never executed always true always false

    1 module GHC.CmmToAsm.CFG.Weight
    2    ( Weights (..)
    3    , defaultWeights
    4    , parseWeights
    5    )
    6 where
    7 
    8 import GHC.Prelude
    9 import GHC.Utils.Panic
   10 
   11 -- | Edge weights to use when generating a CFG from CMM
   12 data Weights = Weights
   13    { uncondWeight       :: Int
   14    , condBranchWeight   :: Int
   15    , switchWeight       :: Int
   16    , callWeight         :: Int
   17    , likelyCondWeight   :: Int
   18    , unlikelyCondWeight :: Int
   19    , infoTablePenalty   :: Int
   20    , backEdgeBonus      :: Int
   21    }
   22 
   23 -- | Default edge weights
   24 defaultWeights :: Weights
   25 defaultWeights = Weights
   26    { uncondWeight       = 1000
   27    , condBranchWeight   = 800
   28    , switchWeight       = 1
   29    , callWeight         = -10
   30    , likelyCondWeight   = 900
   31    , unlikelyCondWeight = 300
   32    , infoTablePenalty   = 300
   33    , backEdgeBonus      = 400
   34    }
   35 
   36 parseWeights :: String -> Weights -> Weights
   37 parseWeights s oldWeights =
   38         foldl' (\cfg (n,v) -> update n v cfg) oldWeights assignments
   39     where
   40         assignments = map assignment $ settings s
   41         update "uncondWeight" n w =
   42             w {uncondWeight = n}
   43         update "condBranchWeight" n w =
   44             w {condBranchWeight = n}
   45         update "switchWeight" n w =
   46             w {switchWeight = n}
   47         update "callWeight" n w =
   48             w {callWeight = n}
   49         update "likelyCondWeight" n w =
   50             w {likelyCondWeight = n}
   51         update "unlikelyCondWeight" n w =
   52             w {unlikelyCondWeight = n}
   53         update "infoTablePenalty" n w =
   54             w {infoTablePenalty = n}
   55         update "backEdgeBonus" n w =
   56             w {backEdgeBonus = n}
   57         update other _ _
   58             = panic $ other ++
   59                       " is not a CFG weight parameter. " ++
   60                       exampleString
   61         settings s
   62             | (s1,rest) <- break (== ',') s
   63             , null rest
   64             = [s1]
   65             | (s1,rest) <- break (== ',') s
   66             = s1 : settings (drop 1 rest)
   67 
   68         assignment as
   69             | (name, _:val) <- break (== '=') as
   70             = (name,read val)
   71             | otherwise
   72             = panic $ "Invalid CFG weight parameters." ++ exampleString
   73 
   74         exampleString = "Example parameters: uncondWeight=1000," ++
   75             "condBranchWeight=800,switchWeight=0,callWeight=300" ++
   76             ",likelyCondWeight=900,unlikelyCondWeight=300" ++
   77             ",infoTablePenalty=300,backEdgeBonus=400"
   78