futhark-0.19.5: src/Futhark/CodeGen/ImpGen/Kernels/Base.hs
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE TypeFamilies #-}
module Futhark.CodeGen.ImpGen.Kernels.Base
( KernelConstants (..),
keyWithEntryPoint,
CallKernelGen,
InKernelGen,
Locks (..),
HostEnv (..),
Target (..),
KernelEnv (..),
computeThreadChunkSize,
groupReduce,
groupScan,
isActive,
sKernelThread,
sKernelGroup,
sReplicate,
sIota,
sCopy,
compileThreadResult,
compileGroupResult,
virtualiseGroups,
groupLoop,
kernelLoop,
groupCoverSpace,
precomputeSegOpIDs,
atomicUpdateLocking,
AtomicBinOp,
Locking (..),
AtomicUpdate (..),
DoAtomicUpdate,
)
where
import Control.Monad.Except
import Data.List (elemIndex, find, zip4)
import qualified Data.Map.Strict as M
import Data.Maybe
import qualified Data.Set as S
import qualified Futhark.CodeGen.ImpCode.Kernels as Imp
import Futhark.CodeGen.ImpGen
import Futhark.Error
import Futhark.IR.KernelsMem
import qualified Futhark.IR.Mem.IxFun as IxFun
import Futhark.MonadFreshNames
import Futhark.Transform.Rename
import Futhark.Util (chunks, dropLast, mapAccumLM, maybeNth, nubOrd, takeLast)
import Futhark.Util.IntegralExp (divUp, quot, rem)
import Prelude hiding (quot, rem)
-- | Which target are we ultimately generating code for? While most
-- of the kernels code is the same, there are some cases where we
-- generate special code based on the ultimate low-level API we are
-- targeting.
data Target = CUDA | OpenCL
-- | Information about the locks available for accumulators.
data Locks = Locks
{ locksArray :: VName,
locksCount :: Int
}
data HostEnv = HostEnv
{ hostAtomics :: AtomicBinOp,
hostTarget :: Target,
hostLocks :: M.Map VName Locks
}
data KernelEnv = KernelEnv
{ kernelAtomics :: AtomicBinOp,
kernelConstants :: KernelConstants,
kernelLocks :: M.Map VName Locks
}
type CallKernelGen = ImpM KernelsMem HostEnv Imp.HostOp
type InKernelGen = ImpM KernelsMem KernelEnv Imp.KernelOp
data KernelConstants = KernelConstants
{ kernelGlobalThreadId :: Imp.TExp Int32,
kernelLocalThreadId :: Imp.TExp Int32,
kernelGroupId :: Imp.TExp Int32,
kernelGlobalThreadIdVar :: VName,
kernelLocalThreadIdVar :: VName,
kernelGroupIdVar :: VName,
kernelNumGroups :: Imp.TExp Int64,
kernelGroupSize :: Imp.TExp Int64,
kernelNumThreads :: Imp.TExp Int32,
kernelWaveSize :: Imp.TExp Int32,
kernelThreadActive :: Imp.TExp Bool,
-- | A mapping from dimensions of nested SegOps to already
-- computed local thread IDs.
kernelLocalIdMap :: M.Map [SubExp] [Imp.TExp Int32]
}
segOpSizes :: Stms KernelsMem -> S.Set [SubExp]
segOpSizes = onStms
where
onStms = foldMap (onExp . stmExp)
onExp (Op (Inner (SegOp op))) =
S.singleton $ map snd $ unSegSpace $ segSpace op
onExp (If _ tbranch fbranch _) =
onStms (bodyStms tbranch) <> onStms (bodyStms fbranch)
onExp (DoLoop _ _ _ body) =
onStms (bodyStms body)
onExp _ = mempty
precomputeSegOpIDs :: Stms KernelsMem -> InKernelGen a -> InKernelGen a
precomputeSegOpIDs stms m = do
ltid <- kernelLocalThreadId . kernelConstants <$> askEnv
new_ids <- M.fromList <$> mapM (mkMap ltid) (S.toList (segOpSizes stms))
let f env =
env
{ kernelConstants =
(kernelConstants env) {kernelLocalIdMap = new_ids}
}
localEnv f m
where
mkMap ltid dims = do
let dims' = map (sExt32 . toInt64Exp) dims
ids' <- mapM (dPrimVE "ltid_pre") $ unflattenIndex dims' ltid
return (dims, ids')
keyWithEntryPoint :: Maybe Name -> Name -> Name
keyWithEntryPoint fname key =
nameFromString $ maybe "" ((++ ".") . nameToString) fname ++ nameToString key
allocLocal :: AllocCompiler KernelsMem r Imp.KernelOp
allocLocal mem size =
sOp $ Imp.LocalAlloc mem size
kernelAlloc ::
Pattern KernelsMem ->
SubExp ->
Space ->
InKernelGen ()
kernelAlloc (Pattern _ [_]) _ ScalarSpace {} =
-- Handled by the declaration of the memory block, which is then
-- translated to an actual scalar variable during C code generation.
return ()
kernelAlloc (Pattern _ [mem]) size (Space "local") =
allocLocal (patElemName mem) $ Imp.bytes $ toInt64Exp size
kernelAlloc (Pattern _ [mem]) _ _ =
compilerLimitationS $ "Cannot allocate memory block " ++ pretty mem ++ " in kernel."
kernelAlloc dest _ _ =
error $ "Invalid target for in-kernel allocation: " ++ show dest
splitSpace ::
(ToExp w, ToExp i, ToExp elems_per_thread) =>
Pattern KernelsMem ->
SplitOrdering ->
w ->
i ->
elems_per_thread ->
ImpM lore r op ()
splitSpace (Pattern [] [size]) o w i elems_per_thread = do
num_elements <- Imp.elements . TPrimExp <$> toExp w
let i' = toInt64Exp i
elems_per_thread' <- Imp.elements . TPrimExp <$> toExp elems_per_thread
computeThreadChunkSize o i' elems_per_thread' num_elements (mkTV (patElemName size) int64)
splitSpace pat _ _ _ _ =
error $ "Invalid target for splitSpace: " ++ pretty pat
updateAcc :: VName -> [SubExp] -> [SubExp] -> InKernelGen ()
updateAcc acc is vs = sComment "UpdateAcc" $ do
-- See the ImpGen implementation of UpdateAcc for general notes.
let is' = map toInt64Exp is
(c, space, arrs, dims, op) <- lookupAcc acc is'
sWhen (inBounds (map DimFix is') dims) $
case op of
Nothing ->
forM_ (zip arrs vs) $ \(arr, v) -> copyDWIMFix arr is' v []
Just lam -> do
dLParams $ lambdaParams lam
let (_x_params, y_params) =
splitAt (length vs) $ map paramName $ lambdaParams lam
forM_ (zip y_params vs) $ \(yp, v) -> copyDWIM yp [] v []
atomics <- kernelAtomics <$> askEnv
case atomicUpdateLocking atomics lam of
AtomicPrim f -> f space arrs is'
AtomicCAS f -> f space arrs is'
AtomicLocking f -> do
c_locks <- M.lookup c . kernelLocks <$> askEnv
case c_locks of
Just (Locks locks num_locks) -> do
let locking =
Locking locks 0 1 0 $
pure . (`rem` fromIntegral num_locks) . flattenIndex dims
f locking space arrs is'
Nothing ->
error $ "Missing locks for " ++ pretty acc
compileThreadExp :: ExpCompiler KernelsMem KernelEnv Imp.KernelOp
compileThreadExp (Pattern _ [dest]) (BasicOp (ArrayLit es _)) =
forM_ (zip [0 ..] es) $ \(i, e) ->
copyDWIMFix (patElemName dest) [fromIntegral (i :: Int64)] e []
compileThreadExp _ (BasicOp (UpdateAcc acc is vs)) =
updateAcc acc is vs
compileThreadExp dest e =
defCompileExp dest e
-- | Assign iterations of a for-loop to all threads in the kernel.
-- The passed-in function is invoked with the (symbolic) iteration.
-- 'threadOperations' will be in effect in the body. For
-- multidimensional loops, use 'groupCoverSpace'.
kernelLoop ::
IntExp t =>
Imp.TExp t ->
Imp.TExp t ->
Imp.TExp t ->
(Imp.TExp t -> InKernelGen ()) ->
InKernelGen ()
kernelLoop tid num_threads n f =
localOps threadOperations $
if n == num_threads
then f tid
else do
-- Compute how many elements this thread is responsible for.
