gecko/xpcom/analysis/mayreturn.js

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2012-05-21 04:12:37 -07:00
/* 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);
}
}
}
};