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Bug 1022773 - Ignore trivial |return nullptr;| statements that cross GC boundaries, r=bhackett

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--HG--
extra : rebase_source : ff35099b7d21a082f49b04d86f6e293543649caf
This commit is contained in:
Steve Fink 2014-06-25 15:35:53 -07:00
parent 53a9930d07
commit e0ff56cc39
1 changed files with 16 additions and 1 deletions
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17
js/src/devtools/rootAnalysis/analyzeRoots.js
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@ -85,6 +85,19 @@ function expressionUsesVariable(exp, variable)
return false;
}
// Detect simple |return nullptr;| statements.
function isReturningImmobileValue(edge, variable)
{
if (variable.Kind == "Return") {
if (edge.Exp[0].Kind == "Var" && sameVariable(edge.Exp[0].Variable, variable)) {
if (edge.Exp[1].Kind == "Int" && edge.Exp[1].String == "0") {
return true;
}
}
}
return false;
}
// If the edge uses the given variable, return the earliest point at which the
// use is definite. Usually, that means the source of the edge (anything that
// reaches that source point will end up using the variable, but there may be
@ -108,6 +121,8 @@ function edgeUsesVariable(edge, variable, body)
switch (edge.Kind) {
case "Assign":
if (isReturningImmobileValue(edge, variable))
return 0;
if (expressionUsesVariable(edge.Exp[0], variable))
return src;
return expressionUsesVariable(edge.Exp[1], variable) ? src : 0;
@ -175,7 +190,7 @@ function edgeKillsVariable(edge, variable)
if (edge.Kind == "Assign") {
var lhs = edge.Exp[0];
if (lhs.Kind == "Var" && sameVariable(lhs.Variable, variable))
return true;
return !isReturningImmobileValue(edge, variable);
}
if (edge.Kind != "Call")