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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. *)
(* *)
(**************************************************************************)
(* Compilation of pattern matching
Based upon Lefessant-Maranget ``Optimizing Pattern-Matching'' ICFP'2001.
A previous version was based on Peyton-Jones, ``The Implementation of
functional programming languages'', chapter 5.
Overview of the implementation
==============================
1. Precompilation
-----------------
(split_and_precompile)
We first split the initial pattern matching (or "pm") along its first column
-- simplifying pattern heads in the process --, so that we obtain an ordered
list of pms.
For every pm in this list, and any two patterns in its first column, either
the patterns have the same head, or their heads match disjoint sets of
values. (In particular, two extension constructors that may or may not be
equal due to hidden rebinding cannot occur in the same simple pm.)
2. Compilation
--------------
The compilation of one of these pms obtained after precompiling is done as
follows:
(divide)
We split the match along the first column again, this time grouping rows
which start with the same head, and removing the first column.
As a result we get a "division", which is a list a "cells" of the form:
discriminating pattern head * specialized pm
(compile_list + compile_match)
We then map over the division to compile each cell: we simply restart the
whole process on the second element of each cell.
Each cell is now of the form:
discriminating pattern head * lambda
(combine_constant, combine_construct, combine_array, ...)
We recombine the cells using a switch or some ifs, and if the matching can
fail, introduce a jump to the next pm that could potentially match the
scrutiny.
3. Chaining of pms
------------------
(comp_match_handlers)
Once the pms have been compiled, we stitch them back together in the order
produced by precompilation, resulting in the following structure:
{v
catch
catch
<first body>
with <exit i> ->
<second body>
with <exit j> ->
<third body>
v}
Additionally, bodies whose corresponding exit-number is never used are
discarded. So for instance, if in the pseudo-example above we know that exit
[i] is never taken, we would actually generate:
{v
catch
<first body>
with <exit j> ->
<third body>
v}
*)
open Misc
open Asttypes
open Types
open Typedtree
open Lambda
open Parmatch
open Printf
open Printpat
module Scoped_location = Debuginfo.Scoped_location
let dbg = false
(*
Compatibility predicate that considers potential rebindings of constructors
of an extension type.
"may_compat p q" returns false when p and q never admit a common instance;
returns true when they may have a common instance.
*)
module MayCompat = Parmatch.Compat (struct
let equal = Types.may_equal_constr
end)
let may_compat = MayCompat.compat
and may_compats = MayCompat.compats
(*
Many functions on the various data structures of the algorithm :
- Pattern matrices.
- Default environments: mapping from matrices to exit numbers.
- Contexts: matrices whose column are partitioned into
left and right.
- Jump summaries: mapping from exit numbers to contexts
*)
let string_of_lam lam =
Printlambda.lambda Format.str_formatter lam;
Format.flush_str_formatter ()
let all_record_args lbls =
match lbls with
| [] -> fatal_error "Matching.all_record_args"
| (_, { lbl_all }, _) :: _ ->
let t =
Array.map
(fun lbl -> (mknoloc (Longident.Lident "?temp?"), lbl, omega))
lbl_all
in
List.iter (fun ((_, lbl, _) as x) -> t.(lbl.lbl_pos) <- x) lbls;
Array.to_list t
let rec expand_record p =
match p.pat_desc with
| Tpat_record (l, _) ->
{ p with pat_desc = Tpat_record (all_record_args l, Closed) }
| Tpat_alias (p, _, _) -> expand_record p
| _ -> p
let expand_record_head head =
match Pattern_head.desc head with
| Record _ ->
head |> Pattern_head.to_omega_pattern |> expand_record
|> Pattern_head.deconstruct |> fst
| _ -> head
let head_loc ~scopes head =
Scoped_location.of_location ~scopes (Pattern_head.loc head)
type 'a clause = 'a * lambda
module Non_empty_clause = struct
type 'a t = ('a * Typedtree.pattern list) clause
let of_initial = function
| [], _ -> assert false
| pat :: patl, act -> ((pat, patl), act)
let map_head f ((p, patl), act) = ((f p, patl), act)
end
type simple_view =
[ `Any
| `Constant of constant
| `Tuple of pattern list
| `Construct of Longident.t loc * constructor_description * pattern list
| `Variant of label * pattern option * row_desc ref
| `Record of
(Longident.t loc * label_description * pattern) list * closed_flag
| `Array of pattern list
| `Lazy of pattern ]
type half_simple_view =
[ simple_view | `Or of pattern * pattern * row_desc option ]
type general_view =
[ half_simple_view
| `Var of Ident.t * string loc
| `Alias of pattern * Ident.t * string loc ]
module General : sig
type pattern = general_view pattern_data
type clause = pattern Non_empty_clause.t
val view : Typedtree.pattern -> pattern
val erase : [< general_view ] pattern_data -> Typedtree.pattern
end = struct
type pattern = general_view pattern_data
type clause = pattern Non_empty_clause.t
let view_desc = function
| Tpat_any -> `Any
| Tpat_var (id, str) -> `Var (id, str)
| Tpat_alias (p, id, str) -> `Alias (p, id, str)
| Tpat_constant cst -> `Constant cst
| Tpat_tuple ps -> `Tuple ps
| Tpat_construct (cstr, cstr_descr, args) ->
`Construct (cstr, cstr_descr, args)
| Tpat_variant (cstr, arg, row_desc) -> `Variant (cstr, arg, row_desc)
| Tpat_record (fields, closed) -> `Record (fields, closed)
| Tpat_array ps -> `Array ps
| Tpat_or (p, q, row_desc) -> `Or (p, q, row_desc)
| Tpat_lazy p -> `Lazy p
let view p : pattern = { p with pat_desc = view_desc p.pat_desc }
let erase_desc = function
| `Any -> Tpat_any
| `Var (id, str) -> Tpat_var (id, str)
| `Alias (p, id, str) -> Tpat_alias (p, id, str)
| `Constant cst -> Tpat_constant cst
| `Tuple ps -> Tpat_tuple ps
| `Construct (cstr, cst_descr, args) ->
Tpat_construct (cstr, cst_descr, args)
| `Variant (cstr, arg, row_desc) -> Tpat_variant (cstr, arg, row_desc)
| `Record (fields, closed) -> Tpat_record (fields, closed)
| `Array ps -> Tpat_array ps
| `Or (p, q, row_desc) -> Tpat_or (p, q, row_desc)
| `Lazy p -> Tpat_lazy p
let erase p = { p with pat_desc = erase_desc p.pat_desc }
end
module Half_simple : sig
(** Half-simplified patterns are patterns where:
- records are expanded so that they possess all fields
- aliases are removed and replaced by bindings in actions.
Or-patterns are not removed, they are only "half-simplified":
- aliases under or-patterns are kept
- or-patterns whose right-hand-side is subsumed by their lhs
are simplified to their lhs.
For instance: [(_ :: _ | 1 :: _)] is changed into [_ :: _]
- or-patterns whose left-hand-side is not simplified
are preserved: (p|q) is changed into (simpl(p)|simpl(q))
{v
# match lazy (print_int 3; 3) with _ | lazy 2 -> ();;
- : unit = ()
# match lazy (print_int 3; 3) with lazy 2 | _ -> ();;
3- : unit = ()
v}
In particular, or-patterns may still occur in the leading column,
so this is only a "half-simplification". *)
type pattern = half_simple_view pattern_data
type clause = pattern Non_empty_clause.t
val of_clause : arg:lambda -> General.clause -> clause
end = struct
type pattern = half_simple_view pattern_data
type clause = pattern Non_empty_clause.t
let rec simpl_under_orpat p =
match p.pat_desc with
| Tpat_any
| Tpat_var _ ->
p
| Tpat_alias (q, id, s) ->
{ p with pat_desc = Tpat_alias (simpl_under_orpat q, id, s) }
| Tpat_or (p1, p2, o) ->
let p1, p2 = (simpl_under_orpat p1, simpl_under_orpat p2) in
if le_pat p1 p2 then
p1
else
{ p with pat_desc = Tpat_or (p1, p2, o) }
| Tpat_record (lbls, closed) ->
let all_lbls = all_record_args lbls in
{ p with pat_desc = Tpat_record (all_lbls, closed) }
| _ -> p
(* Explode or-patterns and turn aliases into bindings in actions *)
let of_clause ~arg cl =
let rec aux (((p, patl), action) : General.clause) : clause =
let continue p (view : general_view) : clause =
aux (({ p with pat_desc = view }, patl), action)
in
let stop p (view : half_simple_view) : clause =
(({ p with pat_desc = view }, patl), action)
in
match p.pat_desc with
| `Any -> stop p `Any
| `Var (id, s) -> continue p (`Alias (omega, id, s))
| `Alias (p, id, _) ->
let k = Typeopt.value_kind p.pat_env p.pat_type in
aux
( (General.view p, patl),
bind_with_value_kind Alias (id, k) arg action )
| `Record ([], _) as view -> stop p view
| `Record (lbls, closed) ->
let full_view = `Record (all_record_args lbls, closed) in
stop p full_view
| `Or _ -> (
let orpat = General.view (simpl_under_orpat (General.erase p)) in
match orpat.pat_desc with
| `Or _ as or_view -> stop orpat or_view
| other_view -> continue orpat other_view
)
| ( `Constant _ | `Tuple _ | `Construct _ | `Variant _ | `Array _
| `Lazy _ ) as view ->
stop p view
in
aux cl
end
exception Cannot_flatten
module Simple : sig
type pattern = simple_view pattern_data
type clause = pattern Non_empty_clause.t
val head : pattern -> Pattern_head.t
val explode_or_pat :
Half_simple.pattern * Typedtree.pattern list ->
arg:Ident.t option ->
mk_action:(vars:Ident.t list -> lambda) ->
vars:Ident.t list ->
clause list ->
clause list
end = struct
type pattern = simple_view pattern_data
type clause = pattern Non_empty_clause.t
let head p =
fst (Pattern_head.deconstruct (General.erase (p :> General.pattern)))
let alpha env (p : pattern) : pattern =
let alpha_pat env p = Typedtree.alpha_pat env p in
let pat_desc =
match p.pat_desc with
| `Any -> `Any
| `Constant cst -> `Constant cst
| `Tuple ps -> `Tuple (List.map (alpha_pat env) ps)
| `Construct (cstr, cst_descr, args) ->
`Construct (cstr, cst_descr, List.map (alpha_pat env) args)
| `Variant (cstr, argo, row_desc) ->
`Variant (cstr, Option.map (alpha_pat env) argo, row_desc)
| `Record (fields, closed) ->
let alpha_field env (lid, l, p) = (lid, l, alpha_pat env p) in
`Record (List.map (alpha_field env) fields, closed)
| `Array ps -> `Array (List.map (alpha_pat env) ps)
| `Lazy p -> `Lazy (alpha_pat env p)
in
{ p with pat_desc }
let mk_alpha_env arg aliases ids =
List.map
(fun id ->
( id,
if List.mem id aliases then
match arg with
| Some v -> v
| _ -> raise Cannot_flatten
else
Ident.create_local (Ident.name id) ))
ids
let explode_or_pat ((p : Half_simple.pattern), patl) ~arg ~mk_action ~vars
(rem : clause list) : clause list =
let rec explode p aliases rem =
let split_explode p aliases rem = explode (General.view p) aliases rem in
match p.pat_desc with
| `Or (p1, p2, _) ->
split_explode p1 aliases (split_explode p2 aliases rem)
| `Alias (p, id, _) -> split_explode p (id :: aliases) rem
| `Var (id, str) ->
explode
{ p with pat_desc = `Alias (Parmatch.omega, id, str) }
aliases rem
| #simple_view as view ->
let env = mk_alpha_env arg aliases vars in
( (alpha env { p with pat_desc = view }, patl),
mk_action ~vars:(List.map snd env) )
:: rem
in
explode (p : Half_simple.pattern :> General.pattern) [] rem
end
let expand_record_simple : Simple.pattern -> Simple.pattern =
fun p ->
match p.pat_desc with
| `Record (l, _) -> { p with pat_desc = `Record (all_record_args l, Closed) }
| _ -> p
type initial_clause = pattern list clause
type matrix = pattern list list
let add_omega_column pss = List.map (fun ps -> omega :: ps) pss
let rec rev_split_at n ps =
if n <= 0 then
([], ps)
else
match ps with
| p :: rem ->
let left, right = rev_split_at (n - 1) rem in
(p :: left, right)
| _ -> assert false
exception NoMatch
let matcher discr (p : Simple.pattern) rem =
let discr = expand_record_head discr in
let p = expand_record_simple p in
let omegas = omegas (Pattern_head.arity discr) in
let ph, args = Pattern_head.deconstruct (General.erase p) in
let yes () = args @ rem in
let no () = raise NoMatch in
let yesif b =
if b then
yes ()
else
no ()
in
match (Pattern_head.desc discr, Pattern_head.desc ph) with
| Any, _ -> rem
| ( ( Constant _ | Construct _ | Variant _ | Lazy | Array _ | Record _
| Tuple _ ),
Any ) ->
omegas @ rem
| Constant cst, Constant cst' -> yesif (const_compare cst cst' = 0)
| Constant _, (Construct _ | Variant _ | Lazy | Array _ | Record _ | Tuple _)
->
no ()
| Construct cstr, Construct cstr' ->
(* NB: may_equal_constr considers (potential) constructor rebinding;
Types.may_equal_constr does check that the arities are the same,
preserving row-size coherence. *)
yesif (Types.may_equal_constr cstr cstr')
| Construct _, (Constant _ | Variant _ | Lazy | Array _ | Record _ | Tuple _)
->
no ()
| Variant { tag; has_arg }, Variant { tag = tag'; has_arg = has_arg' } ->
yesif (tag = tag' && has_arg = has_arg')
| Variant _, (Constant _ | Construct _ | Lazy | Array _ | Record _ | Tuple _)
->
no ()
| Array n1, Array n2 -> yesif (n1 = n2)
| Array _, (Constant _ | Construct _ | Variant _ | Lazy | Record _ | Tuple _)
->
no ()
| Tuple n1, Tuple n2 -> yesif (n1 = n2)
| Tuple _, (Constant _ | Construct _ | Variant _ | Lazy | Array _ | Record _)
->
no ()
| Record l, Record l' ->
(* we already expanded the record fully *)
yesif (List.length l = List.length l')
| Record _, (Constant _ | Construct _ | Variant _ | Lazy | Array _ | Tuple _)
->
no ()
| Lazy, Lazy -> yes ()
| Lazy, (Constant _ | Construct _ | Variant _ | Array _ | Record _ | Tuple _)
->
no ()
let ncols = function
| [] -> 0
| ps :: _ -> List.length ps
module Context : sig
type t
val empty : t
