[Webkit-unassigned] [Bug 157534] New: [JSC] It should be possible to always safely move GetByVal

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=157534

            Bug ID: 157534
           Summary: [JSC] It should be possible to always safely move
                    GetByVal
    Classification: Unclassified
           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: benjamin at webkit.org

FTL had a but where GetByVal would be moved by Loop Invariant Code Motion invalidating assumption used to remove bounds checking (see https://bugs.webkit.org/show_bug.cgi?id=157502).

The fix was to move IntegerRange optimization after LICM to make sure the code is not moved after CheckInBounds is eliminated.

It would be better to have a deterministic way of knowing if a GetByVal can be moved and where it is safe to move it. For example, it should be explicitly illegal to hoist a GetByVal above its CheckInBounds.

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