198 lines
7.2 KiB
OCaml
198 lines
7.2 KiB
OCaml
(***********************************************************************)
|
|
(* *)
|
|
(* Objective Caml *)
|
|
(* *)
|
|
(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
|
|
(* *)
|
|
(* Copyright 1996 Institut National de Recherche en Informatique et *)
|
|
(* Automatique. Distributed only by permission. *)
|
|
(* *)
|
|
(***********************************************************************)
|
|
|
|
(* $Id$ *)
|
|
|
|
(* Elimination of useless Llet(Alias) bindings.
|
|
Also transform let-bound references into variables. *)
|
|
|
|
open Asttypes
|
|
open Lambda
|
|
|
|
(* To transform let-bound references into variables *)
|
|
|
|
exception Real_reference
|
|
|
|
let rec eliminate_ref id = function
|
|
Lvar v as lam ->
|
|
if Ident.same v id then raise Real_reference else lam
|
|
| Lconst cst as lam -> lam
|
|
| Lapply(e1, el) ->
|
|
Lapply(eliminate_ref id e1, List.map (eliminate_ref id) el)
|
|
| Lfunction(kind, params, body) as lam ->
|
|
if IdentSet.mem id (free_variables lam)
|
|
then raise Real_reference
|
|
else lam
|
|
| Llet(str, v, e1, e2) ->
|
|
Llet(str, v, eliminate_ref id e1, eliminate_ref id e2)
|
|
| Lletrec(idel, e2) ->
|
|
Lletrec(List.map (fun (v, e) -> (v, eliminate_ref id e)) idel,
|
|
eliminate_ref id e2)
|
|
| Lprim(Pfield 0, [Lvar v]) when Ident.same v id ->
|
|
Lvar id
|
|
| Lprim(Psetfield(0, _), [Lvar v; e]) when Ident.same v id ->
|
|
Lassign(id, eliminate_ref id e)
|
|
| Lprim(Poffsetref delta, [Lvar v]) when Ident.same v id ->
|
|
Lassign(id, Lprim(Poffsetint delta, [Lvar id]))
|
|
| Lprim(p, el) ->
|
|
Lprim(p, List.map (eliminate_ref id) el)
|
|
| Lswitch(e, sw) ->
|
|
Lswitch(eliminate_ref id e,
|
|
{sw_numconsts = sw.sw_numconsts;
|
|
sw_consts =
|
|
List.map (fun (n, e) -> (n, eliminate_ref id e)) sw.sw_consts;
|
|
sw_numblocks = sw.sw_numblocks;
|
|
sw_blocks =
|
|
List.map (fun (n, e) -> (n, eliminate_ref id e)) sw.sw_blocks;
|
|
sw_checked = sw.sw_checked})
|
|
| Lstaticfail ->
|
|
Lstaticfail
|
|
| Lcatch(e1, e2) ->
|
|
Lcatch(eliminate_ref id e1, eliminate_ref id e2)
|
|
| Ltrywith(e1, v, e2) ->
|
|
Ltrywith(eliminate_ref id e1, v, eliminate_ref id e2)
|
|
| Lifthenelse(e1, e2, e3) ->
|
|
Lifthenelse(eliminate_ref id e1,
|
|
eliminate_ref id e2,
|
|
eliminate_ref id e3)
|
|
| Lsequence(e1, e2) ->
|
|
Lsequence(eliminate_ref id e1, eliminate_ref id e2)
|
|
| Lwhile(e1, e2) ->
|
|
Lwhile(eliminate_ref id e1, eliminate_ref id e2)
|
|
| Lfor(v, e1, e2, dir, e3) ->
|
|
Lfor(v, eliminate_ref id e1, eliminate_ref id e2,
|
|
dir, eliminate_ref id e3)
|
|
| Lassign(v, e) ->
|
|
Lassign(v, eliminate_ref id e)
|
|
| Lsend(m, o, el) ->
|
|
Lsend(eliminate_ref id m, eliminate_ref id o,
|
|
List.map (eliminate_ref id) el)
|
|
| Levent(l, ev) ->
|
|
Levent(eliminate_ref id l, ev)
|
|
|
|
(* Simplification of lets *)
|
|
|
|
let simplify_lambda lam =
|
|
(* First pass: count the occurrences of all identifiers *)
|
|
let occ = Hashtbl.create 83 in
|
|
let count_var v =
|
|
try
|
|
!(Hashtbl.find occ v)
|
|
with Not_found ->
|
|
0 in
|
|
let rec count = function
|
|
Lvar v ->
|
|
begin try
|
|
incr(Hashtbl.find occ v)
|
|
with Not_found ->
|
|
Hashtbl.add occ v (ref 1)
|
|
end
|
|
| Lconst cst -> ()
|
|
| Lapply(l1, ll) -> count l1; List.iter count ll
|
|
| Lfunction(kind, params, l) -> count l
|
|
| Llet(str, v, Lvar w, l2) ->
|
|
(* v will be replaced by w in l2, so each occurrence of v in l2
|
|
increases w's refcount *)
|
|
count l2;
|
|
let vc = count_var v in
|
