• Jakob Gruber's avatar
    [compiler] Allow deopts to slightly exceed the stack limit · 4547c5ef
    Jakob Gruber authored
    We recently extended function-entry stack checks by an offset
    representing the difference in optimized and unoptimized frame sizes,
    with the intent of avoiding stack overflows during deopts. Although
    the generated code is very efficient (just a single additional
    register subtraction, executed exactly once per call), perf impact
    is measurable.
    
    To avoid the overhead in most cases, this CL adds a stack slack,
    currently set to 256 bytes, by which deopts are allowed to exceed the
    real V8 stack limit. For function-entry stack checks with an offset
    less than stack slack, the offset is not applied and the more
    efficient version of the stack check is emitted.
    
    The V8 limit is chosen to be smaller than OS stack size (assumed to
    be at least 1 MB). This guarantee is upheld even with slack.
    
    Bug: chromium:1020989,v8:9534
    Change-Id: Idee2e7ad1fa7810bf086a9f72ce00a9717010310
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1910099Reviewed-by: 's avatarGeorg Neis <neis@chromium.org>
    Reviewed-by: 's avatarTobias Tebbi <tebbi@chromium.org>
    Commit-Queue: Jakob Gruber <jgruber@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#65025}
    4547c5ef
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