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(**************************************************************************)
(* *)
(* OCaml *)
(* *)
(* 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 GNU Lesser General Public License version 2.1, with the *)
(* special exception on linking described in the file LICENSE. *)
(* *)
(**************************************************************************)
(* Transformation of Mach code into a list of pseudo-instructions. *)
open Reg
open Mach
type label = Cmm.label
type instruction =
{ mutable desc: instruction_desc;
mutable next: instruction;
arg: Reg.t array;
res: Reg.t array;
dbg: Debuginfo.t;
live: Reg.Set.t }
and instruction_desc =
Lend
| Lop of operation
| Lreloadretaddr
| Lreturn
| Llabel of label
| Lbranch of label
| Lcondbranch of test * label
| Lcondbranch3 of label option * label option * label option
| Lswitch of label array
| Lsetuptrap of label
| Lpushtrap
| Lpoptrap
| Lraise of Cmm.raise_kind
let has_fallthrough = function
| Lreturn | Lbranch _ | Lswitch _ | Lraise _
| Lop Itailcall_ind _ | Lop (Itailcall_imm _) -> false
| _ -> true
type fundecl =
{ fun_name: string;
fun_body: instruction;
fun_fast: bool;
fun_dbg : Debuginfo.t;
fun_spacetime_shape : Mach.spacetime_shape option;
}
(* Invert a test *)
let invert_integer_test = function
Isigned cmp -> Isigned(Cmm.negate_comparison cmp)
| Iunsigned cmp -> Iunsigned(Cmm.negate_comparison cmp)
let invert_test = function
Itruetest -> Ifalsetest
| Ifalsetest -> Itruetest
| Iinttest(cmp) -> Iinttest(invert_integer_test cmp)
| Iinttest_imm(cmp, n) -> Iinttest_imm(invert_integer_test cmp, n)
| Ifloattest(cmp, neg) -> Ifloattest(cmp, not neg)
| Ieventest -> Ioddtest
| Ioddtest -> Ieventest
(* The "end" instruction *)
let rec end_instr =
{ desc = Lend;
next = end_instr;
arg = [||];
res = [||];
dbg = Debuginfo.none;
live = Reg.Set.empty }
(* Cons an instruction (live, debug empty) *)
let instr_cons d a r n =
{ desc = d; next = n; arg = a; res = r;
dbg = Debuginfo.none; live = Reg.Set.empty }
(* Cons a simple instruction (arg, res, live empty) *)
let cons_instr d n =
{ desc = d; next = n; arg = [||]; res = [||];
dbg = Debuginfo.none; live = Reg.Set.empty }
(* Build an instruction with arg, res, dbg, live taken from
the given Mach.instruction *)
let copy_instr d i n =
{ desc = d; next = n;
arg = i.Mach.arg; res = i.Mach.res;
dbg = i.Mach.dbg; live = i.Mach.live }
(*
Label the beginning of the given instruction sequence.
- If the sequence starts with a branch, jump over it.
- If the sequence is the end, (tail call position), just do nothing
*)
let get_label n = match n.desc with
Lbranch lbl -> (lbl, n)
| Llabel lbl -> (lbl, n)
| Lend -> (-1, n)
| _ -> let lbl = Cmm.new_label() in (lbl, cons_instr (Llabel lbl) n)
(* Check the fallthrough label *)
let check_label n = match n.desc with
| Lbranch lbl -> lbl
| Llabel lbl -> lbl
| _ -> -1
(* Discard all instructions up to the next label.
This function is to be called before adding a non-terminating
instruction. *)
let rec discard_dead_code n =
match n.desc with
Lend -> n
| Llabel _ -> n
(* Do not discard Lpoptrap/Lpushtrap or Istackoffset instructions,
as this may cause a stack imbalance later during assembler generation. *)
| Lpoptrap | Lpushtrap -> n
| Lop(Istackoffset _) -> n
| _ -> discard_dead_code n.next
(*
Add a branch in front of a continuation.
Discard dead code in the continuation.
Does not insert anything if we're just falling through
or if we jump to dead code after the end of function (lbl=-1)
*)
let add_branch lbl n =
if lbl >= 0 then
let n1 = discard_dead_code n in
match n1.desc with
| Llabel lbl1 when lbl1 = lbl -> n1
| _ -> cons_instr (Lbranch lbl) n1
else
discard_dead_code n
let try_depth = ref 0
(* Association list: exit handler -> (handler label, try-nesting factor) *)
let exit_label = ref []
let find_exit_label_try_depth k =
try
List.assoc k !exit_label
with
| Not_found -> Misc.fatal_error "Linearize.find_exit_label"
let find_exit_label k =
let (label, t) = find_exit_label_try_depth k in
assert(t = !try_depth);
label
let is_next_catch n = match !exit_label with
| (n0,(_,t))::_ when n0=n && t = !try_depth -> true
| _ -> false
let local_exit k =
snd (find_exit_label_try_depth k) = !try_depth
(* Linearize an instruction [i]: add it in front of the continuation [n] *)
let rec linear i n =
match i.Mach.desc with
Iend -> n
| Iop(Itailcall_ind _ | Itailcall_imm _ as op) ->
if not Config.spacetime then
copy_instr (Lop op) i (discard_dead_code n)
else
copy_instr (Lop op) i (linear i.Mach.next n)
| Iop(Imove | Ireload | Ispill)
when i.Mach.arg.(0).loc = i.Mach.res.(0).loc ->
