[Webkit-unassigned] [Bug 141369] New: DFG::clobberize() should be the sole mechanism for describing the effectfulness of a DFG node

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=141369

            Bug ID: 141369
           Summary: DFG::clobberize() should be the sole mechanism for
                    describing the effectfulness of a DFG node
    Classification: Unclassified
           Product: WebKit
           Version: 528+ (Nightly build)
          Hardware: All
                OS: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: fpizlo at apple.com

We previously used the NodeMightClobber and NodeClobbersWorld NodeFlags to describe effectfulness.  Starting over a year ago, we introduced a more powerful mechanism - the DFG::clobberize() function.  Now we only have one remaining client of the old NodeFlags, and everyone else uses DFG::clobberize().  We should get rid of those NodeFlags and finally switch everyone over to DFG::clobberize().  This means that going forward, there will only be two places where the effectfulness of a node has to be described:

- DFG::clobberize()
- DFG::AbstractInterpreter

Unfortunately, the AbstractInterpreter has to duplicate the knowledge of effects, mostly because of efficiency concerns: calling into clobberize() from the abstract interpreter would slow things down too much.  Also, AbstractInterpreter might still have a more precise model of effects in some places, particularly when dealing with structure transitions.

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