Change spill cost function back to inverse length of live range.

[ghc-hetmet.git] / compiler / nativeGen / RegSpillCost.hs

diff --git a/compiler/nativeGen/RegSpillCost.hs b/compiler/nativeGen/RegSpillCost.hs
index e639c67..d987937 100644 (file)
--- a/compiler/nativeGen/RegSpillCost.hs
+++ b/compiler/nativeGen/RegSpillCost.hs
@@ -132,7 +132,7 @@ chooseSpill
        -> Reg
 
 chooseSpill info graph
- = let cost    = spillCost info graph
+ = let cost    = spillCost_length info graph
        node    = minimumBy (\n1 n2 -> compare (cost $ nodeId n1) (cost $ nodeId n2))
                $ eltsUFM $ graphMap graph
 
@@ -177,14 +177,14 @@ chooseSpill info graph
 --  Without live range splitting, its's better to spill from the outside in so set the cost of very
 --     long live ranges to zero
 --
-
-spillCost
+{-
+spillCost_chaitin
        :: SpillCostInfo
        -> Graph Reg RegClass Reg
        -> Reg
        -> Float
 
-spillCost info graph reg
+spillCost_chaitin info graph reg
        -- Spilling a live range that only lives for 1 instruction isn't going to help
        --      us at all - and we definately want to avoid trying to re-spill previously
        --      inserted spill code.
@@ -200,6 +200,21 @@ spillCost info graph reg
        | otherwise     = fromIntegral (uses + defs) / fromIntegral (nodeDegree graph reg)
        where (_, defs, uses, lifetime)
                = fromMaybe (reg, 0, 0, 0) $ lookupUFM info reg
+-}
+
+-- Just spill the longest live range.
+spillCost_length
+       :: SpillCostInfo
+       -> Graph Reg RegClass Reg
+       -> Reg
+       -> Float
+
+spillCost_length info _ reg
+       | lifetime <= 1         = 1/0
+       | otherwise             = 1 / fromIntegral lifetime
+       where (_, _, _, lifetime)
+               = fromMaybe (reg, 0, 0, 0) $ lookupUFM info reg
+
 
 
 lifeMapFromSpillCostInfo :: SpillCostInfo -> UniqFM (Reg, Int)