ToOpenCL.hs

{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TupleSections #-}
-- | This module defines a translation from imperative code with
-- kernels to imperative code with OpenCL calls.
module Futhark.CodeGen.ImpGen.Kernels.ToOpenCL
  ( kernelsToOpenCL
  )
  where

import Control.Monad.State
import Control.Monad.Identity
import Control.Monad.Writer
import Control.Monad.Reader
import Data.Maybe
import qualified Data.Set as S
import qualified Data.Map.Strict as M
import qualified Data.Semigroup as Sem

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

import Futhark.Error
import qualified Futhark.CodeGen.Backends.GenericC as GenericC
import Futhark.CodeGen.Backends.SimpleRepresentation
import Futhark.CodeGen.ImpCode.Kernels hiding (Program)
import qualified Futhark.CodeGen.ImpCode.Kernels as ImpKernels
import Futhark.CodeGen.ImpCode.OpenCL hiding (Program)
import qualified Futhark.CodeGen.ImpCode.OpenCL as ImpOpenCL
import Futhark.MonadFreshNames
import Futhark.Util (zEncodeString)
import Futhark.Util.Pretty (pretty, prettyOneLine)

-- | Translate a kernels-program to an OpenCL-program.
kernelsToOpenCL :: ImpKernels.Program
                -> Either InternalError ImpOpenCL.Program
kernelsToOpenCL (ImpKernels.Functions funs) = do
  (prog', ToOpenCL extra_funs kernels requirements sizes) <-
    runWriterT $ fmap Functions $ forM funs $ \(fname, fun) ->
    (fname,) <$> runReaderT (traverse onHostOp fun) fname
  let kernel_names = M.keys kernels
      opencl_code = openClCode $ M.elems kernels
      opencl_prelude = pretty $ genOpenClPrelude requirements
  return $ ImpOpenCL.Program opencl_code opencl_prelude kernel_names
    (S.toList $ kernelUsedTypes requirements) sizes $
    ImpOpenCL.Functions (M.toList extra_funs) <> prog'

pointerQuals ::  Monad m => String -> m [C.TypeQual]
pointerQuals "global"     = return [C.ctyquals|__global|]
pointerQuals "local"      = return [C.ctyquals|__local|]
pointerQuals "private"    = return [C.ctyquals|__private|]
pointerQuals "constant"   = return [C.ctyquals|__constant|]
pointerQuals "write_only" = return [C.ctyquals|__write_only|]
pointerQuals "read_only"  = return [C.ctyquals|__read_only|]
pointerQuals "kernel"     = return [C.ctyquals|__kernel|]
pointerQuals s            = fail $ "'" ++ s ++ "' is not an OpenCL kernel address space."

type UsedFunctions = [(String,C.Func)] -- The ordering is important!

data OpenClRequirements =
  OpenClRequirements { kernelUsedTypes :: S.Set PrimType
                     , _kernelConstants :: [(VName, KernelConstExp)]
                     }

instance Sem.Semigroup OpenClRequirements where
  OpenClRequirements ts1 consts1 <> OpenClRequirements ts2 consts2 =
    OpenClRequirements (ts1 <> ts2) (consts1 <> consts2)

instance Monoid OpenClRequirements where
  mempty = OpenClRequirements mempty mempty
  mappend = (Sem.<>)

data ToOpenCL = ToOpenCL { clExtraFuns :: M.Map Name ImpOpenCL.Function
                         , clKernels :: M.Map KernelName C.Func
                         , clRequirements :: OpenClRequirements
                         , clSizes :: M.Map VName (SizeClass, Name)
                         }

instance Sem.Semigroup ToOpenCL where
  ToOpenCL f1 k1 r1 sz1 <> ToOpenCL f2 k2 r2 sz2 =
    ToOpenCL (f1<>f2) (k1<>k2) (r1<>r2) (sz1<>sz2)

instance Monoid ToOpenCL where
  mempty = ToOpenCL mempty mempty mempty mempty
  mappend = (Sem.<>)

type OnKernelM = ReaderT Name (WriterT ToOpenCL (Either InternalError))

onHostOp :: HostOp -> OnKernelM OpenCL
onHostOp (CallKernel k) = onKernel k
onHostOp (ImpKernels.GetSize v key size_class) = do
  fname <- ask
  tell mempty { clSizes = M.singleton key (size_class, fname) }
  return $ ImpOpenCL.GetSize v key
onHostOp (ImpKernels.CmpSizeLe v key size_class x) = do
  fname <- ask
  tell mempty { clSizes = M.singleton key (size_class, fname) }
  return $ ImpOpenCL.CmpSizeLe v key x
onHostOp (ImpKernels.GetSizeMax v size_class) =
  return $ ImpOpenCL.GetSizeMax v size_class

