306 lines
11 KiB
OCaml
306 lines
11 KiB
OCaml
(***********************************************************************)
|
|
(* *)
|
|
(* Objective Caml *)
|
|
(* *)
|
|
(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
|
|
(* *)
|
|
(* Copyright 1996 Institut National de Recherche en Informatique et *)
|
|
(* en Automatique. All rights reserved. This file is distributed *)
|
|
(* under the terms of the Q Public License version 1.0. *)
|
|
(* *)
|
|
(***********************************************************************)
|
|
|
|
(* $Id$ *)
|
|
|
|
(* 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; sw_nofail = sw.sw_nofail})
|
|
| Lstaticfail as l -> l
|
|
| Lstaticraise _ as l -> l
|
|
| Lcatch(e1, e2) ->
|
|
Lcatch(eliminate_ref id e1, eliminate_ref id e2)
|
|
| Lstaticcatch(e1, i, e2) ->
|
|
Lstaticcatch(eliminate_ref id e1, i, 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)
|
|
| Lifused(v, e) ->
|
|
Lifused(v, eliminate_ref id e)
|
|
|
|
|
|
(* 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
|
|
and incr_var v =
|
|
try
|
|
incr(Hashtbl.find occ v)
|
|
with Not_found ->
|
|
Hashtbl.add occ v (ref 1) in
|
|
|
|
(* Also count occurrences of (exit n) statements with no arguments *)
|
|
let exits = Hashtbl.create 17 in
|
|
let count_exit i =
|
|
try
|
|
!(Hashtbl.find exits i)
|
|
with
|
|
| Not_found -> 0
|
|
and incr_exit i =
|
|
try
|
|
incr(Hashtbl.find exits i)
|
|
with
|
|
| Not_found -> Hashtbl.add exits i (ref 1) in
|
|
(* And occurences of Lstaticfail, in every staticcatch scope *)
|
|
let count_fail = ref (ref 0) in
|
|
let at_catch = ref [] in
|
|
|
|
|
|
let rec count = function
|
|
| Lvar v -> incr_var v
|
|
| Lconst cst -> ()
|
|
| Lapply(l1, ll) -> count l1; List.iter count ll
|
|
| Lfunction(kind, params, l) -> count l
|
|
| Llet(str, v, Lvar w, l2) when not !Clflags.debug ->
|
|
(* 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) ->
|
|
(* switch may generate Lstaticfail *)
|
|
if
|
|
(not sw.sw_nofail) &&
|
|
(sw.sw_numconsts > List.length sw.sw_consts ||
|
|
sw.sw_numblocks > List.length sw.sw_blocks)
|
|
then
|
|
!count_fail := !(!count_fail) + 2 ;
|
|
count l;
|
|
List.iter (fun (n, l) -> count l) sw.sw_consts;
|
|
List.iter (fun (n, l) -> count l) sw.sw_blocks ;
|
|
| Lstaticfail -> incr !count_fail
|
|
| Lstaticraise (i,ls) -> incr_exit i ; List.iter count ls
|
|
| Lcatch(l1, l2) as l ->
|
|
let save_count_fail = !count_fail in
|
|
count_fail := ref 0 ;
|
|
count l1;
|
|
let this_count = !(!count_fail) in
|
|
at_catch := (l,!(!count_fail)) :: !at_catch ;
|
|
count_fail := save_count_fail ;
|
|
(* If l1 does not contain staticfail,
|
|
l2 will be removed, so don't count its variables *)
|
|
if this_count > 0 then
|
|
count l2
|
|
| Lstaticcatch(l1, (i,_), l2) ->
|
|
count l1;
|
|
(* If l1 does not contain (exit i),
|
|
l2 will be removed, so don't count its variables *)
|
|
if count_exit i > 0 then
|
|
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(_, 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, _) -> count l