val is_empty : t -> bool
val start : int -> t
val eprintf : t -> unit
val specialize : Pattern_head.t -> t -> t
val lshift : t -> t
val rshift : t -> t
val rshift_num : int -> t -> t
val lub : pattern -> t -> t
val matches : t -> matrix -> bool
val combine : t -> t
val select_columns : matrix -> t -> t
val union : t -> t -> t
end = struct
module Row = struct
type t = { left : pattern list; right : pattern list }
let eprintf { left; right } =
Format.eprintf "LEFT:%a RIGHT:%a\n" pretty_line left pretty_line right
let le c1 c2 = le_pats c1.left c2.left && le_pats c1.right c2.right
let lshift { left; right } =
match right with
| x :: xs -> { left = x :: left; right = xs }
| _ -> assert false
let lforget { left; right } =
match right with
| _ :: xs -> { left = omega :: left; right = xs }
| _ -> assert false
let rshift { left; right } =
match left with
| p :: ps -> { left = ps; right = p :: right }
| _ -> assert false
let rshift_num n { left; right } =
let shifted, left = rev_split_at n left in
{ left; right = shifted @ right }
(** Recombination of contexts (eg: (_,_)::p1::p2::rem -> (p1,p2)::rem)
All mutable fields are replaced by '_', since side-effects in
guards can alter these fields *)
let combine { left; right } =
match left with
| p :: ps -> { left = ps; right = set_args_erase_mutable p right }
| _ -> assert false
end
type t = Row.t list
let empty = []
let start n : t = [ { left = []; right = omegas n } ]
let is_empty = function
| [] -> true
| _ -> false
let eprintf ctx = List.iter Row.eprintf ctx
let lshift ctx =
if List.length ctx < !Clflags.match_context_rows then
List.map Row.lshift ctx
else
(* Context pruning *)
get_mins Row.le (List.map Row.lforget ctx)
let rshift ctx = List.map Row.rshift ctx
let rshift_num n ctx = List.map (Row.rshift_num n) ctx
let combine ctx = List.map Row.combine ctx
let specialize head ctx =
let non_empty = function
| { Row.left = _; right = [] } ->
fatal_error "Matching.Context.specialize"
| { Row.left; right = p :: ps } -> (left, p, ps)
in
let ctx = List.map non_empty ctx in
let rec filter_rec = function
| [] -> []
| (left, p, right) :: rem -> (
let p = General.view p in
match p.pat_desc with
| `Or (p1, p2, _) ->
filter_rec ((left, p1, right) :: (left, p2, right) :: rem)
| `Alias (p, _, _) -> filter_rec ((left, p, right) :: rem)
| `Var _ -> filter_rec ((left, omega, right) :: rem)
| #simple_view as view -> (
let p = { p with pat_desc = view } in
match matcher head p right with
| exception NoMatch -> filter_rec rem
| right ->
let left = Pattern_head.to_omega_pattern head :: left in
{ Row.left; right }
:: filter_rec rem
)
)
in
filter_rec ctx
let select_columns pss ctx =
let n = ncols pss in
let lub_row ps { Row.left; right } =
let transfer, right = rev_split_at n right in
match lubs transfer ps with
| exception Empty -> None
| inter -> Some { Row.left = inter @ left; right }
in
let lub_with_ctx ps = List.filter_map (lub_row ps) ctx in
List.flatten (List.map lub_with_ctx pss)
let lub p ctx =
List.filter_map
(fun { Row.left; right } ->
match right with
| q :: rem -> (
try Some { Row.left; right = lub p q :: rem } with Empty -> None
)
| _ -> fatal_error "Matching.Context.lub")
ctx
let matches ctx pss =
List.exists
(fun { Row.right = qs } -> List.exists (fun ps -> may_compats qs ps) pss)
ctx
let union pss qss = get_mins Row.le (pss @ qss)
end
let rec flatten_pat_line size p k =
match p.pat_desc with
| Tpat_any -> omegas size :: k
| Tpat_tuple args -> args :: k
| Tpat_or (p1, p2, _) ->
flatten_pat_line size p1 (flatten_pat_line size p2 k)
| Tpat_alias (p, _, _) ->
(* Note: if this 'as' pat is here, then this is a
useless binding, solves PR#3780 *)
flatten_pat_line size p k
| _ -> fatal_error "Matching.flatten_pat_line"
let flatten_matrix size pss =
List.fold_right
(fun ps r ->
match ps with
| [ p ] -> flatten_pat_line size p r
| _ -> fatal_error "Matching.flatten_matrix")
pss []
(** A default environment (referred to as "reachable trap handlers" in the
paper), is an ordered list of [matrix * raise_num] pairs, and is used to
decide where to jump next if none of the rows in a given matrix match the
input.
In such situations, one thing you can do is to jump to the first (leftmost)
[raise_num] in that list (by doing a raise to the static-cach handler number
[raise_num]); and you can assume that if the associated pm doesn't match
either, it will do the same thing, etc.
This is what [mk_failaction_neg] (and its callers) does.
A more sophisticated alternative is to use what you know about the input
(what you might already have matched) and the current pm (what you know you
can't match) to directly jump to a pm that might match it instead of the
next one; that is why we don't just keep [raise_num]s but also the
associated matrices.
[mk_failaction_pos] does (a slightly more sophisticated version of) this.
*)
module Default_environment : sig
type t
val is_empty : t -> bool
val pop : t -> ((matrix * int) * t) option
val empty : t
val cons : matrix -> int -> t -> t
val specialize : Pattern_head.t -> t -> t
val pop_column : t -> t
val pop_compat : pattern -> t -> t
val flatten : int -> t -> t
val pp : t -> unit
end = struct
type t = (matrix * int) list
(** All matrices in the list should have the same arity -- their rows should
have the same number of columns -- as it should match the arity of the
current scrutiny vector. *)
let empty = []
let is_empty = function
| [] -> true
| _ -> false
let cons matrix raise_num default =
match matrix with
| [] -> default
| _ -> (matrix, raise_num) :: default
let specialize_matrix arity matcher pss =
let rec filter_rec = function
| [] -> []
| (p, ps) :: rem -> (
let p = General.view p in
match p.pat_desc with
| `Alias (p, _, _) -> filter_rec ((p, ps) :: rem)
| `Var _ -> filter_rec ((omega, ps) :: rem)
| `Or (p1, p2, _) -> filter_rec_or p1 p2 ps rem
| #simple_view as view -> (
let p = { p with pat_desc = view } in
match matcher p ps with
| exception NoMatch -> filter_rec rem
| specialized ->
assert (List.length specialized = List.length ps + arity);
specialized :: filter_rec rem
)
)
(* Filter just one row, without a `rem` accumulator
of further rows to process.
The following equality holds:
filter_rec ((p :: ps) :: rem)
= filter_one p ps @ filter_rec rem
*)
and filter_one p ps =
filter_rec [ (p, ps) ]
and filter_rec_or p1 p2 ps rem =
match arity with
| 0 -> (
(* if K has arity 0, specializing ((K|K)::rem) returns just (rem):
if either sides works (filters into a non-empty list),
no need to keep the other. *)
match filter_one p1 ps with
| [] -> filter_rec ((p2, ps) :: rem)
| matches -> matches @ filter_rec rem
)
| 1 -> (
(* if K has arity 1, ((K p | K q) :: rem) can be expressed
as ((p | q) :: rem): even if both sides of an or-pattern
match, we can compress the output in a single row,
instead of duplicating the row.
In particular, filtering a single row (the filter_one calls)
returns a result that respects the following properties:
- "row count": the result is either an empty list or a single row
- "row shape": if there is a row in the result, it contains one
pattern consed to the tail [ps] of our input row; in particular
the row is not empty. *)
match (filter_one p1 ps, filter_one p2 ps) with
| [], row
| row, [] ->
row @ filter_rec rem
| [ (arg1 :: _) ], [ (arg2 :: _) ] ->
(* By the row shape property,
the wildcard patterns can only be ps. *)
(* The output below is a single row,
respecting the row count property. *)
({ arg1 with
pat_desc = Tpat_or (arg1, arg2, None);
pat_loc = Location.none
}
:: ps
)
:: filter_rec rem
| (_ :: _ :: _), _
| _, (_ :: _ :: _) ->
(* Cannot happen from the row count property. *)
assert false
| [ [] ], _
| _, [ [] ] ->
(* Cannot happen from the row shape property. *)
assert false
)
| _ ->
(* we cannot preserve the or-pattern as in the arity-1 case,
because we cannot express
(K (p1, .., pn) | K (q1, .. qn))
as (p1 .. pn | q1 .. qn) *)
filter_rec ((p1, ps) :: (p2, ps) :: rem)
in
filter_rec pss
let specialize_ arity matcher env =
let rec make_rec = function
| [] -> []
| (([] :: _), i) :: _ -> [ ([ [] ], i) ]
| (pss, i) :: rem -> (
(* we already handled the empty-row case
so we know that all rows in pss are non-empty *)
let non_empty = function
| [] -> assert false
| p :: ps -> (p, ps)
in
let pss = List.map non_empty pss in
match specialize_matrix arity matcher pss with
| [] -> make_rec rem
| [] :: _ -> [ ([ [] ], i) ]
| pss -> (pss, i) :: make_rec rem
)
in
make_rec env
let specialize head def =
specialize_ (Pattern_head.arity head) (matcher head) def
let pop_column def = specialize_ 0 (fun _p rem -> rem) def
let pop_compat p def =
let compat_matcher q rem =
if may_compat p (General.erase q) then
rem
else
raise NoMatch
in
specialize_ 0 compat_matcher def
let pop = function
| [] -> None
| def :: defs -> Some (def, defs)
let pp def =
Format.eprintf "+++++ Defaults +++++\n";
List.iter
(fun (pss, i) -> Format.eprintf "Matrix for %d\n%a" i pretty_matrix pss)
def;
Format.eprintf "+++++++++++++++++++++\n"
let flatten size def =
List.map (fun (pss, i) -> (flatten_matrix size pss, i)) def
end
module Jumps : sig
type t
val is_empty : t -> bool
val empty : t
val singleton : int -> Context.t -> t
val add : int -> Context.t -> t -> t
val union : t -> t -> t
val unions : t list -> t
val map : (Context.t -> Context.t) -> t -> t
val remove : int -> t -> t
val extract : int -> t -> Context.t * t
val eprintf : t -> unit
end = struct
type t = (int * Context.t) list
let eprintf (env : t) =
List.iter
(fun (i, ctx) ->
Printf.eprintf "jump for %d\n" i;
Context.eprintf ctx)
env
let rec extract i = function
| [] -> (Context.empty, [])
| ((j, pss) as x) :: rem as all ->
if i = j then
(pss, rem)
else if j < i then
(Context.empty, all)
else
let r, rem = extract i rem in
(r, x :: rem)
let rec remove i = function
| [] -> []
| (j, _) :: rem when i = j -> rem
| x :: rem -> x :: remove i rem
let empty = []
and is_empty = function
| [] -> true
| _ -> false
let singleton i ctx =
if Context.is_empty ctx then
[]
else
[ (i, ctx) ]
let add i ctx jumps =
let rec add = function
| [] -> [ (i, ctx) ]
| ((j, qss) as x) :: rem as all ->
if j > i then
x :: add rem
else if j < i then
(i, ctx) :: all
else
(i, Context.union ctx qss) :: rem
in
if Context.is_empty ctx then
jumps
else
add jumps
let rec union (env1 : t) env2 =
match (env1, env2) with
| [], _ -> env2
| _, [] -> env1
| ((i1, pss1) as x1) :: rem1, ((i2, pss2) as x2) :: rem2 ->
if i1 = i2 then
(i1, Context.union pss1 pss2) :: union rem1 rem2
else if i1 > i2 then
x1 :: union rem1 env2
else
x2 :: union env1 rem2
let rec merge = function
| env1 :: env2 :: rem -> union env1 env2 :: merge rem
| envs -> envs
let rec unions envs =
match envs with
| [] -> []
| [ env ] -> env
| _ -> unions (merge envs)
let map f env = List.map (fun (i, pss) -> (i, f pss)) env
end
(* Pattern matching before any compilation *)
type 'row pattern_matching = {
mutable cases : 'row list;
args : (lambda * let_kind) list;
(** args are not just Ident.t in at least the following cases:
- when matching the arguments of a constructor,
direct field projections are used (make_field_args)
- with lazy patterns args can be of the form [Lazy.force ...]
(inline_lazy_force). *)
default : Default_environment.t
}
type handler = {
provenance : matrix;
exit : int;
vars : (Ident.t * Lambda.value_kind) list;
pm : initial_clause pattern_matching
}
type 'head_pat pm_or_compiled = {
body : 'head_pat Non_empty_clause.t pattern_matching;
handlers : handler list;
or_matrix : matrix
}
(* Pattern matching after application of both the or-pat rule and the
mixture rule *)
type pm_half_compiled =
| PmOr of Simple.pattern pm_or_compiled
| PmVar of { inside : pm_half_compiled }
| Pm of Simple.clause pattern_matching
(* Only used inside the various split functions, we only keep [me] when we're
done splitting / precompiling. *)
type pm_half_compiled_info = {
me : pm_half_compiled;
matrix : matrix;
(* the matrix matched by [me]. Is used to extend the list of reachable trap
handlers (aka "default environments") when returning from recursive
calls. *)
top_default : Default_environment.t
}
let erase_cases f cases =
List.map (fun ((p, ps), act) -> (f p :: ps, act)) cases
let erase_pm pm =
{ pm with cases = erase_cases General.erase pm.cases }
let pretty_cases cases =
List.iter
(fun (ps, _l) ->
List.iter (fun p -> Format.eprintf " %a%!" top_pretty p) ps;
Format.eprintf "\n")
cases
let pretty_pm pm =
pretty_cases pm.cases;
if not (Default_environment.is_empty pm.default) then
Default_environment.pp pm.default
let rec pretty_precompiled = function
| Pm pm ->
Format.eprintf "++++ PM ++++\n";
pretty_pm (erase_pm pm)
| PmVar x ->
Format.eprintf "++++ VAR ++++\n";
pretty_precompiled x.inside
| PmOr x ->
Format.eprintf "++++ OR ++++\n";
pretty_pm (erase_pm x.body);
pretty_matrix Format.err_formatter x.or_matrix;
List.iter
(fun { exit = i; pm; _ } ->
eprintf "++ Handler %d ++\n" i;
pretty_pm pm)
x.handlers
let pretty_precompiled_res first nexts =
pretty_precompiled first;
List.iter
(fun (e, pmh) ->
eprintf "** DEFAULT %d **\n" e;
pretty_precompiled pmh)
nexts
(* Identifying some semantically equivalent lambda-expressions,
Our goal here is also to
find alpha-equivalent (simple) terms *)
(* However, as shown by PR#6359 such sharing may hinders the
lambda-code invariant that all bound idents are unique,
when switches are compiled to test sequences.
