futhark-0.25.3: src/Futhark/CodeGen/ImpGen/GPU/SegScan/SinglePass.hs
{-# LANGUAGE TypeFamilies #-}
-- | Code generation for segmented and non-segmented scans. Uses a
-- fast single-pass algorithm, but which only works on NVIDIA GPUs and
-- with some constraints on the operator. We use this when we can.
module Futhark.CodeGen.ImpGen.GPU.SegScan.SinglePass (compileSegScan) where
import Control.Monad
import Data.List (zip4)
import Data.Maybe
import Futhark.CodeGen.ImpCode.GPU qualified as Imp
import Futhark.CodeGen.ImpGen
import Futhark.CodeGen.ImpGen.GPU.Base
import Futhark.IR.GPUMem
import Futhark.IR.Mem.LMAD qualified as LMAD
import Futhark.Transform.Rename
import Futhark.Util (mapAccumLM, takeLast)
import Futhark.Util.IntegralExp (IntegralExp (mod, rem), divUp, quot)
import Prelude hiding (mod, quot, rem)
xParams, yParams :: SegBinOp GPUMem -> [LParam GPUMem]
xParams scan =
take (length (segBinOpNeutral scan)) (lambdaParams (segBinOpLambda scan))
yParams scan =
drop (length (segBinOpNeutral scan)) (lambdaParams (segBinOpLambda scan))
alignTo :: (IntegralExp a) => a -> a -> a
alignTo x a = (x `divUp` a) * a
createLocalArrays ::
Count GroupSize SubExp ->
SubExp ->
[PrimType] ->
InKernelGen (VName, [VName], [VName], VName, [VName])
createLocalArrays (Count groupSize) m types = do
let groupSizeE = pe64 groupSize
workSize = pe64 m * groupSizeE
prefixArraysSize =
foldl (\acc tySize -> alignTo acc tySize + tySize * groupSizeE) 0 $
map primByteSize types
maxTransposedArraySize =
foldl1 sMax64 $ map (\ty -> workSize * primByteSize ty) types
warpSize :: (Num a) => a
warpSize = 32
maxWarpExchangeSize =
foldl (\acc tySize -> alignTo acc tySize + tySize * fromInteger warpSize) 0 $
map primByteSize types
maxLookbackSize = maxWarpExchangeSize + warpSize
size = Imp.bytes $ maxLookbackSize `sMax64` prefixArraysSize `sMax64` maxTransposedArraySize
(_, byteOffsets) <-
mapAccumLM
( \off tySize -> do
off' <- dPrimVE "byte_offsets" $ alignTo off tySize + pe64 groupSize * tySize
pure (off', off)
)
0
$ map primByteSize types
(_, warpByteOffsets) <-
mapAccumLM
( \off tySize -> do
off' <- dPrimVE "warp_byte_offset" $ alignTo off tySize + warpSize * tySize
pure (off', off)
)
warpSize
$ map primByteSize types
sComment "Allocate reused shared memeory" $ pure ()
localMem <- sAlloc "local_mem" size (Space "local")
transposeArrayLength <- dPrimV "trans_arr_len" workSize
sharedId <- sArrayInMem "shared_id" int32 (Shape [constant (1 :: Int32)]) localMem
transposedArrays <-
forM types $ \ty ->
sArrayInMem
"local_transpose_arr"
ty
(Shape [tvSize transposeArrayLength])
localMem
prefixArrays <-
forM (zip byteOffsets types) $ \(off, ty) -> do
let off' = off `quot` primByteSize ty
sArray
"local_prefix_arr"
ty
(Shape [groupSize])
localMem
$ LMAD.iota off' [pe64 groupSize]
warpscan <- sArrayInMem "warpscan" int8 (Shape [constant (warpSize :: Int64)]) localMem
warpExchanges <-
forM (zip warpByteOffsets types) $ \(off, ty) -> do
let off' = off `quot` primByteSize ty
sArray
"warp_exchange"
ty
(Shape [constant (warpSize :: Int64)])
localMem
$ LMAD.iota off' [warpSize]
pure (sharedId, transposedArrays, prefixArrays, warpscan, warpExchanges)
inBlockScanLookback ::
KernelConstants ->
Imp.TExp Int64 ->
VName ->
[VName] ->
Lambda GPUMem ->
InKernelGen ()
inBlockScanLookback constants arrs_full_size flag_arr arrs scan_lam = everythingVolatile $ do