-- Formula: (n - tid) / num_threads (rounded up).
let elems_for_this = (n - tid) `divUp` num_threads
sFor "i" elems_for_this $ \i -> f $ i * num_threads + tid
-- | Assign iterations of a for-loop to threads in the workgroup. The
-- passed-in function is invoked with the (symbolic) iteration. For
-- multidimensional loops, use 'groupCoverSpace'.
groupLoop ::
Imp.TExp Int64 ->
(Imp.TExp Int64 -> InKernelGen ()) ->
InKernelGen ()
groupLoop n f = do
constants <- kernelConstants <$> askEnv
kernelLoop
(sExt64 $ kernelLocalThreadId constants)
(kernelGroupSize constants)
n
f
-- | Iterate collectively though a multidimensional space, such that
-- all threads in the group participate. The passed-in function is
-- invoked with a (symbolic) point in the index space.
groupCoverSpace ::
[Imp.TExp Int64] ->
([Imp.TExp Int64] -> InKernelGen ()) ->
InKernelGen ()
groupCoverSpace ds f =
groupLoop (product ds) $ f . unflattenIndex ds
compileGroupExp :: ExpCompiler KernelsMem KernelEnv Imp.KernelOp
-- The static arrays stuff does not work inside kernels.
compileGroupExp (Pattern _ [dest]) (BasicOp (ArrayLit es _)) =
forM_ (zip [0 ..] es) $ \(i, e) ->
copyDWIMFix (patElemName dest) [fromIntegral (i :: Int64)] e []
compileGroupExp _ (BasicOp (UpdateAcc acc is vs)) =
updateAcc acc is vs
compileGroupExp (Pattern _ [dest]) (BasicOp (Replicate ds se)) = do
let ds' = map toInt64Exp $ shapeDims ds
groupCoverSpace ds' $ \is ->
copyDWIMFix (patElemName dest) is se (drop (shapeRank ds) is)
sOp $ Imp.Barrier Imp.FenceLocal
compileGroupExp (Pattern _ [dest]) (BasicOp (Iota n e s it)) = do
n' <- toExp n
e' <- toExp e
s' <- toExp s
groupLoop (TPrimExp n') $ \i' -> do
x <-
dPrimV "x" $
TPrimExp $
BinOpExp (Add it OverflowUndef) e' $
BinOpExp (Mul it OverflowUndef) (untyped i') s'
copyDWIMFix (patElemName dest) [i'] (Var (tvVar x)) []
sOp $ Imp.Barrier Imp.FenceLocal
-- When generating code for a scalar in-place update, we must make
-- sure that only one thread performs the write. When writing an
-- array, the group-level copy code will take care of doing the right
-- thing.
compileGroupExp (Pattern _ [pe]) (BasicOp (Update _ slice se))
| null $ sliceDims slice = do
sOp $ Imp.Barrier Imp.FenceLocal
ltid <- kernelLocalThreadId . kernelConstants <$> askEnv
sWhen (ltid .==. 0) $
copyDWIM (patElemName pe) (map (fmap toInt64Exp) slice) se []
sOp $ Imp.Barrier Imp.FenceLocal
compileGroupExp dest e =
defCompileExp dest e
sanityCheckLevel :: SegLevel -> InKernelGen ()
sanityCheckLevel SegThread {} = return ()
sanityCheckLevel SegGroup {} =
error "compileGroupOp: unexpected group-level SegOp."
localThreadIDs :: [SubExp] -> InKernelGen [Imp.TExp Int64]
localThreadIDs dims = do
ltid <- sExt64 . kernelLocalThreadId . kernelConstants <$> askEnv
let dims' = map toInt64Exp dims
maybe (unflattenIndex dims' ltid) (map sExt64)
. M.lookup dims
. kernelLocalIdMap
. kernelConstants
<$> askEnv
compileGroupSpace :: SegLevel -> SegSpace -> InKernelGen ()
compileGroupSpace lvl space = do
sanityCheckLevel lvl
let (ltids, dims) = unzip $ unSegSpace space
zipWithM_ dPrimV_ ltids =<< localThreadIDs dims
ltid <- kernelLocalThreadId . kernelConstants <$> askEnv
dPrimV_ (segFlat space) ltid
-- Construct the necessary lock arrays for an intra-group histogram.
prepareIntraGroupSegHist ::
Count GroupSize SubExp ->
[HistOp KernelsMem] ->
InKernelGen [[Imp.TExp Int64] -> InKernelGen ()]
prepareIntraGroupSegHist group_size =
fmap snd . mapAccumLM onOp Nothing
where
onOp l op = do
constants <- kernelConstants <$> askEnv
atomicBinOp <- kernelAtomics <$> askEnv
let local_subhistos = histDest op
case (l, atomicUpdateLocking atomicBinOp $ histOp op) of
(_, AtomicPrim f) -> return (l, f (Space "local") local_subhistos)
(_, AtomicCAS f) -> return (l, f (Space "local") local_subhistos)
(Just l', AtomicLocking f) -> return (l, f l' (Space "local") local_subhistos)
(Nothing, AtomicLocking f) -> do
locks <- newVName "locks"
let num_locks = toInt64Exp $ unCount group_size
dims = map toInt64Exp $ shapeDims (histShape op) ++ [histWidth op]
l' = Locking locks 0 1 0 (pure . (`rem` num_locks) . flattenIndex dims)
locks_t = Array int32 (Shape [unCount group_size]) NoUniqueness
locks_mem <- sAlloc "locks_mem" (typeSize locks_t) $ Space "local"
dArray locks int32 (arrayShape locks_t) $
ArrayIn locks_mem $
IxFun.iota $
map pe64 $ arrayDims locks_t
sComment "All locks start out unlocked" $
groupCoverSpace [kernelGroupSize constants] $ \is ->
copyDWIMFix locks is (intConst Int32 0) []
return (Just l', f l' (Space "local") local_subhistos)
whenActive :: SegLevel -> SegSpace -> InKernelGen () -> InKernelGen ()
whenActive lvl space m
| SegNoVirtFull <- segVirt lvl = m
| otherwise = do
group_size <- kernelGroupSize . kernelConstants <$> askEnv
-- XXX: the following check is too naive - we should also handle
-- the multi-dimensional case.
if [group_size] == map (toInt64Exp . snd) (unSegSpace space)
then m
else sWhen (isActive $ unSegSpace space) m
compileGroupOp :: OpCompiler KernelsMem KernelEnv Imp.KernelOp
compileGroupOp pat (Alloc size space) =
kernelAlloc pat size space
compileGroupOp pat (Inner (SizeOp (SplitSpace o w i elems_per_thread))) =
splitSpace pat o w i elems_per_thread
compileGroupOp pat (Inner (SegOp (SegMap lvl space _ body))) = do
void $ compileGroupSpace lvl space
whenActive lvl space $
localOps threadOperations $
compileStms mempty (kernelBodyStms body) $
zipWithM_ (compileThreadResult space) (patternElements pat) $
kernelBodyResult body
sOp $ Imp.ErrorSync Imp.FenceLocal
compileGroupOp pat (Inner (SegOp (SegScan lvl space scans _ body))) = do
compileGroupSpace lvl space
let (ltids, dims) = unzip $ unSegSpace space
dims' = map toInt64Exp dims
whenActive lvl space $
compileStms mempty (kernelBodyStms body) $
forM_ (zip (patternNames pat) $ kernelBodyResult body) $ \(dest, res) ->
copyDWIMFix
dest
(map Imp.vi64 ltids)
(kernelResultSubExp res)
[]
sOp $ Imp.ErrorSync Imp.FenceLocal
let segment_size = last dims'
crossesSegment from to =
(sExt64 to - sExt64 from) .>. (sExt64 to `rem` segment_size)
-- groupScan needs to treat the scan output as a one-dimensional
-- array of scan elements, so we invent some new flattened arrays
-- here. XXX: this assumes that the original index function is just
-- row-major, but does not actually verify it.
dims_flat <- dPrimV "dims_flat" $ product dims'
let flattened pe = do
MemLocation mem _ _ <-
entryArrayLocation <$> lookupArray (patElemName pe)
let pe_t = typeOf pe
arr_dims = Var (tvVar dims_flat) : drop (length dims') (arrayDims pe_t)
sArray
(baseString (patElemName pe) ++ "_flat")
(elemType pe_t)
(Shape arr_dims)
$ ArrayIn mem $ IxFun.iota $ map pe64 arr_dims
num_scan_results = sum $ map (length . segBinOpNeutral) scans
arrs_flat <- mapM flattened $ take num_scan_results $ patternElements pat
forM_ scans $ \scan -> do
let scan_op = segBinOpLambda scan
groupScan (Just crossesSegment) (product dims') (product dims') scan_op arrs_flat
compileGroupOp pat (Inner (SegOp (SegRed lvl space ops _ body))) = do
compileGroupSpace lvl space
let (ltids, dims) = unzip $ unSegSpace space
(red_pes, map_pes) =
splitAt (segBinOpResults ops) $ patternElements pat
dims' = map toInt64Exp dims
mkTempArr t =
sAllocArray "red_arr" (elemType t) (Shape dims <> arrayShape t) $ Space "local"
tmp_arrs <- mapM mkTempArr $ concatMap (lambdaReturnType . segBinOpLambda) ops
let tmps_for_ops = chunks (map (length . segBinOpNeutral) ops) tmp_arrs
whenActive lvl space $
compileStms mempty (kernelBodyStms body) $ do
let (red_res, map_res) =
splitAt (segBinOpResults ops) $ kernelBodyResult body
forM_ (zip tmp_arrs red_res) $ \(dest, res) ->
copyDWIMFix dest (map Imp.vi64 ltids) (kernelResultSubExp res) []
zipWithM_ (compileThreadResult space) map_pes map_res
sOp $ Imp.ErrorSync Imp.FenceLocal
case dims' of
-- Nonsegmented case (or rather, a single segment) - this we can
-- handle directly with a group-level reduction.
