X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fcmm%2FOptimizationFuel.hs;h=175dcd09b18a4c602cb9531796d0f4b7abf89673;hb=a46bdb63d919da9478bcd1bee2933dc19bc174ab;hp=3d5b64522d91b32717deb4816dbc1559349847a1;hpb=0d80489c9b9f2421f65d8dd86c1e50c6bb429715;p=ghc-hetmet.git

diff --git a/compiler/cmm/OptimizationFuel.hs b/compiler/cmm/OptimizationFuel.hs
index 3d5b645..175dcd0 100644
--- a/compiler/cmm/OptimizationFuel.hs
+++ b/compiler/cmm/OptimizationFuel.hs
@@ -1,5 +1,11 @@
+-- | Optimisation fuel is used to control the amount of work the optimiser does.
+--
+-- Every optimisation step consumes a certain amount of fuel and stops when
+-- it runs out of fuel.  This can be used e.g. to debug optimiser bugs: Run
+-- the optimiser with varying amount of fuel to find out the exact number of
+-- steps where a bug is introduced in the output.
 module OptimizationFuel
-    ( OptimizationFuel ,  canRewriteWithFuel, maybeRewriteWithFuel, oneLessFuel
+    ( OptimizationFuel,  canRewriteWithFuel, maybeRewriteWithFuel, oneLessFuel
     , OptFuelState, initOptFuelState --, setTotalFuel
     , tankFilledTo, diffFuel
     , FuelConsumer
@@ -17,7 +23,7 @@ import ZipCfg
 --import GHC.Exts (State#)
 import Panic
 import Data.IORef
-import Monad
+import Control.Monad
 import StaticFlags (opt_Fuel)
 import UniqSupply
 
@@ -59,7 +65,7 @@ diffFuel (OptimizationFuel f) (OptimizationFuel f') = f - f'
 -- type OptimizationFuel = State# () -- would like this, but it won't work
 data OptimizationFuel = OptimizationFuel
   deriving Show
-tankFilledTo _ = undefined -- should be impossible to evaluate
+tankFilledTo _ = panic "tankFilledTo" -- should be impossible to evaluate
   -- realWorld# might come in handy, too...
 canRewriteWithFuel OptimizationFuel = True
 maybeRewriteWithFuel _ ma = ma