The definitive fix is the systematic introduction of exit/catch
in case action sharing is present.
*)
module StoreExp = Switch.Store (struct
type t = lambda
type key = lambda
let compare_key = Stdlib.compare
let make_key = Lambda.make_key
end)
let make_exit i = Lstaticraise (i, [])
(* Introduce a catch, if worth it *)
let make_catch d k =
match d with
| Lstaticraise (_, []) -> k d
| _ ->
let e = next_raise_count () in
Lstaticcatch (k (make_exit e), (e, []), d)
(* Introduce a catch, if worth it, delayed version *)
let rec as_simple_exit = function
| Lstaticraise (i, []) -> Some i
| Llet (Alias, _k, _, _, e) -> as_simple_exit e
| _ -> None
let make_catch_delayed handler =
match as_simple_exit handler with
| Some i -> (i, fun act -> act)
| None -> (
let i = next_raise_count () in
(*
Printf.eprintf "SHARE LAMBDA: %i\n%s\n" i (string_of_lam handler);
*)
( i,
fun body ->
match body with
| Lstaticraise (j, _) ->
if i = j then
handler
else
body
| _ -> Lstaticcatch (body, (i, []), handler) )
)
let raw_action l =
match make_key l with
| Some l -> l
| None -> l
let same_actions = function
| [] -> None
| [ (_, act) ] -> Some act
| (_, act0) :: rem -> (
match make_key act0 with
| None -> None
| key0_opt ->
let same_act (_, act) = make_key act = key0_opt in
if List.for_all same_act rem then
Some act0
else
None
)
let safe_before ((p, ps), act_p) l =
(* Test for swapping two clauses *)
let same_actions act1 act2 =
match (make_key act1, make_key act2) with
| Some key1, Some key2 -> key1 = key2
| None, _
| _, None ->
false
in
List.for_all
(fun ((q, qs), act_q) ->
same_actions act_p act_q
|| not (may_compats (General.erase p :: ps) (General.erase q :: qs)))
l
let half_simplify_nonempty ~arg (cls : Typedtree.pattern Non_empty_clause.t) :
Half_simple.clause =
cls |> Non_empty_clause.map_head General.view |> Half_simple.of_clause ~arg
let half_simplify_clause ~arg (cls : Typedtree.pattern list clause) =
cls |> Non_empty_clause.of_initial |> half_simplify_nonempty ~arg
(* Once matchings are *fully* simplified, one can easily find
their nature. *)
let rec what_is_cases ~skip_any cases =
match cases with
| [] -> Pattern_head.omega
| ((p, _), _) :: rem -> (
let head = Simple.head p in
match Pattern_head.desc head with
| Any when skip_any -> what_is_cases ~skip_any rem
| _ -> head
)
let what_is_first_case = what_is_cases ~skip_any:false
let what_is_cases = what_is_cases ~skip_any:true
let pm_free_variables { cases } =
List.fold_right
(fun (_, act) r -> Ident.Set.union (free_variables act) r)
cases Ident.Set.empty
(* Basic grouping predicates *)
let can_group discr pat =
match (Pattern_head.desc discr, Pattern_head.desc (Simple.head pat)) with
| Any, Any
| Constant (Const_int _), Constant (Const_int _)
| Constant (Const_char _), Constant (Const_char _)
| Constant (Const_string _), Constant (Const_string _)
| Constant (Const_float _), Constant (Const_float _)
| Constant (Const_int32 _), Constant (Const_int32 _)
| Constant (Const_int64 _), Constant (Const_int64 _)
| Constant (Const_nativeint _), Constant (Const_nativeint _) ->
true
| Construct { cstr_tag = Cstr_extension _ as discr_tag }, Construct pat_cstr
->
(* Extension constructors with distinct names may be equal thanks to
constructor rebinding. So we need to produce a specialized
submatrix for each syntactically-distinct constructor (with a threading
of exits such that each submatrix falls back to the
potentially-compatible submatrices below it). *)
Types.equal_tag discr_tag pat_cstr.cstr_tag
| Construct _, Construct _
| Tuple _, (Tuple _ | Any)
| Record _, (Record _ | Any)
| Array _, Array _
| Variant _, Variant _
| Lazy, Lazy ->
true
| ( _,
( Any
| Constant
( Const_int _ | Const_char _ | Const_string _ | Const_float _
| Const_int32 _ | Const_int64 _ | Const_nativeint _ )
| Construct _ | Tuple _ | Record _ | Array _ | Variant _ | Lazy ) ) ->
false
let is_or p =
match p.pat_desc with
| Tpat_or _ -> true
| _ -> false
let rec omega_like p =
match p.pat_desc with
| Tpat_any
| Tpat_var _ ->
true
| Tpat_alias (p, _, _) -> omega_like p
| Tpat_or (p1, p2, _) -> omega_like p1 || omega_like p2
| _ -> false
let simple_omega_like p =
match Pattern_head.desc (Simple.head p) with
| Any -> true
| _ -> false
let equiv_pat p q = le_pat p q && le_pat q p
let rec extract_equiv_head p l =
match l with
| (((q, _), _) as cl) :: rem ->
if equiv_pat p (General.erase q) then
let others, rem = extract_equiv_head p rem in
(cl :: others, rem)
else
([], l)
| _ -> ([], l)
module Or_matrix = struct
(* Splitting a matrix uses an or-matrix that contains or-patterns (at
the head of some of its rows).
The property that we want to maintain for the rows of the
or-matrix is that if the row p::ps is before q::qs and p is an
or-pattern, and v::vs matches p but not ps, then we don't need to
try q::qs. This is necessary because the compilation of the
or-pattern p will exit to a sub-matrix and never come back.
For this to hold, (p::ps) and (q::qs) must satisfy one of:
- disjointness: p and q are not compatible
- ordering: if p and q are compatible, ps is more general than qs
(this only works if the row p::ps is not guarded; otherwise the
guard could fail and q::qs should still be tried)
*)
(* Conditions for appending to the Or matrix *)
let disjoint p q = not (may_compat p q)
let safe_below (ps, act) qs =
(not (is_guarded act)) && Parmatch.le_pats ps qs
let safe_below_or_matrix l (q, qs) =
List.for_all
(fun ((p, ps), act_p) ->
let p = General.erase p in
match p.pat_desc with
| Tpat_or _ -> disjoint p q || safe_below (ps, act_p) qs
| _ -> true)
l
(* Insert or append a clause in the Or matrix:
- insert: adding the clause in the middle of the or_matrix
- append: adding the clause at the bottom of the or_matrix
If neither are possible we add to the bottom of the No matrix.
*)
let insert_or_append (head, ps, act) rev_ors rev_no =
let safe_to_insert rem (p, ps) seen =
let _, not_e = extract_equiv_head p rem in
(* check append condition for head of O *)
safe_below_or_matrix not_e (p, ps)
&& (* check insert condition for tail of O *)
List.for_all (fun ((q, _), _) -> disjoint p (General.erase q)) seen
in
let rec attempt seen = function
(* invariant: the new clause is safe to append at the end of
[seen] (but maybe not [rem] yet) *)
| [] -> (((head, ps), act) :: rev_ors, rev_no)
| (((q, qs), act_q) as cl) :: rem ->
let p = General.erase head in
let q = General.erase q in
if (not (is_or q)) || disjoint p q then
attempt (cl :: seen) rem
else if
Typedtree.pat_bound_idents p = []
&& Typedtree.pat_bound_idents q = []
&& equiv_pat p q
then
(* attempt insertion, for equivalent orpats with no variables *)
if safe_to_insert rem (p, ps) seen then
(List.rev_append seen (((head, ps), act) :: cl :: rem), rev_no)
else
(* fail to insert or append *)
(rev_ors, ((head, ps), act) :: rev_no)
else if safe_below (qs, act_q) ps then
attempt (cl :: seen) rem
else
(rev_ors, ((head, ps), act) :: rev_no)
in
attempt [] rev_ors
end
(* Reconstruct default information from half_compiled pm list *)
let as_matrix cases =
get_mins le_pats (List.map (fun ((p, ps), _) -> General.erase p :: ps) cases)
(*
Split a matching along the first column.
Splitting is first directed by or-patterns, then by
tests (e.g. constructors)/variable transitions.
The approach is greedy, every split function attempts to
raise rows as much as possible in the top matrix,
then splitting applies again to the remaining rows.
Some precompilation of or-patterns and
variable pattern occurs. Mostly this means that bindings
are performed now, being replaced by let-bindings
in actions (cf. Half_simple.of_clause).
Additionally, if the match argument is a variable, matchings whose
first column is made of variables only are split further
(cf. precompile_var).
---
Note: we assume that the first column of each pattern is coherent -- all
patterns match values of the same type. This comes from the fact that
we make aggressive splitting decisions, splitting pattern heads that
may be different into different submatrices; in particular, in a given
submatrix the first column is formed of first arguments to the same
constructor.
GADTs are not an issue because we split columns left-to-right, and
GADT typing also introduces typing equations left-to-right. In
particular, a leftmost column in matching.ml will be well-typed under
a set of equations accepted by the type-checker, and those equations
are forced to remain consistent: they can equate known types to
abstract types, but they cannot equate two incompatible known types
together, and in particular incompatible pattern heads do not appear
in a leftmost column.
Parmatch has to be more conservative because it splits less
aggressively: submatrices will contain not just the arguments of
a given pattern head, but also other lines that may be compatible with
it, in particular those with a leftmost omega and those starting with
an extension constructor that may be equal to it.
*)
let rec split_or argo (cls : Half_simple.clause list) args def =
let rec do_split (rev_before : Simple.clause list) rev_ors rev_no = function
| [] ->
cons_next (List.rev rev_before) (List.rev rev_ors) (List.rev rev_no)
| cl :: rem when not (safe_before cl rev_no) ->
do_split rev_before rev_ors (cl :: rev_no) rem
| (((p, ps), act) as cl) :: rem -> (
match p.pat_desc with
| #simple_view as view when safe_before cl rev_ors ->
do_split
((({ p with pat_desc = view }, ps), act) :: rev_before)
rev_ors rev_no rem
| _ ->
let rev_ors, rev_no =
Or_matrix.insert_or_append (p, ps, act) rev_ors rev_no
in
do_split rev_before rev_ors rev_no rem
)
and cons_next yes yesor no =
let def, nexts =
match no with
| [] -> (def, [])
| _ ->
let { me = next; matrix; top_default = def }, nexts =
do_split [] [] [] no
in
let idef = next_raise_count () in
(Default_environment.cons matrix idef def, (idef, next) :: nexts)
in
match yesor with
| [] -> split_no_or yes args def nexts
| _ -> precompile_or argo yes yesor args def nexts
in
do_split [] [] [] cls
and split_no_or cls args def k =
(* We split the remaining clauses in as few pms as possible while maintaining
the property stated earlier (cf. {1. Precompilation}), i.e. for
any pm in the result, it is possible to decide for any two patterns
on the first column whether their heads are equal or not.
This generally means that we'll have two kinds of pms: ones where the first
column is made of variables only, and ones where the head is actually a
discriminating pattern.
There is some subtlety regarding the handling of extension constructors
(where it is not always possible to syntactically decide whether two
different heads match different values), but this is handled by the
[can_group] function. *)
let rec split (cls : Simple.clause list) =
let discr = what_is_first_case cls in
collect discr [] [] cls
and collect group_discr rev_yes rev_no = function
| [ (((p, ps), _) as cl) ]
when rev_yes <> [] && simple_omega_like p && List.for_all omega_like ps ->
(* This enables an extra division in some frequent cases:
last row is made of variables only
Splitting a matrix there creates two default environments (instead of
one for the non-split matrix), the first of which often gets
specialized away by further refinement, and the second one jumping
directly to the catch-all case -- this produces better code.
This optimisation is tested in the first part of
testsuite/tests/basic/patmatch_split_no_or.ml *)
collect group_discr rev_yes (cl :: rev_no) []
| (((p, _), _) as cl) :: rem ->
if can_group group_discr p && safe_before cl rev_no then
collect group_discr (cl :: rev_yes) rev_no rem
else if should_split group_discr then (
assert (rev_no = []);
let yes = List.rev rev_yes in
insert_split group_discr yes (cl :: rem) def k
) else
collect group_discr rev_yes (cl :: rev_no) rem
| [] ->
let yes = List.rev rev_yes and no = List.rev rev_no in
insert_split group_discr yes no def k
and insert_split group_discr yes no def k =
let precompile_group =
match Pattern_head.desc group_discr with
| Any -> precompile_var
| _ -> do_not_precompile
in
match no with
| [] -> precompile_group args yes def k
| _ ->
let { me = next; matrix; top_default = def }, nexts = split no in
let idef = next_raise_count () in
precompile_group args yes
(Default_environment.cons matrix idef def)
((idef, next) :: nexts)
and should_split group_discr =
match Pattern_head.desc group_discr with
| Construct { cstr_tag = Cstr_extension _ } ->
(* it is unlikely that we will raise anything, so we split now *)
true
| _ -> false
in
split cls
and precompile_var args cls def k =
(* Strategy: pop the first column,
precompile the rest, add a PmVar to all precompiled submatrices.
