Signedness -> [DimSize]
                      -> CompilerM op s [C.Definition]
arrayLibraryFunctions space pt signed shape = do
  let rank = length shape
      pt' = signedPrimTypeToCType signed pt
      name = arrayName pt signed rank
      arr_name = "futhark_" ++ name
      array_type = [C.cty|struct $id:arr_name|]

  new_array <- publicName $ "new_" ++ name
  new_raw_array <- publicName $ "new_raw_" ++ name
  free_array <- publicName $ "free_" ++ name
  values_array <- publicName $ "values_" ++ name
  values_raw_array <- publicName $ "values_raw_" ++ name
  shape_array <- publicName $ "shape_" ++ name

  let shape_names = [ "dim"++show i | i <- [0..rank-1] ]
      shape_params = [ [C.cparam|typename int64_t $id:k|] | k <- shape_names ]
      arr_size = cproduct [ [C.cexp|$id:k|] | k <- shape_names ]
      arr_size_array = cproduct [ [C.cexp|arr->shape[$int:i]|] | i <- [0..rank-1] ]
  copy <- asks envCopy

  arr_raw_mem <- rawMem [C.cexp|arr->mem|]
  memty <- rawMemCType space

  let prepare_new = do
        resetMem [C.cexp|arr->mem|] space
        allocMem [C.cexp|arr->mem|] [C.cexp|((size_t)$exp:arr_size) * sizeof($ty:pt')|] space
                 [C.cstm|return NULL;|]
        forM_ [0..rank-1] $ \i ->
          let dim_s = "dim"++show i
          in stm [C.cstm|arr->shape[$int:i] = $id:dim_s;|]

  new_body <- collect $ do
    prepare_new
    copy arr_raw_mem [C.cexp|0|] space
         [C.cexp|data|] [C.cexp|0|] DefaultSpace
         [C.cexp|((size_t)$exp:arr_size) * sizeof($ty:pt')|]

  new_raw_body <- collect $ do
    prepare_new
    copy arr_raw_mem [C.cexp|0|] space
         [C.cexp|data|] [C.cexp|offset|] space
         [C.cexp|((size_t)$exp:arr_size) * sizeof($ty:pt')|]

  free_body <- collect $ unRefMem [C.cexp|arr->mem|] space

  values_body <- collect $
    copy [C.cexp|data|] [C.cexp|0|] DefaultSpace
         arr_raw_mem [C.cexp|0|] space
         [C.cexp|((size_t)$exp:arr_size_array) * sizeof($ty:pt')|]

  ctx_ty <- contextType

  headerDecl (ArrayDecl name)
    [C.cedecl|struct $id:arr_name;|]
  headerDecl (ArrayDecl name)
    [C.cedecl|$ty:array_type* $id:new_array($ty:ctx_ty *ctx, $ty:pt' *data, $params:shape_params);|]
  headerDecl (ArrayDecl name)
    [C.cedecl|$ty:array_type* $id:new_raw_array($ty:ctx_ty *ctx, $ty:memty data, int offset, $params:shape_params);|]
  headerDecl (ArrayDecl name)
    [C.cedecl|int $id:free_array($ty:ctx_ty *ctx, $ty:array_type *arr);|]
  headerDecl (ArrayDecl name)
    [C.cedecl|int $id:values_array($ty:ctx_ty *ctx, $ty:array_type *arr, $ty:pt' *data);|]
  headerDecl (ArrayDecl name)
    [C.cedecl|$ty:memty $id:values_raw_array($ty:ctx_ty *ctx, $ty:array_type *arr);|]
  headerDecl (ArrayDecl name)
    [C.cedecl|typename int64_t* $id:shape_array($ty:ctx_ty *ctx, $ty:array_type *arr);|]

  return [C.cunit|
          $ty:array_type* $id:new_array($ty:ctx_ty *ctx, $ty:pt' *data, $params:shape_params) {
            $ty:array_type* bad = NULL;
            $ty:array_type *arr = ($ty:array_type*) malloc(sizeof($ty:array_type));
            if (arr == NULL) {
              return bad;
            }
            $items:(criticalSection new_body)
            return arr;
          }

          $ty:array_type* $id:new_raw_array($ty:ctx_ty *ctx, $ty:memty data, int offset,
                                            $params:shape_params) {
            $ty:array_type* bad = NULL;
            $ty:array_type *arr = ($ty:array_type*) malloc(sizeof($ty:array_type));
            if (arr == NULL) {
              return bad;
            }
            $items:(criticalSection new_raw_body)
            return arr;
          }

          int $id:free_array($ty:ctx_ty *ctx, $ty:array_type *arr) {
            $items:(criticalSection free_body)
            free(arr);
            return 0;
          }

          int $id:values_array($ty:ctx_ty *ctx, $ty:array_type *arr, $ty:pt' *data) {
            $items:(criticalSection values_body)
            return 0;
          }

          $ty:memty $id:values_raw_array($ty:ctx_ty *ctx, $ty:array_type *arr) {
            (void)ctx;
            return $exp:arr_raw_mem;
          }

          typename int64_t* $id:shape_array($ty:ctx_ty *ctx, $ty:array_type *arr) {
            (void)ctx;
            return arr->shape;
          }
          |]

opaqueLibraryFunctions :: String -> [ValueDesc]
                       -> CompilerM op s [C.Definition]
opaqueLibraryFunctions desc vds = do
  name <- publicName $ opaqueName desc vds
  free_opaque <- publicName $ "free_" ++ opaqueName desc vds

  let opaque_type = [C.cty|struct $id:name|]

      freeComponent _ ScalarValue{} =
        return ()
      freeComponent i (ArrayValue _ _ pt signed shape) = do
        let rank = length shape
        free_array <- publicName $ "free_" ++ arrayName pt signed rank
        stm [C.cstm|if ((tmp = $id:free_array(ctx, obj->$id:(tupleField i))) != 0) {
                ret = tmp;
             }|]

  ctx_ty <- contextType

  free_body <- collect $ zipWithM_ freeComponent [0..] vds

  headerDecl (OpaqueDecl desc)
    [C.cedecl|int $id:free_opaque($ty:ctx_ty *ctx, $ty:opaque_type *obj);|]

  return [C.cunit|
          int $id:free_opaque($ty:ctx_ty *ctx, $ty:opaque_type *obj) {
            int ret = 0, tmp;
            $items:free_body
            free(obj);
            return ret;
          }
           |]