[dim'] -> do
forM_ (zip ops tmps_for_ops) $ \(op, tmps) ->
groupReduce (sExt32 dim') (segBinOpLambda op) tmps
sOp $ Imp.ErrorSync Imp.FenceLocal
forM_ (zip red_pes tmp_arrs) $ \(pe, arr) ->
copyDWIMFix (patElemName pe) [] (Var arr) [0]
_ -> do
-- Segmented intra-group reductions are turned into (regular)
-- segmented scans. It is possible that this can be done
-- better, but at least this approach is simple.
-- groupScan operates on flattened arrays. This does not
-- involve copying anything; merely playing with the index
-- function.
dims_flat <- dPrimV "dims_flat" $ product dims'
let flatten arr = do
ArrayEntry arr_loc pt <- lookupArray arr
let flat_shape =
Shape $
Var (tvVar dims_flat) :
drop (length ltids) (memLocationShape arr_loc)
sArray "red_arr_flat" pt flat_shape $
ArrayIn (memLocationName arr_loc) $
IxFun.iota $ map pe64 $ shapeDims flat_shape
let segment_size = last dims'
crossesSegment from to =
(sExt64 to - sExt64 from) .>. (sExt64 to `rem` sExt64 segment_size)
forM_ (zip ops tmps_for_ops) $ \(op, tmps) -> do
tmps_flat <- mapM flatten tmps
groupScan
(Just crossesSegment)
(product dims')
(product dims')
(segBinOpLambda op)
tmps_flat
sOp $ Imp.ErrorSync Imp.FenceLocal
forM_ (zip red_pes tmp_arrs) $ \(pe, arr) ->
copyDWIM
(patElemName pe)
[]
(Var arr)
(map (unitSlice 0) (init dims') ++ [DimFix $ last dims' -1])
sOp $ Imp.Barrier Imp.FenceLocal
compileGroupOp pat (Inner (SegOp (SegHist lvl space ops _ kbody))) = do
compileGroupSpace lvl space
let ltids = map fst $ unSegSpace space
-- We don't need the red_pes, because it is guaranteed by our type
-- rules that they occupy the same memory as the destinations for
-- the ops.
let num_red_res = length ops + sum (map (length . histNeutral) ops)
(_red_pes, map_pes) =
splitAt num_red_res $ patternElements pat
ops' <- prepareIntraGroupSegHist (segGroupSize lvl) ops
-- Ensure that all locks have been initialised.
sOp $ Imp.Barrier Imp.FenceLocal
whenActive lvl space $
compileStms mempty (kernelBodyStms kbody) $ do
let (red_res, map_res) = splitAt num_red_res $ kernelBodyResult kbody
(red_is, red_vs) = splitAt (length ops) $ map kernelResultSubExp red_res
zipWithM_ (compileThreadResult space) map_pes map_res
let vs_per_op = chunks (map (length . histDest) ops) red_vs
forM_ (zip4 red_is vs_per_op ops' ops) $
\(bin, op_vs, do_op, HistOp dest_w _ _ _ shape lam) -> do
let bin' = toInt64Exp bin
dest_w' = toInt64Exp dest_w
bin_in_bounds = 0 .<=. bin' .&&. bin' .<. dest_w'
bin_is = map Imp.vi64 (init ltids) ++ [bin']
vs_params = takeLast (length op_vs) $ lambdaParams lam
sComment "perform atomic updates" $
sWhen bin_in_bounds $ do
dLParams $ lambdaParams lam
sLoopNest shape $ \is -> do
forM_ (zip vs_params op_vs) $ \(p, v) ->
copyDWIMFix (paramName p) [] v is
do_op (bin_is ++ is)
sOp $ Imp.ErrorSync Imp.FenceLocal
compileGroupOp pat _ =
compilerBugS $ "compileGroupOp: cannot compile rhs of binding " ++ pretty pat
compileThreadOp :: OpCompiler KernelsMem KernelEnv Imp.KernelOp
compileThreadOp pat (Alloc size space) =
kernelAlloc pat size space
compileThreadOp pat (Inner (SizeOp (SplitSpace o w i elems_per_thread))) =
splitSpace pat o w i elems_per_thread
compileThreadOp pat _ =
compilerBugS $ "compileThreadOp: cannot compile rhs of binding " ++ pretty pat
-- | Locking strategy used for an atomic update.
data Locking = Locking
{ -- | Array containing the lock.
lockingArray :: VName,
-- | Value for us to consider the lock free.
lockingIsUnlocked :: Imp.TExp Int32,
-- | What to write when we lock it.
lockingToLock :: Imp.TExp Int32,
-- | What to write when we unlock it.
lockingToUnlock :: Imp.TExp Int32,
-- | A transformation from the logical lock index to the
-- physical position in the array. This can also be used
-- to make the lock array smaller.
lockingMapping :: [Imp.TExp Int64] -> [Imp.TExp Int64]
}
-- | A function for generating code for an atomic update. Assumes
-- that the bucket is in-bounds.
type DoAtomicUpdate lore r =
Space -> [VName] -> [Imp.TExp Int64] -> ImpM lore r Imp.KernelOp ()
-- | The mechanism that will be used for performing the atomic update.
-- Approximates how efficient it will be. Ordered from most to least
-- efficient.
data AtomicUpdate lore r
= -- | Supported directly by primitive.
AtomicPrim (DoAtomicUpdate lore r)
| -- | Can be done by efficient swaps.
AtomicCAS (DoAtomicUpdate lore r)
| -- | Requires explicit locking.
AtomicLocking (Locking -> DoAtomicUpdate lore r)
-- | Is there an atomic t'BinOp' corresponding to this t'BinOp'?
type AtomicBinOp =
BinOp ->
Maybe (VName -> VName -> Count Imp.Elements (Imp.TExp Int64) -> Imp.Exp -> Imp.AtomicOp)
-- | Do an atomic update corresponding to a binary operator lambda.
atomicUpdateLocking ::
AtomicBinOp ->
Lambda KernelsMem ->
AtomicUpdate KernelsMem KernelEnv
atomicUpdateLocking atomicBinOp lam
| Just ops_and_ts <- splitOp lam,
all (\(_, t, _, _) -> primBitSize t `elem` [32, 64]) ops_and_ts =
primOrCas ops_and_ts $ \space arrs bucket ->
-- If the operator is a vectorised binary operator on 32/64-bit
-- values, we can use a particularly efficient
-- implementation. If the operator has an atomic implementation
-- we use that, otherwise it is still a binary operator which
-- can be implemented by atomic compare-and-swap if 32/64 bits.
forM_ (zip arrs ops_and_ts) $ \(a, (op, t, x, y)) -> do
-- Common variables.
old <- dPrim "old" t
(arr', _a_space, bucket_offset) <- fullyIndexArray a bucket
case opHasAtomicSupport space (tvVar old) arr' bucket_offset op of
Just f -> sOp $ f $ Imp.var y t
Nothing ->
atomicUpdateCAS space t a (tvVar old) bucket x $
x <~~ Imp.BinOpExp op (Imp.var x t) (Imp.var y t)
where
opHasAtomicSupport space old arr' bucket' bop = do
let atomic f = Imp.Atomic space . f old arr' bucket'
atomic <$> atomicBinOp bop
primOrCas ops
| all isPrim ops = AtomicPrim
| otherwise = AtomicCAS
isPrim (op, _, _, _) = isJust $ atomicBinOp op
-- If the operator functions purely on single 32/64-bit values, we can
-- use an implementation based on CAS, no matter what the operator
-- does.
atomicUpdateLocking _ op
| [Prim t] <- lambdaReturnType op,
[xp, _] <- lambdaParams op,
primBitSize t `elem` [32, 64] = AtomicCAS $ \space [arr] bucket -> do
old <- dPrim "old" t
atomicUpdateCAS space t arr (tvVar old) bucket (paramName xp) $
compileBody' [xp] $ lambdaBody op
atomicUpdateLocking _ op = AtomicLocking $ \locking space arrs bucket -> do
old <- dPrim "old" int32
continue <- dPrimVol "continue" Bool true
-- Correctly index into locks.
