[project @ 2004-08-17 15:23:47 by simonpj]

[ghc-hetmet.git] / ghc / compiler / utils / Digraph.lhs

diff --git a/ghc/compiler/utils/Digraph.lhs b/ghc/compiler/utils/Digraph.lhs
index 0dfc585..0eff6da 100644 (file)
--- a/ghc/compiler/utils/Digraph.lhs
+++ b/ghc/compiler/utils/Digraph.lhs
@@ -2,7 +2,7 @@
 module Digraph(
 
        -- At present the only one with a "nice" external interface
-       stronglyConnComp, stronglyConnCompR, SCC(..),
+       stronglyConnComp, stronglyConnCompR, SCC(..), flattenSCC, flattenSCCs,
 
        Graph, Vertex, 
        graphFromEdges, buildG, transposeG, reverseE, outdegree, indegree,
@@ -32,17 +32,22 @@ module Digraph(
 ------------------------------------------------------------------------------
 
 
-#define ARR_ELT                (COMMA)
-
-import Util    ( sortLt )
+import Util    ( sortLe )
 
 -- Extensions
-import ST
+import MONAD_ST
 
 -- std interfaces
 import Maybe
 import Array
 import List
+import Outputable
+
+#if __GLASGOW_HASKELL__ >= 504
+import Data.Array.ST  hiding ( indices, bounds )
+#else
+import ST
+#endif
 \end{code}
 
 
@@ -56,12 +61,25 @@ import List
 data SCC vertex = AcyclicSCC vertex
                | CyclicSCC  [vertex]
 
+flattenSCCs :: [SCC a] -> [a]
+flattenSCCs = concatMap flattenSCC
+
+flattenSCC (AcyclicSCC v) = [v]
+flattenSCC (CyclicSCC vs) = vs
+
+instance Outputable a => Outputable (SCC a) where
+   ppr (AcyclicSCC v) = text "NONREC" $$ (nest 3 (ppr v))
+   ppr (CyclicSCC vs) = text "REC" $$ (nest 3 (vcat (map ppr vs)))
+\end{code}
+
+\begin{code}
 stronglyConnComp
        :: Ord key
        => [(node, key, [key])]         -- The graph; its ok for the
                                        -- out-list to contain keys which arent
                                        -- a vertex key, they are ignored
-       -> [SCC node]
+       -> [SCC node]   -- Returned in topologically sorted order
+                       -- Later components depend on earlier ones, but not vice versa
 
 stronglyConnComp edges
   = map get_node (stronglyConnCompR edges)
@@ -76,14 +94,14 @@ stronglyConnCompR
        => [(node, key, [key])]         -- The graph; its ok for the
                                        -- out-list to contain keys which arent
                                        -- a vertex key, they are ignored
-       -> [SCC (node, key, [key])]
+       -> [SCC (node, key, [key])]     -- Topologically sorted
 
 stronglyConnCompR [] = []  -- added to avoid creating empty array in graphFromEdges -- SOF
 stronglyConnCompR edges
   = map decode forest
   where
-    (graph, vertex_fn) = graphFromEdges edges
-    forest            = scc graph
+    (graph, vertex_fn) = _scc_ "graphFromEdges" graphFromEdges edges
+    forest            = _scc_ "Digraph.scc" scc graph
     decode (Node v []) | mentions_itself v = CyclicSCC [vertex_fn v]
                       | otherwise         = AcyclicSCC (vertex_fn v)
     decode other = CyclicSCC (dec other [])
@@ -118,11 +136,7 @@ mapT    :: (Vertex -> a -> b) -> Table a -> Table b
 mapT f t = array (bounds t) [ (,) v (f v (t!v)) | v <- indices t ]
 
 buildG :: Bounds -> [Edge] -> Graph
-#ifdef REALLY_HASKELL_1_3
 buildG bounds edges = accumArray (flip (:)) [] bounds edges
-#else
-buildG bounds edges = accumArray (flip (:)) [] bounds [(,) k v | (k,v) <- edges]
-#endif
 
 transposeG  :: Graph -> Graph
 transposeG g = buildG (bounds g) (reverseE g)
@@ -149,14 +163,16 @@ graphFromEdges edges
   where
     max_v                  = length edges - 1
     bounds          = (0,max_v) :: (Vertex, Vertex)
-    sorted_edges    = sortLt lt edges
+    sorted_edges    = let
+                        (_,k1,_) `le` (_,k2,_) = case k1 `compare` k2 of { GT -> False; other -> True }
+                     in
+                       sortLe le edges
     edges1         = zipWith (,) [0..] sorted_edges
 
     graph          = array bounds [(,) v (mapMaybe key_vertex ks) | (,) v (_,    _, ks) <- edges1]
     key_map        = array bounds [(,) v k                        | (,) v (_,    k, _ ) <- edges1]
     vertex_map     = array bounds edges1
 
-    (_,k1,_) `lt` (_,k2,_) = case k1 `compare` k2 of { LT -> True; other -> False }
 
     -- key_vertex :: key -> Maybe Vertex
     --         returns Nothing for non-interesting vertices
@@ -202,7 +218,7 @@ drawTree         = unlines . draw
 draw (Node x ts) = grp this (space (length this)) (stLoop ts)
  where this          = s1 ++ x ++ " "
 
-       space n       = take n (repeat ' ')
+       space n       = replicate n ' '
 
        stLoop []     = [""]
        stLoop [t]    = grp s2 "  " (draw t)
@@ -224,6 +240,17 @@ draw (Node x ts) = grp this (space (length this)) (stLoop ts)
 %************************************************************************
 
 \begin{code}
+#if __GLASGOW_HASKELL__ >= 504
+newSTArray :: Ix i => (i,i) -> e -> ST s (STArray s i e)
+newSTArray = newArray
+
+readSTArray :: Ix i => STArray s i e -> i -> ST s e
+readSTArray = readArray
+
+writeSTArray :: Ix i => STArray s i e -> i -> e -> ST s ()
+writeSTArray = writeArray
+#endif
+
 type Set s    = STArray s Vertex Bool
 
 mkEmpty      :: Bounds -> ST s (Set s)
@@ -281,9 +308,6 @@ preorder (Node a ts) = a : preorderF ts
 preorderF           :: Forest a -> [a]
 preorderF ts         = concat (map preorder ts)
 
-preOrd :: Graph -> [Vertex]
-preOrd  = preorderF . dff
-
 tabulate        :: Bounds -> [Vertex] -> Table Int
 tabulate bnds vs = array bnds (zipWith (,) vs [1..])
 
@@ -337,12 +361,6 @@ scc g = dfs g (reverse (postOrd (transposeG g)))
 ------------------------------------------------------------
 
 \begin{code}
-tree              :: Bounds -> Forest Vertex -> Graph
-tree bnds ts       = buildG bnds (concat (map flat ts))
-                  where
-                    flat (Node v rs) = [ (v, w) | Node w us <- ts ] ++
-                                       concat (map flat ts)
-
 back              :: Graph -> Table Int -> Graph
 back g post        = mapT select g
  where select v ws = [ w | w <- ws, post!v < post!w ]