valueDescToCType :: ValueDesc -> CompilerM op s C.Type
valueDescToCType (ScalarValue pt signed _) =
  return $ signedPrimTypeToCType signed pt
valueDescToCType (ArrayValue _ space pt signed shape) = do
  let pt' = signedPrimTypeToCType signed pt
      rank = length shape
  exists <- gets $ lookup (pt',rank) . compArrayStructs
  case exists of
    Just (cty, _) -> return cty
    Nothing -> do
      memty <- memToCType space
      name <- publicName $ arrayName pt signed rank
      let struct = [C.cedecl|struct $id:name { $ty:memty mem; typename int64_t shape[$int:rank]; };|]
          stype = [C.cty|struct $id:name|]
      library <- arrayLibraryFunctions space pt signed shape
      modify $ \s -> s { compArrayStructs =
                           ((pt', rank), (stype, struct : library)) : compArrayStructs s
                       }
      return stype

opaqueToCType :: String -> [ValueDesc] -> CompilerM op s C.Type
opaqueToCType desc vds = do
  name <- publicName $ opaqueName desc vds
  exists <- gets $ lookup name . compOpaqueStructs
  case exists of
    Just (ty, _) -> return ty
    Nothing -> do
      members <- zipWithM field vds [(0::Int)..]
      let struct = [C.cedecl|struct $id:name { $sdecls:members };|]
          stype = [C.cty|struct $id:name|]
      headerDecl (OpaqueDecl desc) [C.cedecl|struct $id:name;|]
      library <- opaqueLibraryFunctions desc vds
      modify $ \s -> s { compOpaqueStructs =
                           (name, (stype, struct : library)) :
                           compOpaqueStructs s }
      return stype
  where field vd@ScalarValue{} i = do
          ct <- valueDescToCType vd
          return [C.csdecl|$ty:ct $id:(tupleField i);|]
        field vd i = do
          ct <- valueDescToCType vd
          return [C.csdecl|$ty:ct *$id:(tupleField i);|]

externalValueToCType :: ExternalValue -> CompilerM op s C.Type
externalValueToCType (TransparentValue vd) = valueDescToCType vd
externalValueToCType (OpaqueValue desc vds) = opaqueToCType desc vds

prepareEntryInputs :: [ExternalValue] -> CompilerM op s [C.Param]
prepareEntryInputs = zipWithM prepare [(0::Int)..]
  where prepare pno (TransparentValue vd) = do
          let pname = "in" ++ show pno
          ty <- prepareValue [C.cexp|$id:pname|] vd
          return [C.cparam|const $ty:ty $id:pname|]

        prepare pno (OpaqueValue desc vds) = do
          ty <- opaqueToCType desc vds
          let pname = "in" ++ show pno
              field i ScalarValue{} = [C.cexp|$id:pname->$id:(tupleField i)|]
              field i ArrayValue{} = [C.cexp|$id:pname->$id:(tupleField i)|]
          zipWithM_ prepareValue (zipWith field [0..] vds) vds
          return [C.cparam|const $ty:ty *$id:pname|]

        prepareValue src (ScalarValue pt signed name) = do
          let pt' = signedPrimTypeToCType signed pt
          stm [C.cstm|$id:name = $exp:src;|]
          return pt'

        prepareValue src vd@(ArrayValue mem _ _ _ shape) = do
          ty <- valueDescToCType vd

          stm [C.cstm|$exp:mem = $exp:src->mem;|]

          let rank = length shape
              maybeCopyDim (Var d) i =
                Just [C.cstm|$id:d = $exp:src->shape[$int:i];|]
              maybeCopyDim _ _ = Nothing

          stms $ catMaybes $ zipWith maybeCopyDim shape [0..rank-1]

          return [C.cty|$ty:ty*|]

prepareEntryOutputs :: [ExternalValue] -> CompilerM op s [C.Param]
prepareEntryOutputs = zipWithM prepare [(0::Int)..]
  where prepare pno (TransparentValue vd) = do
          let pname = "out" ++ show pno
          ty <- valueDescToCType vd

          case vd of
            ArrayValue{} -> do
              stm [C.cstm|assert((*$id:pname = ($ty:ty*) malloc(sizeof($ty:ty))) != NULL);|]
              prepareValue [C.cexp|*$id:pname|] vd
              return [C.cparam|$ty:ty **$id:pname|]
            ScalarValue{} -> do
              prepareValue [C.cexp|*$id:pname|] vd
              return [C.cparam|$ty:ty *$id:pname|]

        prepare pno (OpaqueValue desc vds) = do
          let pname = "out" ++ show pno
          ty <- opaqueToCType desc vds
          vd_ts <- mapM valueDescToCType vds

          stm [C.cstm|assert((*$id:pname = ($ty:ty*) malloc(sizeof($ty:ty))) != NULL);|]


          forM_ (zip3 [0..] vd_ts vds) $ \(i,ct,vd) -> do
            let field = [C.cexp|(*$id:pname)->$id:(tupleField i)|]
            case vd of
              ScalarValue{} -> return ()
              _ -> stm [C.cstm|assert(($exp:field = ($ty:ct*) malloc(sizeof($ty:ct))) != NULL);|]
            prepareValue field vd

          return [C.cparam|$ty:ty **$id:pname|]

        prepareValue dest (ScalarValue _ _ name) =
          stm [C.cstm|$exp:dest = $id:name;|]

        prepareValue dest (ArrayValue mem _ _ _ shape) = do
          stm [C.cstm|$exp:dest->mem = $id:mem;|]

          let rank = length shape
              maybeCopyDim (Constant x) i =
                [C.cstm|$exp:dest->shape[$int:i] = $exp:x;|]
              maybeCopyDim (Var d) i =
                [C.cstm|$exp:dest->shape[$int:i] = $id:d;|]
          stms $ zipWith maybeCopyDim shape [0..rank-1]

onEntryPoint :: Name -> Function op
             -> CompilerM op s (C.Definition, C.Definition, C.Initializer)
onEntryPoint fname function@(Function _ outputs inputs _ results args) = do
  let out_args = map (\p -> [C.cexp|&$id:(paramName p)|]) outputs
      in_args = map (\p -> [C.cexp|$id:(paramName p)|]) inputs

  inputdecls <- collect $ mapM_ stubParam inputs
  outputdecls <- collect $ mapM_ stubParam outputs

  let entry_point_name = nameToString fname
  entry_point_function_name <- publicName $ "entry_" ++ entry_point_name

  (entry_point_input_params, unpack_entry_inputs) <-
    collect' $ prepareEntryInputs args
  (entry_point_output_params, pack_entry_outputs) <-
    collect' $ prepareEntryOutputs results

