[Webkit-unassigned] [Bug 64659] New: DFG JIT does not optimize equal-null comparisons and branches

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=64659

           Summary: DFG JIT does not optimize equal-null comparisons and
                    branches
           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 JIT bytecode parser converts equal-null compare/branch opcodes into a tree of JSConstant(null), an equality comparison, and a branch.  The backend never special-cases the equal-to-null case, and treats it as a normal equality comparison; this means that equal-null always takes slow path.  The DFG JIT backend should have a peephole optimization for this case.

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