gecko/xpcom/analysis/mayreturn.js

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/* 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) == RETURN_EXPR) {
let gms = TREE_OPERAND(isn, 0);
if (gms) {
// gms is usually a GIMPLE_MODIFY_STMT but can be a RESULT_DECL
if (TREE_CODE(gms) == GIMPLE_MODIFY_STMT) {
let v = GIMPLE_STMT_OPERAND(gms, 1);
this.vbls.add(v);
state.add(v);
this.retvar = v;
} else if (TREE_CODE(gms) == RESULT_DECL) {
throw new Error("Weird case hit");
}
}
} else if (TREE_CODE(isn) == GIMPLE_MODIFY_STMT) {
let lhs = GIMPLE_STMT_OPERAND(isn, 0);
let rhs = GIMPLE_STMT_OPERAND(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);
}
}
}
};