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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 Mono program algebraically *)
structure MonoReduce :> MONO_REDUCE = struct
open Mono
structure E = MonoEnv
structure U = MonoUtil
fun impure (e, _) =
case e of
EWrite _ => true
| EQuery _ => true
| EDml _ => true
| ENextval _ => true
| EAbs _ => false
| EPrim _ => false
| ERel _ => false
| ENamed _ => false
| ECon (_, _, eo) => (case eo of NONE => false | SOME e => impure e)
| ENone _ => false
| ESome (_, e) => impure e
| EFfi _ => false
| EFfiApp _ => false
| EApp ((EFfi _, _), _) => false
| EApp _ => true
| EUnop (_, e) => impure e
| EBinop (_, e1, e2) => impure e1 orelse impure e2
| ERecord xes => List.exists (fn (_, e, _) => impure e) xes
| EField (e, _) => impure e
| ECase (e, pes, _) => impure e orelse List.exists (fn (_, e) => impure e) pes
| EError (e, _) => impure e
| EStrcat (e1, e2) => impure e1 orelse impure e2
| ESeq (e1, e2) => impure e1 orelse impure e2
| ELet (_, _, e1, e2) => impure e1 orelse impure e2
| EClosure (_, es) => List.exists impure es
val liftExpInExp = Monoize.liftExpInExp
val subExpInExp' =
U.Exp.mapB {typ = fn t => t,
exp = fn (xn, rep) => fn e =>
case e of
ERel xn' =>
(case Int.compare (xn', xn) of
EQUAL => #1 rep
| GREATER=> ERel (xn' - 1)
| LESS => e)
| _ => e,
bind = fn ((xn, rep), U.Exp.RelE _) => (xn+1, liftExpInExp 0 rep)
| (ctx, _) => ctx}
fun subExpInExp (n, e1) e2 =
let
val r = subExpInExp' (n, e1) e2
in
(*Print.prefaces "subExpInExp" [("e1", MonoPrint.p_exp MonoEnv.empty e1),
("e2", MonoPrint.p_exp MonoEnv.empty e2),
("r", MonoPrint.p_exp MonoEnv.empty r)];*)
r
end
fun typ c = c
val swapExpVars =
U.Exp.mapB {typ = fn t => t,
exp = fn lower => fn e =>
case e of
ERel xn =>
if xn = lower then
ERel (lower + 1)
else if xn = lower + 1 then
ERel lower
else
e
| _ => e,
bind = fn (lower, U.Exp.RelE _) => lower+1
| (lower, _) => lower}
val swapExpVarsPat =
U.Exp.mapB {typ = fn t => t,
exp = fn (lower, len) => fn e =>
case e of
ERel xn =>
if xn = lower then
ERel (lower + 1)
else if xn >= lower + 1 andalso xn < lower + 1 + len then
ERel (xn - 1)
else
e
| _ => e,
bind = fn ((lower, len), U.Exp.RelE _) => (lower+1, len)
| (st, _) => st}
datatype result = Yes of E.env | No | Maybe
fun match (env, p : pat, e : exp) =
case (#1 p, #1 e) of
(PWild, _) => Yes env
| (PVar (x, t), _) => Yes (E.pushERel env x t (SOME e))
| (PPrim (Prim.String s), EStrcat ((EPrim (Prim.String s'), _), _)) =>
if String.isPrefix s' s then
Maybe
else
No
| (PPrim p, EPrim p') =>
if Prim.equal (p, p') then
Yes env
else
No
| (PCon (_, PConVar n1, NONE), ECon (_, PConVar n2, NONE)) =>
if n1 = n2 then
Yes env
else
No
| (PCon (_, PConVar n1, SOME p), ECon (_, PConVar n2, SOME e)) =>
if n1 = n2 then
match (env, p, e)
else
No
| (PCon (_, PConFfi {mod = m1, con = con1, ...}, NONE), ECon (_, PConFfi {mod = m2, con = con2, ...}, NONE)) =>
if m1 = m2 andalso con1 = con2 then
Yes env
else
No
| (PCon (_, PConFfi {mod = m1, con = con1, ...}, SOME ep), ECon (_, PConFfi {mod = m2, con = con2, ...}, SOME e)) =>
if m1 = m2 andalso con1 = con2 then
match (env, p, e)
else
No
| (PRecord xps, ERecord xes) =>
let
fun consider (xps, env) =
case xps of
[] => Yes env
| (x, p, _) :: rest =>
case List.find (fn (x', _, _) => x' = x) xes of
NONE => No
| SOME (_, e, _) =>
case match (env, p, e) of
No => No
| Maybe => Maybe
| Yes env => consider (rest, env)
in
consider (xps, env)
end
| _ => Maybe
datatype event =
WritePage
| ReadDb
| WriteDb
| UseRel of int
| Unsure
fun p_event e =
let
open Print.PD
in
case e of
WritePage => string "WritePage"
| ReadDb => string "ReadDb"
| WriteDb => string "WriteDb"
| UseRel n => string ("UseRel" ^ Int.toString n)
| Unsure => string "Unsure"
end
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
| PNone _ => 0
| PSome (_, p) => patBinds p
fun summarize d (e, _) =
case e of
EPrim _ => []
| ERel n => if n >= d then [UseRel (n - d)] else []
| ENamed _ => []
| ECon (_, _, NONE) => []
| ECon (_, _, SOME e) => summarize d e
| ENone _ => []
| ESome (_, e) => summarize d e
| EFfi _ => []
| EFfiApp (_, _, es) => List.concat (map (summarize d) es)
| EApp ((EFfi _, _), e) => summarize d e
| EApp _ => [Unsure]
