-- This is a generic graph coloring library, abstracted over the type of
-- the node keys, nodes and colors.
--
-
-{-# OPTIONS_GHC -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
--- for details
+{-# OPTIONS -fno-warn-missing-signatures #-}
module GraphColor (
module GraphBase,
:: ( Uniquable k, Uniquable cls, Uniquable color
, Eq color, Eq cls, Ord k
, Outputable k, Outputable cls, Outputable color)
- => UniqFM (UniqSet color) -- ^ map of (node class -> set of colors available for this class).
+ => 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.
, UniqFM k ) -- map of regs (r1 -> r2) that were coaleced
-- r1 should be replaced by r2 in the source
-colorGraph colors triv spill graph0
+colorGraph iterative colors triv spill graph0
= let
- -- do aggressive coalesing on the graph
- (graph_coalesced, rsCoalesce)
- = coalesceGraph graph0
+ -- 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
- (ksTriv, ksProblems)
- = colorScan colors triv spill [] emptyUniqSet graph_coalesced
+ -- (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_coalesced ksTriv
+ = assignColors colors graph_scan_coalesced ksTriv
-- try and color the problem nodes
- (graph_prob, ksNoColor) = assignColors colors graph_triv (uniqSetToList ksProblems)
+ -- 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 wrong
+ -- 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
$$ dotGraph (\x -> text "white") triv graph1) -}
else ( graph_prob
- , mkUniqSet ksNoColor
- , listToUFM rsCoalesce)
+ , mkUniqSet ksNoColor -- the nodes that didn't color (spills)
+ , if iterative
+ then (listToUFM kksCoalesce2)
+ else (listToUFM kksCoalesce1))
-colorScan colors triv spill safe prob graph
- -- empty graphs are easy to color.
+-- | 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
- = (safe, prob)
-
- -- Try and find a trivially colorable node.
- | Just node <- find (\node -> triv (nodeClass node)
- (nodeConflicts node)
- (nodeExclusions node))
- $ eltsUFM $ graphMap graph
- , k <- nodeId node
- = colorScan colors triv spill
- (k : safe) prob (delNode k 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
- -- There was no trivially colorable node,
- -- Choose one to potentially leave uncolored. We /might/ be able to find
- -- a color for this later on, but no guarantees.
- | k <- spill graph
- = colorScan colors triv spill
- safe (addOneToUniqSet prob k) (delNode k graph)
-
-- | Try to assign a color to all these nodes.
assignColors colors graph ks
= assignColors' colors graph [] ks
- where assignColors' colors graph prob []
+ where assignColors' _ graph prob []
= (graph, prob)
assignColors' colors graph prob (k:ks)
-- taking into account preferences, neighbors and exclusions.
-- returns Nothing if no color can be assigned to this node.
--
--- TODO: avoid using the prefs of the neighbors, if at all possible.
---
selectColor
:: ( Uniquable k, Uniquable cls, Uniquable color, Eq color)
=> UniqFM (UniqSet color) -- ^ map of (node class -> set of colors available for this class).
$ catMaybes
$ map nodeColor nsConflicts
- -- colors that are still ok
+ -- 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
- -- we got one of our preferences, score!
+ -- 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 : rest <- uniqSetToList 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 : rest <- uniqSetToList colors_ok
+ , c : _ <- uniqSetToList colors_ok
= Just c
- -- leave this node uncolored
+ -- no colors were available for us this time.
+ -- looks like we're going around the loop again..
| otherwise
= Nothing
projects / ghc-hetmet.git / blobdiff