[Webkit-unassigned] [Bug 18752] New: SQUIRRELFISH: thrown exceptions may be erroneously stored in local variables

[bugzilla-daemon at webkit.org]

http://bugs.webkit.org/show_bug.cgi?id=18752

           Summary: SQUIRRELFISH: thrown exceptions may be erroneously
                    stored in local variables
           Product: WebKit
           Version: 526+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: SquirrelFishBlocker
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: cwzwarich at uwaterloo.ca
                CC: mjs at apple.com, ggaren at apple.com, oliver at apple.com


Here is an example:

var x = "PASS";
try { x = (new Number(1)).toString(0); } catch (e) { }
print(x);

On trunk, it prints PASS, but on SquirrelFish it prints an exception. This is
because the VM_CHECK_EXCEPTION(); statements in many opcodes in Machine.cpp are
after the writes to registers, which may store local variables. It shouldn't be
too hard to move all of the checks out, and hopefully it won't be another
performance regression due to compiler insanity.


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