• Jakob Gruber's avatar
    Reland "Reland "[deoptimizer] Change deopt entries into builtins"" · c7cb9bec
    Jakob Gruber authored
    This is a reland of fbfa9bf4
    
    The arm64 was missing proper codegen for CFI, thus sizes were off.
    
    Original change's description:
    > Reland "[deoptimizer] Change deopt entries into builtins"
    >
    > This is a reland of 7f58ced7
    >
    > It fixes the different exit size emitted on x64/Atom CPUs due to
    > performance tuning in TurboAssembler::Call. Additionally, add
    > cctests to verify the fixed size exits.
    >
    > Original change's description:
    > > [deoptimizer] Change deopt entries into builtins
    > >
    > > While the overall goal of this commit is to change deoptimization
    > > entries into builtins, there are multiple related things happening:
    > >
    > > - Deoptimization entries, formerly stubs (i.e. Code objects generated
    > >   at runtime, guaranteed to be immovable), have been converted into
    > >   builtins. The major restriction is that we now need to preserve the
    > >   kRootRegister, which was formerly used on most architectures to pass
    > >   the deoptimization id. The solution differs based on platform.
    > > - Renamed DEOPT_ENTRIES_OR_FOR_TESTING code kind to FOR_TESTING.
    > > - Removed heap/ support for immovable Code generation.
    > > - Removed the DeserializerData class (no longer needed).
    > > - arm64: to preserve 4-byte deopt exits, introduced a new optimization
    > >   in which the final jump to the deoptimization entry is generated
    > >   once per Code object, and deopt exits can continue to emit a
    > >   near-call.
    > > - arm,ia32,x64: change to fixed-size deopt exits. This reduces exit
    > >   sizes by 4/8, 5, and 5 bytes, respectively.
    > >
    > > On arm the deopt exit size is reduced from 12 (or 16) bytes to 8 bytes
    > > by using the same strategy as on arm64 (recalc deopt id from return
    > > address). Before:
    > >
    > >  e300a002       movw r10, <id>
    > >  e59fc024       ldr ip, [pc, <entry offset>]
    > >  e12fff3c       blx ip
    > >
    > > After:
    > >
    > >  e59acb35       ldr ip, [r10, <entry offset>]
    > >  e12fff3c       blx ip
    > >
    > > On arm64 the deopt exit size remains 4 bytes (or 8 bytes in same cases
    > > with CFI). Additionally, up to 4 builtin jumps are emitted per Code
    > > object (max 32 bytes added overhead per Code object). Before:
    > >
    > >  9401cdae       bl <entry offset>
    > >
    > > After:
    > >
    > >  # eager deoptimization entry jump.
    > >  f95b1f50       ldr x16, [x26, <eager entry offset>]
    > >  d61f0200       br x16
    > >  # lazy deoptimization entry jump.
    > >  f95b2b50       ldr x16, [x26, <lazy entry offset>]
    > >  d61f0200       br x16
    > >  # the deopt exit.
    > >  97fffffc       bl <eager deoptimization entry jump offset>
    > >
    > > On ia32 the deopt exit size is reduced from 10 to 5 bytes. Before:
    > >
    > >  bb00000000     mov ebx,<id>
    > >  e825f5372b     call <entry>
    > >
    > > After:
    > >
    > >  e8ea2256ba     call <entry>
    > >
    > > On x64 the deopt exit size is reduced from 12 to 7 bytes. Before:
    > >
    > >  49c7c511000000 REX.W movq r13,<id>
    > >  e8ea2f0700     call <entry>
    > >
    > > After:
    > >
    > >  41ff9560360000 call [r13+<entry offset>]
    > >
    > > Bug: v8:8661,v8:8768
    > > Change-Id: I13e30aedc360474dc818fecc528ce87c3bfeed42
    > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2465834
    > > Commit-Queue: Jakob Gruber <jgruber@chromium.org>
    > > Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
    > > Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
    > > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
    > > Cr-Commit-Position: refs/heads/master@{#70597}
    >
    > Tbr: ulan@chromium.org, tebbi@chromium.org, rmcilroy@chromium.org
    > Bug: v8:8661,v8:8768,chromium:1140165
    > Change-Id: Ibcd5c39c58a70bf2b2ac221aa375fc68d495e144
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2485506
    > Reviewed-by: Jakob Gruber <jgruber@chromium.org>
    > Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
    > