+++ /dev/null
-
--- | Graph Coloring.
--- This is a generic graph coloring library, abstracted over the type of
--- the node keys, nodes and colors.
---
-{-# OPTIONS -fno-warn-missing-signatures #-}
-
-module GraphColor (
- module GraphBase,
- module GraphOps,
- module GraphPpr,
- colorGraph
-)
-
-where
-
-import GraphBase
-import GraphOps
-import GraphPpr
-
-import Unique
-import UniqFM
-import UniqSet
-import Outputable
-
-import Data.Maybe
-import Data.List
-
-
--- | Try to color a graph with this set of colors.
--- Uses Chaitin's algorithm to color the graph.
--- The graph is scanned for nodes which are deamed 'trivially colorable'. These nodes
--- are pushed onto a stack and removed from the graph.
--- Once this process is complete the graph can be colored by removing nodes from
--- the stack (ie in reverse order) and assigning them colors different to their neighbors.
---
-colorGraph
- :: ( Uniquable k, Uniquable cls, Uniquable color
- , Eq color, Eq cls, Ord k
- , Outputable k, Outputable cls, Outputable color)
- => Bool -- ^ whether to do iterative coalescing
- -> UniqFM (UniqSet color) -- ^ map of (node class -> set of colors available for this class).
- -> Triv k cls color -- ^ fn to decide whether a node is trivially colorable.
- -> (Graph k cls color -> k) -- ^ fn to choose a node to potentially leave uncolored if nothing is trivially colorable.
- -> Graph k cls color -- ^ the graph to color.
-
- -> ( Graph k cls color -- the colored graph.
- , UniqSet k -- the set of nodes that we couldn't find a color for.
- , UniqFM k ) -- map of regs (r1 -> r2) that were coaleced
- -- r1 should be replaced by r2 in the source
-
-colorGraph iterative colors triv spill graph0
- = let
- -- if we're not doing iterative coalescing, then just do a single coalescing
- -- pass at the front. This won't be as good but should still eat up a
- -- lot of the reg-reg moves.
- (graph_coalesced, kksCoalesce1)
- = if not iterative
- then coalesceGraph False triv graph0
- else (graph0, [])
-
- -- run the scanner to slurp out all the trivially colorable nodes
- -- (and do coalescing if iterative coalescing is enabled)
- (ksTriv, ksProblems, kksCoalesce2)
- = colorScan iterative triv spill graph_coalesced
-
- -- If iterative coalescing is enabled, the scanner will coalesce the graph as does its business.
- -- We need to apply all the coalescences found by the scanner to the original
- -- graph before doing assignColors.
- --
- -- Because we've got the whole, non-pruned graph here we turn on aggressive coalecing
- -- to force all the (conservative) coalescences found during scanning.
- --
- (graph_scan_coalesced, _)
- = mapAccumL (coalesceNodes True triv) graph_coalesced kksCoalesce2
-
- -- color the trivially colorable nodes
- -- during scanning, keys of triv nodes were added to the front of the list as they were found
- -- this colors them in the reverse order, as required by the algorithm.
- (graph_triv, ksNoTriv)
- = assignColors colors graph_scan_coalesced ksTriv
-
- -- try and color the problem nodes
- -- problem nodes are the ones that were left uncolored because they weren't triv.
- -- theres a change we can color them here anyway.
- (graph_prob, ksNoColor)
- = assignColors colors graph_triv ksProblems
-
- -- if the trivially colorable nodes didn't color then something is probably wrong
- -- with the provided triv function.
- --
- in if not $ null ksNoTriv
- then pprPanic "colorGraph: trivially colorable nodes didn't color!" empty
-{- ( empty
- $$ text "ksTriv = " <> ppr ksTriv
- $$ text "ksNoTriv = " <> ppr ksNoTriv
- $$ empty
- $$ dotGraph (\x -> text "white") triv graph1) -}
-
- else ( graph_prob
- , mkUniqSet ksNoColor -- the nodes that didn't color (spills)
- , if iterative
- then (listToUFM kksCoalesce2)
- else (listToUFM kksCoalesce1))
-
-
--- | Scan through the conflict graph separating out trivially colorable and
--- potentially uncolorable (problem) nodes.