onKernel :: CallKernel -> OnKernelM OpenCL

onKernel called@(Map kernel) = do
  let (funbody, _) =
        GenericC.runCompilerM (Functions []) inKernelOperations blankNameSource mempty $ do
          size <- GenericC.compileExp $ mapKernelSize kernel
          let check = [C.citem|if ($id:(mapKernelThreadNum kernel) >= $exp:size) return;|]
          body <- GenericC.blockScope $ GenericC.compileCode $ mapKernelBody kernel
          return $ check : body

      params = mapMaybe useAsParam $ mapKernelUses kernel

  tell mempty
    { clExtraFuns = mempty
    , clKernels = M.singleton (mapKernelName kernel)
                  [C.cfun|__kernel void $id:(mapKernelName kernel) ($params:params) {
                     const uint $id:(mapKernelThreadNum kernel) = get_global_id(0);
                     $items:funbody
                  }|]
    , clRequirements = OpenClRequirements
                       (typesInKernel called)
                       (mapMaybe useAsConst $ mapKernelUses kernel)
    }

  return $ LaunchKernel
    (calledKernelName called) (kernelArgs called) kernel_size workgroup_size

  where kernel_size = [sizeToExp (mapKernelNumGroups kernel) *
                       sizeToExp (mapKernelGroupSize kernel)]
        workgroup_size = [sizeToExp $ mapKernelGroupSize kernel]

onKernel called@(AnyKernel kernel) = do
  let (kernel_body, _) =
        GenericC.runCompilerM (Functions []) inKernelOperations blankNameSource mempty $
        GenericC.blockScope $ GenericC.compileCode $ kernelBody kernel

      use_params = mapMaybe useAsParam $ kernelUses kernel

      (local_memory_params, local_memory_init) =
        unzip $
        flip evalState (blankNameSource :: VNameSource) $
        mapM prepareLocalMemory $ kernelLocalMemory kernel

      params = catMaybes local_memory_params ++ use_params

  tell mempty { clExtraFuns = mempty
                , clKernels = M.singleton name
                              [C.cfun|__kernel void $id:name ($params:params) {
                                  $items:local_memory_init
                                  $items:kernel_body
                                  }|]
               , clRequirements = OpenClRequirements
                                  (typesInKernel called)
                                  (mapMaybe useAsConst $ kernelUses kernel)
               }

  return $ LaunchKernel
    (calledKernelName called) (kernelArgs called) kernel_size workgroup_size

  where prepareLocalMemory (mem, Left _) = do
          mem_aligned <- newVName $ baseString mem ++ "_aligned"
          return (Just [C.cparam|__local volatile typename int64_t* $id:mem_aligned|],
                  [C.citem|__local volatile char* restrict $id:mem = $id:mem_aligned;|])
        prepareLocalMemory (mem, Right size) = do
          let size' = compilePrimExp size
          return (Nothing,
                  [C.citem|ALIGNED_LOCAL_MEMORY($id:mem, $exp:size');|])
        name = calledKernelName called
        kernel_size = zipWith (*) (kernelNumGroups kernel) (kernelGroupSize kernel)
        workgroup_size = kernelGroupSize kernel

useAsParam :: KernelUse -> Maybe C.Param
useAsParam (ScalarUse name bt) =
  let ctp = case bt of
        -- OpenCL does not permit bool as a kernel parameter type.
        Bool -> [C.cty|unsigned char|]
        _    -> GenericC.primTypeToCType bt
  in Just [C.cparam|$ty:ctp $id:name|]
useAsParam (MemoryUse name) =
  Just [C.cparam|__global unsigned char *$id:name|]
useAsParam ConstUse{} =
  Nothing

useAsConst :: KernelUse -> Maybe (VName, KernelConstExp)
useAsConst (ConstUse v e) = Just (v,e)
useAsConst _ = Nothing

openClCode :: [C.Func] -> String
openClCode kernels =
  pretty [C.cunit|$edecls:funcs|]
  where funcs =
          [[C.cedecl|$func:kernel_func|] |
           kernel_func <- kernels ]

genOpenClPrelude :: OpenClRequirements -> [C.Definition]
genOpenClPrelude (OpenClRequirements ts consts) =
  -- Clang-based OpenCL implementations need this for 'static' to work.
  [C.cedecl|$esc:("#pragma OPENCL EXTENSION cl_clang_storage_class_specifiers : enable")|] :
  [[C.cedecl|$esc:("#pragma OPENCL EXTENSION cl_khr_fp64 : enable")|] | uses_float64] ++
  [C.cunit|
/* Some OpenCL programs dislike empty progams, or programs with no kernels.
 * Declare a dummy kernel to ensure they remain our friends. */
__kernel void dummy_kernel(__global unsigned char *dummy, int n)
{
    const int thread_gid = get_global_id(0);
    if (thread_gid >= n) return;
}

typedef char int8_t;
typedef short int16_t;
typedef int int32_t;
typedef long int64_t;

typedef uchar uint8_t;
typedef ushort uint16_t;
typedef uint uint32_t;
typedef ulong uint64_t;