linear i.Mach.next n
| Iop op ->
copy_instr (Lop op) i (linear i.Mach.next n)
| Ireturn ->
let n1 = copy_instr Lreturn i (discard_dead_code n) in
if !Proc.contains_calls
then cons_instr Lreloadretaddr n1
else n1
| Iifthenelse(test, ifso, ifnot) ->
let n1 = linear i.Mach.next n in
begin match (ifso.Mach.desc, ifnot.Mach.desc, n1.desc) with
Iend, _, Lbranch lbl ->
copy_instr (Lcondbranch(test, lbl)) i (linear ifnot n1)
| _, Iend, Lbranch lbl ->
copy_instr (Lcondbranch(invert_test test, lbl)) i (linear ifso n1)
| Iexit nfail1, Iexit nfail2, _
when is_next_catch nfail1 && local_exit nfail2 ->
let lbl2 = find_exit_label nfail2 in
copy_instr
(Lcondbranch (invert_test test, lbl2)) i (linear ifso n1)
| Iexit nfail, _, _ when local_exit nfail ->
let n2 = linear ifnot n1
and lbl = find_exit_label nfail in
copy_instr (Lcondbranch(test, lbl)) i n2
| _, Iexit nfail, _ when local_exit nfail ->
let n2 = linear ifso n1 in
let lbl = find_exit_label nfail in
copy_instr (Lcondbranch(invert_test test, lbl)) i n2
| Iend, _, _ ->
let (lbl_end, n2) = get_label n1 in
copy_instr (Lcondbranch(test, lbl_end)) i (linear ifnot n2)
| _, Iend, _ ->
let (lbl_end, n2) = get_label n1 in
copy_instr (Lcondbranch(invert_test test, lbl_end)) i
(linear ifso n2)
| _, _, _ ->
(* Should attempt branch prediction here *)
let (lbl_end, n2) = get_label n1 in
let (lbl_else, nelse) = get_label (linear ifnot n2) in
copy_instr (Lcondbranch(invert_test test, lbl_else)) i
(linear ifso (add_branch lbl_end nelse))
end
| Iswitch(index, cases) ->
let lbl_cases = Array.make (Array.length cases) 0 in
let (lbl_end, n1) = get_label(linear i.Mach.next n) in
let n2 = ref (discard_dead_code n1) in
for i = Array.length cases - 1 downto 0 do
let (lbl_case, ncase) =
get_label(linear cases.(i) (add_branch lbl_end !n2)) in
lbl_cases.(i) <- lbl_case;
n2 := discard_dead_code ncase
done;
(* Switches with 1 and 2 branches have been eliminated earlier.
Here, we do something for switches with 3 branches. *)
if Array.length index = 3 then begin
let fallthrough_lbl = check_label !n2 in
let find_label n =
let lbl = lbl_cases.(index.(n)) in
if lbl = fallthrough_lbl then None else Some lbl in
copy_instr (Lcondbranch3(find_label 0, find_label 1, find_label 2))
i !n2
end else
copy_instr (Lswitch(Array.map (fun n -> lbl_cases.(n)) index)) i !n2
| Iloop body ->
let lbl_head = Cmm.new_label() in
let n1 = linear i.Mach.next n in
let n2 = linear body (cons_instr (Lbranch lbl_head) n1) in
cons_instr (Llabel lbl_head) n2
| Icatch(_rec_flag, handlers, body) ->
let (lbl_end, n1) = get_label(linear i.Mach.next n) in
(* CR mshinwell for pchambart:
1. rename "io"
2. Make sure the test cases cover the "Iend" cases too *)
let labels_at_entry_to_handlers = List.map (fun (_nfail, handler) ->
match handler.Mach.desc with
| Iend -> lbl_end
| _ -> Cmm.new_label ())
handlers in
let exit_label_add = List.map2
(fun (nfail, _) lbl -> (nfail, (lbl, !try_depth)))
handlers labels_at_entry_to_handlers in
let previous_exit_label = !exit_label in
exit_label := exit_label_add @ !exit_label;
let n2 = List.fold_left2 (fun n (_nfail, handler) lbl_handler ->
match handler.Mach.desc with
| Iend -> n
| _ -> cons_instr (Llabel lbl_handler) (linear handler n))
n1 handlers labels_at_entry_to_handlers
in
let n3 = linear body (add_branch lbl_end n2) in
exit_label := previous_exit_label;
n3
| Iexit nfail ->
let lbl, t = find_exit_label_try_depth nfail in
(* We need to re-insert dummy pushtrap (which won't be executed),
so as to preserve stack offset during assembler generation.
It would make sense to have a special pseudo-instruction
only to inform the later pass about this stack offset
(corresponding to N traps).
*)
let rec loop i tt =
if t = tt then i
else loop (cons_instr Lpushtrap i) (tt - 1)
in
let n1 = loop (linear i.Mach.next n) !try_depth in
let rec loop i tt =
if t = tt then i
else loop (cons_instr Lpoptrap i) (tt - 1)
in
loop (add_branch lbl n1) !try_depth
| Itrywith(body, handler) ->
let (lbl_join, n1) = get_label (linear i.Mach.next n) in
incr try_depth;
assert (i.Mach.arg = [| |] || Config.spacetime);
let (lbl_body, n2) =
get_label (instr_cons Lpushtrap i.Mach.arg [| |]
(linear body (cons_instr Lpoptrap n1))) in
decr try_depth;
instr_cons (Lsetuptrap lbl_body) i.Mach.arg [| |]
(linear handler (add_branch lbl_join n2))
| Iraise k ->
copy_instr (Lraise k) i (discard_dead_code n)
let fundecl f =
{ fun_name = f.Mach.fun_name;
fun_body = linear f.Mach.fun_body end_instr;
fun_fast = f.Mach.fun_fast;
fun_dbg = f.Mach.fun_dbg;
fun_spacetime_shape = f.Mach.fun_spacetime_shape;
}
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