---
--- Checking whether a node is trivially colorable or not is a resonably expensive operation,
--- so after a triv node is found and removed from the graph it's no good to return to the 'start'
--- of the graph and recheck a bunch of nodes that will probably still be non-trivially colorable.
---
--- To ward against this, during each pass through the graph we collect up a list of triv nodes
--- that were found, and only remove them once we've finished the pass. The more nodes we can delete
--- at once the more likely it is that nodes we've already checked will become trivially colorable
--- for the next pass.
---
--- TODO: add work lists to finding triv nodes is easier.
--- If we've just scanned the graph, and removed triv nodes, then the only
--- nodes that we need to rescan are the ones we've removed edges from.
-
-colorScan
- :: ( Uniquable k, Uniquable cls, Uniquable color
- , Ord k, Eq cls
- , Outputable k, Outputable color)
- => Bool -- ^ whether to do iterative coalescing
- -> Triv k cls color -- ^ fn to decide whether a node is trivially colorable
- -> (Graph k cls color -> k) -- ^ fn to choose a node to potentially leave uncolored if nothing is trivially colorable.
- -> Graph k cls color -- ^ the graph to scan
-
- -> ([k], [k], [(k, k)]) -- triv colorable nodes, problem nodes, pairs of nodes to coalesce
-
-colorScan iterative triv spill graph
- = colorScan_spin iterative triv spill graph [] [] []
-
-colorScan_spin iterative triv spill graph
- ksTriv ksSpill kksCoalesce
-
- -- if the graph is empty then we're done
- | isNullUFM $ graphMap graph
- = (ksTriv, ksSpill, kksCoalesce)
-
- -- Simplify:
- -- Look for trivially colorable nodes.
- -- If we can find some then remove them from the graph and go back for more.
- --
- | nsTrivFound@(_:_)
- <- scanGraph (\node -> triv (nodeClass node) (nodeConflicts node) (nodeExclusions node)
-
- -- for iterative coalescing we only want non-move related
- -- nodes here
- && (not iterative || isEmptyUniqSet (nodeCoalesce node)))
- $ graph
-
- , ksTrivFound <- map nodeId nsTrivFound
- , graph3 <- foldr (\k g -> let Just g' = delNode k g
- in g')
- graph ksTrivFound
-
- = colorScan_spin iterative triv spill graph3
- (ksTrivFound ++ ksTriv)
- ksSpill
- kksCoalesce
-
- -- Coalesce:
- -- If we're doing iterative coalescing and no triv nodes are avaliable
- -- then it's type for a coalescing pass.
- | iterative
- = case coalesceGraph False triv graph of
-
- -- we were able to coalesce something
- -- go back and see if this frees up more nodes to be trivially colorable.
- (graph2, kksCoalesceFound @(_:_))
- -> colorScan_spin iterative triv spill graph2
- ksTriv ksSpill (kksCoalesceFound ++ kksCoalesce)
-
- -- Freeze:
- -- nothing could be coalesced (or was triv),
- -- time to choose a node to freeze and give up on ever coalescing it.
- (graph2, [])
- -> case freezeOneInGraph graph2 of
-
- -- we were able to freeze something
- -- hopefully this will free up something for Simplify
- (graph3, True)
- -> colorScan_spin iterative triv spill graph3
- ksTriv ksSpill kksCoalesce
-
- -- we couldn't find something to freeze either
- -- time for a spill
- (graph3, False)
- -> colorScan_spill iterative triv spill graph3
- ksTriv ksSpill kksCoalesce
-
- -- spill time
- | otherwise
- = colorScan_spill iterative triv spill graph
- ksTriv ksSpill kksCoalesce
-
-
--- Select:
--- we couldn't find any triv nodes or things to freeze or coalesce,
--- and the graph isn't empty yet.. We'll have to choose a spill
--- candidate and leave it uncolored.
