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(* *********************************************************************)
(* *)
(* The Compcert verified compiler *)
(* *)
(* Xavier Leroy, INRIA Paris-Rocquencourt *)
(* *)
(* Copyright Institut National de Recherche en Informatique et en *)
(* Automatique. All rights reserved. This file is distributed *)
(* under the terms of the INRIA Non-Commercial License Agreement. *)
(* *)
(* *********************************************************************)
open Camlcoq
open Switch
open CminorSel
let more_likely (c: condexpr) (ifso: stmt) (ifnot: stmt) = false
module IntOrd =
struct
type t = Integers.Int.int
let compare x y =
if Integers.Int.eq x y then 0 else
if Integers.Int.ltu x y then -1 else 1
end
module IntSet = Set.Make(IntOrd)
let normalize_table tbl =
let rec norm keys accu = function
| [] -> (accu, keys)
| Datatypes.Coq_pair(key, act) :: rem ->
if IntSet.mem key keys
then norm keys accu rem
else norm (IntSet.add key keys) ((key, act) :: accu) rem
in norm IntSet.empty [] tbl
let compile_switch_as_tree default tbl =
let sw = Array.of_list tbl in
Array.stable_sort (fun (n1, _) (n2, _) -> IntOrd.compare n1 n2) sw;
let rec build lo hi minval maxval =
match hi - lo with
| 0 ->
CTaction default
| 1 ->
let (key, act) = sw.(lo) in
if Integers.Int.sub maxval minval = Integers.Int.zero
then CTaction act
else CTifeq(key, act, CTaction default)
| 2 ->
let (key1, act1) = sw.(lo)
and (key2, act2) = sw.(lo+1) in
CTifeq(key1, act1,
if Integers.Int.sub maxval minval = Integers.Int.one
then CTaction act2
else CTifeq(key2, act2, CTaction default))
| 3 ->
let (key1, act1) = sw.(lo)
and (key2, act2) = sw.(lo+1)
and (key3, act3) = sw.(lo+2) in
CTifeq(key1, act1,
CTifeq(key2, act2,
if Integers.Int.sub maxval minval = coqint_of_camlint 2l
then CTaction act3
else CTifeq(key3, act3, CTaction default)))
| _ ->
let mid = (lo + hi) / 2 in
let (pivot, _) = sw.(mid) in
CTiflt(pivot,
build lo mid minval (Integers.Int.sub pivot Integers.Int.one),
build mid hi pivot maxval)
in build 0 (Array.length sw) Integers.Int.zero Integers.Int.max_unsigned
let uint64_of_coqint n = (* force unsigned interpretation *)
Int64.logand (Int64.of_int32 (camlint_of_coqint n)) 0xFFFF_FFFFL
let compile_switch_as_jumptable default cases minkey maxkey =
let tblsize = 1 + Int64.to_int (Int64.sub maxkey minkey) in
assert (tblsize >= 0 && tblsize <= Sys.max_array_length);
let tbl = Array.make tblsize default in
List.iter
(fun (key, act) ->
let pos = Int64.to_int (Int64.sub (uint64_of_coqint key) minkey) in
tbl.(pos) <- act)
cases;
CTjumptable(coqint_of_camlint (Int64.to_int32 minkey),
coqint_of_camlint (Int32.of_int tblsize),
Array.to_list tbl,
CTaction default)
let dense_enough (numcases: int) (minkey: int64) (maxkey: int64) =
let span = Int64.sub maxkey minkey in
assert (span >= 0L);
let tree_size = Int64.mul 4L (Int64.of_int numcases)
and table_size = Int64.add 8L span in
numcases >= 7 (* really small jump tables are less efficient *)
&& span < Int64.of_int Sys.max_array_length
&& table_size <= tree_size
let compile_switch default table =
let (tbl, keys) = normalize_table table in
if IntSet.is_empty keys then CTaction default else begin
let minkey = uint64_of_coqint (IntSet.min_elt keys)
and maxkey = uint64_of_coqint (IntSet.max_elt keys) in
if dense_enough (List.length tbl) minkey maxkey
then compile_switch_as_jumptable default tbl minkey maxkey
else compile_switch_as_tree default tbl
end
|