(locks', _locks_space, locks_offset) <-
fullyIndexArray (lockingArray locking) $ lockingMapping locking bucket
-- Critical section
let try_acquire_lock =
sOp $
Imp.Atomic space $
Imp.AtomicCmpXchg
int32
(tvVar old)
locks'
locks_offset
(untyped $ lockingIsUnlocked locking)
(untyped $ lockingToLock locking)
lock_acquired = tvExp old .==. lockingIsUnlocked locking
-- Even the releasing is done with an atomic rather than a
-- simple write, for memory coherency reasons.
release_lock =
sOp $
Imp.Atomic space $
Imp.AtomicCmpXchg
int32
(tvVar old)
locks'
locks_offset
(untyped $ lockingToLock locking)
(untyped $ lockingToUnlock locking)
break_loop = continue <-- false
-- Preparing parameters. It is assumed that the caller has already
-- filled the arr_params. We copy the current value to the
-- accumulator parameters.
--
-- Note the use of 'everythingVolatile' when reading and writing the
-- buckets. This was necessary to ensure correct execution on a
-- newer NVIDIA GPU (RTX 2080). The 'volatile' modifiers likely
-- make the writes pass through the (SM-local) L1 cache, which is
-- necessary here, because we are really doing device-wide
-- synchronisation without atomics (naughty!).
let (acc_params, _arr_params) = splitAt (length arrs) $ lambdaParams op
bind_acc_params =
everythingVolatile $
sComment "bind lhs" $
forM_ (zip acc_params arrs) $ \(acc_p, arr) ->
copyDWIMFix (paramName acc_p) [] (Var arr) bucket
let op_body =
sComment "execute operation" $
compileBody' acc_params $ lambdaBody op
do_hist =
everythingVolatile $
sComment "update global result" $
zipWithM_ (writeArray bucket) arrs $ map (Var . paramName) acc_params
fence = case space of
Space "local" -> sOp $ Imp.MemFence Imp.FenceLocal
_ -> sOp $ Imp.MemFence Imp.FenceGlobal
-- While-loop: Try to insert your value
sWhile (tvExp continue) $ do
try_acquire_lock
sWhen lock_acquired $ do
dLParams acc_params
bind_acc_params
op_body
do_hist
fence
release_lock
break_loop
fence
where
writeArray bucket arr val = copyDWIMFix arr bucket val []
atomicUpdateCAS ::
Space ->
PrimType ->
VName ->
VName ->
[Imp.TExp Int64] ->
VName ->
InKernelGen () ->
InKernelGen ()
atomicUpdateCAS space t arr old bucket x do_op = do
-- Code generation target:
--
-- old = d_his[idx];
-- do {
-- assumed = old;
-- x = do_op(assumed, y);
-- old = atomicCAS(&d_his[idx], assumed, tmp);
-- } while(assumed != old);
assumed <- tvVar <$> dPrim "assumed" t
run_loop <- dPrimV "run_loop" true
-- XXX: CUDA may generate really bad code if this is not a volatile
-- read. Unclear why. The later reads are volatile, so maybe
-- that's it.
everythingVolatile $ copyDWIMFix old [] (Var arr) bucket
(arr', _a_space, bucket_offset) <- fullyIndexArray arr bucket
-- While-loop: Try to insert your value
let (toBits, fromBits) =
case t of
FloatType Float32 ->
( \v -> Imp.FunExp "to_bits32" [v] int32,
\v -> Imp.FunExp "from_bits32" [v] t
)
FloatType Float64 ->
( \v -> Imp.FunExp "to_bits64" [v] int64,
\v -> Imp.FunExp "from_bits64" [v] t
)
_ -> (id, id)
int
| primBitSize t == 32 = int32
| otherwise = int64
sWhile (tvExp run_loop) $ do
assumed <~~ Imp.var old t
x <~~ Imp.var assumed t
do_op
old_bits_v <- newVName "old_bits"
dPrim_ old_bits_v int
let old_bits = Imp.var old_bits_v int
sOp $
Imp.Atomic space $
Imp.AtomicCmpXchg
int
old_bits_v
arr'
bucket_offset
(toBits (Imp.var assumed t))
(toBits (Imp.var x t))
old <~~ fromBits old_bits
let won = CmpOpExp (CmpEq int) (toBits (Imp.var assumed t)) old_bits
sWhen (isBool won) (run_loop <-- false)
-- | Horizontally fission a lambda that models a binary operator.
splitOp :: ASTLore lore => Lambda lore -> Maybe [(BinOp, PrimType, VName, VName)]
splitOp lam = mapM splitStm $ bodyResult $ lambdaBody lam
where
n = length $ lambdaReturnType lam
splitStm (Var res) = do
Let (Pattern [] [pe]) _ (BasicOp (BinOp op (Var x) (Var y))) <-
find (([res] ==) . patternNames . stmPattern) $
stmsToList $ bodyStms $ lambdaBody lam
i <- Var res `elemIndex` bodyResult (lambdaBody lam)
xp <- maybeNth i $ lambdaParams lam
yp <- maybeNth (n + i) $ lambdaParams lam
guard $ paramName xp == x
guard $ paramName yp == y
Prim t <- Just $ patElemType pe
return (op, t, paramName xp, paramName yp)
splitStm _ = Nothing
computeKernelUses ::
FreeIn a =>
a ->
[VName] ->
CallKernelGen [Imp.KernelUse]
computeKernelUses kernel_body bound_in_kernel = do
let actually_free = freeIn kernel_body `namesSubtract` namesFromList bound_in_kernel
-- Compute the variables that we need to pass to the kernel.
nubOrd <$> readsFromSet actually_free
readsFromSet :: Names -> CallKernelGen [Imp.KernelUse]
readsFromSet free =
fmap catMaybes $
forM (namesToList free) $ \var -> do
t <- lookupType var
vtable <- getVTable
case t of
Array {} -> return Nothing
Acc {} -> return Nothing
Mem (Space "local") -> return Nothing
Mem {} -> return $ Just $ Imp.MemoryUse var
Prim bt ->
isConstExp vtable (Imp.var var bt) >>= \case
Just ce -> return $ Just $ Imp.ConstUse var ce
Nothing -> return $ Just $ Imp.ScalarUse var bt
isConstExp ::
VTable KernelsMem ->
Imp.Exp ->
ImpM lore r op (Maybe Imp.KernelConstExp)
isConstExp vtable size = do
fname <- askFunction
let onLeaf (Imp.ScalarVar name) _ = lookupConstExp name
onLeaf Imp.Index {} _ = Nothing
lookupConstExp name =
constExp =<< hasExp =<< M.lookup name vtable
constExp (Op (Inner (SizeOp (GetSize key _)))) =
Just $ LeafExp (Imp.SizeConst $ keyWithEntryPoint fname key) int32
constExp e = primExpFromExp lookupConstExp e
return $ replaceInPrimExpM onLeaf size
where
hasExp (ArrayVar e _) = e
hasExp (AccVar e _) = e
hasExp (ScalarVar e _) = e
hasExp (MemVar e _) = e
computeThreadChunkSize ::
SplitOrdering ->
Imp.TExp Int64 ->
Imp.Count Imp.Elements (Imp.TExp Int64) ->
Imp.Count Imp.Elements (Imp.TExp Int64) ->
TV Int64 ->
ImpM lore r op ()
computeThreadChunkSize (SplitStrided stride) thread_index elements_per_thread num_elements chunk_var =
chunk_var
<-- sMin64
(Imp.unCount elements_per_thread)
((Imp.unCount num_elements - thread_index) `divUp` toInt64Exp stride)
computeThreadChunkSize SplitContiguous thread_index elements_per_thread num_elements chunk_var = do
starting_point <-
dPrimV "starting_point" $
thread_index * Imp.unCount elements_per_thread
remaining_elements <-
dPrimV "remaining_elements" $
Imp.unCount num_elements - tvExp starting_point
let no_remaining_elements = tvExp remaining_elements .<=. 0
beyond_bounds = Imp.unCount num_elements .<=. tvExp starting_point
sIf
(no_remaining_elements .||. beyond_bounds)
(chunk_var <-- 0)
( sIf
is_last_thread
(chunk_var <-- Imp.unCount last_thread_elements)
(chunk_var <-- Imp.unCount elements_per_thread)
)
where
last_thread_elements =
num_elements - Imp.elements thread_index * elements_per_thread
is_last_thread =
Imp.unCount num_elements
.<. (thread_index + 1) * Imp.unCount elements_per_thread
kernelInitialisationSimple ::
Count NumGroups (Imp.TExp Int64) ->
Count GroupSize (Imp.TExp Int64) ->
CallKernelGen (KernelConstants, InKernelGen ())
kernelInitialisationSimple (Count num_groups) (Count group_size) = do
global_tid <- newVName "global_tid"
local_tid <- newVName "local_tid"
group_id <- newVName "group_tid"
wave_size <- newVName "wave_size"
inner_group_size <- newVName "group_size"
let constants =
KernelConstants
(Imp.vi32 global_tid)
(Imp.vi32 local_tid)
(Imp.vi32 group_id)
global_tid
local_tid
group_id
num_groups
group_size
(sExt32 (group_size * num_groups))
(Imp.vi32 wave_size)
true
mempty
let set_constants = do
dPrim_ global_tid int32
dPrim_ local_tid int32
dPrim_ inner_group_size int64
dPrim_ wave_size int32
dPrim_ group_id int32
sOp (Imp.GetGlobalId global_tid 0)
sOp (Imp.GetLocalId local_tid 0)
sOp (Imp.GetLocalSize inner_group_size 0)
sOp (Imp.GetLockstepWidth wave_size)
sOp (Imp.GetGroupId group_id 0)
return (constants, set_constants)
isActive :: [(VName, SubExp)] -> Imp.TExp Bool
isActive limit = case actives of
[] -> true
x : xs -> foldl (.&&.) x xs
where
(is, ws) = unzip limit
actives = zipWith active is $ map toInt64Exp ws
active i = (Imp.vi64 i .<.)