  (cli_entry_point, cli_init) <- cliEntryPoint fname function

  ctx_ty <- contextType

  headerDecl EntryDecl [C.cedecl|int $id:entry_point_function_name
                                     ($ty:ctx_ty *ctx,
                                      $params:entry_point_output_params,
                                      $params:entry_point_input_params);|]

  return ([C.cedecl|int $id:entry_point_function_name
                         ($ty:ctx_ty *ctx,
                          $params:entry_point_output_params,
                          $params:entry_point_input_params) {
    $items:inputdecls
    $items:outputdecls

    lock_lock(&ctx->lock);

    $items:unpack_entry_inputs

    int ret = $id:(funName fname)(ctx, $args:out_args, $args:in_args);

    if (ret == 0) {
      $items:pack_entry_outputs
    }

    lock_unlock(&ctx->lock);

    return ret;
}
    |],
          cli_entry_point,
          cli_init)
  where stubParam (MemParam name space) =
          declMem name space
        stubParam (ScalarParam name ty) = do
          let ty' = primTypeToCType ty
          decl [C.cdecl|$ty:ty' $id:name;|]

--- CLI interface
--
-- Our strategy for CLI entry points is to parse everything into
-- host memory ('DefaultSpace') and copy the result into host memory
-- after the entry point has returned.  We have some ad-hoc frobbery
-- to copy the host-level memory blocks to another memory space if
-- necessary.  This will break if the Futhark entry point uses
-- non-trivial index functions for its input or output.
--
-- The idea here is to keep the nastyness in the wrapper, whilst not
-- messing up anything else.

printPrimStm :: (C.ToExp a, C.ToExp b) => a -> b -> PrimType -> Signedness -> C.Stm
printPrimStm dest val bt ept =
  [C.cstm|write_scalar($exp:dest, binary_output, &$exp:(primTypeInfo bt ept), &$exp:val);|]

-- | Return a statement printing the given external value.
printStm :: ExternalValue -> C.Exp -> CompilerM op s C.Stm
printStm (OpaqueValue desc _) _ =
  return [C.cstm|printf("#<opaque %s>", $string:desc);|]
printStm (TransparentValue (ScalarValue bt ept _)) e =
  return $ printPrimStm [C.cexp|stdout|] e bt ept
printStm (TransparentValue (ArrayValue _ _ bt ept shape)) e = do
  values_array <- publicName $ "values_" ++ name
  shape_array <- publicName $ "shape_" ++ name
  let num_elems = cproduct [ [C.cexp|$id:shape_array(ctx, $exp:e)[$int:i]|] | i <- [0..rank-1] ]
  return [C.cstm|{
      $ty:bt' *arr = calloc(sizeof($ty:bt'), $exp:num_elems);
      assert(arr != NULL);
      assert($id:values_array(ctx, $exp:e, arr) == 0);
      write_array(stdout, binary_output, &$exp:(primTypeInfo bt ept), arr,
                  $id:shape_array(ctx, $exp:e), $int:rank);
      free(arr);
  }|]
  where rank = length shape
        bt' = primTypeToCType bt
        name = arrayName bt ept rank

readPrimStm :: C.ToExp a => a -> Int -> PrimType -> Signedness -> C.Stm
readPrimStm place i t ept =
  [C.cstm|if (read_scalar(&$exp:(primTypeInfo t ept),&$exp:place) != 0) {
        panic(1, "Error when reading input #%d of type %s (errno: %s).\n",
              $int:i,
              $exp:(primTypeInfo t ept).type_name,
              strerror(errno));
      }|]

readInputs :: [ExternalValue] -> CompilerM op s [(C.Stm, C.Stm, C.Stm, C.Exp)]
readInputs = zipWithM readInput [0..]

readInput :: Int -> ExternalValue -> CompilerM op s (C.Stm, C.Stm, C.Stm, C.Exp)
readInput i (OpaqueValue desc _) = do
  stm [C.cstm|panic(1, "Cannot read input #%d of type %s\n", $int:i, $string:desc);|]
  return ([C.cstm|;|], [C.cstm|;|], [C.cstm|;|], [C.cexp|NULL|])
readInput i (TransparentValue (ScalarValue t ept _)) = do
  dest <- newVName "read_value"
  item [C.citem|$ty:(primTypeToCType t) $id:dest;|]
  stm $ readPrimStm dest i t ept
  return ([C.cstm|;|], [C.cstm|;|], [C.cstm|;|], [C.cexp|$id:dest|])
readInput i (TransparentValue vd@(ArrayValue _ _ t ept dims)) = do
  dest <- newVName "read_value"
  shape <- newVName "read_shape"
  arr <- newVName "read_arr"
  ty <- valueDescToCType vd
  item [C.citem|$ty:ty *$id:dest;|]

  let t' = signedPrimTypeToCType ept t
      rank = length dims
      name = arrayName t ept rank
      dims_exps = [ [C.cexp|$id:shape[$int:j]|] | j <- [0..rank-1] ]
      dims_s = concat $ replicate rank "[]"

  new_array <- publicName $ "new_" ++ name
  free_array <- publicName $ "free_" ++ name

  stm [C.cstm|{
     typename int64_t $id:shape[$int:rank];
     $ty:t' *$id:arr = NULL;
     errno = 0;
     if (read_array(&$exp:(primTypeInfo t ept),
                    (void**) &$id:arr,
                    $id:shape,
                    $int:(length dims))
         != 0) {
       panic(1, "Cannot read input #%d of type %s%s (errno: %s).\n",
                 $int:i,
                 $string:dims_s,
                 $exp:(primTypeInfo t ept).type_name,
                 strerror(errno));
     }
   }|]

  return ([C.cstm|assert(($exp:dest = $id:new_array(ctx, $id:arr, $args:dims_exps)) != 0);|],
          [C.cstm|assert($id:free_array(ctx, $exp:dest) == 0);|],
          [C.cstm|free($id:arr);|],
          [C.cexp|$id:dest|])

prepareOutputs :: [ExternalValue] -> CompilerM op s [(C.Exp, C.Stm)]
prepareOutputs = mapM prepareResult
  where prepareResult ev = do
          ty <- externalValueToCType ev
          result <- newVName "result"