$esc:("#define ALIGNED_LOCAL_MEMORY(m,size) __local unsigned char m[size] __attribute__ ((align))")
|] ++
  cIntOps ++ cFloat32Ops ++ cFloat32Funs ++
  (if uses_float64 then cFloat64Ops ++ cFloat64Funs ++ cFloatConvOps else []) ++
  [ [C.cedecl|$esc:def|] | def <- map constToDefine consts ]
  where uses_float64 = FloatType Float64 `S.member` ts
        constToDefine (name, e) =
          let e' = compilePrimExp e
          in unwords ["#define", zEncodeString (pretty name), "("++prettyOneLine e'++")"]

compilePrimExp :: PrimExp KernelConst -> C.Exp
compilePrimExp e = runIdentity $ GenericC.compilePrimExp compileKernelConst e
  where compileKernelConst (SizeConst key) = return [C.cexp|$id:(pretty key)|]

mapKernelName :: MapKernel -> String
mapKernelName k = "kernel_"++ mapKernelDesc k ++ "_" ++
                  show (baseTag $ mapKernelThreadNum k)

calledKernelName :: CallKernel -> String
calledKernelName (Map k) =
  mapKernelName k
calledKernelName (AnyKernel k) =
  nameToString $ kernelName k

kernelArgs :: CallKernel -> [KernelArg]
kernelArgs (Map kernel) =
  mapMaybe useToArg $ mapKernelUses kernel
kernelArgs (AnyKernel kernel) =
  mapMaybe (fmap (SharedMemoryKArg . memSizeToExp) . localMemorySize)
  (kernelLocalMemory kernel) ++
  mapMaybe useToArg (kernelUses kernel)
  where localMemorySize (_, Left size) = Just size
        localMemorySize (_, Right{}) = Nothing

--- Generating C

inKernelOperations :: GenericC.Operations KernelOp UsedFunctions
inKernelOperations = GenericC.Operations
                     { GenericC.opsCompiler = kernelOps
                     , GenericC.opsMemoryType = kernelMemoryType
                     , GenericC.opsWriteScalar = GenericC.writeScalarPointerWithQuals pointerQuals
                     , GenericC.opsReadScalar = GenericC.readScalarPointerWithQuals pointerQuals
                     , GenericC.opsAllocate = cannotAllocate
                     , GenericC.opsDeallocate = cannotDeallocate
                     , GenericC.opsCopy = copyInKernel
                     , GenericC.opsStaticArray = noStaticArrays
                     , GenericC.opsFatMemory = False
                     }
  where kernelOps :: GenericC.OpCompiler KernelOp UsedFunctions
        kernelOps (GetGroupId v i) =
          GenericC.stm [C.cstm|$id:v = get_group_id($int:i);|]
        kernelOps (GetLocalId v i) =
          GenericC.stm [C.cstm|$id:v = get_local_id($int:i);|]
        kernelOps (GetLocalSize v i) =
          GenericC.stm [C.cstm|$id:v = get_local_size($int:i);|]
        kernelOps (GetGlobalId v i) =
          GenericC.stm [C.cstm|$id:v = get_global_id($int:i);|]
        kernelOps (GetGlobalSize v i) =
          GenericC.stm [C.cstm|$id:v = get_global_size($int:i);|]
        kernelOps (GetLockstepWidth v) =
          GenericC.stm [C.cstm|$id:v = LOCKSTEP_WIDTH;|]
        kernelOps Barrier =
          GenericC.stm [C.cstm|barrier(CLK_LOCAL_MEM_FENCE);|]
        kernelOps MemFence =
          GenericC.stm [C.cstm|mem_fence(CLK_GLOBAL_MEM_FENCE);|]
        kernelOps (Atomic aop) = atomicOps aop

        atomicOps (AtomicAdd old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_add((volatile __global int *)&$id:arr[$exp:ind'], $exp:val');|]

        atomicOps (AtomicSMax old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_max((volatile __global int *)&$id:arr[$exp:ind'], $exp:val');|]

        atomicOps (AtomicSMin old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_min((volatile __global int *)&$id:arr[$exp:ind'], $exp:val');|]

        atomicOps (AtomicUMax old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_max((volatile __global unsigned int *)&$id:arr[$exp:ind'], (unsigned int)$exp:val');|]

        atomicOps (AtomicUMin old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_min((volatile __global unsigned int *)&$id:arr[$exp:ind'], (unsigned int)$exp:val');|]