| EAbs _ => []
| EUnop (_, e) => summarize d e
| EBinop (_, e1, e2) => summarize d e1 @ summarize d e2
| ERecord xets => List.concat (map (summarize d o #2) xets)
| EField (e, _) => summarize d e
| ECase (e, pes, _) =>
let
val lss = map (fn (p, e) => summarize (d + patBinds p) e) pes
in
case lss of
[] => raise Fail "Empty pattern match"
| ls :: lss =>
if List.all (fn ls' => ls' = ls) lss then
summarize d e @ ls
else
[Unsure]
end
| EStrcat (e1, e2) => summarize d e1 @ summarize d e2
| EError (e, _) => summarize d e @ [Unsure]
| EWrite e => summarize d e @ [WritePage]
| ESeq (e1, e2) => summarize d e1 @ summarize d e2
| ELet (_, _, e1, e2) => summarize d e1 @ summarize (d + 1) e2
| EClosure (_, es) => List.concat (map (summarize d) es)
| EQuery {query, body, initial, ...} =>
List.concat [summarize d query,
summarize (d + 2) body,
summarize d initial,
[ReadDb]]
| EDml e => summarize d e @ [WriteDb]
| ENextval e => summarize d e @ [WriteDb]
fun exp env e =
case e of
ERel n =>
(case E.lookupERel env n of
(_, _, SOME e') => #1 e'
| _ => e)
| ENamed n =>
(case E.lookupENamed env n of
(_, _, SOME e', _) => #1 e'
| _ => e)
| EApp ((EAbs (x, t, _, e1), loc), e2) =>
((*Print.prefaces "Considering" [("e1", MonoPrint.p_exp env e1),
("e2", MonoPrint.p_exp env e2)];*)
if impure e2 then
#1 (reduceExp env (ELet (x, t, e2, e1), loc))
else
#1 (reduceExp env (subExpInExp (0, e2) e1)))
| ECase (e', pes, {disc, result}) =>
let
fun push () =
case result of
(TFun (dom, result), loc) =>
if List.all (fn (_, (EAbs _, _)) => true | _ => false) pes then
EAbs ("_", dom, result,
(ECase (liftExpInExp 0 e',
map (fn (p, (EAbs (_, _, _, e), _)) =>
(p, swapExpVarsPat (0, patBinds p) e)
| _ => raise Fail "MonoReduce ECase") pes,
{disc = disc, result = result}), loc))
else
e
| _ => e
fun search pes =
case pes of
[] => push ()
| (p, body) :: pes =>
case match (env, p, e') of
No => search pes
| Maybe => push ()
| Yes env => #1 (reduceExp env body)
in
search pes
end
| EField ((ERecord xes, _), x) =>
(case List.find (fn (x', _, _) => x' = x) xes of
SOME (_, e, _) => #1 e
| NONE => e)
| ELet (x1, t1, (ELet (x2, t2, e1, b1), loc), b2) =>
let
val e' = (ELet (x2, t2, e1,
(ELet (x1, t1, b1,
liftExpInExp 1 b2), loc)), loc)
in
(*Print.prefaces "ELet commute" [("e", MonoPrint.p_exp env (e, loc)),
("e'", MonoPrint.p_exp env e')];*)
#1 (reduceExp env e')
end
| EApp ((ELet (x, t, e, b), loc), e') =>
#1 (reduceExp env (ELet (x, t, e,
(EApp (b, liftExpInExp 0 e'), loc)), loc))
| ELet (x, t, e, (EAbs (x', t' as (TRecord [], _), ran, e'), loc)) =>
EAbs (x', t', ran, (ELet (x, t, liftExpInExp 0 e, swapExpVars 0 e'), loc))
| ELet (x, t, e', b) =>
if impure e' then
let
val effs_e' = summarize 0 e'
val effs_b = summarize 0 b
fun does eff = List.exists (fn eff' => eff' = eff) effs_e'
val writesPage = does WritePage
val readsDb = does ReadDb
val writesDb = does WriteDb
fun verifyUnused eff =
case eff of
UseRel r => r <> 0
| Unsure => false
| _ => true
fun verifyCompatible effs =
case effs of
[] => false
| eff :: effs =>
case eff of
Unsure => false
| UseRel r =>
if r = 0 then
List.all verifyUnused effs
else
verifyCompatible effs
| WritePage => not writesPage andalso verifyCompatible effs
| ReadDb => not writesDb andalso verifyCompatible effs
| WriteDb => not writesDb andalso not readsDb andalso verifyCompatible effs
in
(*Print.prefaces "verifyCompatible"
[("e'", MonoPrint.p_exp env e'),
("b", MonoPrint.p_exp (E.pushERel env x t NONE) b),
("effs_e'", Print.p_list p_event effs_e'),
("effs_b", Print.p_list p_event effs_b)];*)
if verifyCompatible effs_b then
#1 (reduceExp env (subExpInExp (0, e') b))
else
e
end
else
#1 (reduceExp env (subExpInExp (0, e') b))
| EStrcat ((EPrim (Prim.String s1), _), (EPrim (Prim.String s2), _)) =>
EPrim (Prim.String (s1 ^ s2))
| _ => e
and bind (env, b) =
case b of
U.Decl.Datatype (x, n, xncs) => E.pushDatatype env x n xncs
| U.Decl.RelE (x, t) => E.pushERel env x t NONE
| U.Decl.NamedE (x, n, t, eo, s) => E.pushENamed env x n t (Option.map (reduceExp env) eo) s
and reduceExp env = U.Exp.mapB {typ = typ, exp = exp, bind = bind} env
fun decl env d = d
val reduce = U.File.mapB {typ = typ, exp = exp, decl = decl, bind = bind} E.empty
end
|