-- | Change every memory block to be in the global address space,
-- except those who are in the local memory space. This only affects
-- generated code - we still need to make sure that the memory is
-- actually present on the device (and dared as variables in the
-- kernel).
makeAllMemoryGlobal :: CallKernelGen a -> CallKernelGen a
makeAllMemoryGlobal =
localDefaultSpace (Imp.Space "global") . localVTable (M.map globalMemory)
where
globalMemory (MemVar _ entry)
| entryMemSpace entry /= Space "local" =
MemVar Nothing entry {entryMemSpace = Imp.Space "global"}
globalMemory entry =
entry
groupReduce ::
Imp.TExp Int32 ->
Lambda KernelsMem ->
[VName] ->
InKernelGen ()
groupReduce w lam arrs = do
offset <- dPrim "offset" int32
groupReduceWithOffset offset w lam arrs
groupReduceWithOffset ::
TV Int32 ->
Imp.TExp Int32 ->
Lambda KernelsMem ->
[VName] ->
InKernelGen ()
groupReduceWithOffset offset w lam arrs = do
constants <- kernelConstants <$> askEnv
let local_tid = kernelLocalThreadId constants
global_tid = kernelGlobalThreadId constants
barrier
| all primType $ lambdaReturnType lam = sOp $ Imp.Barrier Imp.FenceLocal
| otherwise = sOp $ Imp.Barrier Imp.FenceGlobal
readReduceArgument param arr
| Prim _ <- paramType param = do
let i = local_tid + tvExp offset
copyDWIMFix (paramName param) [] (Var arr) [sExt64 i]
| otherwise = do
let i = global_tid + tvExp offset
copyDWIMFix (paramName param) [] (Var arr) [sExt64 i]
writeReduceOpResult param arr
| Prim _ <- paramType param =
copyDWIMFix arr [sExt64 local_tid] (Var $ paramName param) []
| otherwise =
return ()
let (reduce_acc_params, reduce_arr_params) = splitAt (length arrs) $ lambdaParams lam
skip_waves <- dPrimV "skip_waves" (1 :: Imp.TExp Int32)
dLParams $ lambdaParams lam
offset <-- (0 :: Imp.TExp Int32)
comment "participating threads read initial accumulator" $
sWhen (local_tid .<. w) $
zipWithM_ readReduceArgument reduce_acc_params arrs
let do_reduce = do
comment "read array element" $
zipWithM_ readReduceArgument reduce_arr_params arrs
comment "apply reduction operation" $
compileBody' reduce_acc_params $ lambdaBody lam
comment "write result of operation" $
zipWithM_ writeReduceOpResult reduce_acc_params arrs
in_wave_reduce = everythingVolatile do_reduce
wave_size = kernelWaveSize constants
group_size = kernelGroupSize constants
wave_id = local_tid `quot` wave_size
in_wave_id = local_tid - wave_id * wave_size
num_waves = (sExt32 group_size + wave_size - 1) `quot` wave_size
arg_in_bounds = local_tid + tvExp offset .<. w
doing_in_wave_reductions =
tvExp offset .<. wave_size
apply_in_in_wave_iteration =
(in_wave_id .&. (2 * tvExp offset - 1)) .==. 0
in_wave_reductions = do
offset <-- (1 :: Imp.TExp Int32)
sWhile doing_in_wave_reductions $ do
sWhen
(arg_in_bounds .&&. apply_in_in_wave_iteration)
in_wave_reduce
offset <-- tvExp offset * 2
doing_cross_wave_reductions =
tvExp skip_waves .<. num_waves
is_first_thread_in_wave =
in_wave_id .==. 0
wave_not_skipped =
(wave_id .&. (2 * tvExp skip_waves - 1)) .==. 0
apply_in_cross_wave_iteration =
arg_in_bounds .&&. is_first_thread_in_wave .&&. wave_not_skipped
cross_wave_reductions =
sWhile doing_cross_wave_reductions $ do
barrier
offset <-- tvExp skip_waves * wave_size
sWhen
apply_in_cross_wave_iteration
do_reduce
skip_waves <-- tvExp skip_waves * 2
in_wave_reductions
cross_wave_reductions
groupScan ::
Maybe (Imp.TExp Int32 -> Imp.TExp Int32 -> Imp.TExp Bool) ->
Imp.TExp Int64 ->
Imp.TExp Int64 ->
Lambda KernelsMem ->
[VName] ->
InKernelGen ()
groupScan seg_flag arrs_full_size w lam arrs = do
constants <- kernelConstants <$> askEnv
renamed_lam <- renameLambda lam
let ltid32 = kernelLocalThreadId constants
ltid = sExt64 ltid32
(x_params, y_params) = splitAt (length arrs) $ lambdaParams lam
dLParams (lambdaParams lam ++ lambdaParams renamed_lam)
ltid_in_bounds <- dPrimVE "ltid_in_bounds" $ ltid .<. w
-- The scan works by splitting the group into blocks, which are
-- scanned separately. Typically, these blocks are smaller than
-- the lockstep width, which enables barrier-free execution inside
-- them.
--
-- We hardcode the block size here. The only requirement is that
-- it should not be less than the square root of the group size.
-- With 32, we will work on groups of size 1024 or smaller, which
-- fits every device Troels has seen. Still, it would be nicer if
-- it were a runtime parameter. Some day.
