[Webkit-unassigned] [Bug 79700] New: Old JIT's style of JSVALUE64 strict equality is subtly wrong

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=79700

           Summary: Old JIT's style of JSVALUE64 strict equality is subtly
                    wrong
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: fpizlo at apple.com


It tries to rule out either of the inputs being a double by or'ing the two values together and testing against TagTypeNumber.  But that is guaranteed to be false for integers as well.

It then does a 32-bit comparison, even though it might be comparing cells to non-cells.

This affects both the old JIT and the DFG's non-speculative strict equality comparison, but only for JSVALUE64.

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