          case ev of
            TransparentValue ScalarValue{} -> do
              item [C.citem|$ty:ty $id:result;|]
              return ([C.cexp|$id:result|], [C.cstm|;|])
            TransparentValue (ArrayValue _ _ t ept dims) -> do
              let name = arrayName t ept $ length dims
              free_array <- publicName $ "free_" ++ name
              item [C.citem|$ty:ty *$id:result;|]
              return ([C.cexp|$id:result|],
                      [C.cstm|assert($id:free_array(ctx, $exp:result) == 0);|])
            OpaqueValue desc vds -> do
              free_opaque <- publicName $ "free_" ++ opaqueName desc vds
              item [C.citem|$ty:ty *$id:result;|]
              return ([C.cexp|$id:result|],
                      [C.cstm|assert($id:free_opaque(ctx, $exp:result) == 0);|])

printResult :: [(ExternalValue,C.Exp)] -> CompilerM op s [C.Stm]
printResult vs = fmap concat $ forM vs $ \(v,e) -> do
  p <- printStm v e
  return [p, [C.cstm|printf("\n");|]]

cliEntryPoint :: Name
              -> FunctionT a
              -> CompilerM op s (C.Definition, C.Initializer)
cliEntryPoint fname (Function _ _ _ _ results args) = do
  ((pack_input, free_input, free_parsed, input_args), input_items) <-
    collect' $ unzip4 <$> readInputs args

  ((output_vals, free_outputs), output_decls) <-
    collect' $ unzip <$> prepareOutputs results
  printstms <- printResult $ zip results output_vals

  ctx_ty <- contextType
  sync_ctx <- publicName "context_sync"
  error_ctx <- publicName "context_get_error"

  let entry_point_name = nameToString fname
      cli_entry_point_function_name = "futrts_cli_entry_" ++ entry_point_name
  entry_point_function_name <- publicName $ "entry_" ++ entry_point_name

  pause_profiling <- publicName "context_pause_profiling"
  unpause_profiling <- publicName "context_unpause_profiling"

  let run_it = [C.citems|
                  int r;
                  /* Run the program once. */
                  $stms:pack_input
                  if ($id:sync_ctx(ctx) != 0) {
                    panic(1, "%s", $id:error_ctx(ctx));
                  };
                  // Only profile last run.
                  if (profile_run) {
                    $id:unpause_profiling(ctx);
                  }
                  t_start = get_wall_time();
                  r = $id:entry_point_function_name(ctx,
                                                    $args:(map addrOf output_vals),
                                                    $args:input_args);
                  if (r != 0) {
                    panic(1, "%s", $id:error_ctx(ctx));
                  }
                  if ($id:sync_ctx(ctx) != 0) {
                    panic(1, "%s", $id:error_ctx(ctx));
                  };
                  if (profile_run) {
                    $id:pause_profiling(ctx);
                  }
                  t_end = get_wall_time();
                  long int elapsed_usec = t_end - t_start;
                  if (time_runs && runtime_file != NULL) {
                    fprintf(runtime_file, "%lld\n", (long long) elapsed_usec);
                  }
                  $stms:free_input
                |]

  return ([C.cedecl|static void $id:cli_entry_point_function_name($ty:ctx_ty *ctx) {
    typename int64_t t_start, t_end;
    int time_runs = 0, profile_run = 0;

    // We do not want to profile all the initialisation.
    $id:pause_profiling(ctx);

    /* Declare and read input. */
    set_binary_mode(stdin);
    $items:input_items

    if (end_of_input() != 0) {
      panic(1, "Expected EOF on stdin after reading input for %s.\n", $string:(quote (pretty fname)));
    }

    $items:output_decls

    /* Warmup run */
    if (perform_warmup) {
      $items:run_it
      $stms:free_outputs
    }
    time_runs = 1;
    /* Proper run. */
    for (int run = 0; run < num_runs; run++) {
      // Only profile last run.
      profile_run = run == num_runs -1;
      $items:run_it
      if (run < num_runs-1) {
        $stms:free_outputs
      }
    }

    /* Free the parsed input. */
    $stms:free_parsed

    /* Print the final result. */
    if (binary_output) {
      set_binary_mode(stdout);
    }
    $stms:printstms

    $stms:free_outputs
  }
                |],
          [C.cinit|{ .name = $string:entry_point_name,
                      .fun = $id:cli_entry_point_function_name }|]
    )

benchmarkOptions :: [Option]
benchmarkOptions =
   [ Option { optionLongName = "write-runtime-to"
            , optionShortName = Just 't'
            , optionArgument = RequiredArgument "FILE"
            , optionAction = set_runtime_file
            }
   , Option { optionLongName = "runs"
            , optionShortName = Just 'r'
            , optionArgument = RequiredArgument "INT"
            , optionAction = set_num_runs
            }
   , Option { optionLongName = "debugging"
            , optionShortName = Just 'D'
            , optionArgument = NoArgument
            , optionAction = [C.cstm|futhark_context_config_set_debugging(cfg, 1);|]
            }
   , Option { optionLongName = "log"
            , optionShortName = Just 'L'
            , optionArgument = NoArgument
            , optionAction = [C.cstm|futhark_context_config_set_logging(cfg, 1);|]
            }
   , Option { optionLongName = "entry-point"
            , optionShortName = Just 'e'
            , optionArgument = RequiredArgument "NAME"
            , optionAction = [C.cstm|if (entry_point != NULL) entry_point = optarg;|]
            }
   , Option { optionLongName = "binary-output"
            , optionShortName = Just 'b'
            , optionArgument = NoArgument
            , optionAction = [C.cstm|binary_output = 1;|]
            }
   ]
  where set_runtime_file = [C.cstm|{
          runtime_file = fopen(optarg, "w");
          if (runtime_file == NULL) {
            panic(1, "Cannot open %s: %s\n", optarg, strerror(errno));
          }
        }|]
        set_num_runs = [C.cstm|{
          num_runs = atoi(optarg);
          perform_warmup = 1;
          if (num_runs <= 0) {
            panic(1, "Need a positive number of runs, not %s\n", optarg);
          }
        }|]

-- | The result of compilation to C is four parts, which can be put
-- together in various ways.  The obvious way is to concatenate all of
-- them, which yields a CLI program.  Another is to compile the
-- library part by itself, and use the header file to call into it.
data CParts = CParts { cHeader :: String
                     , cUtils :: String
                       -- ^ Utility definitions that must be visible
                       -- to both CLI and library parts.
                     , cCLI :: String
                     , cLib :: String
                     }

-- | Produce header and implementation files.
asLibrary :: CParts -> (String, String)
asLibrary parts = ("#pragma once\n\n" <> cHeader parts, cUtils parts <> cLib parts)

-- | As executable with command-line interface.
asExecutable :: CParts -> String
asExecutable (CParts a b c d) = a <> b <> c <> d