let block_size = 32
simd_width = kernelWaveSize constants
block_id = ltid32 `quot` block_size
in_block_id = ltid32 - block_id * block_size
doInBlockScan seg_flag' active =
inBlockScan
constants
seg_flag'
arrs_full_size
simd_width
block_size
active
arrs
barrier
array_scan = not $ all primType $ lambdaReturnType lam
barrier
| array_scan =
sOp $ Imp.Barrier Imp.FenceGlobal
| otherwise =
sOp $ Imp.Barrier Imp.FenceLocal
group_offset = sExt64 (kernelGroupId constants) * kernelGroupSize constants
writeBlockResult p arr
| primType $ paramType p =
copyDWIM arr [DimFix $ sExt64 block_id] (Var $ paramName p) []
| otherwise =
copyDWIM arr [DimFix $ group_offset + sExt64 block_id] (Var $ paramName p) []
readPrevBlockResult p arr
| primType $ paramType p =
copyDWIM (paramName p) [] (Var arr) [DimFix $ sExt64 block_id - 1]
| otherwise =
copyDWIM (paramName p) [] (Var arr) [DimFix $ group_offset + sExt64 block_id - 1]
doInBlockScan seg_flag ltid_in_bounds lam
barrier
let is_first_block = block_id .==. 0
when array_scan $ do
sComment "save correct values for first block" $
sWhen is_first_block $
forM_ (zip x_params arrs) $ \(x, arr) ->
unless (primType $ paramType x) $
copyDWIM arr [DimFix $ arrs_full_size + group_offset + sExt64 block_size + ltid] (Var $ paramName x) []
barrier
let last_in_block = in_block_id .==. block_size - 1
sComment "last thread of block 'i' writes its result to offset 'i'" $
sWhen (last_in_block .&&. ltid_in_bounds) $
everythingVolatile $
zipWithM_ writeBlockResult x_params arrs
barrier
let first_block_seg_flag = do
flag_true <- seg_flag
Just $ \from to ->
flag_true (from * block_size + block_size -1) (to * block_size + block_size -1)
comment
"scan the first block, after which offset 'i' contains carry-in for block 'i+1'"
$ doInBlockScan first_block_seg_flag (is_first_block .&&. ltid_in_bounds) renamed_lam
barrier
when array_scan $ do
sComment "move correct values for first block back a block" $
sWhen is_first_block $
forM_ (zip x_params arrs) $ \(x, arr) ->
unless (primType $ paramType x) $
copyDWIM
arr
[DimFix $ arrs_full_size + group_offset + ltid]
(Var arr)
[DimFix $ arrs_full_size + group_offset + sExt64 block_size + ltid]
barrier
let read_carry_in = do
forM_ (zip x_params y_params) $ \(x, y) ->
copyDWIM (paramName y) [] (Var (paramName x)) []
zipWithM_ readPrevBlockResult x_params arrs
y_to_x = forM_ (zip x_params y_params) $ \(x, y) ->
when (primType (paramType x)) $
copyDWIM (paramName x) [] (Var (paramName y)) []
op_to_x
| Nothing <- seg_flag =
compileBody' x_params $ lambdaBody lam
| Just flag_true <- seg_flag = do
inactive <-
dPrimVE "inactive" $ flag_true (block_id * block_size -1) ltid32
sWhen inactive y_to_x
when array_scan barrier
sUnless inactive $ compileBody' x_params $ lambdaBody lam
write_final_result =
forM_ (zip x_params arrs) $ \(p, arr) ->
when (primType $ paramType p) $
copyDWIM arr [DimFix ltid] (Var $ paramName p) []
sComment "carry-in for every block except the first" $
sUnless (is_first_block .||. bNot ltid_in_bounds) $ do
sComment "read operands" read_carry_in
sComment "perform operation" op_to_x
sComment "write final result" write_final_result
barrier
sComment "restore correct values for first block" $
sWhen is_first_block $
forM_ (zip3 x_params y_params arrs) $ \(x, y, arr) ->
if primType (paramType y)
then copyDWIM arr [DimFix ltid] (Var $ paramName y) []
else copyDWIM (paramName x) [] (Var arr) [DimFix $ arrs_full_size + group_offset + ltid]
barrier
inBlockScan ::
KernelConstants ->
Maybe (Imp.TExp Int32 -> Imp.TExp Int32 -> Imp.TExp Bool) ->
Imp.TExp Int64 ->
Imp.TExp Int32 ->
Imp.TExp Int32 ->
Imp.TExp Bool ->
[VName] ->
InKernelGen () ->
Lambda KernelsMem ->
InKernelGen ()
inBlockScan constants seg_flag arrs_full_size lockstep_width block_size active arrs barrier scan_lam = everythingVolatile $ do
skip_threads <- dPrim "skip_threads" int32
let in_block_thread_active =
tvExp skip_threads .<=. in_block_id
actual_params = lambdaParams scan_lam
(x_params, y_params) =
splitAt (length actual_params `div` 2) actual_params
y_to_x =
forM_ (zip x_params y_params) $ \(x, y) ->
when (primType (paramType x)) $
copyDWIM (paramName x) [] (Var (paramName y)) []
-- Set initial y values
sComment "read input for in-block scan" $
sWhen active $ do
zipWithM_ readInitial y_params arrs
-- Since the final result is expected to be in x_params, we may
-- need to copy it there for the first thread in the block.
sWhen (in_block_id .==. 0) y_to_x
when array_scan barrier
let op_to_x
| Nothing <- seg_flag =
compileBody' x_params $ lambdaBody scan_lam
| Just flag_true <- seg_flag = do
inactive <-
dPrimVE "inactive" $
flag_true (ltid32 - tvExp skip_threads) ltid32
sWhen inactive y_to_x
when array_scan barrier
sUnless inactive $ compileBody' x_params $ lambdaBody scan_lam
maybeBarrier =
sWhen
(lockstep_width .<=. tvExp skip_threads)
barrier
sComment "in-block scan (hopefully no barriers needed)" $ do
skip_threads <-- 1
sWhile (tvExp skip_threads .<. block_size) $ do
sWhen (in_block_thread_active .&&. active) $ do
sComment "read operands" $
zipWithM_ (readParam (sExt64 $ tvExp skip_threads)) x_params arrs
sComment "perform operation" op_to_x
maybeBarrier
sWhen (in_block_thread_active .&&. active) $
sComment "write result" $
sequence_ $ zipWith3 writeResult x_params y_params arrs
maybeBarrier
skip_threads <-- tvExp skip_threads * 2
where
block_id = ltid32 `quot` block_size
in_block_id = ltid32 - block_id * block_size
ltid32 = kernelLocalThreadId constants
ltid = sExt64 ltid32
gtid = sExt64 $ kernelGlobalThreadId constants
array_scan = not $ all primType $ lambdaReturnType scan_lam
readInitial p arr
| primType $ paramType p =
copyDWIM (paramName p) [] (Var arr) [DimFix ltid]
| otherwise =
copyDWIM (paramName p) [] (Var arr) [DimFix gtid]
readParam behind p arr
| primType $ paramType p =
copyDWIM (paramName p) [] (Var arr) [DimFix $ ltid - behind]
| otherwise =
copyDWIM (paramName p) [] (Var arr) [DimFix $ gtid - behind + arrs_full_size]
writeResult x y arr
| primType $ paramType x = do
copyDWIM arr [DimFix ltid] (Var $ paramName x) []
copyDWIM (paramName y) [] (Var $ paramName x) []
| otherwise =
copyDWIM (paramName y) [] (Var $ paramName x) []
computeMapKernelGroups :: Imp.TExp Int64 -> CallKernelGen (Imp.TExp Int64, Imp.TExp Int64)
computeMapKernelGroups kernel_size = do
group_size <- dPrim "group_size" int64
fname <- askFunction
let group_size_key = keyWithEntryPoint fname $ nameFromString $ pretty $ tvVar group_size
sOp $ Imp.GetSize (tvVar group_size) group_size_key Imp.SizeGroup
num_groups <- dPrimV "num_groups" $ kernel_size `divUp` tvExp group_size
return (tvExp num_groups, tvExp group_size)
simpleKernelConstants ::
Imp.TExp Int64 ->
String ->
CallKernelGen (KernelConstants, InKernelGen ())
simpleKernelConstants kernel_size desc = do
thread_gtid <- newVName $ desc ++ "_gtid"
thread_ltid <- newVName $ desc ++ "_ltid"
group_id <- newVName $ desc ++ "_gid"
(num_groups, group_size) <- computeMapKernelGroups kernel_size
let set_constants = do
dPrim_ thread_gtid int32
dPrim_ thread_ltid int32
dPrim_ group_id int32
sOp (Imp.GetGlobalId thread_gtid 0)
sOp (Imp.GetLocalId thread_ltid 0)
sOp (Imp.GetGroupId group_id 0)
return
( KernelConstants
(Imp.vi32 thread_gtid)
(Imp.vi32 thread_ltid)
(Imp.vi32 group_id)
thread_gtid
thread_ltid
group_id
num_groups
group_size
(sExt32 (group_size * num_groups))
0
(Imp.vi64 thread_gtid .<. kernel_size)
mempty,
set_constants
)
-- | For many kernels, we may not have enough physical groups to cover
-- the logical iteration space. Some groups thus have to perform
-- double duty; we put an outer loop to accomplish this. The
-- advantage over just launching a bazillion threads is that the cost
-- of memory expansion should be proportional to the number of
-- *physical* threads (hardware parallelism), not the amount of
-- application parallelism.
