• Seth Brenith's avatar
    Always emit unconditional jump in binary-search switch · dd9d4c96
    Seth Brenith authored
    We probably expect a binary-search switch to take log(n) time in all
    cases, but there is currently a possibility of that expectation being
    broken. I'm not aware of any place where this actually happens, but if
    the default handler immediately follows the switch dispatch block in
    assembly order, then unconditional jump instructions for that handler
    would be omitted. This omission could cause linear execution time, where
    every case is checked before falling through to the default handler.
    
    This change introduces a new function to emit an unconditional jump
    instruction regardless of whether the target is the following block, and
    uses that new function when generating a binary-search switch to ensure
    consistently log(n) behavior.
    
    Change-Id: I5cab86fd66386762519035410e3b532dc6fd764c
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3335222Reviewed-by: 's avatarNico Hartmann <nicohartmann@chromium.org>
    Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
    Cr-Commit-Position: refs/heads/main@{#78370}
    dd9d4c96
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