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| author | dias@eecs.tufts.edu <unknown> | 2009-03-18 21:01:38 +0000 |
|---|---|---|
| committer | dias@eecs.tufts.edu <unknown> | 2009-03-18 21:01:38 +0000 |
| commit | 2c8d42f32022f4950606d75d53e45a4c30d210df (patch) | |
| tree | 325b96e7a7c454ae411a048d5e43ee34ff91ff59 /compiler/cmm/DFMonad.hs | |
| parent | 1d34bd56c9dde4dad72d3e8a4cfabdf11337dfb3 (diff) | |
| download | haskell-2c8d42f32022f4950606d75d53e45a4c30d210df.tar.gz | |
Comment explaining use of seq in DFMonad
Diffstat (limited to 'compiler/cmm/DFMonad.hs')
| -rw-r--r-- | compiler/cmm/DFMonad.hs | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/compiler/cmm/DFMonad.hs b/compiler/cmm/DFMonad.hs index 0cf1ead0fc..263d0d4856 100644 --- a/compiler/cmm/DFMonad.hs +++ b/compiler/cmm/DFMonad.hs @@ -192,6 +192,10 @@ instance Monad m => Monad (DFM' m f) where DFM' f >>= k = DFM' (\l s -> do (a, s') <- f l s s' `seq` case k a of DFM' f' -> f' l s') return a = DFM' (\_ s -> return (a, s)) + -- The `seq` is essential to ensure that entire passes of the dataflow engine + -- aren't postponed in a thunk. By making the sequence strict in the state, + -- we ensure that each action in the monad is executed immediately, preventing + -- stack overflows that previously occurred when finally forcing the old state thunks. instance FuelUsingMonad (DFM' FuelMonad f) where fuelRemaining = liftToDFM' fuelRemaining |