virtualiseGroups ::
SegVirt ->
Imp.TExp Int32 ->
(Imp.TExp Int32 -> InKernelGen ()) ->
InKernelGen ()
virtualiseGroups SegVirt required_groups m = do
constants <- kernelConstants <$> askEnv
phys_group_id <- dPrim "phys_group_id" int32
sOp $ Imp.GetGroupId (tvVar phys_group_id) 0
let iterations =
(required_groups - tvExp phys_group_id)
`divUp` sExt32 (kernelNumGroups constants)
sFor "i" iterations $ \i -> do
m . tvExp
=<< dPrimV
"virt_group_id"
(tvExp phys_group_id + i * sExt32 (kernelNumGroups constants))
-- Make sure the virtual group is actually done before we let
-- another virtual group have its way with it.
sOp $ Imp.Barrier Imp.FenceGlobal
virtualiseGroups _ _ m = do
gid <- kernelGroupIdVar . kernelConstants <$> askEnv
m $ Imp.vi32 gid
sKernelThread ::
String ->
Count NumGroups (Imp.TExp Int64) ->
Count GroupSize (Imp.TExp Int64) ->
VName ->
InKernelGen () ->
CallKernelGen ()
sKernelThread = sKernel threadOperations kernelGlobalThreadId
sKernelGroup ::
String ->
Count NumGroups (Imp.TExp Int64) ->
Count GroupSize (Imp.TExp Int64) ->
VName ->
InKernelGen () ->
CallKernelGen ()
sKernelGroup = sKernel groupOperations kernelGroupId
sKernelFailureTolerant ::
Bool ->
Operations KernelsMem KernelEnv Imp.KernelOp ->
KernelConstants ->
Name ->
InKernelGen () ->
CallKernelGen ()
sKernelFailureTolerant tol ops constants name m = do
HostEnv atomics _ locks <- askEnv
body <- makeAllMemoryGlobal $ subImpM_ (KernelEnv atomics constants locks) ops m
uses <- computeKernelUses body mempty
emit $
Imp.Op $
Imp.CallKernel
Imp.Kernel
{ Imp.kernelBody = body,
Imp.kernelUses = uses,
Imp.kernelNumGroups = [untyped $ kernelNumGroups constants],
Imp.kernelGroupSize = [untyped $ kernelGroupSize constants],
Imp.kernelName = name,
Imp.kernelFailureTolerant = tol
}
sKernel ::
Operations KernelsMem KernelEnv Imp.KernelOp ->
(KernelConstants -> Imp.TExp Int32) ->
String ->
Count NumGroups (Imp.TExp Int64) ->
Count GroupSize (Imp.TExp Int64) ->
VName ->
InKernelGen () ->
CallKernelGen ()
sKernel ops flatf name num_groups group_size v f = do
(constants, set_constants) <- kernelInitialisationSimple num_groups group_size
name' <- nameForFun $ name ++ "_" ++ show (baseTag v)
sKernelFailureTolerant False ops constants name' $ do
set_constants
dPrimV_ v $ flatf constants
f
copyInGroup :: CopyCompiler KernelsMem KernelEnv Imp.KernelOp
copyInGroup pt destloc destslice srcloc srcslice = do
dest_space <- entryMemSpace <$> lookupMemory (memLocationName destloc)
src_space <- entryMemSpace <$> lookupMemory (memLocationName srcloc)
case (dest_space, src_space) of
(ScalarSpace destds _, ScalarSpace srcds _) -> do
let destslice' =
replicate (length destslice - length destds) (DimFix 0)
++ takeLast (length destds) destslice
srcslice' =
replicate (length srcslice - length srcds) (DimFix 0)
++ takeLast (length srcds) srcslice
copyElementWise pt destloc destslice' srcloc srcslice'
_ -> do
groupCoverSpace (sliceDims destslice) $ \is ->
copyElementWise
pt
destloc
(map DimFix $ fixSlice destslice is)
srcloc
(map DimFix $ fixSlice srcslice is)
sOp $ Imp.Barrier Imp.FenceLocal
threadOperations, groupOperations :: Operations KernelsMem KernelEnv Imp.KernelOp
threadOperations =
(defaultOperations compileThreadOp)
{ opsCopyCompiler = copyElementWise,
opsExpCompiler = compileThreadExp,
opsStmsCompiler = \_ -> defCompileStms mempty,
opsAllocCompilers =
M.fromList [(Space "local", allocLocal)]
}
groupOperations =
(defaultOperations compileGroupOp)
{ opsCopyCompiler = copyInGroup,
opsExpCompiler = compileGroupExp,
opsStmsCompiler = \_ -> defCompileStms mempty,
opsAllocCompilers =
M.fromList [(Space "local", allocLocal)]
}
-- | Perform a Replicate with a kernel.
sReplicateKernel :: VName -> SubExp -> CallKernelGen ()
sReplicateKernel arr se = do
t <- subExpType se
ds <- dropLast (arrayRank t) . arrayDims <$> lookupType arr
let dims = map toInt64Exp $ ds ++ arrayDims t
(constants, set_constants) <-
simpleKernelConstants (product $ map sExt64 dims) "replicate"
fname <- askFunction
let name =
keyWithEntryPoint fname $
nameFromString $
"replicate_" ++ show (baseTag $ kernelGlobalThreadIdVar constants)
is' = unflattenIndex dims $ sExt64 $ kernelGlobalThreadId constants
sKernelFailureTolerant True threadOperations constants name $ do
set_constants
sWhen (kernelThreadActive constants) $
copyDWIMFix arr is' se $ drop (length ds) is'
replicateName :: PrimType -> String
replicateName bt = "replicate_" ++ pretty bt
replicateForType :: PrimType -> CallKernelGen Name
replicateForType bt = do
let fname = nameFromString $ "builtin#" <> replicateName bt
exists <- hasFunction fname
unless exists $ do
mem <- newVName "mem"
num_elems <- newVName "num_elems"
val <- newVName "val"
let params =
[ Imp.MemParam mem (Space "device"),
Imp.ScalarParam num_elems int32,
Imp.ScalarParam val bt
]
shape = Shape [Var num_elems]
function fname [] params $ do
arr <-
sArray "arr" bt shape $
ArrayIn mem $
IxFun.iota $
map pe64 $ shapeDims shape
sReplicateKernel arr $ Var val
return fname
replicateIsFill :: VName -> SubExp -> CallKernelGen (Maybe (CallKernelGen ()))
replicateIsFill arr v = do
ArrayEntry (MemLocation arr_mem arr_shape arr_ixfun) _ <- lookupArray arr
v_t <- subExpType v
case v_t of
Prim v_t'
| IxFun.isLinear arr_ixfun -> return $
Just $ do
fname <- replicateForType v_t'
emit $
Imp.Call
[]
fname
[ Imp.MemArg arr_mem,
Imp.ExpArg $ untyped $ product $ map toInt64Exp arr_shape,
Imp.ExpArg $ toExp' v_t' v
]
_ -> return Nothing
-- | Perform a Replicate with a kernel.
sReplicate :: VName -> SubExp -> CallKernelGen ()
sReplicate arr se = do
-- If the replicate is of a particularly common and simple form
-- (morally a memset()/fill), then we use a common function.
is_fill <- replicateIsFill arr se
case is_fill of
Just m -> m
Nothing -> sReplicateKernel arr se
-- | Perform an Iota with a kernel.
sIotaKernel ::
VName ->
Imp.TExp Int64 ->
Imp.Exp ->
Imp.Exp ->
IntType ->
CallKernelGen ()
sIotaKernel arr n x s et = do
destloc <- entryArrayLocation <$> lookupArray arr
(constants, set_constants) <- simpleKernelConstants n "iota"
fname <- askFunction
let name =
keyWithEntryPoint fname $
nameFromString $
"iota_" ++ pretty et ++ "_"
++ show (baseTag $ kernelGlobalThreadIdVar constants)
sKernelFailureTolerant True threadOperations constants name $ do
set_constants
let gtid = sExt64 $ kernelGlobalThreadId constants
sWhen (kernelThreadActive constants) $ do
(destmem, destspace, destidx) <- fullyIndexArray' destloc [gtid]
emit $
Imp.Write destmem destidx (IntType et) destspace Imp.Nonvolatile $
BinOpExp
(Add et OverflowWrap)
(BinOpExp (Mul et OverflowWrap) (Imp.sExt et $ untyped gtid) s)
x
iotaName :: IntType -> String
iotaName bt = "iota_" ++ pretty bt
iotaForType :: IntType -> CallKernelGen Name
iotaForType bt = do
let fname = nameFromString $ "builtin#" <> iotaName bt
exists <- hasFunction fname
unless exists $ do
mem <- newVName "mem"
n <- newVName "n"
x <- newVName "x"
s <- newVName "s"
let params =
[ Imp.MemParam mem (Space "device"),
Imp.ScalarParam n int32,
Imp.ScalarParam x $ IntType bt,
Imp.ScalarParam s $ IntType bt
]
shape = Shape [Var n]
n' = Imp.vi64 n
x' = Imp.var x $ IntType bt
s' = Imp.var s $ IntType bt
function fname [] params $ do
arr <-
sArray "arr" (IntType bt) shape $
ArrayIn mem $
IxFun.iota $
map pe64 $ shapeDims shape
sIotaKernel arr (sExt64 n') x' s' bt
return fname
-- | Perform an Iota with a kernel.
