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 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /* May-return analysis.

  * This makes sense only for functions that return a value. The analysis

  * determines the set of variables that may transitively reach the return

  * statement. */

 function MayReturnAnalysis() {

   BackwardAnalysis.apply(this, arguments);

   // May-return variables. We collect them all here.

   this.vbls = create_decl_set();

   // The return value variable itself

   this.retvar = undefined;

 }

 MayReturnAnalysis.prototype = new BackwardAnalysis;

 MayReturnAnalysis.prototype.flowState = function(isn, state) {

   if (TREE_CODE(isn) == GIMPLE_RETURN) {

     let v = return_expr(isn);

     if (!v)

       return;

     if (v.tree_code() == RESULT_DECL) // only an issue with 4.3

       throw new Error("Weird case hit");

     this.vbls.add(v);

     state.add(v);

     this.retvar = v;

   } else if (TREE_CODE(isn) == GIMPLE_ASSIGN) {

     let lhs = gimple_op(isn, 0);

     let rhs = gimple_op(isn, 1);

     if (DECL_P(rhs) && DECL_P(lhs) && state.has(lhs)) {

       this.vbls.add(rhs);

       state.add(rhs);

     }

     for (let e in isn_defs(isn, 'strong')) {

       if (DECL_P(e)) {

         state.remove(e);

       }

     }

   }

 };