-- | Compile imperative program to a C program.  Always uses the
-- function named "main" as entry point, so make sure it is defined.
compileProg :: MonadFreshNames m =>
               Operations op ()
            -> CompilerM op () ()
            -> String
            -> [Space]
            -> [Option]
            -> Functions op
            -> m CParts
compileProg ops extra header_extra spaces options prog@(Functions funs) = do
  src <- getNameSource
  let ((prototypes, definitions, entry_points), endstate) =
        runCompilerM prog ops src () compileProg'
      (entry_point_decls, cli_entry_point_decls, entry_point_inits) =
        unzip3 entry_points
      option_parser = generateOptionParser "parse_options" $ benchmarkOptions++options

  let headerdefs = [C.cunit|
$esc:("/*\n * Headers\n*/\n")
$esc:("#include <stdint.h>")
$esc:("#include <stddef.h>")
$esc:("#include <stdbool.h>")
$esc:(header_extra)

$esc:("\n/*\n * Initialisation\n*/\n")
$edecls:(initDecls endstate)

$esc:("\n/*\n * Arrays\n*/\n")
$edecls:(arrayDecls endstate)

$esc:("\n/*\n * Opaque values\n*/\n")
$edecls:(opaqueDecls endstate)

$esc:("\n/*\n * Entry points\n*/\n")
$edecls:(entryDecls endstate)

$esc:("\n/*\n * Miscellaneous\n*/\n")
$edecls:(miscDecls endstate)
                           |]

  let utildefs = [C.cunit|
$esc:("#include <stdio.h>")
$esc:("#include <stdlib.h>")
$esc:("#include <stdbool.h>")
$esc:("#include <math.h>")
$esc:("#include <stdint.h>")
/* If NDEBUG is set, the assert() macro will do nothing. Since Futhark
   (unfortunately) makes use of assert() for error detection (and even some
   side effects), we want to avoid that. */
$esc:("#undef NDEBUG")
$esc:("#include <assert.h>")

$esc:panic_h

$esc:timing_h
|]

  let clidefs = [C.cunit|
$esc:("#include <string.h>")
$esc:("#include <inttypes.h>")
$esc:("#include <errno.h>")
$esc:("#include <ctype.h>")
$esc:("#include <errno.h>")
$esc:("#include <getopt.h>")

$esc:values_h

$esc:("#define __private")

static int binary_output = 0;
static typename FILE *runtime_file;
static int perform_warmup = 0;
static int num_runs = 1;
// If the entry point is NULL, the program will terminate after doing initialisation and such.
static const char *entry_point = "main";

$esc:tuning_h

$func:option_parser

$edecls:cli_entry_point_decls

typedef void entry_point_fun(struct futhark_context*);

struct entry_point_entry {
  const char *name;
  entry_point_fun *fun;
};

int main(int argc, char** argv) {
  fut_progname = argv[0];

  struct entry_point_entry entry_points[] = {
    $inits:entry_point_inits
  };

  struct futhark_context_config *cfg = futhark_context_config_new();
  assert(cfg != NULL);

  int parsed_options = parse_options(cfg, argc, argv);
  argc -= parsed_options;
  argv += parsed_options;

  if (argc != 0) {
    panic(1, "Excess non-option: %s\n", argv[0]);
  }

  struct futhark_context *ctx = futhark_context_new(cfg);
  assert (ctx != NULL);

  if (entry_point != NULL) {
    int num_entry_points = sizeof(entry_points) / sizeof(entry_points[0]);
    entry_point_fun *entry_point_fun = NULL;
    for (int i = 0; i < num_entry_points; i++) {
      if (strcmp(entry_points[i].name, entry_point) == 0) {
        entry_point_fun = entry_points[i].fun;
        break;
      }
    }

    if (entry_point_fun == NULL) {
      fprintf(stderr, "No entry point '%s'.  Select another with --entry-point.  Options are:\n",
                      entry_point);
      for (int i = 0; i < num_entry_points; i++) {
        fprintf(stderr, "%s\n", entry_points[i].name);
      }
      return 1;
    }

    entry_point_fun(ctx);

    if (runtime_file != NULL) {
      fclose(runtime_file);
    }

    futhark_debugging_report(ctx);
  }

  futhark_context_free(ctx);
  futhark_context_config_free(cfg);
  return 0;
}
                        |]

  let early_decls = DL.toList $ compEarlyDecls endstate
  let lib_decls = DL.toList $ compLibDecls endstate
  let libdefs = [C.cunit|
$esc:("#ifdef _MSC_VER\n#define inline __inline\n#endif")
$esc:("#include <string.h>")
$esc:("#include <inttypes.h>")
$esc:("#include <ctype.h>")
$esc:("#include <errno.h>")
$esc:("#include <assert.h>")

$esc:lock_h

$edecls:early_decls

$edecls:lib_decls

$edecls:(tupleDefinitions endstate)

$edecls:prototypes

$edecls:builtin

$edecls:(map funcToDef definitions)

$edecls:(arrayDefinitions endstate)

$edecls:(opaqueDefinitions endstate)

$edecls:entry_point_decls
  |]

  return $ CParts (pretty headerdefs) (pretty utildefs) (pretty clidefs) (pretty libdefs)
    where
      compileProg' = do
          (memstructs, memfuns, memreport) <- unzip3 <$> mapM defineMemorySpace spaces

          (prototypes, definitions) <- unzip <$> mapM compileFun funs

          mapM_ libDecl memstructs
          entry_points <- mapM (uncurry onEntryPoint) $ filter (functionEntry . snd) funs
          extra
          mapM_ libDecl $ concat memfuns
          profilereport <- gets $ DL.toList . compProfileItems

          ctx_ty <- contextType
          headerDecl MiscDecl [C.cedecl|void futhark_debugging_report($ty:ctx_ty *ctx);|]
          libDecl [C.cedecl|void futhark_debugging_report($ty:ctx_ty *ctx) {
                      if (ctx->detail_memory || ctx->profiling) {
                        $items:memreport
                      }
                      if (ctx->profiling) {
                        $items:profilereport
                      }
                    }|]

          return (prototypes, definitions, entry_points)

      funcToDef func = C.FuncDef func loc
        where loc = case func of
                       C.OldFunc _ _ _ _ _ _ l -> l
                       C.Func _ _ _ _ _ l      -> l

      builtin = cIntOps ++ cFloat32Ops ++ cFloat64Ops ++ cFloatConvOps ++
                cFloat32Funs ++ cFloat64Funs