If the rest doesn't generate any split, abort and do_not_precompile. *)
match args with
| [] -> assert false
| _ :: ((Lvar v, _) as arg) :: rargs -> (
(* We will use the name of the head column of the submatrix
we compile, and this is the *second* column of our argument. *)
match cls with
| [ _ ] ->
(* as split as it can *)
do_not_precompile args cls def k
| _ -> (
(* Precompile *)
let var_args = arg :: rargs in
let var_cls =
List.map
(fun ((p, ps), act) ->
assert (simple_omega_like p);
(* we learned by pattern-matching on [args]
that [p::ps] has at least two arguments,
so [ps] must be non-empty *)
half_simplify_clause ~arg:(fst arg) (ps, act))
cls
and var_def = Default_environment.pop_column def in
let { me = first; matrix }, nexts =
split_or (Some v) var_cls var_args var_def
in
(* Compute top information *)
match nexts with
| [] ->
(* If you need *)
do_not_precompile args cls def k
| _ ->
let rec rebuild_matrix pmh =
match pmh with
| Pm pm -> as_matrix pm.cases
| PmOr { or_matrix = m } -> m
| PmVar x -> add_omega_column (rebuild_matrix x.inside)
in
let rebuild_default nexts def =
(* We can't just do:
{[
List.map
(fun (mat, e) -> add_omega_column mat, e)
top_default (* assuming it'd been bound. *)
]}
As we would be losing information: [def] is more precise
than [add_omega_column (pop_column def)]. *)
List.fold_right
(fun (e, pmh) ->
Default_environment.cons
(add_omega_column (rebuild_matrix pmh))
e)
nexts def
in
let rebuild_nexts nexts k =
map_end (fun (e, pm) -> (e, PmVar { inside = pm })) nexts k
in
let rfirst =
{ me = PmVar { inside = first };
matrix = add_omega_column matrix;
top_default = rebuild_default nexts def
}
and rnexts = rebuild_nexts nexts k in
(rfirst, rnexts)
)
)
| _ -> do_not_precompile args cls def k
and do_not_precompile args cls def k =
( { me = Pm { cases = cls; args; default = def };
matrix = as_matrix cls;
top_default = def
},
k )
and precompile_or argo (cls : Simple.clause list) ors args def k =
let rec do_cases = function
| [] -> ([], [])
| ((p, patl), action) :: rem -> (
match p.pat_desc with
| #simple_view as view ->
let new_ord, new_to_catch = do_cases rem in
( (({ p with pat_desc = view }, patl), action) :: new_ord,
new_to_catch )
| `Or _ ->
let orp = General.erase p in
let others, rem = extract_equiv_head orp rem in
let orpm =
{ cases =
(patl, action)
:: List.map (fun ((_, ps), action) -> (ps, action)) others;
args =
( match args with
| _ :: r -> r
| _ -> assert false
);
default = Default_environment.pop_compat orp def
}
in
let pm_fv = pm_free_variables orpm in
let vars =
(* bound variables of the or-pattern and used in the orpm
actions *)
Typedtree.pat_bound_idents_full orp
|> List.filter (fun (id, _, _) -> Ident.Set.mem id pm_fv)
|> List.map (fun (id, _, ty) ->
(id, Typeopt.value_kind orp.pat_env ty))
in
let or_num = next_raise_count () in
let new_patl = Parmatch.omega_list patl in
let mk_new_action ~vars =
Lstaticraise (or_num, List.map (fun v -> Lvar v) vars)
in
let rem_cases, rem_handlers = do_cases rem in
let cases =
Simple.explode_or_pat (p, new_patl) ~arg:argo
~mk_action:mk_new_action ~vars:(List.map fst vars) rem_cases
in
let handler =
{ provenance = [ [ orp ] ];
exit = or_num;
vars;
pm = orpm
}
in
(cases, handler :: rem_handlers)
)
in
let cases, handlers = do_cases ors in
let matrix =
as_matrix
((cls : Simple.clause list :> General.clause list)
@ (ors : Half_simple.clause list :> General.clause list)
)
and body = { cases = cls @ cases; args; default = def } in
( { me = PmOr { body; handlers; or_matrix = matrix };
matrix;
top_default = def
},
k )
let dbg_split_and_precompile pm next nexts =
if
dbg
&& (nexts <> []
||
match next with
| PmOr _ -> true
| _ -> false
)
then (
Format.eprintf "** SPLIT **\n";
pretty_pm (erase_pm pm);
pretty_precompiled_res next nexts
)
let split_and_precompile_simplified pm =
let { me = next }, nexts = split_no_or pm.cases pm.args pm.default [] in
dbg_split_and_precompile pm next nexts;
(next, nexts)
let split_and_precompile_half_simplified ~arg pm =
let { me = next }, nexts = split_or arg pm.cases pm.args pm.default in
dbg_split_and_precompile pm next nexts;
(next, nexts)
let split_and_precompile ~arg_id ~arg_lambda pm =
let pm =
{ pm with cases = List.map (half_simplify_clause ~arg:arg_lambda) pm.cases }
in
split_and_precompile_half_simplified ~arg:arg_id pm
(* General divide functions *)
type cell = {
pm : initial_clause pattern_matching;
ctx : Context.t;
discr : Pattern_head.t
}
(** a submatrix after specializing by discriminant pattern;
[ctx] is the context shared by all rows. *)
let make_matching get_expr_args head def ctx = function
| [] -> fatal_error "Matching.make_matching"
| arg :: rem ->
let def = Default_environment.specialize head def
and args = get_expr_args head arg rem
and ctx = Context.specialize head ctx in
{ pm = { cases = []; args; default = def }; ctx; discr = head }
let make_line_matching get_expr_args head def = function
| [] -> fatal_error "Matching.make_line_matching"
| arg :: rem ->
{ cases = [];
args = get_expr_args head arg rem;
default = Default_environment.specialize head def
}
type 'a division = {
args : (lambda * let_kind) list;
cells : ('a * cell) list
}
let add_in_div make_matching_fun eq_key key patl_action division =
let cells =
match List.find_opt (fun (k, _) -> eq_key key k) division.cells with
| None ->
let cell = make_matching_fun division.args in
cell.pm.cases <- [ patl_action ];
(key, cell) :: division.cells
| Some (_, cell) ->
cell.pm.cases <- patl_action :: cell.pm.cases;
division.cells
in
{ division with cells }
let divide get_expr_args eq_key get_key get_pat_args ctx
(pm : Simple.clause pattern_matching) =
let add ((p, patl), action) division =
let ph = Simple.head p in
let p = General.erase p in
add_in_div
(make_matching get_expr_args ph pm.default ctx)
eq_key (get_key p)
(get_pat_args p patl, action)
division
in
List.fold_right add pm.cases { args = pm.args; cells = [] }
let add_line patl_action pm =
pm.cases <- patl_action :: pm.cases;
pm
let divide_line make_ctx get_expr_args get_pat_args discr ctx
(pm : Simple.clause pattern_matching) =
let add ((p, patl), action) submatrix =
let p = General.erase p in
add_line (get_pat_args p patl, action) submatrix
in
let pm =
List.fold_right add pm.cases
(make_line_matching get_expr_args discr pm.default pm.args)
in
{ pm; ctx = make_ctx ctx; discr }
let drop_pat_arg _p rem = rem
let drop_expr_arg _head _arg rem = rem
(* Then come various functions,
There is one set of functions per matching style
(constants, constructors etc.)
- get_{expr,pat}_args and get_key are for the compiled matrices,
note that selection and getting arguments are separated.
- make_*_matching combines the previous functions for producing
new ``pattern_matching'' records.
*)
(* Matching against a constant *)
let get_key_constant caller = function
| { pat_desc = Tpat_constant cst } -> cst
| p ->
Format.eprintf "BAD: %s" caller;
pretty_pat p;
assert false
let get_pat_args_constant = drop_pat_arg
let get_expr_args_constant = drop_expr_arg
let divide_constant ctx m =
divide
get_expr_args_constant
(fun c d -> const_compare c d = 0)
(get_key_constant "divide")
get_pat_args_constant ctx m
(* Matching against a constructor *)
let get_key_constr = function
| { pat_desc = Tpat_construct (_, cstr, _) } -> cstr.cstr_tag
| _ -> assert false
let get_pat_args_constr p rem =
match p with
| { pat_desc = Tpat_construct (_, _, args) } -> args @ rem
| _ -> assert false
let get_expr_args_constr ~scopes head (arg, _mut) rem =
let cstr =
match Pattern_head.desc head with
| Construct cstr -> cstr
| _ -> fatal_error "Matching.get_expr_args_constr"
in
let loc = head_loc ~scopes head in
let make_field_accesses binding_kind first_pos last_pos argl =
let rec make_args pos =
if pos > last_pos then
argl
else
(Lprim (Pfield pos, [ arg ], loc), binding_kind) :: make_args (pos + 1)
in
make_args first_pos
in
if cstr.cstr_inlined <> None then
(arg, Alias) :: rem
else
match cstr.cstr_tag with
| Cstr_constant _
| Cstr_block _ ->
make_field_accesses Alias 0 (cstr.cstr_arity - 1) rem
| Cstr_unboxed -> (arg, Alias) :: rem
| Cstr_extension _ -> make_field_accesses Alias 1 cstr.cstr_arity rem
let divide_constructor ~scopes ctx pm =
divide
(get_expr_args_constr ~scopes)
( = )
get_key_constr
get_pat_args_constr
ctx pm
(* Matching against a variant *)
let get_expr_args_variant_constant = drop_expr_arg
let get_expr_args_variant_nonconst ~scopes head (arg, _mut) rem =
let loc = head_loc ~scopes head in
(Lprim (Pfield 1, [ arg ], loc), Alias) :: rem
let divide_variant ~scopes row ctx { cases = cl; args; default = def } =
let row = Btype.row_repr row in
let rec divide = function
| [] -> { args; cells = [] }
| ((p, patl), action) :: rem
-> (
let lab, pato = match p.pat_desc with
| `Variant (lab, pato, _) -> lab, pato
| _ -> assert false
in
let head = Simple.head p in
let variants = divide rem in
if
try Btype.row_field_repr (List.assoc lab row.row_fields) = Rabsent
with Not_found -> true
then
variants
else
let tag = Btype.hash_variant lab in
match pato with
| None ->
add_in_div
(make_matching get_expr_args_variant_constant head def ctx)
( = ) (Cstr_constant tag) (patl, action) variants
| Some pat ->
add_in_div
(make_matching
(get_expr_args_variant_nonconst ~scopes)
head def ctx)
( = ) (Cstr_block tag)
(pat :: patl, action)
variants
)
in
divide cl
(*
Three ``no-test'' cases
*)
(* Matching against a variable *)
let get_pat_args_var = drop_pat_arg
let get_expr_args_var = drop_expr_arg
let divide_var ctx pm =
divide_line Context.lshift
get_expr_args_var
get_pat_args_var
Pattern_head.omega ctx pm
(* Matching and forcing a lazy value *)
let get_pat_args_lazy p rem =
match p with
| { pat_desc = Tpat_any } -> omega :: rem
| { pat_desc = Tpat_lazy arg } -> arg :: rem
| _ -> assert false
(* Inlining the tag tests before calling the primitive that works on
lazy blocks. This is also used in translcore.ml.
No other call than Obj.tag when the value has been forced before.
*)
let prim_obj_tag = Primitive.simple ~name:"caml_obj_tag" ~arity:1 ~alloc:false
let get_mod_field modname field =
lazy
(let mod_ident = Ident.create_persistent modname in
let env =
Env.add_persistent_structure mod_ident Env.initial_safe_string
in
match Env.open_pers_signature modname env with
| exception Not_found ->
fatal_error ("Module " ^ modname ^ " unavailable.")
| env -> (
match Env.find_value_by_name (Longident.Lident field) env with
| exception Not_found ->
fatal_error ("Primitive " ^ modname ^ "." ^ field ^ " not found.")
| path, _ -> transl_value_path Loc_unknown env path
))
let code_force_lazy_block = get_mod_field "CamlinternalLazy" "force_lazy_block"
let code_force_lazy = get_mod_field "CamlinternalLazy" "force"
(* inline_lazy_force inlines the beginning of the code of Lazy.force. When
the value argument is tagged as:
- forward, take field 0
- lazy, call the primitive that forces (without testing again the tag)
- anything else, return it
Using Lswitch below relies on the fact that the GC does not shortcut
Forward(val_out_of_heap).
*)
let inline_lazy_force_cond arg loc =
let idarg = Ident.create_local "lzarg" in
let varg = Lvar idarg in
let tag = Ident.create_local "tag" in
let tag_var = Lvar tag in
let force_fun = Lazy.force code_force_lazy_block in
Llet
( Strict,
Pgenval,
idarg,
arg,
Llet
( Alias,
Pgenval,
tag,
Lprim (Pccall prim_obj_tag, [ varg ], loc),
Lifthenelse
(* if (tag == Obj.forward_tag) then varg.(0) else ... *)
( Lprim
( Pintcomp Ceq,
[ tag_var; Lconst (Const_base (Const_int Obj.forward_tag)) ],
loc ),
Lprim (Pfield 0, [ varg ], loc),
Lifthenelse
(* if (tag == Obj.lazy_tag) then Lazy.force varg else ... *)
( Lprim
( Pintcomp Ceq,
[ tag_var; Lconst (Const_base (Const_int Obj.lazy_tag)) ],
loc ),
Lapply
{ ap_should_be_tailcall = false;
ap_loc = loc;
ap_func = force_fun;
ap_args = [ varg ];
ap_inlined = Default_inline;
ap_specialised = Default_specialise
},
(* ... arg *)
varg ) ) ) )
let inline_lazy_force_switch arg loc =
let idarg = Ident.create_local "lzarg" in
let varg = Lvar idarg in
let force_fun = Lazy.force code_force_lazy_block in
Llet
( Strict,
Pgenval,
idarg,
arg,
Lifthenelse
( Lprim (Pisint, [ varg ], loc),
varg,
Lswitch
( varg,
{ sw_numconsts = 0;
sw_consts = [];
sw_numblocks = 256;
(* PR#6033 - tag ranges from 0 to 255 *)
sw_blocks =
[ (Obj.forward_tag, Lprim (Pfield 0, [ varg ], loc));
( Obj.lazy_tag,
Lapply
{ ap_should_be_tailcall = false;
ap_loc = loc;
ap_func = force_fun;
ap_args = [ varg ];
ap_inlined = Default_inline;
ap_specialised = Default_specialise
} )
];
sw_failaction = Some varg
},
loc ) ) )
let inline_lazy_force arg loc =
if !Clflags.afl_instrument then
(* Disable inlining optimisation if AFL instrumentation active,
so that the GC forwarding optimisation is not visible in the
instrumentation output.
