michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /* May-return analysis.
michael@0:  * This makes sense only for functions that return a value. The analysis
michael@0:  * determines the set of variables that may transitively reach the return
michael@0:  * statement. */
michael@0: 
michael@0: function MayReturnAnalysis() {
michael@0:   BackwardAnalysis.apply(this, arguments);
michael@0:   // May-return variables. We collect them all here.
michael@0:   this.vbls = create_decl_set();
michael@0:   // The return value variable itself
michael@0:   this.retvar = undefined;
michael@0: }
michael@0: 
michael@0: MayReturnAnalysis.prototype = new BackwardAnalysis;
michael@0: 
michael@0: MayReturnAnalysis.prototype.flowState = function(isn, state) {
michael@0:   if (TREE_CODE(isn) == GIMPLE_RETURN) {
michael@0:     let v = return_expr(isn);
michael@0:     if (!v)
michael@0:       return;
michael@0:     if (v.tree_code() == RESULT_DECL) // only an issue with 4.3
michael@0:       throw new Error("Weird case hit");
michael@0:     this.vbls.add(v);
michael@0:     state.add(v);
michael@0:     this.retvar = v;
michael@0:   } else if (TREE_CODE(isn) == GIMPLE_ASSIGN) {
michael@0:     let lhs = gimple_op(isn, 0);
michael@0:     let rhs = gimple_op(isn, 1);
michael@0:     if (DECL_P(rhs) && DECL_P(lhs) && state.has(lhs)) {
michael@0:       this.vbls.add(rhs);
michael@0:       state.add(rhs);
michael@0:     }
michael@0: 
michael@0:     for (let e in isn_defs(isn, 'strong')) {
michael@0:       if (DECL_P(e)) {
michael@0:         state.remove(e);
michael@0:       }
michael@0:     }
michael@0:   }
michael@0: };