[Webkit-unassigned] [Bug 64574] New: DFG JIT does not optimize Branch as well as it could

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=64574

           Summary: DFG JIT does not optimize Branch as well as it could
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: fpizlo at apple.com


The DFG speculative JIT will terminate speculation if a Branch did not encounter an integer or a boolean.  Terminating speculation in this case is not profitable, since proving that the Branch encountered either integer or boolean does not provide any useful data flow information (at least not in the current DFG JIT architecture).  The non-speculative JIT always performs slow calls for Branches.  Both JITs should use the same implementation of Branch, which does no speculation, and only performs a slow call if necessary.

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