(see https://github.com/stedolan/crowbar/issues/14) *)
Lapply
{ ap_should_be_tailcall = false;
ap_loc = loc;
ap_func = Lazy.force code_force_lazy;
ap_args = [ arg ];
ap_inlined = Default_inline;
ap_specialised = Default_specialise
}
else if !Clflags.native_code then
(* Lswitch generates compact and efficient native code *)
inline_lazy_force_switch arg loc
else
(* generating bytecode: Lswitch would generate too many rather big
tables (~ 250 elts); conditionals are better *)
inline_lazy_force_cond arg loc
let get_expr_args_lazy ~scopes head (arg, _mut) rem =
let loc = head_loc ~scopes head in
(inline_lazy_force arg loc, Strict) :: rem
let divide_lazy ~scopes head ctx pm =
divide_line (Context.specialize head)
(get_expr_args_lazy ~scopes)
get_pat_args_lazy
head ctx pm
(* Matching against a tuple pattern *)
let get_pat_args_tuple arity p rem =
match p with
| { pat_desc = Tpat_any } -> omegas arity @ rem
| { pat_desc = Tpat_tuple args } -> args @ rem
| _ -> assert false
let get_expr_args_tuple ~scopes head (arg, _mut) rem =
let loc = head_loc ~scopes head in
let arity = Pattern_head.arity head in
let rec make_args pos =
if pos >= arity then
rem
else
(Lprim (Pfield pos, [ arg ], loc), Alias) :: make_args (pos + 1)
in
make_args 0
let divide_tuple ~scopes head ctx pm =
let arity = Pattern_head.arity head in
divide_line (Context.specialize head)
(get_expr_args_tuple ~scopes)
(get_pat_args_tuple arity)
head ctx pm
(* Matching against a record pattern *)
let record_matching_line num_fields lbl_pat_list =
let patv = Array.make num_fields omega in
List.iter (fun (_, lbl, pat) -> patv.(lbl.lbl_pos) <- pat) lbl_pat_list;
Array.to_list patv
let get_pat_args_record num_fields p rem =
match p with
| { pat_desc = Tpat_any } -> record_matching_line num_fields [] @ rem
| { pat_desc = Tpat_record (lbl_pat_list, _) } ->
record_matching_line num_fields lbl_pat_list @ rem
| _ -> assert false
let get_expr_args_record ~scopes head (arg, _mut) rem =
let loc = head_loc ~scopes head in
let all_labels =
match Pattern_head.desc head with
| Record (lbl :: _) -> lbl.lbl_all
| Record []
| _ ->
assert false
in
let rec make_args pos =
if pos >= Array.length all_labels then
rem
else
let lbl = all_labels.(pos) in
let access =
match lbl.lbl_repres with
| Record_regular
| Record_inlined _ ->
Lprim (Pfield lbl.lbl_pos, [ arg ], loc)
| Record_unboxed _ -> arg
| Record_float -> Lprim (Pfloatfield lbl.lbl_pos, [ arg ], loc)
| Record_extension _ -> Lprim (Pfield (lbl.lbl_pos + 1), [ arg ], loc)
in
let str =
match lbl.lbl_mut with
| Immutable -> Alias
| Mutable -> StrictOpt
in
(access, str) :: make_args (pos + 1)
in
make_args 0
let divide_record all_labels ~scopes head ctx pm =
(* There is some redundancy in the expansions here, [head] is
expanded here and again in the matcher. It would be
nicer to have a type-level distinction between expanded heads
and non-expanded heads, to be able to reason confidently on
when expansions must happen. *)
let head = expand_record_head head in
divide_line (Context.specialize head)
(get_expr_args_record ~scopes)
(get_pat_args_record (Array.length all_labels))
head ctx pm
(* Matching against an array pattern *)
let get_key_array = function
| { pat_desc = Tpat_array patl } -> List.length patl
| _ -> assert false
let get_pat_args_array p rem =
match p with
| { pat_desc = Tpat_array patl } -> patl @ rem
| _ -> assert false
let get_expr_args_array ~scopes kind head (arg, _mut) rem =
let len =
match Pattern_head.desc head with
| Array len -> len
| _ -> assert false
in
let loc = head_loc ~scopes head in
let rec make_args pos =
if pos >= len then
rem
else
( Lprim
(Parrayrefu kind, [ arg; Lconst (Const_base (Const_int pos)) ], loc),
StrictOpt )
:: make_args (pos + 1)
in
make_args 0
let divide_array ~scopes kind ctx pm =
divide
(get_expr_args_array ~scopes kind)
( = )
get_key_array get_pat_args_array
ctx pm
(*
Specific string test sequence
Will be called by the bytecode compiler, from bytegen.ml.
The strategy is first dichotomic search (we perform 3-way tests
with compare_string), then sequence of equality tests
when there are less then T=strings_test_threshold static strings to match.
Increasing T entails (slightly) less code, decreasing T
(slightly) favors runtime speed.
T=8 looks a decent tradeoff.
*)
(* Utilities *)
let strings_test_threshold = 8
let prim_string_notequal =
Pccall (Primitive.simple ~name:"caml_string_notequal" ~arity:2 ~alloc:false)
let prim_string_compare =
Pccall (Primitive.simple ~name:"caml_string_compare" ~arity:2 ~alloc:false)
let bind_sw arg k =
match arg with
| Lvar _ -> k arg
| _ ->
let id = Ident.create_local "switch" in
Llet (Strict, Pgenval, id, arg, k (Lvar id))
(* Sequential equality tests *)
let make_string_test_sequence loc arg sw d =
let d, sw =
match d with
| None -> (
match sw with
| (_, d) :: sw -> (d, sw)
| [] -> assert false
)
| Some d -> (d, sw)
in
bind_sw arg (fun arg ->
List.fold_right
(fun (str, lam) k ->
Lifthenelse
( Lprim
( prim_string_notequal,
[ arg; Lconst (Const_immstring str) ],
loc ),
k,
lam ))
sw d)
let rec split k xs =
match xs with
| [] -> assert false
| x0 :: xs ->
if k <= 1 then
([], x0, xs)
else
let xs, y0, ys = split (k - 2) xs in
(x0 :: xs, y0, ys)
let zero_lam = Lconst (Const_base (Const_int 0))
let tree_way_test loc arg lt eq gt =
Lifthenelse
( Lprim (Pintcomp Clt, [ arg; zero_lam ], loc),
lt,
Lifthenelse (Lprim (Pintcomp Clt, [ zero_lam; arg ], loc), gt, eq) )
(* Dichotomic tree *)
let rec do_make_string_test_tree loc arg sw delta d =
let len = List.length sw in
if len <= strings_test_threshold + delta then
make_string_test_sequence loc arg sw d
else
let lt, (s, act), gt = split len sw in
bind_sw
(Lprim (prim_string_compare, [ arg; Lconst (Const_immstring s) ], loc))
(fun r ->
tree_way_test loc r
(do_make_string_test_tree loc arg lt delta d)
act
(do_make_string_test_tree loc arg gt delta d))
(* Entry point *)
let expand_stringswitch loc arg sw d =
match d with
| None -> bind_sw arg (fun arg -> do_make_string_test_tree loc arg sw 0 None)
| Some e ->
bind_sw arg (fun arg ->
make_catch e (fun d ->
do_make_string_test_tree loc arg sw 1 (Some d)))
(**********************)
(* Generic test trees *)
(**********************)
(* Sharing *)
(* Add handler, if shared *)
let handle_shared () =
let hs = ref (fun x -> x) in
let handle_shared act =
match act with
| Switch.Single act -> act
| Switch.Shared act ->
let i, h = make_catch_delayed act in
let ohs = !hs in
(hs := fun act -> h (ohs act));
make_exit i
in
(hs, handle_shared)
let share_actions_tree sw d =
let store = StoreExp.mk_store () in
(* Default action is always shared *)
let d =
match d with
| None -> None
| Some d -> Some (store.Switch.act_store_shared () d)
in
(* Store all other actions *)
let sw =
List.map (fun (cst, act) -> (cst, store.Switch.act_store () act)) sw
in
(* Retrieve all actions, including potential default *)
let acts = store.Switch.act_get_shared () in
(* Array of actual actions *)
let hs, handle_shared = handle_shared () in
let acts = Array.map handle_shared acts in
(* Reconstruct default and switch list *)
let d =
match d with
| None -> None
| Some d -> Some acts.(d)
in
let sw = List.map (fun (cst, j) -> (cst, acts.(j))) sw in
(!hs, sw, d)
(* Note: dichotomic search requires sorted input with no duplicates *)
let rec uniq_lambda_list sw =
match sw with
| []
| [ _ ] ->
sw
| ((c1, _) as p1) :: ((c2, _) :: sw2 as sw1) ->
if const_compare c1 c2 = 0 then
uniq_lambda_list (p1 :: sw2)
else
p1 :: uniq_lambda_list sw1
let sort_lambda_list l =
let l = List.stable_sort (fun (x, _) (y, _) -> const_compare x y) l in
uniq_lambda_list l
let rec do_tests_fail loc fail tst arg = function
| [] -> fail
| (c, act) :: rem ->
Lifthenelse
( Lprim (tst, [ arg; Lconst (Const_base c) ], loc),
do_tests_fail loc fail tst arg rem,
act )
let rec do_tests_nofail loc tst arg = function
| [] -> fatal_error "Matching.do_tests_nofail"
| [ (_, act) ] -> act
| (c, act) :: rem ->
Lifthenelse
( Lprim (tst, [ arg; Lconst (Const_base c) ], loc),
do_tests_nofail loc tst arg rem,
act )
let make_test_sequence loc fail tst lt_tst arg const_lambda_list =
let const_lambda_list = sort_lambda_list const_lambda_list in
let hs, const_lambda_list, fail =
share_actions_tree const_lambda_list fail
in
let rec make_test_sequence const_lambda_list =
if List.length const_lambda_list >= 4 && lt_tst <> Pignore then
split_sequence const_lambda_list
else
match fail with
| None -> do_tests_nofail loc tst arg const_lambda_list
| Some fail -> do_tests_fail loc fail tst arg const_lambda_list
and split_sequence const_lambda_list =
let list1, list2 =
rev_split_at (List.length const_lambda_list / 2) const_lambda_list
in
Lifthenelse
( Lprim (lt_tst, [ arg; Lconst (Const_base (fst (List.hd list2))) ], loc),
make_test_sequence list1,
make_test_sequence list2 )
in
hs (make_test_sequence const_lambda_list)
module SArg = struct
type primitive = Lambda.primitive
let eqint = Pintcomp Ceq
let neint = Pintcomp Cne
let leint = Pintcomp Cle
let ltint = Pintcomp Clt
let geint = Pintcomp Cge
let gtint = Pintcomp Cgt
type act = Lambda.lambda
type loc = Lambda.scoped_location
let make_prim p args = Lprim (p, args, Loc_unknown)
let make_offset arg n =
match n with
| 0 -> arg
| _ -> Lprim (Poffsetint n, [ arg ], Loc_unknown)
let bind arg body =
let newvar, newarg =
match arg with
| Lvar v -> (v, arg)
| _ ->
let newvar = Ident.create_local "switcher" in
(newvar, Lvar newvar)
in
bind Alias newvar arg (body newarg)
let make_const i = Lconst (Const_base (Const_int i))
let make_isout h arg = Lprim (Pisout, [ h; arg ], Loc_unknown)
let make_isin h arg = Lprim (Pnot, [ make_isout h arg ], Loc_unknown)
let make_if cond ifso ifnot = Lifthenelse (cond, ifso, ifnot)
let make_switch loc arg cases acts =
let l = ref [] in
for i = Array.length cases - 1 downto 0 do
l := (i, acts.(cases.(i))) :: !l
done;
Lswitch
( arg,
{ sw_numconsts = Array.length cases;
sw_consts = !l;
sw_numblocks = 0;
sw_blocks = [];
sw_failaction = None
},
loc )
let make_catch = make_catch_delayed
let make_exit = make_exit
end
(* Action sharing for Lswitch argument *)
let share_actions_sw sw =
(* Attempt sharing on all actions *)
let store = StoreExp.mk_store () in
let fail =
match sw.sw_failaction with
| None -> None
| Some fail ->
(* Fail is translated to exit, whatever happens *)
Some (store.Switch.act_store_shared () fail)
in
let consts =
List.map (fun (i, e) -> (i, store.Switch.act_store () e)) sw.sw_consts
and blocks =
List.map (fun (i, e) -> (i, store.Switch.act_store () e)) sw.sw_blocks
in
let acts = store.Switch.act_get_shared () in
let hs, handle_shared = handle_shared () in
let acts = Array.map handle_shared acts in
let fail =
match fail with
| None -> None
| Some fail -> Some acts.(fail)
in
( !hs,
{ sw with
sw_consts = List.map (fun (i, j) -> (i, acts.(j))) consts;
sw_blocks = List.map (fun (i, j) -> (i, acts.(j))) blocks;
sw_failaction = fail
} )
(* Reintroduce fail action in switch argument,
for the sake of avoiding carrying over huge switches *)
let reintroduce_fail sw =
match sw.sw_failaction with
| None ->
let t = Hashtbl.create 17 in
let seen (_, l) =
match as_simple_exit l with
| Some i ->
let old = try Hashtbl.find t i with Not_found -> 0 in
Hashtbl.replace t i (old + 1)
| None -> ()
in
List.iter seen sw.sw_consts;
List.iter seen sw.sw_blocks;
let i_max = ref (-1) and max = ref (-1) in
Hashtbl.iter
(fun i c ->
if c > !max then (
i_max := i;
max := c
))
t;
if !max >= 3 then
let default = !i_max in
let remove =
List.filter (fun (_, lam) ->
match as_simple_exit lam with
| Some j -> j <> default
| None -> true)
in
{ sw with
sw_consts = remove sw.sw_consts;
sw_blocks = remove sw.sw_blocks;
sw_failaction = Some (make_exit default)
}
else
sw
| Some _ -> sw
module Switcher = Switch.Make (SArg)
open Switch
let rec last def = function
| [] -> def
| [ (x, _) ] -> x
| _ :: rem -> last def rem
let get_edges low high l =
match l with
| [] -> (low, high)
| (x, _) :: _ -> (x, last high l)
let as_interval_canfail fail low high l =
let store = StoreExp.mk_store () in
let do_store _tag act =
let i = store.act_store () act in
(*
eprintf "STORE [%s] %i %s\n" tag i (string_of_lam act) ;
*)
i
in
let rec nofail_rec cur_low cur_high cur_act = function
| [] ->
if cur_high = high then
[ (cur_low, cur_high, cur_act) ]
else
[ (cur_low, cur_high, cur_act); (cur_high + 1, high, 0) ]
| (i, act_i) :: rem as all ->
let act_index = do_store "NO" act_i in
if cur_high + 1 = i then
if act_index = cur_act then
nofail_rec cur_low i cur_act rem
else if act_index = 0 then
(cur_low, i - 1, cur_act) :: fail_rec i i rem
else
(cur_low, i - 1, cur_act) :: nofail_rec i i act_index rem
else if act_index = 0 then
(cur_low, cur_high, cur_act)
:: fail_rec (cur_high + 1) (cur_high + 1) all
else
(cur_low, cur_high, cur_act)
:: (cur_high + 1, i - 1, 0)
:: nofail_rec i i act_index rem
and fail_rec cur_low cur_high = function
| [] -> [ (cur_low, cur_high, 0) ]
| (i, act_i) :: rem ->
let index = do_store "YES" act_i in
if index = 0 then
fail_rec cur_low i rem
else
(cur_low, i - 1, 0) :: nofail_rec i i index rem
in
let init_rec = function
| [] -> [ (low, high, 0) ]
| (i, act_i) :: rem ->
let index = do_store "INIT" act_i in
if index = 0 then
fail_rec low i rem
else if low < i then
(low, i - 1, 0) :: nofail_rec i i index rem
else
nofail_rec i i index rem
in
assert (do_store "FAIL" fail = 0);
(* fail has action index 0 *)
let r = init_rec l in
(Array.of_list r, store)
let as_interval_nofail l =
let store = StoreExp.mk_store () in
let rec some_hole = function
| []
| [ _ ] ->
false
| (i, _) :: ((j, _) :: _ as rem) -> j > i + 1 || some_hole rem
in
let rec i_rec cur_low cur_high cur_act = function
| [] -> [ (cur_low, cur_high, cur_act) ]
| (i, act) :: rem ->
let act_index = store.act_store () act in
if act_index = cur_act then
i_rec cur_low i cur_act rem
else
(cur_low, cur_high, cur_act) :: i_rec i i act_index rem
in
let inters =
match l with
| (i, act) :: rem ->
let act_index =
(* In case there is some hole and that a switch is emitted,
action 0 will be used as the action of unreachable
cases (cf. switch.ml, make_switch).
