[Webkit-unassigned] [Bug 65294] New: DFG JIT - may speculate based on wrong arguments.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=65294

           Summary: DFG JIT - may speculate based on wrong arguments.
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: barraclough at apple.com


In the case of a DFG compiled function calling to and compiling a second function that also compiles through the DFG JIT (i.e. compilation triggered with DFGOperations.cpp), we call compileFor passing the caller functions exec state, rather than the callee's.  This may lead to mis-optimization, since the DFG compiler will example the exec state's arguments on the assumption that these will be passed to the callee - it is wanting the callee exec state, not the caller's exec state.

Fixing this for all cases of compilation is tricksy, due to the way the numeric sort function is compiled, & the structure of the calls in the Interpreter::execute methods.  Only fix for compilation from the JIT, in other calls don't speculate based on arguments for now.

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