      panic_h  = $(embedStringFile "rts/c/panic.h")
      values_h = $(embedStringFile "rts/c/values.h")
      timing_h = $(embedStringFile "rts/c/timing.h")
      lock_h   = $(embedStringFile "rts/c/lock.h")
      tuning_h = $(embedStringFile "rts/c/tuning.h")

compileFun :: (Name, Function op) -> CompilerM op s (C.Definition, C.Func)
compileFun (fname, Function _ outputs inputs body _ _) = do
  (outparams, out_ptrs) <- unzip <$> mapM compileOutput outputs
  inparams <- mapM compileInput inputs
  body' <- blockScope $ compileFunBody out_ptrs outputs body
  ctx_ty <- contextType
  return ([C.cedecl|static int $id:(funName fname)($ty:ctx_ty *ctx,
                                                   $params:outparams, $params:inparams);|],
          [C.cfun|static int $id:(funName fname)($ty:ctx_ty *ctx,
                                                 $params:outparams, $params:inparams) {
             $items:body'
             return 0;
}|])
  where compileInput (ScalarParam name bt) = do
          let ctp = primTypeToCType bt
          return [C.cparam|$ty:ctp $id:name|]
        compileInput (MemParam name space) = do
          ty <- memToCType space
          return [C.cparam|$ty:ty $id:name|]

        compileOutput (ScalarParam name bt) = do
          let ctp = primTypeToCType bt
          p_name <- newVName $ "out_" ++ baseString name
          return ([C.cparam|$ty:ctp *$id:p_name|], [C.cexp|$id:p_name|])
        compileOutput (MemParam name space) = do
          ty <- memToCType space
          p_name <- newVName $ baseString name ++ "_p"
          return ([C.cparam|$ty:ty *$id:p_name|], [C.cexp|$id:p_name|])

compilePrimValue :: PrimValue -> C.Exp

compilePrimValue (IntValue (Int8Value k)) = [C.cexp|$int:k|]
compilePrimValue (IntValue (Int16Value k)) = [C.cexp|$int:k|]
compilePrimValue (IntValue (Int32Value k)) = [C.cexp|$int:k|]
compilePrimValue (IntValue (Int64Value k)) = [C.cexp|$int:k|]

compilePrimValue (FloatValue (Float64Value x))
  | isInfinite x =
      if x > 0 then [C.cexp|INFINITY|] else [C.cexp|-INFINITY|]
  | isNaN x =
      [C.cexp|NAN|]
  | otherwise =
      [C.cexp|$double:x|]
compilePrimValue (FloatValue (Float32Value x))
  | isInfinite x =
      if x > 0 then [C.cexp|INFINITY|] else [C.cexp|-INFINITY|]
  | isNaN x =
      [C.cexp|NAN|]
  | otherwise =
      [C.cexp|$float:x|]

compilePrimValue (BoolValue b) =
  [C.cexp|$int:b'|]
  where b' :: Int
        b' = if b then 1 else 0

compilePrimValue Checked =
  [C.cexp|0|]

derefPointer :: C.Exp -> C.Exp -> C.Type -> C.Exp
derefPointer ptr i res_t =
  [C.cexp|(($ty:res_t)$exp:ptr)[$exp:i]|]

volQuals :: Volatility -> [C.TypeQual]
volQuals Volatile = [C.ctyquals|volatile|]
volQuals Nonvolatile = []

writeScalarPointerWithQuals :: PointerQuals op s -> WriteScalar op s
writeScalarPointerWithQuals quals_f dest i elemtype space vol v = do
  quals <- quals_f space
  let quals' = volQuals vol ++ quals
      deref = derefPointer dest i
              [C.cty|$tyquals:quals' $ty:elemtype*|]
  stm [C.cstm|$exp:deref = $exp:v;|]

readScalarPointerWithQuals :: PointerQuals op s -> ReadScalar op s
readScalarPointerWithQuals quals_f dest i elemtype space vol = do
  quals <- quals_f space
  let quals' = volQuals vol ++ quals
  return $ derefPointer dest i [C.cty|$tyquals:quals' $ty:elemtype*|]

compileExpToName :: String -> PrimType -> Exp -> CompilerM op s VName
compileExpToName _ _ (LeafExp (ScalarVar v) _) =
  return v
compileExpToName desc t e = do
  desc' <- newVName desc
  e' <- compileExp e
  decl [C.cdecl|$ty:(primTypeToCType t) $id:desc' = $e';|]
  return desc'

compileExp :: Exp -> CompilerM op s C.Exp

compileExp = compilePrimExp compileLeaf
  where compileLeaf (ScalarVar src) =
          return [C.cexp|$id:src|]

        compileLeaf (Index src (Count iexp) restype DefaultSpace vol) = do
          src' <- rawMem src
          derefPointer src'
            <$> compileExp iexp
            <*> pure [C.cty|$tyquals:(volQuals vol) $ty:(primTypeToCType restype)*|]

        compileLeaf (Index src (Count iexp) restype (Space space) vol) =
          join $ asks envReadScalar
          <*> rawMem src <*> compileExp iexp
          <*> pure (primTypeToCType restype) <*> pure space <*> pure vol

        compileLeaf (Index src (Count iexp) _ ScalarSpace{} _) = do
          iexp' <- compileExp iexp
          return [C.cexp|$id:src[$exp:iexp']|]

        compileLeaf (SizeOf t) =
          return [C.cexp|(typename int32_t)sizeof($ty:t')|]
          where t' = primTypeToCType t

-- | Tell me how to compile a @v@, and I'll Compile any @PrimExp v@ for you.
compilePrimExp :: Monad m => (v -> m C.Exp) -> PrimExp v -> m C.Exp

compilePrimExp _ (ValueExp val) =
  return $ compilePrimValue val

compilePrimExp f (LeafExp v _) =
  f v

compilePrimExp f (UnOpExp Complement{} x) = do
  x' <- compilePrimExp f x
  return [C.cexp|~$exp:x'|]

compilePrimExp f (UnOpExp Not{} x) = do
  x' <- compilePrimExp f x
  return [C.cexp|!$exp:x'|]

compilePrimExp f (UnOpExp Abs{} x) = do
  x' <- compilePrimExp f x
  return [C.cexp|abs($exp:x')|]

compilePrimExp f (UnOpExp (FAbs Float32) x) = do
  x' <- compilePrimExp f x
  return [C.cexp|(float)fabs($exp:x')|]

compilePrimExp f (UnOpExp (FAbs Float64) x) = do
  x' <- compilePrimExp f x
  return [C.cexp|fabs($exp:x')|]

compilePrimExp f (UnOpExp SSignum{} x) = do
  x' <- compilePrimExp f x
  return [C.cexp|($exp:x' > 0) - ($exp:x' < 0)|]

compilePrimExp f (UnOpExp USignum{} x) = do
  x' <- compilePrimExp f x
  return [C.cexp|($exp:x' > 0) - ($exp:x' < 0) != 0|]

compilePrimExp f (CmpOpExp cmp x y) = do
  x' <- compilePrimExp f x
  y' <- compilePrimExp f y
  return $ case cmp of
    CmpEq{} -> [C.cexp|$exp:x' == $exp:y'|]

