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(* Copyright (c) 2008, Adam Chlipala
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* - The names of contributors may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*)
(* Simplify a Core program algebraically, without unfolding definitions *)
structure ReduceLocal :> REDUCE_LOCAL = struct
open Core
structure IM = IntBinaryMap
datatype env_item =
Unknown
| Known of exp
| Lift of int
type env = env_item list
val deKnown = List.filter (fn Known _ => false
| _ => true)
fun exp env (all as (e, loc)) =
case e of
EPrim _ => all
| ERel n =>
let
fun find (n', env, nudge, lift) =
case env of
[] => raise Fail "ReduceLocal.exp: ERel"
| Lift lift' :: rest => find (n', rest, nudge + lift', lift + lift')
| Unknown :: rest =>
if n' = 0 then
(ERel (n + nudge), loc)
else
find (n' - 1, rest, nudge, lift + 1)
| Known e :: rest =>
if n' = 0 then
((*print "SUBSTITUTING\n";*)
exp (Lift lift :: rest) e)
else
find (n' - 1, rest, nudge - 1, lift)
in
find (n, env, 0, 0)
end
| ENamed _ => all
| ECon (dk, pc, cs, eo) => (ECon (dk, pc, cs, Option.map (exp env) eo), loc)
| EFfi _ => all
| EFfiApp (m, f, es) => (EFfiApp (m, f, map (exp env) es), loc)
| EApp (e1, e2) =>
let
val e1 = exp env e1
val e2 = exp env e2
in
case #1 e1 of
EAbs (_, _, _, b) => exp (Known e2 :: deKnown env) b
| _ => (EApp (e1, e2), loc)
end
| EAbs (x, dom, ran, e) => (EAbs (x, dom, ran, exp (Unknown :: env) e), loc)
| ECApp (e, c) => (ECApp (exp env e, c), loc)
| ECAbs (x, k, e) => (ECAbs (x, k, exp env e), loc)
| ERecord xcs => (ERecord (map (fn (x, e, t) => (x, exp env e, t)) xcs), loc)
| EField (e, c, others) =>
let
val e = exp env e
fun default () = (EField (e, c, others), loc)
in
case (#1 e, #1 c) of
(ERecord xcs, CName x) =>
(case List.find (fn ((CName x', _), _, _) => x' = x | _ => false) xcs of
NONE => default ()
| SOME (_, e, _) => e)
| _ => default ()
end
| EConcat (e1, c1, e2, c2) => (EConcat (exp env e1, c1, exp env e2, c2), loc)
| ECut (e, c, others) => (ECut (exp env e, c, others), loc)
| ECutMulti (e, c, others) => (ECutMulti (exp env e, c, others), loc)
| EFold _ => all
| ECase (e, pes, others) =>
let
fun patBinds (p, _) =
case p of
PWild => 0
| PVar _ => 1
| PPrim _ => 0
| PCon (_, _, _, NONE) => 0
| PCon (_, _, _, SOME p) => patBinds p
| PRecord xpts => foldl (fn ((_, p, _), n) => n + patBinds p) 0 xpts
in
(ECase (exp env e,
map (fn (p, e) => (p,
exp (List.tabulate (patBinds p, fn _ => Unknown) @ env) e))
pes, others), loc)
end
| EWrite e => (EWrite (exp env e), loc)
| EClosure (n, es) => (EClosure (n, map (exp env) es), loc)
| ELet (x, t, e1, e2) => (ELet (x, t, exp env e1, exp (Unknown :: env) e2), loc)
fun reduce file =
let
fun doDecl (d as (_, loc)) =
case #1 d of
DCon _ => d
| DDatatype _ => d
| DVal (x, n, t, e, s) =>
let
val e = exp [] e
in
(DVal (x, n, t, e, s), loc)
end
| DValRec vis =>
(DValRec (map (fn (x, n, t, e, s) => (x, n, t, exp [] e, s)) vis), loc)
| DExport _ => d
| DTable _ => d
| DSequence _ => d
| DDatabase _ => d
| DCookie _ => d
in
map doDecl file
end
end
|
