Bug 158368 – Eager FTL failure for strict comparison of NaN with number check

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Joseph Pecoraro]

Created attachment 280480 [details]
[TEST] JS Reduction

* SUMMARY
Eager FTL failure for strict comparison of NaN with number check

* TEST
function isNaNOnDouble(value)
{
    return (+value) !== value;
}
noInline(isNaNOnDouble);

function testIsNaNOnDoubles()
{
    var value = isNaNOnDouble(-0);
    if (value)
        throw "isNaNOnDouble(-0) = " + value;

    var value = isNaNOnDouble(NaN);
    if (!value)
        throw "isNaNOnDouble(NaN) = " + value;

    var value = isNaNOnDouble(Number.POSITIVE_INFINITY);
    if (value)
        throw "isNaNOnDouble(Number.POSITIVE_INFINITY) = " + value;
}
noInline(testIsNaNOnDoubles);

for (var i = 0; i < 1e6; ++i) {
    testIsNaNOnDoubles();
}


* STEPS TO REPRODUCE
1. $ DYLD_FRAMEWORK_PATH=$build/Release $build/Release/jsc --useFTLJIT=true --useConcurrentJIT=false --thresholdForJITAfterWarmUp=100 --thresholdForJITAfterWarmUp=10 --thresholdForJITSoon=10 --thresholdForOptimizeAfterWarmUp=20 --thresholdForOptimizeAfterLongWarmUp=20 --thresholdForOptimizeSoon=20 --thresholdForFTLOptimizeAfterWarmUp=20 --thresholdForFTLOptimizeSoon=20 number-compare-strict.js

Exception: isNaNOnDouble(NaN) = false

* NOTES
- The issue only reproduces if --useConcurrentJIT=false

[Benjamin Poulain]

I'll take it. Scary stuff.

[Radar WebKit Bug Importer]

<rdar://problem/26634629>

[Benjamin Poulain]

Created attachment 280501 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 280501 [details]
Patch

Clearing flags on attachment: 280501

Committed r201678: <http://trac.webkit.org/changeset/201678>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.