    FCmpLt{} -> [C.cexp|$exp:x' < $exp:y'|]
    FCmpLe{} -> [C.cexp|$exp:x' <= $exp:y'|]

    CmpLlt{} -> [C.cexp|$exp:x' < $exp:y'|]
    CmpLle{} -> [C.cexp|$exp:x' <= $exp:y'|]

    _ -> [C.cexp|$id:(pretty cmp)($exp:x', $exp:y')|]

compilePrimExp f (ConvOpExp conv x) = do
  x' <- compilePrimExp f x
  return [C.cexp|$id:(pretty conv)($exp:x')|]

compilePrimExp f (BinOpExp bop x y) = do
  x' <- compilePrimExp f x
  y' <- compilePrimExp f y
  -- Note that integer addition, subtraction, and multiplication are
  -- not handled by explicit operators, but rather by functions.  This
  -- is because we want to implicitly convert them to unsigned
  -- numbers, so we can do overflow without invoking undefined
  -- behaviour.
  return $ case bop of
             FAdd{} -> [C.cexp|$exp:x' + $exp:y'|]
             FSub{} -> [C.cexp|$exp:x' - $exp:y'|]
             FMul{} -> [C.cexp|$exp:x' * $exp:y'|]
             FDiv{} -> [C.cexp|$exp:x' / $exp:y'|]
             Xor{} -> [C.cexp|$exp:x' ^ $exp:y'|]
             And{} -> [C.cexp|$exp:x' & $exp:y'|]
             Or{} -> [C.cexp|$exp:x' | $exp:y'|]
             Shl{} -> [C.cexp|$exp:x' << $exp:y'|]
             LogAnd{} -> [C.cexp|$exp:x' && $exp:y'|]
             LogOr{} -> [C.cexp|$exp:x' || $exp:y'|]
             _ -> [C.cexp|$id:(pretty bop)($exp:x', $exp:y')|]

compilePrimExp f (FunExp h args _) = do
  args' <- mapM (compilePrimExp f) args
  return [C.cexp|$id:(funName (nameFromString h))($args:args')|]

compileCode :: Code op -> CompilerM op s ()

compileCode (Op op) =
  join $ asks envOpCompiler <*> pure op

compileCode Skip = return ()

compileCode (Comment s code) = do
  items <- blockScope $ compileCode code
  let comment = "// " ++ s
  stm [C.cstm|$comment:comment
              { $items:items }
             |]

compileCode (DebugPrint s (Just e)) = do
  e' <- compileExp e
  stm [C.cstm|if (ctx->debugging) {
          fprintf(stderr, $string:fmtstr, $exp:s, ($ty:ety)$exp:e', '\n');
       }|]
  where (fmt, ety) = case primExpType e of
                       IntType _ -> ("llu", [C.cty|long long int|])
                       FloatType _ -> ("f", [C.cty|double|])
                       _ -> ("d", [C.cty|int|])
        fmtstr = "%s: %" ++ fmt ++ "%c"

compileCode (DebugPrint s Nothing) =
  stm [C.cstm|if (ctx->debugging) {
          fprintf(stderr, "%s\n", $exp:s);
       }|]

compileCode c
  | Just (name, vol, t, e, c') <- declareAndSet c = do
    let ct = primTypeToCType t
    e' <- compileExp e
    item [C.citem|$tyquals:(volQuals vol) $ty:ct $id:name = $exp:e';|]
    compileCode c'

compileCode (c1 :>>: c2) = compileCode c1 >> compileCode c2

compileCode (Assert e msg (loc, locs)) = do
  e' <- compileExp e
  err <- collect $ join $
         asks (opsError . envOperations) <*> pure msg <*> pure stacktrace
  stm [C.cstm|if (!$exp:e') { $items:err }|]
  where stacktrace = prettyStacktrace 0 $ map locStr $ loc:locs

compileCode (Allocate _ _ ScalarSpace{}) =
  -- Handled by the declaration of the memory block, which is
  -- translated to an actual array.
  return ()

compileCode (Allocate name (Count e) space) = do
  size <- compileExp e
  allocMem name size space [C.cstm|return 1;|]

compileCode (Free name space) =
  unRefMem name space

compileCode (For i it bound body) = do
  let i' = C.toIdent i
      it' = primTypeToCType $ IntType it
  bound' <- compileExp bound
  body'  <- blockScope $ compileCode body
  stm [C.cstm|for ($ty:it' $id:i' = 0; $id:i' < $exp:bound'; $id:i'++) {
            $items:body'
          }|]

compileCode (While cond body) = do
  cond' <- compileExp cond
  body' <- blockScope $ compileCode body
  stm [C.cstm|while ($exp:cond') {
            $items:body'
          }|]

compileCode (If cond tbranch fbranch) = do
  cond' <- compileExp cond
  tbranch' <- blockScope $ compileCode tbranch
  fbranch' <- blockScope $ compileCode fbranch
  stm $ case (tbranch', fbranch') of
    (_, []) ->
      [C.cstm|if ($exp:cond') { $items:tbranch' }|]
    ([], _) ->
      [C.cstm|if (!($exp:cond')) { $items:fbranch' }|]
    _ ->
      [C.cstm|if ($exp:cond') { $items:tbranch' } else { $items:fbranch' }|]

compileCode (Copy dest (Count destoffset) DefaultSpace src (Count srcoffset) DefaultSpace (Count size)) = do
  destoffset' <- compileExp destoffset
  srcoffset' <- compileExp srcoffset
  size' <- compileExp size
  dest' <- rawMem dest
  src' <- rawMem src
  stm [C.cstm|memmove($exp:dest' + $exp:destoffset',
                      $exp:src' + $exp:srcoffset',
                      $exp:size');|]