Hence, this action will be shared *)
if some_hole rem then
store.act_store_shared () act
else
store.act_store () act
in
assert (act_index = 0);
i_rec i i act_index rem
| _ -> assert false
in
(Array.of_list inters, store)
let sort_int_lambda_list l =
List.sort
(fun (i1, _) (i2, _) ->
if i1 < i2 then
-1
else if i2 < i1 then
1
else
0)
l
let as_interval fail low high l =
let l = sort_int_lambda_list l in
( get_edges low high l,
match fail with
| None -> as_interval_nofail l
| Some act -> as_interval_canfail act low high l )
let call_switcher loc fail arg low high int_lambda_list =
let edges, (cases, actions) = as_interval fail low high int_lambda_list in
Switcher.zyva loc edges arg cases actions
let rec list_as_pat = function
| [] -> fatal_error "Matching.list_as_pat"
| [ pat ] -> pat
| pat :: rem -> { pat with pat_desc = Tpat_or (pat, list_as_pat rem, None) }
let complete_pats_constrs = function
| p :: _ as pats ->
List.map (pat_of_constr p)
(complete_constrs p (List.map get_key_constr pats))
| _ -> assert false
(*
Following two ``failaction'' function compute n, the trap handler
to jump to in case of failure of elementary tests
*)
let mk_failaction_neg partial ctx def =
match partial with
| Partial -> (
match Default_environment.pop def with
| Some ((_, idef), _) ->
(Some (Lstaticraise (idef, [])), Jumps.singleton idef ctx)
| None ->
(* Act as Total, this means
If no appropriate default matrix exists,
then this switch cannot fail *)
(None, Jumps.empty)
)
| Total -> (None, Jumps.empty)
(* In line with the article and simpler than before *)
let mk_failaction_pos partial seen ctx defs =
if dbg then (
Format.eprintf "**POS**\n";
Default_environment.pp defs;
()
);
let rec scan_def env to_test defs =
match (to_test, Default_environment.pop defs) with
| [], _
| _, None ->
List.fold_left
(fun (klist, jumps) (pats, i) ->
let action = Lstaticraise (i, []) in
let klist =
List.fold_right
(fun pat r -> (get_key_constr pat, action) :: r)
pats klist
and jumps =
Jumps.add i (Context.lub (list_as_pat pats) ctx) jumps
in
(klist, jumps))
([], Jumps.empty) env
| _, Some ((pss, idef), rem) -> (
let now, later =
List.partition (fun (_p, p_ctx) -> Context.matches p_ctx pss) to_test
in
match now with
| [] -> scan_def env to_test rem
| _ -> scan_def ((List.map fst now, idef) :: env) later rem
)
in
let fail_pats = complete_pats_constrs seen in
if List.length fail_pats < !Clflags.match_context_rows then (
let fail, jmps =
scan_def []
(List.map (fun pat -> (pat, Context.lub pat ctx)) fail_pats)
defs
in
if dbg then (
eprintf "POSITIVE JUMPS [%i]:\n" (List.length fail_pats);
Jumps.eprintf jmps
);
(None, fail, jmps)
) else (
(* Too many non-matched constructors -> reduced information *)
if dbg then eprintf "POS->NEG!!!\n%!";
let fail, jumps = mk_failaction_neg partial ctx defs in
if dbg then
eprintf "FAIL: %s\n"
( match fail with
| None -> "<none>"
| Some lam -> string_of_lam lam
);
(fail, [], jumps)
)
let combine_constant loc arg cst partial ctx def
(const_lambda_list, total, _pats) =
let fail, local_jumps = mk_failaction_neg partial ctx def in
let lambda1 =
match cst with
| Const_int _ ->
let int_lambda_list =
List.map
(function
| Const_int n, l -> (n, l)
| _ -> assert false)
const_lambda_list
in
call_switcher loc fail arg min_int max_int int_lambda_list
| Const_char _ ->
let int_lambda_list =
List.map
(function
| Const_char c, l -> (Char.code c, l)
| _ -> assert false)
const_lambda_list
in
call_switcher loc fail arg 0 255 int_lambda_list
| Const_string _ ->
(* Note as the bytecode compiler may resort to dichotomic search,
the clauses of stringswitch are sorted with duplicates removed.
This partly applies to the native code compiler, which requires
no duplicates *)
let const_lambda_list = sort_lambda_list const_lambda_list in
let sw =
List.map
(fun (c, act) ->
match c with
| Const_string (s, _, _) -> (s, act)
| _ -> assert false)
const_lambda_list
in
let hs, sw, fail = share_actions_tree sw fail in
hs (Lstringswitch (arg, sw, fail, loc))
| Const_float _ ->
make_test_sequence loc fail (Pfloatcomp CFneq) (Pfloatcomp CFlt) arg
const_lambda_list
| Const_int32 _ ->
make_test_sequence loc fail
(Pbintcomp (Pint32, Cne))
(Pbintcomp (Pint32, Clt))
arg const_lambda_list
| Const_int64 _ ->
make_test_sequence loc fail
(Pbintcomp (Pint64, Cne))
(Pbintcomp (Pint64, Clt))
arg const_lambda_list
| Const_nativeint _ ->
make_test_sequence loc fail
(Pbintcomp (Pnativeint, Cne))
(Pbintcomp (Pnativeint, Clt))
arg const_lambda_list
in
(lambda1, Jumps.union local_jumps total)
let split_cases tag_lambda_list =
let rec split_rec = function
| [] -> ([], [])
| (cstr, act) :: rem -> (
let consts, nonconsts = split_rec rem in
match cstr with
| Cstr_constant n -> ((n, act) :: consts, nonconsts)
| Cstr_block n -> (consts, (n, act) :: nonconsts)
| Cstr_unboxed -> (consts, (0, act) :: nonconsts)
| Cstr_extension _ -> assert false
)
in
let const, nonconst = split_rec tag_lambda_list in
(sort_int_lambda_list const, sort_int_lambda_list nonconst)
let split_extension_cases tag_lambda_list =
let rec split_rec = function
| [] -> ([], [])
| (cstr, act) :: rem -> (
let consts, nonconsts = split_rec rem in
match cstr with
| Cstr_extension (path, true) -> ((path, act) :: consts, nonconsts)
| Cstr_extension (path, false) -> (consts, (path, act) :: nonconsts)
| _ -> assert false
)
in
split_rec tag_lambda_list
let combine_constructor loc arg pat_env cstr partial ctx def
(tag_lambda_list, total1, pats) =
match cstr.cstr_tag with
| Cstr_extension _ ->
(* Special cases for extensions *)
let fail, local_jumps = mk_failaction_neg partial ctx def in
let lambda1 =
let consts, nonconsts = split_extension_cases tag_lambda_list in
let default, consts, nonconsts =
match fail with
| None -> (
match (consts, nonconsts) with
| _, (_, act) :: rem -> (act, consts, rem)
| (_, act) :: rem, _ -> (act, rem, nonconsts)
| _ -> assert false
)
| Some fail -> (fail, consts, nonconsts)
in
let nonconst_lambda =
match nonconsts with
| [] -> default
| _ ->
let tag = Ident.create_local "tag" in
let tests =
List.fold_right
(fun (path, act) rem ->
let ext = transl_extension_path loc pat_env path in
Lifthenelse
(Lprim (Pintcomp Ceq, [ Lvar tag; ext ], loc), act, rem))
nonconsts default
in
Llet (Alias, Pgenval, tag, Lprim (Pfield 0, [ arg ], loc), tests)
in
List.fold_right
(fun (path, act) rem ->
let ext = transl_extension_path loc pat_env path in
Lifthenelse (Lprim (Pintcomp Ceq, [ arg; ext ], loc), act, rem))
consts nonconst_lambda
in
(lambda1, Jumps.union local_jumps total1)
| _ ->
(* Regular concrete type *)
let ncases = List.length tag_lambda_list
and nconstrs = cstr.cstr_consts + cstr.cstr_nonconsts in
let sig_complete = ncases = nconstrs in
let fail_opt, fails, local_jumps =
if sig_complete then
(None, [], Jumps.empty)
else
mk_failaction_pos partial pats ctx def
in
let tag_lambda_list = fails @ tag_lambda_list in
let consts, nonconsts = split_cases tag_lambda_list in
let lambda1 =
match (fail_opt, same_actions tag_lambda_list) with
| None, Some act -> act (* Identical actions, no failure *)
| _ -> (
match
(cstr.cstr_consts, cstr.cstr_nonconsts, consts, nonconsts)
with
| 1, 1, [ (0, act1) ], [ (0, act2) ] ->
(* Typically, match on lists, will avoid isint primitive in that
case *)
Lifthenelse (arg, act2, act1)
| n, 0, _, [] ->
(* The type defines constant constructors only *)
call_switcher loc fail_opt arg 0 (n - 1) consts
| n, _, _, _ -> (
let act0 =
(* = Some act when all non-const constructors match to act *)
match (fail_opt, nonconsts) with
| Some a, [] -> Some a
| Some _, _ ->
if List.length nonconsts = cstr.cstr_nonconsts then
same_actions nonconsts
else
None
| None, _ -> same_actions nonconsts
in
match act0 with
| Some act ->
Lifthenelse
( Lprim (Pisint, [ arg ], loc),
call_switcher loc fail_opt arg 0 (n - 1) consts,
act )
| None ->
(* Emit a switch, as bytecode implements this sophisticated
instruction *)
let sw =
{ sw_numconsts = cstr.cstr_consts;
sw_consts = consts;
sw_numblocks = cstr.cstr_nonconsts;
sw_blocks = nonconsts;
sw_failaction = fail_opt
}
in
let hs, sw = share_actions_sw sw in
let sw = reintroduce_fail sw in
hs (Lswitch (arg, sw, loc))
)
)
in
(lambda1, Jumps.union local_jumps total1)
let make_test_sequence_variant_constant fail arg int_lambda_list =
let _, (cases, actions) = as_interval fail min_int max_int int_lambda_list in
Switcher.test_sequence arg cases actions
let call_switcher_variant_constant loc fail arg int_lambda_list =
call_switcher loc fail arg min_int max_int int_lambda_list
let call_switcher_variant_constr loc fail arg int_lambda_list =
let v = Ident.create_local "variant" in
Llet
( Alias,
Pgenval,
v,
Lprim (Pfield 0, [ arg ], loc),
call_switcher loc fail (Lvar v) min_int max_int int_lambda_list )
let combine_variant loc row arg partial ctx def (tag_lambda_list, total1, _pats)
=
let row = Btype.row_repr row in
let num_constr = ref 0 in
if row.row_closed then
List.iter
(fun (_, f) ->
match Btype.row_field_repr f with
| Rabsent
| Reither (true, _ :: _, _, _) ->
()
| _ -> incr num_constr)
row.row_fields
else
num_constr := max_int;
let test_int_or_block arg if_int if_block =
Lifthenelse (Lprim (Pisint, [ arg ], loc), if_int, if_block)
in
let sig_complete = List.length tag_lambda_list = !num_constr
and one_action = same_actions tag_lambda_list in
let fail, local_jumps =
if
sig_complete
||
match partial with
| Total -> true
| _ -> false
then
(None, Jumps.empty)
else
mk_failaction_neg partial ctx def
in
let consts, nonconsts = split_cases tag_lambda_list in
let lambda1 =
match (fail, one_action) with
| None, Some act -> act
| _, _ -> (
match (consts, nonconsts) with
| [ (_, act1) ], [ (_, act2) ] when fail = None ->
test_int_or_block arg act1 act2
| _, [] ->
(* One can compare integers and pointers *)
make_test_sequence_variant_constant fail arg consts
| [], _ -> (
let lam = call_switcher_variant_constr loc fail arg nonconsts in
(* One must not dereference integers *)
match fail with
| None -> lam
| Some fail -> test_int_or_block arg fail lam
)
| _, _ ->
let lam_const = call_switcher_variant_constant loc fail arg consts
and lam_nonconst =
call_switcher_variant_constr loc fail arg nonconsts
in
test_int_or_block arg lam_const lam_nonconst
)
in
(lambda1, Jumps.union local_jumps total1)
let combine_array loc arg kind partial ctx def (len_lambda_list, total1, _pats)
=
let fail, local_jumps = mk_failaction_neg partial ctx def in
let lambda1 =
let newvar = Ident.create_local "len" in
let switch =
call_switcher loc fail (Lvar newvar) 0 max_int len_lambda_list
in
bind Alias newvar (Lprim (Parraylength kind, [ arg ], loc)) switch
in
(lambda1, Jumps.union local_jumps total1)
(* Insertion of debugging events *)
let rec event_branch repr lam =
match (lam, repr) with
| _, None -> lam
| Levent (lam', ev), Some r ->
incr r;
Levent
( lam',
{ lev_loc = ev.lev_loc;
lev_kind = ev.lev_kind;
lev_repr = repr;
lev_env = ev.lev_env
} )
| Llet (str, k, id, lam, body), _ ->
Llet (str, k, id, lam, event_branch repr body)
| Lstaticraise _, _ -> lam
| _, Some _ ->
Printlambda.lambda Format.str_formatter lam;
fatal_error ("Matching.event_branch: " ^ Format.flush_str_formatter ())
(*
This exception is raised when the compiler cannot produce code
because control cannot reach the compiled clause,
Unused is raised initially in compile_test.