flg_x <- dPrim "flg_x" p_int8
flg_y <- dPrim "flg_y" p_int8
let flg_param_x = Param mempty (tvVar flg_x) (MemPrim p_int8)
flg_param_y = Param mempty (tvVar flg_y) (MemPrim p_int8)
flg_y_exp = tvExp flg_y
statusP = (2 :: Imp.TExp Int8)
statusX = (0 :: Imp.TExp Int8)
dLParams (lambdaParams scan_lam)
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)) []
y_to_x_flg =
copyDWIM (tvVar flg_x) [] (Var (tvVar flg_y)) []
-- Set initial y values
sComment "read input for in-block scan" $ do
zipWithM_ readInitial (flg_param_y : y_params) (flag_arr : 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) $ do
y_to_x
y_to_x_flg
when array_scan barrier
let op_to_x = do
sIf
(flg_y_exp .==. statusP .||. flg_y_exp .==. statusX)
( do
y_to_x_flg
y_to_x
)
(compileBody' x_params $ lambdaBody scan_lam)
sComment "in-block scan (hopefully no barriers needed)" $ do
skip_threads <-- 1
sWhile (tvExp skip_threads .<. block_size) $ do
sWhen in_block_thread_active $ do
sComment "read operands" $
zipWithM_
(readParam (sExt64 $ tvExp skip_threads))
(flg_param_x : x_params)
(flag_arr : arrs)
sComment "perform operation" op_to_x
sComment "write result" $
sequence_ $
zipWith3
writeResult
(flg_param_x : x_params)
(flg_param_y : y_params)
(flag_arr : arrs)
skip_threads <-- tvExp skip_threads * 2
where
p_int8 = IntType Int8
block_size = 32
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
barrier
| array_scan =
sOp $ Imp.Barrier Imp.FenceGlobal
| otherwise =
sOp $ Imp.Barrier Imp.FenceLocal
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) []
-- | Compile 'SegScan' instance to host-level code with calls to a
-- single-pass kernel.
compileSegScan ::
Pat LetDecMem ->
SegLevel ->
SegSpace ->
SegBinOp GPUMem ->
KernelBody GPUMem ->
CallKernelGen ()
compileSegScan pat lvl space scanOp kbody = do
attrs <- lvlKernelAttrs lvl
let Pat all_pes = pat
scanOpNe = segBinOpNeutral scanOp
tys = map (\(Prim pt) -> pt) $ lambdaReturnType $ segBinOpLambda scanOp
n = product $ map pe64 $ segSpaceDims space
sumT :: Integer
maxT :: Integer
sumT = foldl (\bytes typ -> bytes + primByteSize typ) 0 tys
primByteSize' = max 4 . primByteSize
sumT' = foldl (\bytes typ -> bytes + primByteSize' typ) 0 tys `div` 4
maxT = maximum (map primByteSize tys)
m :: (Num a) => a
m = fromIntegral $ max 1 $ min mem_constraint reg_constraint
-- TODO: Make these constants dynamic by querying device
k_reg = 64
k_mem = 95
mem_constraint = max k_mem sumT `div` maxT
reg_constraint = (k_reg - 1 - sumT') `div` (2 * sumT')
group_size = kAttrGroupSize attrs
group_size' = pe64 $ unCount group_size
num_groups <-
Count . tvSize <$> dPrimV "num_groups" (n `divUp` (group_size' * m))
let num_groups' = pe64 (unCount num_groups)
num_threads <-
dPrimVE "num_threads" $ num_groups' * group_size'
let (gtids, dims) = unzip $ unSegSpace space
dims' = map pe64 dims
segmented = length dims' > 1
not_segmented_e = if segmented then false else true
segment_size = last dims'
statusX, statusA, statusP :: (Num a) => a
statusX = 0
statusA = 1
statusP = 2
emit $ Imp.DebugPrint "Sequential elements per thread (m) " $ Just $ untyped (m :: Imp.TExp Int32)
emit $ Imp.DebugPrint "Memory constraint" $ Just $ untyped (fromIntegral mem_constraint :: Imp.TExp Int32)
emit $ Imp.DebugPrint "Register constraint" $ Just $ untyped (fromIntegral reg_constraint :: Imp.TExp Int32)
