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|
type uop = Neg
type bop = Add | Sub | CLe | CEq
type bref = int (* Block references. *)
type 'op seqi = [ `Nop | `Uop of uop * 'op | `Bop of 'op * bop * 'op ]
type 'op jmpi = [ `Brz of 'op * bref * bref | `Jmp of bref ]
type ('ins, 'op) bb =
{ bb_phis: [ `Phi of 'op list ] array
; bb_inss: 'ins array
; bb_jmp: 'op jmpi
}
(* ** Liveness analysis. ** *)
type iref = IRPhi of (bref * int) | IRIns of (bref * int)
type iprog = ((iref seqi, iref) bb) array
module IRSet = Set.Make(
struct type t = iref let compare = compare end
)
let liveness (p: iprog) =
let module H = Hashtbl in
let changed = ref true in (* Witness for fixpoint. *)
let lh = H.create 1001 in
let liveout ir =
try H.find lh ir with Not_found ->
let e = IRSet.empty in H.add lh ir e; e in
let setlive ir ir' = (* Mark ir live at ir'. *)
let lir' = liveout ir' in
if not (IRSet.mem ir lir') then begin
changed := true;
H.replace lh ir' (IRSet.add ir lir');
end in
let succs (b, i) = (* Successor nodes of an instruction. *)
let bb = p.(b) in
if i+1 = Array.length bb.bb_inss then
if b+1 = Array.length p then [] else
match bb.bb_jmp with
| `Brz (_, b1, b2) -> [(b1, 0); (b2, 0)]
| `Jmp b1 -> [(b1, 0)]
else [(b, i+1)] in
let gen (b, i) = IRSet.of_list
begin match p.(b).bb_inss.(i) with
| `Uop (_, i1) -> [i1]
| `Bop (i1, _, i2) -> [i1; i2]
| `Nop -> []
end in
let livein ir =
let s = liveout ir in
let s = IRSet.union s (gen ir) in
IRSet.remove (IRIns ir) s in
while !changed do
changed := false;
for b = Array.length p - 1 downto 0 do
let bb = p.(b) in
for i = Array.length bb.bb_inss - 1 downto 0 do
let ir = (b, i) in
let live = List.fold_left (fun live ir' ->
IRSet.union live (livein ir')
) IRSet.empty (succs ir) in
IRSet.iter (fun ir' -> setlive ir' ir) live
done;
Array.iter (fun (`Phi il) ->
let blk ir = match ir with
| IRPhi (b, _) | IRIns (b, _) -> b in
List.iter (fun ir ->
let br = blk ir in
let bb = p.(br) in
setlive ir (br, Array.length bb.bb_inss - 1)
) il
) bb.bb_phis;
done
done;
lh (* Return the final hash table. *)
(* ** Register allocation. ** *)
type loc = LVoid | LReg of int | LSpill of int
|