compile_list (for compiling switch results) catch Unused
comp_match_handlers (for compiling split matches)
may reraise Unused
*)
exception Unused
let compile_list compile_fun division =
let rec c_rec totals = function
| [] -> ([], Jumps.unions totals, [])
| (key, cell) :: rem -> (
if Context.is_empty cell.ctx then
c_rec totals rem
else
try
let lambda1, total1 = compile_fun cell.ctx cell.pm in
let c_rem, total, new_discrs =
c_rec (Jumps.map Context.combine total1 :: totals) rem
in
( (key, lambda1) :: c_rem,
total,
Pattern_head.to_omega_pattern cell.discr :: new_discrs )
with Unused -> c_rec totals rem
)
in
c_rec [] division
let compile_orhandlers compile_fun lambda1 total1 ctx to_catch =
let rec do_rec r total_r = function
| [] -> (r, total_r)
| { provenance = mat; exit = i; vars; pm } :: rem -> (
try
let ctx = Context.select_columns mat ctx in
let handler_i, total_i = compile_fun ctx pm in
match raw_action r with
| Lstaticraise (j, args) ->
if i = j then
( List.fold_right2
(bind_with_value_kind Alias)
vars args handler_i,
Jumps.map (Context.rshift_num (ncols mat)) total_i )
else
do_rec r total_r rem
| _ ->
do_rec
(Lstaticcatch (r, (i, vars), handler_i))
(Jumps.union (Jumps.remove i total_r)
(Jumps.map (Context.rshift_num (ncols mat)) total_i))
rem
with Unused ->
do_rec (Lstaticcatch (r, (i, vars), lambda_unit)) total_r rem
)
in
do_rec lambda1 total1 to_catch
let compile_test compile_fun partial divide combine ctx to_match =
let division = divide ctx to_match in
let c_div = compile_list compile_fun division.cells in
match c_div with
| [], _, _ -> (
match mk_failaction_neg partial ctx to_match.default with
| None, _ -> raise Unused
| Some l, total -> (l, total)
)
| _ -> combine ctx to_match.default c_div
(* Attempt to avoid some useless bindings by lowering them *)
(* Approximation of v present in lam *)
let rec approx_present v = function
| Lconst _ -> false
| Lstaticraise (_, args) ->
List.exists (fun lam -> approx_present v lam) args
| Lprim (_, args, _) -> List.exists (fun lam -> approx_present v lam) args
| Llet (Alias, _k, _, l1, l2) -> approx_present v l1 || approx_present v l2
| Lvar vv -> Ident.same v vv
| _ -> true
let rec lower_bind v arg lam =
match lam with
| Lifthenelse (cond, ifso, ifnot) -> (
let pcond = approx_present v cond
and pso = approx_present v ifso
and pnot = approx_present v ifnot in
match (pcond, pso, pnot) with
| false, false, false -> lam
| false, true, false -> Lifthenelse (cond, lower_bind v arg ifso, ifnot)
| false, false, true -> Lifthenelse (cond, ifso, lower_bind v arg ifnot)
| _, _, _ -> bind Alias v arg lam
)
| Lswitch (ls, ({ sw_consts = [ (i, act) ]; sw_blocks = [] } as sw), loc)
when not (approx_present v ls) ->
Lswitch (ls, { sw with sw_consts = [ (i, lower_bind v arg act) ] }, loc)
| Lswitch (ls, ({ sw_consts = []; sw_blocks = [ (i, act) ] } as sw), loc)
when not (approx_present v ls) ->
Lswitch (ls, { sw with sw_blocks = [ (i, lower_bind v arg act) ] }, loc)
| Llet (Alias, k, vv, lv, l) ->
if approx_present v lv then
bind Alias v arg lam
else
Llet (Alias, k, vv, lv, lower_bind v arg l)
| _ -> bind Alias v arg lam
let bind_check str v arg lam =
match (str, arg) with
| _, Lvar _ -> bind str v arg lam
| Alias, _ -> lower_bind v arg lam
| _, _ -> bind str v arg lam
let comp_exit ctx m =
match Default_environment.pop m.default with
| Some ((_, i), _) -> (Lstaticraise (i, []), Jumps.singleton i ctx)
| None -> fatal_error "Matching.comp_exit"
let rec comp_match_handlers comp_fun partial ctx first_match next_matchs =
match next_matchs with
| [] -> comp_fun partial ctx first_match
| rem -> (
let rec c_rec body total_body = function
| [] -> (body, total_body)
(* Hum, -1 means never taken
| (-1,pm)::rem -> c_rec body total_body rem *)
| (i, pm) :: rem -> (
let ctx_i, total_rem = Jumps.extract i total_body in
if Context.is_empty ctx_i then
c_rec body total_body rem
else
try
let li, total_i =
comp_fun
( match rem with
| [] -> partial
| _ -> Partial
)
ctx_i pm
in
c_rec
(Lstaticcatch (body, (i, []), li))
(Jumps.union total_i total_rem)
rem
with Unused ->
c_rec (Lstaticcatch (body, (i, []), lambda_unit)) total_rem rem
)
in
try
let first_lam, total = comp_fun Partial ctx first_match in
c_rec first_lam total rem
with Unused -> (
match next_matchs with
| [] -> raise Unused
| (_, x) :: xs -> comp_match_handlers comp_fun partial ctx x xs
)
)
(* To find reasonable names for variables *)
let rec name_pattern default = function
| ((pat, _), _) :: rem -> (
match pat.pat_desc with
| Tpat_var (id, _) -> id
| Tpat_alias (_, id, _) -> id
| _ -> name_pattern default rem
)
| _ -> Ident.create_local default
let arg_to_var arg cls =
match arg with
| Lvar v -> (v, arg)
| _ ->
let v = name_pattern "*match*" cls in
(v, Lvar v)
(*
The main compilation function.
Input:
repr=used for inserting debug events
partial=exhaustiveness information from Parmatch
ctx=a context
m=a pattern matching
Output: a lambda term, a jump summary {..., exit number -> context, .. }
*)
let rec compile_match ~scopes repr partial ctx
(m : initial_clause pattern_matching) =
match m.cases with
| ([], action) :: rem ->
if is_guarded action then
let lambda, total =
compile_match ~scopes None partial ctx { m with cases = rem }
in
(event_branch repr (patch_guarded lambda action), total)
else
(event_branch repr action, Jumps.empty)
| nonempty_cases ->
compile_match_nonempty ~scopes repr partial ctx
{ m with cases = List.map Non_empty_clause.of_initial nonempty_cases }
and compile_match_nonempty ~scopes repr partial ctx
(m : Typedtree.pattern Non_empty_clause.t pattern_matching) =
match m with
| { cases = []; args = [] } -> comp_exit ctx m
| { args = (arg, str) :: argl } ->
let v, newarg = arg_to_var arg m.cases in
let args = (newarg, Alias) :: argl in
let cases = List.map (half_simplify_nonempty ~arg:newarg) m.cases in
let m = { m with args; cases } in
let first_match, rem =
split_and_precompile_half_simplified ~arg:(Some v) m in
combine_handlers ~scopes repr partial ctx (v, str, arg) first_match rem
| _ -> assert false
and compile_match_simplified ~scopes repr partial ctx
(m : Simple.clause pattern_matching) =
match m with
| { cases = []; args = [] } -> comp_exit ctx m
| { args = ((Lvar v as arg), str) :: argl } ->
let args = (arg, Alias) :: argl in
let m = { m with args } in
let first_match, rem = split_and_precompile_simplified m in
combine_handlers ~scopes repr partial ctx (v, str, arg) first_match rem
| _ -> assert false
and combine_handlers ~scopes repr partial ctx (v, str, arg) first_match rem =
let lam, total =
comp_match_handlers
(( if dbg then
do_compile_matching_pr ~scopes
else
do_compile_matching ~scopes
)
repr)
partial ctx first_match rem
in
(bind_check str v arg lam, total)
(* verbose version of do_compile_matching, for debug *)
and do_compile_matching_pr ~scopes repr partial ctx x =
Format.eprintf "COMPILE: %s\nMATCH\n"
( match partial with
| Partial -> "Partial"
| Total -> "Total"
);
pretty_precompiled x;
Format.eprintf "CTX\n";
Context.eprintf ctx;
let ((_, jumps) as r) = do_compile_matching ~scopes repr partial ctx x in
Format.eprintf "JUMPS\n";
Jumps.eprintf jumps;
r
and do_compile_matching ~scopes repr partial ctx pmh =
match pmh with
| Pm pm -> (
let arg =
match pm.args with
| (first_arg, _) :: _ -> first_arg
| _ ->
(* We arrive in do_compile_matching from:
- compile_matching
- recursive call on PmVars
The first one explicitly checks that [args] is nonempty, the
second one is only generated when the inner pm first looks at
a variable (i.e. there is something to look at).
*)
assert false
in
let ph = what_is_cases pm.cases in
let pomega = Pattern_head.to_omega_pattern ph in
let ploc = head_loc ~scopes ph in
match Pattern_head.desc ph with
| Any ->
compile_no_test ~scopes
divide_var
Context.rshift repr partial ctx pm
| Tuple _ ->
compile_no_test ~scopes
(divide_tuple ~scopes ph)
Context.combine repr partial ctx pm
| Record [] -> assert false
| Record (lbl :: _) ->
compile_no_test ~scopes
(divide_record ~scopes lbl.lbl_all ph)
Context.combine repr partial ctx pm
| Constant cst ->
compile_test
(compile_match ~scopes repr partial)
partial divide_constant
(combine_constant ploc arg cst partial)
ctx pm
| Construct cstr ->
compile_test
(compile_match ~scopes repr partial)
partial (divide_constructor ~scopes)
(combine_constructor ploc arg
(Pattern_head.env ph) cstr partial)
ctx pm
| Array _ ->
let kind = Typeopt.array_pattern_kind pomega in
compile_test
(compile_match ~scopes repr partial)
partial (divide_array ~scopes kind)
(combine_array ploc arg kind partial)
ctx pm
| Lazy ->
compile_no_test ~scopes
(divide_lazy ~scopes ph)
Context.combine repr partial ctx pm
| Variant { cstr_row = row } ->
compile_test
(compile_match ~scopes repr partial)
partial (divide_variant ~scopes !row)
(combine_variant ploc !row arg partial)
ctx pm
)
| PmVar { inside = pmh } ->
let lam, total =
do_compile_matching ~scopes repr partial (Context.lshift ctx) pmh
in
(lam, Jumps.map Context.rshift total)
| PmOr { body; handlers } ->
let lam, total =
compile_match_simplified ~scopes repr partial ctx body in
compile_orhandlers (compile_match ~scopes repr partial)
lam total ctx handlers
and compile_no_test ~scopes divide up_ctx repr partial ctx to_match =
let { pm = this_match; ctx = this_ctx } = divide ctx to_match in
let lambda, total =
compile_match ~scopes repr partial this_ctx this_match in
(lambda, Jumps.map up_ctx total)
(* The entry points *)
(*
If there is a guard in a matching or a lazy pattern,
then set exhaustiveness info to Partial.
(because of side effects, assume the worst).
Notice that exhaustiveness information is trusted by the compiler,
that is, a match flagged as Total should not fail at runtime.
More specifically, for instance if match y with x::_ -> x is flagged
total (as it happens during JoCaml compilation) then y cannot be []
at runtime. As a consequence, the static Total exhaustiveness information
have to be downgraded to Partial, in the dubious cases where guards
or lazy pattern execute arbitrary code that may perform side effects
and change the subject values.
LM:
Lazy pattern was PR#5992, initial patch by lpw25.
I have generalized the patch, so as to also find mutable fields.