emit $ Imp.DebugPrint "sumT'" $ Just $ untyped (fromIntegral sumT' :: Imp.TExp Int32)
globalId <- genZeroes "id_counter" 1
statusFlags <- sAllocArray "status_flags" int8 (Shape [unCount num_groups]) (Space "device")
(aggregateArrays, incprefixArrays) <-
fmap unzip $
forM tys $ \ty ->
(,)
<$> sAllocArray "aggregates" ty (Shape [unCount num_groups]) (Space "device")
<*> sAllocArray "incprefixes" ty (Shape [unCount num_groups]) (Space "device")
sReplicate statusFlags $ intConst Int8 statusX
sKernelThread "segscan" (segFlat space) (defKernelAttrs num_groups group_size) $ do
constants <- kernelConstants <$> askEnv
(sharedId, transposedArrays, prefixArrays, warpscan, exchanges) <-
createLocalArrays (kAttrGroupSize attrs) (intConst Int64 m) tys
dynamicId <- dPrim "dynamic_id" int32
sWhen (kernelLocalThreadId constants .==. 0) $ do
(globalIdMem, _, globalIdOff) <- fullyIndexArray globalId [0]
sOp $
Imp.Atomic DefaultSpace $
Imp.AtomicAdd
Int32
(tvVar dynamicId)
globalIdMem
(Count $ unCount globalIdOff)
(untyped (1 :: Imp.TExp Int32))
copyDWIMFix sharedId [0] (tvSize dynamicId) []
let localBarrier = Imp.Barrier Imp.FenceLocal
localFence = Imp.MemFence Imp.FenceLocal
globalFence = Imp.MemFence Imp.FenceGlobal
sOp localBarrier
copyDWIMFix (tvVar dynamicId) [] (Var sharedId) [0]
sOp localBarrier
blockOff <-
dPrimV "blockOff" $
sExt64 (tvExp dynamicId) * m * kernelGroupSize constants
sgmIdx <- dPrimVE "sgm_idx" $ tvExp blockOff `mod` segment_size
boundary <-
dPrimVE "boundary" $
sExt32 $
sMin64 (m * group_size') (segment_size - sgmIdx)
segsize_compact <-
dPrimVE "segsize_compact" $
sExt32 $
sMin64 (m * group_size') segment_size
privateArrays <-
forM tys $ \ty ->
sAllocArray
"private"
ty
(Shape [intConst Int64 m])
(ScalarSpace [intConst Int64 m] ty)
sComment "Load and map" $
sFor "i" m $ \i -> do
-- The map's input index
phys_tid <-
dPrimVE "phys_tid" $
tvExp blockOff
+ sExt64 (kernelLocalThreadId constants)
+ i * kernelGroupSize constants
dIndexSpace (zip gtids dims') phys_tid
-- Perform the map
let in_bounds =
compileStms mempty (kernelBodyStms kbody) $ do
let (all_scan_res, map_res) = splitAt (segBinOpResults [scanOp]) $ kernelBodyResult kbody
-- Write map results to their global memory destinations
forM_ (zip (takeLast (length map_res) all_pes) map_res) $ \(dest, src) ->
copyDWIMFix (patElemName dest) (map Imp.le64 gtids) (kernelResultSubExp src) []
-- Write to-scan results to private memory.
forM_ (zip privateArrays $ map kernelResultSubExp all_scan_res) $ \(dest, src) ->
copyDWIMFix dest [i] src []
out_of_bounds =
forM_ (zip privateArrays scanOpNe) $ \(dest, ne) ->
copyDWIMFix dest [i] ne []
sIf (phys_tid .<. n) in_bounds out_of_bounds
sComment "Transpose scan inputs" $ do
forM_ (zip transposedArrays privateArrays) $ \(trans, priv) -> do
sOp localBarrier
sFor "i" m $ \i -> do
sharedIdx <-
dPrimVE "sharedIdx" $
sExt64 (kernelLocalThreadId constants)
+ i * kernelGroupSize constants
copyDWIMFix trans [sharedIdx] (Var priv) [i]
sOp localBarrier
sFor "i" m $ \i -> do
sharedIdx <- dPrimV "sharedIdx" $ kernelLocalThreadId constants * m + i
copyDWIMFix priv [sExt64 i] (Var trans) [sExt64 $ tvExp sharedIdx]
sOp $ Imp.ErrorSync Imp.FenceLocal
sComment "Per thread scan" $ do
-- We don't need to touch the first element, so only m-1
-- iterations here.
