(* Pasted from Pottier's PP compiler *)
(** This module implements a data structure for interference graphs.
It provides functions that help construct, transform and inspect
interference graphs. *)
(* Interference graphs record two kinds of edges: interference edges
(``these two vertices cannot receive the same color'') and
preference edges (``these two vertices should preferably receive
the same color''). Furthermore, each kind of edge can relate either
two pseudo-registers or one pseudo-register and one hardware
register. Thus, an interference graph keeps track of four kinds of
relationships.
This module automatically maintains the invariant that two vertices
[x] and [y] cannot be related by both an interference edge and a
preference edge. When such a situation appears (for instance,
because of coalescing), the preference edge is automatically
removed. *)
type graph
(* The vertices of an interference graph initially correspond to
pseudo-registers. However, interference graphs support coalescing,
which means that a new graph can be constructed by coalescing two
vertices in an existing graph. As a result, in general, the vertices
of an interference graph correspond to sets of pseudo-registers. *)
(* ------------------------------------------------------------------------- *)
(* Operations over vertices: sets of vertices, maps over vertices. *)
module Vertex : sig
type t
(* The usual operations on sets, see [Set.S] in Objective Caml's
documentation. *)
module Set : Set.S with type elt = t
(* The usual operations on maps, see [Map.S] in Objective Caml's
documentation. One slight difference is that [find] expects
the key to be present in the map -- it will fail otherwise. *)
module Map : Map.S with type key = t
end
(* ------------------------------------------------------------------------- *)
(* Building interference graphs. *)
(* [create regs] creates an interference graph whose vertices are
the pseudo-registers [regs] and that does not have any edges. *)
val create: Register.Set.t -> graph
(* [mki graph regs1 regs2] adds interference edges between all pairs
of (pseudo- or hardware) registers [r1] and [r2], where [r1] ranges
over [regs1], [r2] ranges over [regs2], and [r1] and [r2] are
distinct. *)
val mki: graph ->
Register.Set.t * I8051.RegisterSet.t ->
Register.Set.t * I8051.RegisterSet.t ->
graph
(* [mkiph graph regs hwregs] adds interference edges between all pairs
of a pseudo-register [r] and a hardware register [hwr], where [r]
ranges over [regs] and [hwr] ranges over [hwregs]. *)
val mkiph: graph -> Register.Set.t -> I8051.RegisterSet.t -> graph
(* [mkppp graph r1 r2] adds a preference edge between the
pseudo-registers [r1] and [r2]. *)
val mkppp: graph -> Register.t -> Register.t -> graph
(* [mkpph graph r h] adds a preference edge between the
pseudo-register [r] and the hardware register [h]. *)
val mkpph: graph -> Register.t -> I8051.register -> graph
(* ------------------------------------------------------------------------- *)
(* Transforming interference graphs. *)
(* [coalesce graph v1 v2] is a new graph where the vertices [v1] and
[v2] are coalesced. [v1] and [v2] must not interfere. The new
coalesced vertex is known under the name [v2]. *)
val coalesce: graph -> Vertex.t -> Vertex.t -> graph
(* [coalesceh graph v h] coalesces the vertex [v] with the hardware register
[h]. This produces a new graph where [v] no longer exists and all edges
leading to [v] are replaced with edges leading to [h]. *)
val coalesceh: graph -> Vertex.t -> I8051.register -> graph
(* [remove graph v] is a new graph where vertex [v] is removed. *)
val remove: graph -> Vertex.t -> graph
(* [freeze graph x] is a new graph where all preference edges carried
by [x] are removed. *)
val freeze: graph -> Vertex.t -> graph
(* [restrict graph p] is a new graph where only those vertices that
satisfy predicate [p] are kept. *)
val restrict: graph -> (Vertex.t -> bool) -> graph
(* [droph graph] is a new graph where all information concerning hardware
registers has been dropped. *)
val droph: graph -> graph
(* ------------------------------------------------------------------------- *)
(* Inspecting interference graphs. *)
(* [lookup graph r] returns the graph vertex associated with
pseudo-register [r]. *)
val lookup: graph -> Register.t -> Vertex.t
(* Conversely, [registers graph v] returns the set of pseudo-registers
associated with vertex [v]. *)
val registers: graph -> Vertex.t -> Register.Set.t
(* [degree graph v] is the degree of the vertex [v], that is, the number
of vertices and hardware registers that [v] interferes with. *)
val degree: graph -> Vertex.t -> int
(* [lowest graph] returns [Some (v, d)], where the vertex [v] has
minimum degree [d], or returns [None] if the graph is empty. *)
val lowest: graph -> (Vertex.t * int) option
(* [lowest_non_move_related graph] returns [Some (v, d)], where the
vertex [v] has minimum degree [d] among the vertices that are not
move-related, or returns [None] if all vertices are move-related. A
vertex is move-related if it carries a preference edge. *)
val lowest_non_move_related: graph -> (Vertex.t * int) option
(* [minimum f graph] returns a vertex [v] such that the value of [f x]
is minimal. The values returned by [f] are compared using Objective
Caml's generic comparison operator [<]. If the graph is empty,
[None] is returned. *)
val minimum: (Vertex.t -> 'a) -> graph -> Vertex.t option
(* [fold f graph accu] folds over all vertices. *)
val fold: (Vertex.t -> 'a -> 'a) -> graph -> 'a -> 'a
(* [ipp graph v] is the set of vertices that the vertex [v] interferes
with. *)
val ipp: graph -> Vertex.t -> Vertex.Set.t
(* [iph graph v] is the set of hardware registers that the vertex [v]
interferes with. *)
val iph: graph -> Vertex.t -> I8051.RegisterSet.t
(* [ppp graph v] is the set of vertices that should preferably be
assigned the same color as the vertex [v]. *)
val ppp: graph -> Vertex.t -> Vertex.Set.t
(* [pph graph v] is the set of hardware registers that [v] should
preferably be assigned. *)
val pph: graph -> Vertex.t -> I8051.RegisterSet.t
(* [pppick graph p] returns an arbitrary preference edge that
satisfies the predicate [p], if the graph contains one. *)
type ppedge =
Vertex.t * Vertex.t
val pppick: graph -> (ppedge -> bool) -> ppedge option
(* [phpick graph p] returns an arbitrary preference edge that
satisfies the predicate [p], if the graph contains one. *)
type phedge =
Vertex.t * I8051.register
val phpick: graph -> (phedge -> bool) -> phedge option
(* ------------------------------------------------------------------------- *)
(* Displaying interference graphs. *)
(* [print_vertex graph v] produces a string representation of the
vertex [v]. *)
val print_vertex: graph -> Vertex.t -> string
(* [print f graph] prints a representation of the interference graph
[graph] in [dot] format to the output channel [f]. Interference
edges are drawn as plain lines; preference edges are drawn as
dotted lines. *)
val print: out_channel -> graph -> unit