[Webkit-unassigned] [Bug 192441] New: speculationFromCell() should speculate non-Identifier strings as SpecString instead of SpecStringVar.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=192441

            Bug ID: 192441
           Summary: speculationFromCell() should speculate non-Identifier
                    strings as SpecString instead of SpecStringVar.
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: mark.lam at apple.com

This is because a regular String (non-Identifier) can be converted into an Identifier.  During DFG/FTL compilation, AbstractValue::checkConsistency() may expect a value to be of type SpecStringVar, but the mutator thread may have converted the string into an Identifier.  This creates a race where AbstractValue::checkConsistency() may fail because it sees a SpecStringIdent when it expects the a SpecStringVar.  

The fix is to speculate non-Identifier strings as type SpecString which allows it to be SpecStringVar or SpecStringIndent.

<rdar://problem/46480355>

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