Bug 143104 – REGRESSION: js/regress/inline-arguments-local-escape.html is flaky

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Alexey Proskuryakov]

This test has started to flakily fail on multiple bots, presumably due to http://trac.webkit.org/changeset/181993

https://webkit-test-results.appspot.com/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=js%2Fregress%2Finline-arguments-local-escape.html

[Radar WebKit Bug Importer]

<rdar://problem/20310708>

[Alexey Proskuryakov]

This test is still flakily failing.

[Filip Pizlo]

(In reply to comment #2)
> This test is still flakily failing.

OK, looking at it now.

[Filip Pizlo]

Turns out to be a pretty bad bug.  PreciseLocalClobberize's readTop() method is totally wrong for accesses to "escaped" arguments.  There are a handful of ways to fix this and I'll investigate.  Here's a version of the test that crashes every time:


function foo() {
    return arguments;
}

function bar(a, b, c, i) {
    var a = foo(b, c, 42);
    return a[i];
}

noInline(bar);

var expected = [2, 3, 42];
for (var i = 0; i < 10000; ++i) {
    var result = bar(1, 2, 3, i % 3);
    if (result != expected[i % 3])
        throw "Error: bad result: " + result;
}

[Filip Pizlo]

Same bug, involving ForwardVarargs:

function foo() {
    return arguments;
}

function baz(a, b, c) {
    return a + b + c;
}

function bar(a, b, c) {
    var args = foo(b, c, 42);
    return baz.apply(void 0, args);
}

noInline(bar);

for (var i = 0; i < 10000; ++i) {
    var result = bar(1, 2, 3);
    if (result != 47)
        throw "Error: bad result: " + result;
}

[Filip Pizlo]

Created attachment 249738 [details]
hopefully the patch

Not yet ready for review.  I'm still running tests.

[Filip Pizlo]

Comment on attachment 249738 [details]
hopefully the patch

Looks like it works!

[Geoffrey Garen]

Comment on attachment 249738 [details]
hopefully the patch

r=me

[WebKit Commit Bot]

Comment on attachment 249738 [details]
hopefully the patch

Clearing flags on attachment: 249738

Committed r182148: <http://trac.webkit.org/changeset/182148>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.