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65 lines
2.2 KiB
65 lines
2.2 KiB
(*
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* Copyright (c) 2016 - present Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*)
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open! IStd
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module F = Format
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module L = Logging
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(** backward analysis for computing set of maybe-live variables at each program point *)
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module Domain = AbstractDomain.FiniteSet(Var)
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(* compilers 101-style backward transfer functions for liveness analysis. gen a variable when it is
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read, kill the variable when it is assigned *)
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module TransferFunctions (CFG : ProcCfg.S) = struct
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module CFG = CFG
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module Domain = Domain
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type extras = ProcData.no_extras
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(* add all of the vars read in [exp] to the live set *)
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let exp_add_live exp astate =
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let (ids, pvars) = Exp.get_vars exp in
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let astate' =
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List.fold
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~f:(fun astate_acc id -> Domain.add (Var.of_id id) astate_acc)
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~init:astate
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ids in
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List.fold
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~f:(fun astate_acc pvar -> Domain.add (Var.of_pvar pvar) astate_acc)
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~init:astate'
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pvars
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let exec_instr astate _ _ = function
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| Sil.Load (lhs_id, rhs_exp, _, _) ->
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Domain.remove (Var.of_id lhs_id) astate
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|> exp_add_live rhs_exp
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| Sil.Store (Lvar lhs_pvar, _, rhs_exp, _) ->
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let astate' =
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if Pvar.is_global lhs_pvar
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then astate (* never kill globals *)
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else Domain.remove (Var.of_pvar lhs_pvar) astate in
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exp_add_live rhs_exp astate'
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| Sil.Store (lhs_exp, _, rhs_exp, _) ->
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exp_add_live lhs_exp astate
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|> exp_add_live rhs_exp
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| Sil.Prune (exp, _, _, _) ->
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exp_add_live exp astate
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| Sil.Call (ret_id, call_exp, params, _, _) ->
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Option.value_map ~f:(fun (ret_id, _) -> Domain.remove (Var.of_id ret_id) astate)
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~default:astate ret_id
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|> exp_add_live call_exp
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|> (fun x -> List.fold_right ~f:exp_add_live (List.map ~f:fst params) ~init:x)
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| Sil.Declare_locals _ | Remove_temps _ | Abstract _ | Nullify _ ->
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astate
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end
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module Analyzer =
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AbstractInterpreter.Make (ProcCfg.Backward(ProcCfg.Exceptional)) (TransferFunctions)
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