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| -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 |