*)
let is_lazy_pat p =
match p.pat_desc with
| Tpat_lazy _ -> true
| Tpat_alias _
| Tpat_variant _
| Tpat_record _
| Tpat_tuple _
| Tpat_construct _
| Tpat_array _
| Tpat_or _
| Tpat_constant _
| Tpat_var _
| Tpat_any ->
false
let has_lazy p = Typedtree.exists_pattern is_lazy_pat p
let is_record_with_mutable_field p =
match p.pat_desc with
| Tpat_record (lps, _) ->
List.exists
(fun (_, lbl, _) ->
match lbl.Types.lbl_mut with
| Mutable -> true
| Immutable -> false)
lps
| Tpat_alias _
| Tpat_variant _
| Tpat_lazy _
| Tpat_tuple _
| Tpat_construct _
| Tpat_array _
| Tpat_or _
| Tpat_constant _
| Tpat_var _
| Tpat_any ->
false
let has_mutable p = Typedtree.exists_pattern is_record_with_mutable_field p
(* Downgrade Total when
1. Matching accesses some mutable fields;
2. And there are guards or lazy patterns.
*)
let check_partial has_mutable has_lazy pat_act_list = function
| Partial -> Partial
| Total ->
if
pat_act_list = []
|| (* allow empty case list *)
List.exists
(fun (pats, lam) ->
has_mutable pats && (is_guarded lam || has_lazy pats))
pat_act_list
then
Partial
else
Total
let check_partial_list pats_act_list =
check_partial (List.exists has_mutable) (List.exists has_lazy) pats_act_list
let check_partial pat_act_list =
check_partial has_mutable has_lazy pat_act_list
(* have toplevel handler when appropriate *)
let check_total total lambda i handler_fun =
if Jumps.is_empty total then
lambda
else
Lstaticcatch (lambda, (i, []), handler_fun ())
let compile_matching ~scopes repr handler_fun arg pat_act_list partial =
let partial = check_partial pat_act_list partial in
match partial with
| Partial -> (
let raise_num = next_raise_count () in
let pm =
{ cases = List.map (fun (pat, act) -> ([ pat ], act)) pat_act_list;
args = [ (arg, Strict) ];
default = Default_environment.(cons [ [ omega ] ] raise_num empty)
}
in
try
let lambda, total =
compile_match ~scopes repr partial (Context.start 1) pm in
check_total total lambda raise_num handler_fun
with Unused -> assert false
(* ; handler_fun() *)
)
| Total ->
let pm =
{ cases = List.map (fun (pat, act) -> ([ pat ], act)) pat_act_list;
args = [ (arg, Strict) ];
default = Default_environment.empty
}
in
let lambda, total =
compile_match ~scopes repr partial (Context.start 1) pm in
assert (Jumps.is_empty total);
lambda
let partial_function ~scopes loc () =
let sloc = Scoped_location.of_location ~scopes loc in
let slot =
transl_extension_path sloc Env.initial_safe_string Predef.path_match_failure
in
let fname, line, char =
Location.get_pos_info loc.Location.loc_start in
Lprim
( Praise Raise_regular,
[ Lprim
( Pmakeblock (0, Immutable, None),
[ slot;
Lconst
(Const_block
( 0,
[ Const_base (Const_string (fname, loc, None));
Const_base (Const_int line);
Const_base (Const_int char)
] ))
],
sloc )
],
sloc )
let for_function ~scopes loc repr param pat_act_list partial =
let f () = partial_function ~scopes loc () in
compile_matching ~scopes repr f param pat_act_list partial
(* In the following two cases, exhaustiveness info is not available! *)
let for_trywith ~scopes param pat_act_list =
compile_matching ~scopes None
(fun () -> Lprim (Praise Raise_reraise, [ param ], Loc_unknown))
param pat_act_list Partial
let simple_for_let ~scopes loc param pat body =
compile_matching ~scopes None (partial_function ~scopes loc)
param [ (pat, body) ] Partial
(* Optimize binding of immediate tuples
The goal of the implementation of 'for_let' below, which replaces
'simple_for_let', is to avoid tuple allocation in cases such as
this one:
let (x,y) =
let foo = ... in
if foo then (1, 2) else (3,4)
in bar
The compiler easily optimizes the simple `let (x,y) = (1,2) in ...`
case (call to Matching.for_multiple_match from Translcore), but
didn't optimize situations where the rhs tuples are hidden under
a more complex context.
The idea comes from Alain Frisch who suggested and implemented
the following compilation method, based on Lassign:
let x = dummy in let y = dummy in
begin
let foo = ... in
if foo then
(let x1 = 1 in let y1 = 2 in x <- x1; y <- y1)
else
(let x2 = 3 in let y2 = 4 in x <- x2; y <- y2)
end;
bar
The current implementation from Gabriel Scherer uses Lstaticcatch /
Lstaticraise instead:
catch
let foo = ... in
if foo then
(let x1 = 1 in let y1 = 2 in exit x1 y1)
else
(let x2 = 3 in let y2 = 4 in exit x2 y2)
with x y ->
bar
The catch/exit is used to avoid duplication of the let body ('bar'
in the example), on 'if' branches for example; it is useless for
linear contexts such as 'let', but we don't need to be careful to
generate nice code because Simplif will remove such useless
catch/exit.
*)
let rec map_return f = function
| Llet (str, k, id, l1, l2) -> Llet (str, k, id, l1, map_return f l2)
| Lletrec (l1, l2) -> Lletrec (l1, map_return f l2)
| Lifthenelse (lcond, lthen, lelse) ->
Lifthenelse (lcond, map_return f lthen, map_return f lelse)
| Lsequence (l1, l2) -> Lsequence (l1, map_return f l2)
| Levent (l, ev) -> Levent (map_return f l, ev)
| Ltrywith (l1, id, l2) -> Ltrywith (map_return f l1, id, map_return f l2)
| Lstaticcatch (l1, b, l2) ->
Lstaticcatch (map_return f l1, b, map_return f l2)
| Lswitch (s, sw, loc) ->
let map_cases cases =
List.map (fun (i, l) -> (i, map_return f l)) cases
in
Lswitch
( s,
{ sw with
sw_consts = map_cases sw.sw_consts;
sw_blocks = map_cases sw.sw_blocks;
sw_failaction = Option.map (map_return f) sw.sw_failaction
},
loc )
| Lstringswitch (s, cases, def, loc) ->
Lstringswitch
( s,
List.map (fun (s, l) -> (s, map_return f l)) cases,
Option.map (map_return f) def,
loc )
| (Lstaticraise _ | Lprim (Praise _, _, _)) as l -> l
| ( Lvar _ | Lconst _ | Lapply _ | Lfunction _ | Lsend _ | Lprim _ | Lwhile _
| Lfor _ | Lassign _ | Lifused _ ) as l ->
f l
(* The 'opt' reference indicates if the optimization is worthy.
It is shared by the different calls to 'assign_pat' performed from
'map_return'. For example with the code
let (x, y) = if foo then z else (1,2)
the else-branch will activate the optimization for both branches.
That means that the optimization is activated if *there exists* an
interesting tuple in one hole of the let-rhs context. We could
choose to activate it only if *all* holes are interesting. We made
that choice because being optimistic is extremely cheap (one static
exit/catch overhead in the "wrong cases"), while being pessimistic
can be costly (one unnecessary tuple allocation).
*)
let assign_pat ~scopes opt nraise catch_ids loc pat lam =
let rec collect acc pat lam =
match (pat.pat_desc, lam) with
| Tpat_tuple patl, Lprim (Pmakeblock _, lams, _) ->
opt := true;
List.fold_left2 collect acc patl lams
| Tpat_tuple patl, Lconst (Const_block (_, scl)) ->
opt := true;
let collect_const acc pat sc = collect acc pat (Lconst sc) in
List.fold_left2 collect_const acc patl scl
| _ ->
(* pattern idents will be bound in staticcatch (let body), so we
refresh them here to guarantee binders uniqueness *)
let pat_ids = pat_bound_idents pat in
let fresh_ids = List.map (fun id -> (id, Ident.rename id)) pat_ids in
(fresh_ids, alpha_pat fresh_ids pat, lam) :: acc
in
(* sublets were accumulated by 'collect' with the leftmost tuple
pattern at the bottom of the list; to respect right-to-left
evaluation order for tuples, we must evaluate sublets
top-to-bottom. To preserve tail-rec, we will fold_left the
reversed list. *)
let rev_sublets = List.rev (collect [] pat lam) in
let exit =
(* build an Ident.tbl to avoid quadratic refreshing costs *)
let add t (id, fresh_id) = Ident.add id fresh_id t in
let add_ids acc (ids, _pat, _lam) = List.fold_left add acc ids in
let tbl = List.fold_left add_ids Ident.empty rev_sublets in
let fresh_var id = Lvar (Ident.find_same id tbl) in
Lstaticraise (nraise, List.map fresh_var catch_ids)
in
let push_sublet code (_ids, pat, lam) =
simple_for_let ~scopes loc lam pat code in
List.fold_left push_sublet exit rev_sublets
let for_let ~scopes loc param pat body =
match pat.pat_desc with
| Tpat_any ->
(* This eliminates a useless variable (and stack slot in bytecode)
for "let _ = ...". See #6865. *)
Lsequence (param, body)
| Tpat_var (id, _) ->
(* fast path, and keep track of simple bindings to unboxable numbers *)
let k = Typeopt.value_kind pat.pat_env pat.pat_type in
Llet (Strict, k, id, param, body)
| _ ->
let opt = ref false in
let nraise = next_raise_count () in
let catch_ids = pat_bound_idents_full pat in
let ids_with_kinds =
List.map
(fun (id, _, typ) -> (id, Typeopt.value_kind pat.pat_env typ))
catch_ids
in
let ids = List.map (fun (id, _, _) -> id) catch_ids in
let bind =
map_return (assign_pat ~scopes opt nraise ids loc pat) param in
if !opt then
Lstaticcatch (bind, (nraise, ids_with_kinds), body)
else
simple_for_let ~scopes loc param pat body
(* Handling of tupled functions and matchings *)
(* Easy case since variables are available *)
let for_tupled_function ~scopes loc paraml pats_act_list partial =
let partial = check_partial_list pats_act_list partial in
let raise_num = next_raise_count () in
let omegas = [ List.map (fun _ -> omega) paraml ] in
let pm =
{ cases = pats_act_list;
args = List.map (fun id -> (Lvar id, Strict)) paraml;
default = Default_environment.(cons omegas raise_num empty)
}
in
try
let lambda, total =
compile_match ~scopes None partial
(Context.start (List.length paraml)) pm
in
check_total total lambda raise_num (partial_function ~scopes loc)
with Unused -> partial_function ~scopes loc ()
let flatten_pattern size p =
match p.pat_desc with
| Tpat_tuple args -> args
| Tpat_any -> omegas size
| _ -> raise Cannot_flatten
let flatten_cases size cases =
List.map
(function
| (p, []), action -> (
match flatten_pattern size (General.erase p) with
| p :: ps -> ((p, ps), action)
| [] -> assert false
)
| _ -> fatal_error "Matching.flatten_hc_cases")
cases
let flatten_pm size args pm =
{ args;
cases = flatten_cases size pm.cases;
default = Default_environment.flatten size pm.default
}
let flatten_handler size handler =
{ handler with provenance = flatten_matrix size handler.provenance }
type pm_flattened =
| FPmOr of pattern pm_or_compiled
| FPm of pattern Non_empty_clause.t pattern_matching
let flatten_precompiled size args pmh =
match pmh with
| Pm pm -> FPm (flatten_pm size args pm)
| PmOr { body = b; handlers = hs; or_matrix = m } ->
FPmOr
{ body = flatten_pm size args b;
handlers = List.map (flatten_handler size) hs;
or_matrix = flatten_matrix size m
}
| PmVar _ -> assert false
(*
compiled_flattened is a ``comp_fun'' argument to comp_match_handlers.
Hence it needs a fourth argument, which it ignores
*)
let compile_flattened ~scopes repr partial ctx pmh =
match pmh with
| FPm pm -> compile_match_nonempty ~scopes repr partial ctx pm
| FPmOr { body = b; handlers = hs } ->
let lam, total = compile_match_nonempty ~scopes repr partial ctx b in
compile_orhandlers (compile_match ~scopes repr partial) lam total ctx hs
let do_for_multiple_match ~scopes loc paraml pat_act_list partial =
let repr = None in
let partial = check_partial pat_act_list partial in
let raise_num, arg, pm1 =
let raise_num, default =
match partial with
| Partial ->
let raise_num = next_raise_count () in
(raise_num, Default_environment.(cons [ [ omega ] ] raise_num empty))
| Total -> (-1, Default_environment.empty)
in
let loc = Scoped_location.of_location ~scopes loc in
let arg = Lprim (Pmakeblock (0, Immutable, None), paraml, loc) in
( raise_num,
arg,
{ cases = List.map (fun (pat, act) -> ([ pat ], act)) pat_act_list;
args = [ (arg, Strict) ];
default
} )
in
try
try
(* Once for checking that compilation is possible *)
let next, nexts =
split_and_precompile ~arg_id:None ~arg_lambda:arg pm1
in
let size = List.length paraml
and idl = List.map (fun _ -> Ident.create_local "*match*") paraml in
let args = List.map (fun id -> (Lvar id, Alias)) idl in
let flat_next = flatten_precompiled size args next
and flat_nexts =
List.map (fun (e, pm) -> (e, flatten_precompiled size args pm)) nexts
in
let lam, total =
comp_match_handlers (compile_flattened ~scopes repr) partial
(Context.start size) flat_next flat_nexts
in
List.fold_right2 (bind Strict) idl paraml
( match partial with
| Partial ->
check_total total lam raise_num (partial_function ~scopes loc)
| Total ->
assert (Jumps.is_empty total);
lam
)
with Cannot_flatten -> (
let lambda, total =
compile_match ~scopes None partial (Context.start 1) pm1 in
match partial with
| Partial ->
check_total total lambda raise_num (partial_function ~scopes loc)
| Total ->
assert (Jumps.is_empty total);
lambda
)
with Unused -> assert false
(* ; partial_function loc () *)
(* PR#4828: Believe it or not, the 'paraml' argument below
may not be side effect free. *)
let param_to_var param =
match param with
| Lvar v -> (v, None)
| _ -> (Ident.create_local "*match*", Some param)
let bind_opt (v, eo) k =
match eo with
| None -> k
| Some e -> Lambda.bind Strict v e k
let for_multiple_match ~scopes loc paraml pat_act_list partial =
let v_paraml = List.map param_to_var paraml in
let paraml = List.map (fun (v, _) -> Lvar v) v_paraml in
List.fold_right bind_opt v_paraml
(do_for_multiple_match ~scopes loc paraml pat_act_list partial)
|