|
begin try
|
|
let r = Hashtbl.find occ w in r := !r + vc
|
|
with Not_found ->
|
|
Hashtbl.add occ w (ref vc)
|
|
end
|
|
| Llet(str, v, l1, l2) ->
|
|
count l2;
|
|
(* If v is unused, l1 will be removed, so don't count its variables *)
|
|
if str = Strict or count_var v > 0 then count l1
|
|
| Lletrec(bindings, body) ->
|
|
List.iter (fun (v, l) -> count l) bindings;
|
|
count body
|
|
| Lprim(p, ll) -> List.iter count ll
|
|
| Lswitch(l, sw) ->
|
|
count l;
|
|
List.iter (fun (n, l) -> count l) sw.sw_consts;
|
|
List.iter (fun (n, l) -> count l) sw.sw_blocks
|
|
| Lstaticfail -> ()
|
|
| Lcatch(l1, l2) -> count l1; count l2
|
|
| Ltrywith(l1, v, l2) -> count l1; count l2
|
|
| Lifthenelse(l1, l2, l3) -> count l1; count l2; count l3
|
|
| Lsequence(l1, l2) -> count l1; count l2
|
|
| Lwhile(l1, l2) -> count l1; count l2
|
|
| Lfor(v, l1, l2, dir, l3) -> count l1; count l2; count l3
|
|
| Lassign(v, l) ->
|
|
(* Lalias-bound variables are never assigned, so don't increase
|
|
v's refcount *)
|
|
count l
|
|
| Lsend(m, o, ll) -> List.iter count (m::o::ll)
|
|
| Levent(l, ev) -> count l
|
|
in
|
|
count lam;
|
|
(* Second pass: remove Lalias bindings of unused variables,
|
|
and substitute the bindings of variables used exactly once. *)
|
|
let subst = Hashtbl.create 83 in
|
|
let rec simplif = function
|
|
Lvar v as l ->
|
|
begin try
|
|
Hashtbl.find subst v
|
|
with Not_found ->
|
|
l
|
|
end
|
|
| Lconst cst as l -> l
|
|
| Lapply(l1, ll) -> Lapply(simplif l1, List.map simplif ll)
|
|
| Lfunction(kind, params, l) -> Lfunction(kind, params, simplif l)
|
|
| Llet(str, v, Lvar w, l2) ->
|
|
Hashtbl.add subst v (simplif (Lvar w));
|
|
simplif l2
|
|
| Llet(Strict, v, Lprim(Pmakeblock(0, Mutable), [linit]), lbody)
|
|
when not !Clflags.debug ->
|
|
let slinit = simplif linit in
|
|
let slbody = simplif lbody in
|
|
begin try
|
|
Llet(Strict, v, slinit, eliminate_ref v slbody)
|
|
with Real_reference ->
|
|
Llet(Strict, v, Lprim(Pmakeblock(0, Mutable), [slinit]), slbody)
|
|
end
|
|
| Llet(Strict, v, l1, l2) -> Llet(Strict, v, simplif l1, simplif l2)
|
|
| Llet(Alias, v, l1, l2) ->
|
|
begin match count_var v with
|
|
0 -> simplif l2
|
|
| 1 -> Hashtbl.add subst v (simplif l1); simplif l2
|
|
| n -> Llet(Alias, v, simplif l1, simplif l2)
|
|
end
|
|
| Llet(StrictOpt, v, l1, l2) ->
|
|
begin match count_var v with
|
|
0 -> simplif l2
|
|
| n -> Llet(Alias, v, simplif l1, simplif l2)
|
|
end
|
|
| Lletrec(bindings, body) ->
|
|
Lletrec(List.map (fun (v, l) -> (v, simplif l)) bindings, simplif body)
|
|
| Lprim(p, ll) -> Lprim(p, List.map simplif ll)
|
|
| Lswitch(l, sw) ->
|
|
Lswitch(simplif l,
|
|
{sw_numconsts = sw.sw_numconsts;
|
|
sw_consts = List.map (fun (n, e) -> (n, simplif e)) sw.sw_consts;
|
|
sw_numblocks = sw.sw_numblocks;
|
|
sw_blocks = List.map (fun (n, e) -> (n, simplif e)) sw.sw_blocks;
|
|
sw_checked = sw.sw_checked})
|
|
| Lstaticfail -> Lstaticfail
|
|
| Lcatch(l1, l2) -> Lcatch(simplif l1, simplif l2)
|
|
| Ltrywith(l1, v, l2) -> Ltrywith(simplif l1, v, simplif l2)
|
|
| Lifthenelse(l1, l2, l3) -> Lifthenelse(simplif l1, simplif l2, simplif l3)
|
|
| Lsequence(l1, l2) -> Lsequence(simplif l1, simplif l2)
|
|
| Lwhile(l1, l2) -> Lwhile(simplif l1, simplif l2)
|
|
| Lfor(v, l1, l2, dir, l3) ->
|
|
Lfor(v, simplif l1, simplif l2, dir, simplif l3)
|
|
| Lassign(v, l) -> Lassign(v, simplif l)
|
|
| Lsend(m, o, ll) -> Lsend(simplif m, simplif o, List.map simplif ll)
|
|
| Levent(l, ev) -> Levent(simplif l, ev)
|
|
in
|
|
simplif lam
|