-- | Types for the general graph colorer.
module GraphBase (
Triv,
Graph (..),
initGraph,
graphMapModify,
Node (..), newNode,
)
where
import GhcPrelude
import UniqSet
import UniqFM
-- | A fn to check if a node is trivially colorable
-- For graphs who's color classes are disjoint then a node is 'trivially colorable'
-- when it has less neighbors and exclusions than available colors for that node.
--
-- For graph's who's color classes overlap, ie some colors alias other colors, then
-- this can be a bit more tricky. There is a general way to calculate this, but
-- it's likely be too slow for use in the code. The coloring algorithm takes
-- a canned function which can be optimised by the user to be specific to the
-- specific graph being colored.
--
-- for details, see "A Generalised Algorithm for Graph-Coloring Register Allocation"
-- Smith, Ramsey, Holloway - PLDI 2004.
--
type Triv k cls color
= cls -- the class of the node we're trying to color.
-> UniqSet k -- the node's neighbors.
-> UniqSet color -- the node's exclusions.
-> Bool
-- | The Interference graph.
-- There used to be more fields, but they were turfed out in a previous revision.
-- maybe we'll want more later..
--
data Graph k cls color
= Graph {
-- | All active nodes in the graph.
graphMap :: UniqFM (Node k cls color) }
-- | An empty graph.
initGraph :: Graph k cls color
initGraph
= Graph
{ graphMap = emptyUFM }
-- | Modify the finite map holding the nodes in the graph.
graphMapModify
:: (UniqFM (Node k cls color) -> UniqFM (Node k cls color))
-> Graph k cls color -> Graph k cls color
graphMapModify f graph
= graph { graphMap = f (graphMap graph) }
-- | Graph nodes.
-- Represents a thing that can conflict with another thing.
-- For the register allocater the nodes represent registers.
--
data Node k cls color
= Node {
-- | A unique identifier for this node.
nodeId :: k
-- | The class of this node,
-- determines the set of colors that can be used.
, nodeClass :: cls
-- | The color of this node, if any.
, nodeColor :: Maybe color
-- | Neighbors which must be colored differently to this node.
, nodeConflicts :: UniqSet k
-- | Colors that cannot be used by this node.
, nodeExclusions :: UniqSet color
-- | Colors that this node would prefer to be, in decending order.
, nodePreference :: [color]
-- | Neighbors that this node would like to be colored the same as.
, nodeCoalesce :: UniqSet k }
-- | An empty node.
newNode :: k -> cls -> Node k cls color
newNode k cls
= Node
{ nodeId = k
, nodeClass = cls
, nodeColor = Nothing
, nodeConflicts = emptyUniqSet
, nodeExclusions = emptyUniqSet
, nodePreference = []
, nodeCoalesce = emptyUniqSet }