globalIdx <-
dPrimVE "gidx" $
(kernelLocalThreadId constants * m) + 1
sFor "i" (m - 1) $ \i -> do
let xs = map paramName $ xParams scanOp
ys = map paramName $ yParams scanOp
-- determine if start of segment
new_sgm <-
if segmented
then dPrimVE "new_sgm" $ (globalIdx + sExt32 i - boundary) `mod` segsize_compact .==. 0
else pure false
-- skip scan of first element in segment
sUnless new_sgm $ do
forM_ (zip privateArrays $ zip3 xs ys tys) $ \(src, (x, y, ty)) -> do
dPrim_ x ty
dPrim_ y ty
copyDWIMFix x [] (Var src) [i]
copyDWIMFix y [] (Var src) [i + 1]
compileStms mempty (bodyStms $ lambdaBody $ segBinOpLambda scanOp) $
forM_ (zip privateArrays $ map resSubExp $ bodyResult $ lambdaBody $ segBinOpLambda scanOp) $ \(dest, res) ->
copyDWIMFix dest [i + 1] res []
sComment "Publish results in shared memory" $ do
forM_ (zip prefixArrays privateArrays) $ \(dest, src) ->
copyDWIMFix dest [sExt64 $ kernelLocalThreadId constants] (Var src) [m - 1]
sOp localBarrier
let crossesSegment = do
guard segmented
Just $ \from to ->
let from' = (from + 1) * m - 1
to' = (to + 1) * m - 1
in (to' - from') .>. (to' + segsize_compact - boundary) `mod` segsize_compact
scanOp' <- renameLambda $ segBinOpLambda scanOp
accs <- mapM (dPrim "acc") tys
sComment "Scan results (with warp scan)" $ do
groupScan
crossesSegment
num_threads
(kernelGroupSize constants)
scanOp'
prefixArrays
sOp $ Imp.ErrorSync Imp.FenceLocal
let firstThread acc prefixes =
copyDWIMFix (tvVar acc) [] (Var prefixes) [sExt64 (kernelGroupSize constants) - 1]
notFirstThread acc prefixes =
copyDWIMFix (tvVar acc) [] (Var prefixes) [sExt64 (kernelLocalThreadId constants) - 1]
sIf
(kernelLocalThreadId constants .==. 0)
(zipWithM_ firstThread accs prefixArrays)
(zipWithM_ notFirstThread accs prefixArrays)
sOp localBarrier
prefixes <- forM (zip scanOpNe tys) $ \(ne, ty) ->
dPrimV "prefix" $ TPrimExp $ toExp' ty ne
blockNewSgm <- dPrimVE "block_new_sgm" $ sgmIdx .==. 0
sComment "Perform lookback" $ do
sWhen (blockNewSgm .&&. kernelLocalThreadId constants .==. 0) $ do
everythingVolatile $
forM_ (zip accs incprefixArrays) $ \(acc, incprefixArray) ->
copyDWIMFix incprefixArray [tvExp dynamicId] (tvSize acc) []
sOp globalFence
everythingVolatile $
copyDWIMFix statusFlags [tvExp dynamicId] (intConst Int8 statusP) []
forM_ (zip scanOpNe accs) $ \(ne, acc) ->
copyDWIMFix (tvVar acc) [] ne []
-- end sWhen
let warpSize = kernelWaveSize constants
sWhen (bNot blockNewSgm .&&. kernelLocalThreadId constants .<. warpSize) $ do
sWhen (kernelLocalThreadId constants .==. 0) $ do
sIf
(not_segmented_e .||. boundary .==. sExt32 (group_size' * m))
( do
everythingVolatile $
forM_ (zip aggregateArrays accs) $ \(aggregateArray, acc) ->
copyDWIMFix aggregateArray [tvExp dynamicId] (tvSize acc) []
sOp globalFence
everythingVolatile $
copyDWIMFix statusFlags [tvExp dynamicId] (intConst Int8 statusA) []
)
( do
everythingVolatile $
forM_ (zip incprefixArrays accs) $ \(incprefixArray, acc) ->
copyDWIMFix incprefixArray [tvExp dynamicId] (tvSize acc) []
sOp globalFence
everythingVolatile $
copyDWIMFix statusFlags [tvExp dynamicId] (intConst Int8 statusP) []
)
everythingVolatile $
copyDWIMFix warpscan [0] (Var statusFlags) [tvExp dynamicId - 1]