---
-colorScan_spill iterative triv spill graph
- ksTriv ksSpill kksCoalesce
-
- = let kSpill = spill graph
- Just graph' = delNode kSpill graph
- in colorScan_spin iterative triv spill graph'
- ksTriv (kSpill : ksSpill) kksCoalesce
-
-
--- | Try to assign a color to all these nodes.
-
-assignColors
- :: ( Uniquable k, Uniquable cls, Uniquable color, Eq color )
- => UniqFM (UniqSet color) -- ^ map of (node class -> set of colors available for this class).
- -> Graph k cls color -- ^ the graph
- -> [k] -- ^ nodes to assign a color to.
- -> ( Graph k cls color -- the colored graph
- , [k]) -- the nodes that didn't color.
-
-assignColors colors graph ks
- = assignColors' colors graph [] ks
-
- where assignColors' _ graph prob []
- = (graph, prob)
-
- assignColors' colors graph prob (k:ks)
- = case assignColor colors k graph of
-
- -- couldn't color this node
- Nothing -> assignColors' colors graph (k : prob) ks
-
- -- this node colored ok, so do the rest
- Just graph' -> assignColors' colors graph' prob ks
-
-
- assignColor colors u graph
- | Just c <- selectColor colors graph u
- = Just (setColor u c graph)
-
- | otherwise
- = Nothing
-
-
-
--- | Select a color for a certain node
--- taking into account preferences, neighbors and exclusions.
--- returns Nothing if no color can be assigned to this node.
---
-selectColor
- :: ( Uniquable k, Uniquable cls, Uniquable color, Eq color)
- => UniqFM (UniqSet color) -- ^ map of (node class -> set of colors available for this class).
- -> Graph k cls color -- ^ the graph
- -> k -- ^ key of the node to select a color for.
- -> Maybe color
-
-selectColor colors graph u
- = let -- lookup the node
- Just node = lookupNode graph u
-
- -- lookup the available colors for the class of this node.
- Just colors_avail
- = lookupUFM colors (nodeClass node)
-
- -- find colors we can't use because they're already being used
- -- by a node that conflicts with this one.
- Just nsConflicts
- = sequence
- $ map (lookupNode graph)
- $ uniqSetToList
- $ nodeConflicts node
-
- colors_conflict = mkUniqSet
- $ catMaybes
- $ map nodeColor nsConflicts
-
- -- the prefs of our neighbors
- colors_neighbor_prefs
- = mkUniqSet
- $ concat $ map nodePreference nsConflicts
-
- -- colors that are still valid for us
- colors_ok_ex = minusUniqSet colors_avail (nodeExclusions node)
- colors_ok = minusUniqSet colors_ok_ex colors_conflict
-
- -- the colors that we prefer, and are still ok
- colors_ok_pref = intersectUniqSets
- (mkUniqSet $ nodePreference node) colors_ok
-
- -- the colors that we could choose while being nice to our neighbors
- colors_ok_nice = minusUniqSet
- colors_ok colors_neighbor_prefs
-
- -- the best of all possible worlds..
- colors_ok_pref_nice
- = intersectUniqSets
- colors_ok_nice colors_ok_pref
-
- -- make the decision
- chooseColor
-
- -- everyone is happy, yay!
- | not $ isEmptyUniqSet colors_ok_pref_nice
- , c : _ <- filter (\x -> elementOfUniqSet x colors_ok_pref_nice)
- (nodePreference node)
- = Just c
-
- -- we've got one of our preferences
- | not $ isEmptyUniqSet colors_ok_pref
- , c : _ <- filter (\x -> elementOfUniqSet x colors_ok_pref)
- (nodePreference node)
- = Just c
-
- -- it wasn't a preference, but it was still ok
- | not $ isEmptyUniqSet colors_ok
- , c : _ <- uniqSetToList colors_ok
- = Just c
-
- -- no colors were available for us this time.
- -- looks like we're going around the loop again..
- | otherwise
- = Nothing
-
- in chooseColor
-
-
-
projects / ghc-hetmet.git / blobdiff