|
|
| Lifused(v, l) ->
|
|
if count_var v > 0 then count l
|
|
in
|
|
count lam;
|
|
(* Second pass: remove Lalias bindings of unused variables,
|
|
and substitute the bindings of variables used exactly once. *)
|
|
(* Also treat ``catch body with (i) handler''
|
|
- if (exit i) does not occur in body, suppress catch
|
|
- if (exit i) occurs exactly once in body,
|
|
substitute it with handler *)
|
|
let subst = Hashtbl.create 83
|
|
and subst_exit = Hashtbl.create 17
|
|
and subst_fail = ref Lstaticfail 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) when not !Clflags.debug ->
|
|
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(Variable, v, slinit, eliminate_ref v slbody)
|
|
with Real_reference ->
|
|
Llet(Strict, v, Lprim(Pmakeblock(0, Mutable), [slinit]), slbody)
|
|
end
|
|
| Llet(Alias, v, l1, l2) ->
|
|
begin match count_var v with
|
|
0 -> simplif l2
|
|
| 1 when not !Clflags.debug ->
|
|
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
|
|
| Llet(kind, v, l1, l2) -> Llet(kind, v, simplif l1, simplif l2)
|
|
| 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) ->
|
|
let new_l = simplif l
|
|
and new_consts = List.map (fun (n, e) -> (n, simplif e)) sw.sw_consts
|
|
and new_blocks = List.map (fun (n, e) -> (n, simplif e)) sw.sw_blocks in
|
|
Lswitch
|
|
(new_l,{sw with sw_consts = new_consts ; sw_blocks = new_blocks})
|
|
| Lstaticfail as l -> !subst_fail
|
|
| Lstaticraise (i,[]) as l ->
|
|
begin try
|
|
Hashtbl.find subst_exit i
|
|
with
|
|
| Not_found -> l
|
|
end
|
|
| Lstaticraise (i,ls) ->
|
|
Lstaticraise (i, List.map simplif ls)
|
|
| Lcatch(l1, l2) as l ->
|
|
let nfail =
|
|
try
|
|
List.assq l !at_catch
|
|
with
|
|
| Not_found -> Misc.fatal_error "Simplif: catch" in
|
|
begin match nfail with
|
|
| 0 -> simplif l1
|
|
| 1 ->
|
|
let new_l2 = simplif l2 in
|
|
let save_subst_fail = !subst_fail in
|
|
subst_fail := new_l2 ;
|
|
let r = simplif l1 in
|
|
subst_fail := save_subst_fail ;
|
|
r
|
|
| _ ->
|
|
let save_subst_fail = !subst_fail in
|
|
subst_fail := Lstaticfail ;
|
|
let r = simplif l1 in
|
|
subst_fail := save_subst_fail ;
|
|
Lcatch (r,simplif l2)
|
|
end
|
|
| Lstaticcatch (l1,(i,[]),l2) ->
|
|
begin match count_exit i with
|
|
| 0 -> simplif l1
|
|
| 1 ->
|
|
Hashtbl.add subst_exit i (simplif l2) ;
|
|
simplif l1
|
|
| _ ->
|
|
Lstaticcatch (simplif l1, (i,[]), simplif l2)
|
|
end
|
|
| Lstaticcatch(l1, (i,args), l2) ->
|
|
begin match count_exit i with
|
|
| 0 -> simplif l1
|
|
| _ ->
|
|
Lstaticcatch (simplif l1, (i,args), simplif l2)
|
|
end
|
|
| Ltrywith(l1, v, l2) -> Ltrywith(simplif l1, v, simplif l2)
|
|
| Lifthenelse(l1, l2, l3) -> Lifthenelse(simplif l1, simplif l2, simplif l3)
|
|
| Lsequence(Lifused(v, l1), l2) ->
|
|
if count_var v > 0
|
|
then Lsequence(simplif l1, simplif l2)
|
|
else simplif l2
|
|
| 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)
|
|
| Lifused(v, l) ->
|
|
if count_var v > 0 then simplif l else lambda_unit
|
|
in
|
|
simplif lam
|