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single pass scan group virtualization #2041

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merged 4 commits into from
Nov 17, 2023
Merged

single pass scan group virtualization #2041

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6c280fd
single pass scan group virtualization
sortraev Oct 19, 2023
5efb3a0
restore statusFlags initialization
sortraev Nov 8, 2023
4d5979a
Address athas' change requests.
sortraev Nov 17, 2023
5928623
More style fixes.
sortraev Nov 17, 2023
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52 changes: 21 additions & 31 deletions src/Futhark/CodeGen/ImpGen/GPU/SegScan.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,8 +14,8 @@ import Futhark.IR.GPUMem

-- The single-pass scan does not support multiple operators, so jam
-- them together here.
combineScans :: [SegBinOp GPUMem] -> SegBinOp GPUMem
combineScans ops =
combineScanOps :: [SegBinOp GPUMem] -> SegBinOp GPUMem
combineScanOps ops =
SegBinOp
{ segBinOpComm = mconcat (map segBinOpComm ops),
segBinOpLambda = lam',
Expand Down Expand Up @@ -48,30 +48,18 @@ bodyHas f = any (f' . stmExp) . bodyStms
{ walkOnBody = const $ guard . not . bodyHas f
}

canBeSinglePass :: [SegBinOp GPUMem] -> KernelBody GPUMem -> Maybe (SegBinOp GPUMem)
canBeSinglePass ops kbody
| all ok ops,
not $ bodyHas freshArray (Body () (kernelBodyStms kbody) []) =
Just $ combineScans ops
| otherwise =
Nothing
canBeSinglePass :: [SegBinOp GPUMem] -> Maybe (SegBinOp GPUMem)
canBeSinglePass scan_ops =
if all ok scan_ops
then Just $ combineScanOps scan_ops
else Nothing
where
ok op =
segBinOpShape op == mempty
&& all primType (lambdaReturnType (segBinOpLambda op))
&& not (bodyHas isAssert (lambdaBody (segBinOpLambda op)))
isAssert (BasicOp Assert {}) = True
isAssert _ = False
-- XXX: Currently single pass scans cannot handle construction of
-- arrays in the kernel body (#2013), because of insufficient
-- memory expansion. This can in principle be fixed.
freshArray (BasicOp Manifest {}) = True
freshArray (BasicOp Iota {}) = True
freshArray (BasicOp Replicate {}) = True
freshArray (BasicOp Scratch {}) = True
freshArray (BasicOp Concat {}) = True
freshArray (BasicOp ArrayLit {}) = True
freshArray _ = False

-- | Compile 'SegScan' instance to host-level code with calls to
-- various kernels.
Expand All @@ -82,17 +70,19 @@ compileSegScan ::
[SegBinOp GPUMem] ->
KernelBody GPUMem ->
CallKernelGen ()
compileSegScan pat lvl space scans kbody = sWhen (0 .<. n) $ do
emit $ Imp.DebugPrint "\n# SegScan" Nothing
target <- hostTarget <$> askEnv
case target of
CUDA
| Just scan' <- canBeSinglePass scans kbody ->
SinglePass.compileSegScan pat lvl space scan' kbody
HIP
| Just scan' <- canBeSinglePass scans kbody ->
SinglePass.compileSegScan pat lvl space scan' kbody
_ -> TwoPass.compileSegScan pat lvl space scans kbody
emit $ Imp.DebugPrint "" Nothing
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compileSegScan pat lvl space scan_ops map_kbody =
sWhen (0 .<. n) $ do
emit $ Imp.DebugPrint "\n# SegScan" Nothing
target <- hostTarget <$> askEnv

case (targetSupportsSinglePass target, canBeSinglePass scan_ops) of
(True, Just scan_ops') ->
SinglePass.compileSegScan pat lvl space scan_ops' map_kbody
_ ->
TwoPass.compileSegScan pat lvl space scan_ops map_kbody
where
n = product $ map pe64 $ segSpaceDims space
targetSupportsSinglePass HIP = True
targetSupportsSinglePass CUDA = True
targetSupportsSinglePass _ = False

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