-- sWhen
sOp localFence
status <- dPrim "status" int8 :: InKernelGen (TV Int8)
copyDWIMFix (tvVar status) [] (Var warpscan) [0]
sIf
(tvExp status .==. statusP)
( sWhen (kernelLocalThreadId constants .==. 0) $
everythingVolatile $
forM_ (zip prefixes incprefixArrays) $ \(prefix, incprefixArray) ->
copyDWIMFix (tvVar prefix) [] (Var incprefixArray) [tvExp dynamicId - 1]
)
( do
readOffset <-
dPrimV "readOffset" $
sExt32 $
tvExp dynamicId - sExt64 (kernelWaveSize constants)
let loopStop = warpSize * (-1)
sameSegment readIdx
| segmented =
let startIdx = sExt64 (tvExp readIdx + 1) * kernelGroupSize constants * m - 1
in tvExp blockOff - startIdx .<=. sgmIdx
| otherwise = true
sWhile (tvExp readOffset .>. loopStop) $ do
readI <- dPrimV "read_i" $ tvExp readOffset + kernelLocalThreadId constants
aggrs <- forM (zip scanOpNe tys) $ \(ne, ty) ->
dPrimV "aggr" $ TPrimExp $ toExp' ty ne
flag <- dPrimV "flag" (statusX :: Imp.TExp Int8)
everythingVolatile . sWhen (tvExp readI .>=. 0) $ do
sIf
(sameSegment readI)
( do
copyDWIMFix (tvVar flag) [] (Var statusFlags) [sExt64 $ tvExp readI]
sIf
(tvExp flag .==. statusP)
( forM_ (zip incprefixArrays aggrs) $ \(incprefix, aggr) ->
copyDWIMFix (tvVar aggr) [] (Var incprefix) [sExt64 $ tvExp readI]
)
( sWhen (tvExp flag .==. statusA) $ do
forM_ (zip aggrs aggregateArrays) $ \(aggr, aggregate) ->
copyDWIMFix (tvVar aggr) [] (Var aggregate) [sExt64 $ tvExp readI]
)
)
(copyDWIMFix (tvVar flag) [] (intConst Int8 statusP) [])
-- end sIf
-- end sWhen
forM_ (zip exchanges aggrs) $ \(exchange, aggr) ->
copyDWIMFix exchange [sExt64 $ kernelLocalThreadId constants] (tvSize aggr) []
copyDWIMFix warpscan [sExt64 $ kernelLocalThreadId constants] (tvSize flag) []
-- execute warp-parallel reduction but only if the last read flag in not STATUS_P
copyDWIMFix (tvVar flag) [] (Var warpscan) [sExt64 warpSize - 1]
sWhen (tvExp flag .<. (2 :: Imp.TExp Int8)) $ do
lam' <- renameLambda scanOp'
inBlockScanLookback
constants
num_threads
warpscan
exchanges
lam'
-- all threads of the warp read the result of reduction
copyDWIMFix (tvVar flag) [] (Var warpscan) [sExt64 warpSize - 1]
forM_ (zip aggrs exchanges) $ \(aggr, exchange) ->
copyDWIMFix (tvVar aggr) [] (Var exchange) [sExt64 warpSize - 1]
-- update read offset
sIf
(tvExp flag .==. statusP)
(readOffset <-- loopStop)
( sWhen (tvExp flag .==. statusA) $ do
readOffset <-- tvExp readOffset - zExt32 warpSize
)
-- update prefix if flag different than STATUS_X:
sWhen (tvExp flag .>. (statusX :: Imp.TExp Int8)) $ do
lam <- renameLambda scanOp'
let (xs, ys) = splitAt (length tys) $ map paramName $ lambdaParams lam
forM_ (zip xs aggrs) $ \(x, aggr) -> dPrimV_ x (tvExp aggr)
forM_ (zip ys prefixes) $ \(y, prefix) -> dPrimV_ y (tvExp prefix)
compileStms mempty (bodyStms $ lambdaBody lam) $
forM_ (zip3 prefixes tys $ map resSubExp $ bodyResult $ lambdaBody lam) $
\(prefix, ty, res) -> prefix <-- TPrimExp (toExp' ty res)
sOp localFence
)
-- end sWhile
-- end sIf
sWhen (kernelLocalThreadId constants .==. 0) $ do
scanOp'''' <- renameLambda scanOp'
let xs = map paramName $ take (length tys) $ lambdaParams scanOp''''
ys = map paramName $ drop (length tys) $ lambdaParams scanOp''''