        atomicOps (AtomicAnd old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_and((volatile __global unsigned int *)&$id:arr[$exp:ind'], (unsigned int)$exp:val');|]

        atomicOps (AtomicOr old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_or((volatile __global unsigned int *)&$id:arr[$exp:ind'], (unsigned int)$exp:val');|]

        atomicOps (AtomicXor old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_xor((volatile __global unsigned int *)&$id:arr[$exp:ind'], (unsigned int)$exp:val');|]

        atomicOps (AtomicCmpXchg old arr ind cmp val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          cmp' <- GenericC.compileExp cmp
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_cmpxchg((volatile __global int *)&$id:arr[$exp:ind'], $exp:cmp', $exp:val');|]

        atomicOps (AtomicXchg old arr ind val) = do
          ind' <- GenericC.compileExp $ innerExp ind
          val' <- GenericC.compileExp val
          GenericC.stm [C.cstm|$id:old = atomic_xchg((volatile __global int *)&$id:arr[$exp:ind'], $exp:val');|]

        cannotAllocate :: GenericC.Allocate KernelOp UsedFunctions
        cannotAllocate _ =
          fail "Cannot allocate memory in kernel"

        cannotDeallocate :: GenericC.Deallocate KernelOp UsedFunctions
        cannotDeallocate _ _ =
          fail "Cannot deallocate memory in kernel"

        copyInKernel :: GenericC.Copy KernelOp UsedFunctions
        copyInKernel _ _ _ _ _ _ _ =
          fail "Cannot bulk copy in kernel."

        noStaticArrays :: GenericC.StaticArray KernelOp UsedFunctions
        noStaticArrays _ _ _ _ =
          fail "Cannot create static array in kernel."

        kernelMemoryType space = do
          quals <- pointerQuals space
          return [C.cty|$tyquals:quals $ty:defaultMemBlockType|]

--- Checking requirements

useToArg :: KernelUse -> Maybe KernelArg
useToArg (MemoryUse mem)  = Just $ MemKArg mem
useToArg (ScalarUse v bt) = Just $ ValueKArg (LeafExp (ScalarVar v) bt) bt
useToArg ConstUse{}       = Nothing

typesInKernel :: CallKernel -> S.Set PrimType
typesInKernel (Map kernel) = typesInCode $ mapKernelBody kernel
typesInKernel (AnyKernel kernel) = typesInCode $ kernelBody kernel

typesInCode :: ImpKernels.KernelCode -> S.Set PrimType
typesInCode Skip = mempty
typesInCode (c1 :>>: c2) = typesInCode c1 <> typesInCode c2
typesInCode (For _ it e c) = IntType it `S.insert` typesInExp e <> typesInCode c
typesInCode (While e c) = typesInExp e <> typesInCode c
typesInCode DeclareMem{} = mempty
typesInCode (DeclareScalar _ t) = S.singleton t
typesInCode (DeclareArray _ _ t _) = S.singleton t
typesInCode (Allocate _ (Count e) _) = typesInExp e
typesInCode Free{} = mempty
typesInCode (Copy _ (Count e1) _ _ (Count e2) _ (Count e3)) =
  typesInExp e1 <> typesInExp e2 <> typesInExp e3
typesInCode (Write _ (Count e1) t _ _ e2) =
  typesInExp e1 <> S.singleton t <> typesInExp e2
typesInCode (SetScalar _ e) = typesInExp e
typesInCode SetMem{} = mempty
typesInCode (Call _ _ es) = mconcat $ map typesInArg es
  where typesInArg MemArg{} = mempty
        typesInArg (ExpArg e) = typesInExp e
typesInCode (If e c1 c2) =
  typesInExp e <> typesInCode c1 <> typesInCode c2
typesInCode (Assert e _ _) = typesInExp e
typesInCode (Comment _ c) = typesInCode c
typesInCode (DebugPrint _ _ e) = typesInExp e
typesInCode Op{} = mempty

typesInExp :: Exp -> S.Set PrimType
typesInExp (ValueExp v) = S.singleton $ primValueType v
typesInExp (BinOpExp _ e1 e2) = typesInExp e1 <> typesInExp e2
typesInExp (CmpOpExp _ e1 e2) = typesInExp e1 <> typesInExp e2
typesInExp (ConvOpExp op e) = S.fromList [from, to] <> typesInExp e
  where (from, to) = convOpType op
typesInExp (UnOpExp _ e) = typesInExp e
typesInExp (FunExp _ args t) = S.singleton t <> mconcat (map typesInExp args)
typesInExp (LeafExp (Index _ (Count e) t _ _) _) = S.singleton t <> typesInExp e
typesInExp (LeafExp ScalarVar{} _) = mempty
typesInExp (LeafExp (SizeOf t) _) = S.singleton t