compileCode (Copy dest (Count destoffset) destspace src (Count srcoffset) srcspace (Count size)) = do
  copy <- asks envCopy
  join $ copy
    <$> rawMem dest <*> compileExp destoffset <*> pure destspace
    <*> rawMem src <*> compileExp srcoffset <*> pure srcspace
    <*> compileExp size

compileCode (Write dest (Count idx) elemtype DefaultSpace vol elemexp) = do
  dest' <- rawMem dest
  deref <- derefPointer dest'
           <$> compileExp idx
           <*> pure [C.cty|$tyquals:(volQuals vol) $ty:(primTypeToCType elemtype)*|]
  elemexp' <- compileExp elemexp
  stm [C.cstm|$exp:deref = $exp:elemexp';|]

compileCode (Write dest (Count idx) _ ScalarSpace{} _ elemexp) = do
  idx' <- compileExp idx
  elemexp' <- compileExp elemexp
  stm [C.cstm|$id:dest[$exp:idx'] = $exp:elemexp';|]

compileCode (Write dest (Count idx) elemtype (Space space) vol elemexp) =
  join $ asks envWriteScalar
    <*> rawMem dest
    <*> compileExp idx
    <*> pure (primTypeToCType elemtype)
    <*> pure space
    <*> pure vol
    <*> compileExp elemexp

compileCode (DeclareMem name space) =
  declMem name space

compileCode (DeclareScalar name vol t) = do
  let ct = primTypeToCType t
  decl [C.cdecl|$tyquals:(volQuals vol) $ty:ct $id:name;|]

compileCode (DeclareArray name ScalarSpace{} _ _) =
  error $ "Cannot declare array " ++ pretty name ++ " in scalar space."

compileCode (DeclareArray name DefaultSpace t vs) = do
  name_realtype <- newVName $ baseString name ++ "_realtype"
  let ct = primTypeToCType t
  case vs of
    ArrayValues vs' -> do
      let vs'' = [[C.cinit|$exp:(compilePrimValue v)|] | v <- vs']
      libDecl [C.cedecl|static $ty:ct $id:name_realtype[$int:(length vs')] = {$inits:vs''};|]
    ArrayZeros n ->
      libDecl [C.cedecl|static $ty:ct $id:name_realtype[$int:n];|]
  -- Fake a memory block.
  contextField (pretty name)
    [C.cty|struct memblock|] $
    Just [C.cexp|(struct memblock){NULL, (char*)$id:name_realtype, 0}|]
  item [C.citem|struct memblock $id:name = ctx->$id:name;|]

compileCode (DeclareArray name (Space space) t vs) =
  join $ asks envStaticArray <*>
  pure name <*> pure space <*> pure t <*> pure vs

-- For assignments of the form 'x = x OP e', we generate C assignment
-- operators to make the resulting code slightly nicer.  This has no
-- effect on performance.
compileCode (SetScalar dest (BinOpExp op (LeafExp (ScalarVar x) _) y))
  | dest == x, Just f <- assignmentOperator op = do
      y' <- compileExp y
      stm [C.cstm|$exp:(f dest y');|]

compileCode (SetScalar dest src) = do
  src' <- compileExp src
  stm [C.cstm|$id:dest = $exp:src';|]

compileCode (SetMem dest src space) =
  setMem dest src space

compileCode (Call dests fname args) = do
  args' <- mapM compileArg args
  let out_args = [ [C.cexp|&$id:d|] | d <- dests ]
      args'' | isBuiltInFunction fname = args'
             | otherwise = [C.cexp|ctx|] : out_args ++ args'
  case dests of
    [dest] | isBuiltInFunction fname ->
      stm [C.cstm|$id:dest = $id:(funName fname)($args:args'');|]
    _        -> do
      ret <- newVName "call_ret"
      item [C.citem|int $id:ret = $id:(funName fname)($args:args'');|]
      stm [C.cstm|assert($id:ret == 0);|]
  where compileArg (MemArg m) = return [C.cexp|$exp:m|]
        compileArg (ExpArg e) = compileExp e

blockScope :: CompilerM op s () -> CompilerM op s [C.BlockItem]
blockScope = fmap snd . blockScope'

blockScope' :: CompilerM op s a -> CompilerM op s (a, [C.BlockItem])
blockScope' m = do
  old_allocs <- gets compDeclaredMem
  (x, items) <- pass $ do
    (x, w) <- listen m
    let items = DL.toList $ accItems w
    return ((x, items), const mempty)
  new_allocs <- gets $ filter (`notElem` old_allocs) . compDeclaredMem
  modify $ \s -> s { compDeclaredMem = old_allocs }
  releases <- collect $ mapM_ (uncurry unRefMem) new_allocs
  return (x, items <> releases)

compileFunBody :: [C.Exp] -> [Param] -> Code op -> CompilerM op s ()
compileFunBody output_ptrs outputs code = do
  mapM_ declareOutput outputs
  compileCode code
  zipWithM_ setRetVal' output_ptrs outputs
  where declareOutput (MemParam name space) =
          declMem name space
        declareOutput (ScalarParam name pt) = do
          let ctp = primTypeToCType pt
          decl [C.cdecl|$ty:ctp $id:name;|]

        setRetVal' p (MemParam name space) = do
          resetMem [C.cexp|*$exp:p|] space
          setMem [C.cexp|*$exp:p|] name space
        setRetVal' p (ScalarParam name _) =
          stm [C.cstm|*$exp:p = $id:name;|]

declareAndSet :: Code op -> Maybe (VName, Volatility, PrimType, Exp, Code op)
declareAndSet (DeclareScalar name vol t :>>: (SetScalar dest e :>>: c))
  | name == dest = Just (name, vol, t, e, c)
declareAndSet ((DeclareScalar name vol t :>>: SetScalar dest e) :>>: c)
  | name == dest = Just (name, vol, t, e, c)
declareAndSet _ = Nothing

assignmentOperator :: BinOp -> Maybe (VName -> C.Exp -> C.Exp)
assignmentOperator Add{}  = Just $ \d e -> [C.cexp|$id:d += $exp:e|]
assignmentOperator Sub{} = Just $ \d e -> [C.cexp|$id:d -= $exp:e|]
assignmentOperator Mul{} = Just $ \d e -> [C.cexp|$id:d *= $exp:e|]
assignmentOperator _     = Nothing

-- | Return an expression multiplying together the given expressions.
-- If an empty list is given, the expression @1@ is returned.
cproduct :: [C.Exp] -> C.Exp
cproduct []     = [C.cexp|1|]
cproduct (e:es) = foldl mult e es
  where mult x y = [C.cexp|$exp:x * $exp:y|]