1 {-# LANGUAGE TypeFamilies #-}
2 -- | Optimisation fuel is used to control the amount of work the optimiser does.
4 -- Every optimisation step consumes a certain amount of fuel and stops when
5 -- it runs out of fuel. This can be used e.g. to debug optimiser bugs: Run
6 -- the optimiser with varying amount of fuel to find out the exact number of
7 -- steps where a bug is introduced in the output.
8 module OptimizationFuel
9 ( OptimizationFuel, amountOfFuel, tankFilledTo, anyFuelLeft, oneLessFuel
10 , OptFuelState, initOptFuelState
11 , FuelConsumer, FuelUsingMonad, FuelState
12 , fuelGet, fuelSet, lastFuelPass, setFuelPass
13 , fuelExhausted, fuelDec1, tryWithFuel
14 , runFuelIO, fuelConsumingPass
22 import StaticFlags (opt_Fuel)
29 import Compiler.Hoopl.GHC (getFuel, setFuel)
31 #include "HsVersions.h"
34 -- We limit the number of transactions executed using a record of flags
35 -- stored in an HscEnv. The flags store the name of the last optimization
36 -- pass and the amount of optimization fuel remaining.
38 OptFuelState { pass_ref :: IORef String
39 , fuel_ref :: IORef OptimizationFuel
41 initOptFuelState :: IO OptFuelState
43 do pass_ref' <- newIORef "unoptimized program"
44 fuel_ref' <- newIORef (tankFilledTo opt_Fuel)
45 return OptFuelState {pass_ref = pass_ref', fuel_ref = fuel_ref'}
47 type FuelConsumer a = OptimizationFuel -> (a, OptimizationFuel)
49 tankFilledTo :: Int -> OptimizationFuel
50 amountOfFuel :: OptimizationFuel -> Int
52 anyFuelLeft :: OptimizationFuel -> Bool
53 oneLessFuel :: OptimizationFuel -> OptimizationFuel
56 newtype OptimizationFuel = OptimizationFuel Int
59 tankFilledTo = OptimizationFuel
60 amountOfFuel (OptimizationFuel f) = f
62 anyFuelLeft (OptimizationFuel f) = f > 0
63 oneLessFuel (OptimizationFuel f) = ASSERT (f > 0) (OptimizationFuel (f - 1))
65 -- type OptimizationFuel = State# () -- would like this, but it won't work
66 data OptimizationFuel = OptimizationFuel
68 tankFilledTo _ = OptimizationFuel
69 amountOfFuel _ = maxBound
72 oneLessFuel _ = OptimizationFuel
75 data FuelState = FuelState { fs_fuel :: OptimizationFuel, fs_lastpass :: String }
76 newtype FuelUniqSM a = FUSM { unFUSM :: FuelState -> UniqSM (a, FuelState) }
78 fuelConsumingPass :: String -> FuelConsumer a -> FuelUniqSM a
79 fuelConsumingPass name f = do setFuelPass name
81 let (a, fuel') = f fuel
85 runFuelIO :: OptFuelState -> FuelUniqSM a -> IO a
86 runFuelIO fs (FUSM f) =
87 do pass <- readIORef (pass_ref fs)
88 fuel <- readIORef (fuel_ref fs)
89 u <- mkSplitUniqSupply 'u'
90 let (a, FuelState fuel' pass') = initUs_ u $ f (FuelState fuel pass)
91 writeIORef (pass_ref fs) pass'
92 writeIORef (fuel_ref fs) fuel'
95 instance Monad FuelUniqSM where
96 FUSM f >>= k = FUSM (\s -> f s >>= \(a, s') -> unFUSM (k a) s')
97 return a = FUSM (\s -> return (a, s))
99 instance MonadUnique FuelUniqSM where
100 getUniqueSupplyM = liftUniq getUniqueSupplyM
101 getUniqueM = liftUniq getUniqueM
102 getUniquesM = liftUniq getUniquesM
104 liftUniq :: UniqSM x -> FuelUniqSM x
105 liftUniq x = FUSM (\s -> x >>= (\u -> return (u, s)))
107 class Monad m => FuelUsingMonad m where
108 fuelGet :: m OptimizationFuel
109 fuelSet :: OptimizationFuel -> m ()
110 lastFuelPass :: m String
111 setFuelPass :: String -> m ()
113 fuelExhausted :: FuelUsingMonad m => m Bool
114 fuelExhausted = fuelGet >>= return . anyFuelLeft
116 fuelDec1 :: FuelUsingMonad m => m ()
117 fuelDec1 = fuelGet >>= fuelSet . oneLessFuel
119 tryWithFuel :: FuelUsingMonad m => a -> m (Maybe a)
120 tryWithFuel r = do f <- fuelGet
121 if anyFuelLeft f then fuelSet (oneLessFuel f) >> return (Just r)
124 instance FuelUsingMonad FuelUniqSM where
125 fuelGet = extract fs_fuel
126 lastFuelPass = extract fs_lastpass
127 fuelSet fuel = FUSM (\s -> return ((), s { fs_fuel = fuel }))
128 setFuelPass pass = FUSM (\s -> return ((), s { fs_lastpass = pass }))
130 extract :: (FuelState -> a) -> FuelUniqSM a
131 extract f = FUSM (\s -> return (f s, s))
133 instance FuelMonad FuelUniqSM where
134 getFuel = liftM amountOfFuel fuelGet
135 setFuel = fuelSet . tankFilledTo
137 -- Don't bother to checkpoint the unique supply; it doesn't matter
138 instance CheckpointMonad FuelUniqSM where
139 type Checkpoint FuelUniqSM = FuelState
140 checkpoint = FUSM $ \fuel -> return (fuel, fuel)
141 restart fuel = FUSM $ \_ -> return ((), fuel)