sWhen (boundary .==. sExt32 (group_size' * m)) $ do
forM_ (zip xs prefixes) $ \(x, prefix) -> dPrimV_ x $ tvExp prefix
forM_ (zip ys accs) $ \(y, acc) -> dPrimV_ y $ tvExp acc
compileStms mempty (bodyStms $ lambdaBody scanOp'''') $
everythingVolatile $
forM_ (zip incprefixArrays $ map resSubExp $ bodyResult $ lambdaBody scanOp'''') $
\(incprefixArray, res) -> copyDWIMFix incprefixArray [tvExp dynamicId] res []
sOp globalFence
everythingVolatile $ copyDWIMFix statusFlags [tvExp dynamicId] (intConst Int8 statusP) []
forM_ (zip exchanges prefixes) $ \(exchange, prefix) ->
copyDWIMFix exchange [0] (tvSize prefix) []
forM_ (zip3 accs tys scanOpNe) $ \(acc, ty, ne) ->
tvVar acc <~~ toExp' ty ne
-- end sWhen
-- end sWhen
sWhen (bNot $ tvExp dynamicId .==. 0) $ do
sOp localBarrier
forM_ (zip exchanges prefixes) $ \(exchange, prefix) ->
copyDWIMFix (tvVar prefix) [] (Var exchange) [0]
sOp localBarrier
-- end sWhen
-- end sComment
scanOp''''' <- renameLambda scanOp'
scanOp'''''' <- renameLambda scanOp'
sComment "Distribute results" $ do
let (xs, ys) = splitAt (length tys) $ map paramName $ lambdaParams scanOp'''''
(xs', ys') = splitAt (length tys) $ map paramName $ lambdaParams scanOp''''''
forM_ (zip4 (zip prefixes accs) (zip xs xs') (zip ys ys') tys) $
\((prefix, acc), (x, x'), (y, y'), ty) -> do
dPrim_ x ty
dPrim_ y ty
dPrimV_ x' $ tvExp prefix
dPrimV_ y' $ tvExp acc
sIf
(kernelLocalThreadId constants * m .<. boundary .&&. bNot blockNewSgm)
( compileStms mempty (bodyStms $ lambdaBody scanOp'''''') $
forM_ (zip3 xs tys $ map resSubExp $ bodyResult $ lambdaBody scanOp'''''') $
\(x, ty, res) -> x <~~ toExp' ty res
)
(forM_ (zip xs accs) $ \(x, acc) -> copyDWIMFix x [] (Var $ tvVar acc) [])
-- calculate where previous thread stopped, to determine number of
-- elements left before new segment.
stop <-
dPrimVE "stopping_point" $
segsize_compact - (kernelLocalThreadId constants * m - 1 + segsize_compact - boundary) `rem` segsize_compact
sFor "i" m $ \i -> do
sWhen (sExt32 i .<. stop - 1) $ do
forM_ (zip privateArrays ys) $ \(src, y) ->
-- only include prefix for the first segment part per thread
copyDWIMFix y [] (Var src) [i]
compileStms mempty (bodyStms $ lambdaBody scanOp''''') $
forM_ (zip privateArrays $ map resSubExp $ bodyResult $ lambdaBody scanOp''''') $
\(dest, res) ->
copyDWIMFix dest [i] res []
sComment "Transpose scan output and Write it to global memory in coalesced fashion" $ do
forM_ (zip3 transposedArrays privateArrays $ map patElemName all_pes) $ \(locmem, priv, dest) -> do
-- sOp localBarrier
sFor "i" m $ \i -> do
sharedIdx <-
dPrimV "sharedIdx" $
sExt64 (kernelLocalThreadId constants * m) + i
copyDWIMFix locmem [tvExp sharedIdx] (Var priv) [i]
sOp localBarrier
sFor "i" m $ \i -> do
flat_idx <-
dPrimVE "flat_idx" $
tvExp blockOff
+ kernelGroupSize constants * i
+ sExt64 (kernelLocalThreadId constants)
dIndexSpace (zip gtids dims') flat_idx
sWhen (flat_idx .<. n) $ do
copyDWIMFix
dest
(map Imp.le64 gtids)
(Var locmem)
[sExt64 $ flat_idx - tvExp blockOff]
sOp localBarrier
sComment "If this is the last block, reset the dynamicId" $
sWhen (tvExp dynamicId .==. num_groups' - 1) $
copyDWIMFix globalId [0] (constant (0 :: Int32)) []
{-# NOINLINE compileSegScan #-}