[Webkit-unassigned] [Bug 42182] New: Change how numeric compare functions are detected

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=42182

           Summary: Change how numeric compare functions are detected
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Mac OS X 10.5
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: barraclough at apple.com


There are three problems with the current mechanism:

* It requires that a function executable be bytecode compiled without being JIT generated (in order to copy the bytecode from the numeric compare function).  This is a problem since we have an invariant when running with the JIT that functions are never bytecode compiled without also being JIT generated (after checking the codeblock we assume the function has JIT code).  To help maintain this invariant 
* This implementation will prevent us from experimenting with alternate compilation paths which do not compile via bytecode.
* It doesn't work.  Functions passing more than two arguments will match if they are comparing their last two arguments, not the first two.  Generally the mapping back from bytecode to semantics may be more complex then initially expected.

(bug can be triggered by following test: "javascript: alert([3,1,5,2,4].sort(function(w, x, y){ return x - y; }));")

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