sIota ::
VName ->
Imp.TExp Int64 ->
Imp.Exp ->
Imp.Exp ->
IntType ->
CallKernelGen ()
sIota arr n x s et = do
ArrayEntry (MemLocation arr_mem _ arr_ixfun) _ <- lookupArray arr
if IxFun.isLinear arr_ixfun
then do
fname <- iotaForType et
emit $
Imp.Call
[]
fname
[Imp.MemArg arr_mem, Imp.ExpArg $ untyped n, Imp.ExpArg x, Imp.ExpArg s]
else sIotaKernel arr n x s et
sCopy :: CopyCompiler KernelsMem HostEnv Imp.HostOp
sCopy
bt
destloc@(MemLocation destmem _ _)
destslice
srcloc@(MemLocation srcmem _ _)
srcslice =
do
-- Note that the shape of the destination and the source are
-- necessarily the same.
let shape = sliceDims srcslice
kernel_size = product shape
(constants, set_constants) <- simpleKernelConstants kernel_size "copy"
fname <- askFunction
let name =
keyWithEntryPoint fname $
nameFromString $
"copy_" ++ show (baseTag $ kernelGlobalThreadIdVar constants)
sKernelFailureTolerant True threadOperations constants name $ do
set_constants
let gtid = sExt64 $ kernelGlobalThreadId constants
dest_is = unflattenIndex shape gtid
src_is = dest_is
(_, destspace, destidx) <-
fullyIndexArray' destloc $ fixSlice destslice dest_is
(_, srcspace, srcidx) <-
fullyIndexArray' srcloc $ fixSlice srcslice src_is
sWhen (gtid .<. kernel_size) $
emit $
Imp.Write destmem destidx bt destspace Imp.Nonvolatile $
Imp.index srcmem srcidx bt srcspace Imp.Nonvolatile
compileGroupResult ::
SegSpace ->
PatElem KernelsMem ->
KernelResult ->
InKernelGen ()
compileGroupResult _ pe (TileReturns [(w, per_group_elems)] what) = do
n <- toInt64Exp . arraySize 0 <$> lookupType what
constants <- kernelConstants <$> askEnv
let ltid = sExt64 $ kernelLocalThreadId constants
offset =
toInt64Exp per_group_elems
* sExt64 (kernelGroupId constants)
-- Avoid loop for the common case where each thread is statically
-- known to write at most one element.
localOps threadOperations $
if toInt64Exp per_group_elems == kernelGroupSize constants
then
sWhen (ltid + offset .<. toInt64Exp w) $
copyDWIMFix (patElemName pe) [ltid + offset] (Var what) [ltid]
else sFor "i" (n `divUp` kernelGroupSize constants) $ \i -> do
j <- dPrimVE "j" $ kernelGroupSize constants * i + ltid
sWhen (j + offset .<. toInt64Exp w) $
copyDWIMFix (patElemName pe) [j + offset] (Var what) [j]
compileGroupResult space pe (TileReturns dims what) = do
let gids = map fst $ unSegSpace space
out_tile_sizes = map (toInt64Exp . snd) dims
group_is = zipWith (*) (map Imp.vi64 gids) out_tile_sizes
local_is <- localThreadIDs $ map snd dims
is_for_thread <-
mapM (dPrimV "thread_out_index") $
zipWith (+) group_is local_is
localOps threadOperations $
sWhen (isActive $ zip (map tvVar is_for_thread) $ map fst dims) $
copyDWIMFix (patElemName pe) (map tvExp is_for_thread) (Var what) local_is
compileGroupResult space pe (RegTileReturns dims_n_tiles what) = do
constants <- kernelConstants <$> askEnv
let gids = map fst $ unSegSpace space
(dims, group_tiles, reg_tiles) = unzip3 dims_n_tiles
group_tiles' = map toInt64Exp group_tiles
reg_tiles' = map toInt64Exp reg_tiles
-- Which group tile is this group responsible for?
let group_tile_is = map Imp.vi64 gids
-- Within the group tile, which register tile is this thread
-- responsible for?
reg_tile_is <-
mapM (dPrimVE "reg_tile_i") $
unflattenIndex group_tiles' $ sExt64 $ kernelLocalThreadId constants
-- Compute output array slice for the register tile belonging to
-- this thread.
let regTileSliceDim (group_tile, group_tile_i) (reg_tile, reg_tile_i) = do
tile_dim_start <-
dPrimVE "tile_dim_start" $
reg_tile * (group_tile * group_tile_i + reg_tile_i)
return $ DimSlice tile_dim_start reg_tile 1
reg_tile_slices <-
zipWithM
regTileSliceDim
(zip group_tiles' group_tile_is)
(zip reg_tiles' reg_tile_is)
localOps threadOperations $
sLoopNest (Shape reg_tiles) $ \is_in_reg_tile -> do
let dest_is = fixSlice reg_tile_slices is_in_reg_tile
src_is = reg_tile_is ++ is_in_reg_tile
sWhen (foldl1 (.&&.) $ zipWith (.<.) dest_is $ map toInt64Exp dims) $
copyDWIMFix (patElemName pe) dest_is (Var what) src_is
compileGroupResult space pe (Returns _ what) = do
constants <- kernelConstants <$> askEnv
in_local_memory <- arrayInLocalMemory what
let gids = map (Imp.vi64 . fst) $ unSegSpace space
if not in_local_memory
then
localOps threadOperations $
sWhen (kernelLocalThreadId constants .==. 0) $
copyDWIMFix (patElemName pe) gids what []
else -- If the result of the group is an array in local memory, we
-- store it by collective copying among all the threads of the
-- group. TODO: also do this if the array is in global memory
-- (but this is a bit more tricky, synchronisation-wise).
copyDWIMFix (patElemName pe) gids what []
compileGroupResult _ _ WriteReturns {} =
compilerLimitationS "compileGroupResult: WriteReturns not handled yet."
compileGroupResult _ _ ConcatReturns {} =
compilerLimitationS "compileGroupResult: ConcatReturns not handled yet."
compileThreadResult ::
SegSpace ->
PatElem KernelsMem ->
KernelResult ->
InKernelGen ()
compileThreadResult _ _ RegTileReturns {} =
compilerLimitationS "compileThreadResult: RegTileReturns not yet handled."
compileThreadResult space pe (Returns _ what) = do
let is = map (Imp.vi64 . fst) $ unSegSpace space
copyDWIMFix (patElemName pe) is what []
compileThreadResult _ pe (ConcatReturns SplitContiguous _ per_thread_elems what) = do
constants <- kernelConstants <$> askEnv
let offset =
toInt64Exp per_thread_elems
* sExt64 (kernelGlobalThreadId constants)
n <- toInt64Exp . arraySize 0 <$> lookupType what
copyDWIM (patElemName pe) [DimSlice offset n 1] (Var what) []
compileThreadResult _ pe (ConcatReturns (SplitStrided stride) _ _ what) = do
offset <- sExt64 . kernelGlobalThreadId . kernelConstants <$> askEnv
n <- toInt64Exp . arraySize 0 <$> lookupType what
copyDWIM (patElemName pe) [DimSlice offset n $ toInt64Exp stride] (Var what) []
compileThreadResult _ pe (WriteReturns (Shape rws) _arr dests) = do
constants <- kernelConstants <$> askEnv
let rws' = map toInt64Exp rws
forM_ dests $ \(slice, e) -> do
let slice' = map (fmap toInt64Exp) slice
condInBounds (DimFix i) rw =
0 .<=. i .&&. i .<. rw
condInBounds (DimSlice i n s) rw =
0 .<=. i .&&. i + n * s .<. rw
write =
foldl (.&&.) (kernelThreadActive constants) $
zipWith condInBounds slice' rws'
sWhen write $ copyDWIM (patElemName pe) slice' e []
compileThreadResult _ _ TileReturns {} =
compilerBugS "compileThreadResult: TileReturns unhandled."
arrayInLocalMemory :: SubExp -> InKernelGen Bool
arrayInLocalMemory (Var name) = do
res <- lookupVar name
case res of
ArrayVar _ entry ->
(Space "local" ==) . entryMemSpace
<$> lookupMemory (memLocationName (entryArrayLocation entry))
_ -> return False
arrayInLocalMemory Constant {} = return False