[Webkit-unassigned] [Bug 232679] New: Differential Testing: negative Date compute NaN in FTL

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Nov 3 12:58:26 PDT 2021


            Bug ID: 232679
           Summary: Differential Testing: negative Date compute NaN in FTL
           Product: WebKit
           Version: WebKit Local Build
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: lukas.bernhard at rub.de

During differential testing of webkit I found a sample triggering a miscomputation in FTL related to using Date in a negative integer context.

The sample is invoked as:
WebKitBuild/Release/bin/jsc --validateOptions=true --useConcurrentJIT=false --useConcurrentGC=false --thresholdForJITSoon=10 --thresholdForJITAfterWarmUp=10 --thresholdForOptimizeAfterWarmUp=100 --thresholdForOptimizeAfterLongWarmUp=100 --thresholdForOptimizeSoon=100 --thresholdForFTLOptimizeAfterWarmUp=1000 --thresholdForFTLOptimizeSoon=1000 --validateBCE=true --useFTLJIT=true sample.js

function main() {
    let v1 = 0;
    while (v1++ < 9) { } 

    let v19 = 0;
    let v45;
    do {
        function v22() {
            const v44 = new Date(123);
            v45 = -v44;
            for (let v49 = -4096; v49 < 100; v49++) { } 
    } while (v19++ < 7); 
    print(v45); // -123 without FTL, NaN with FTL (also -123 in spidermonkey)

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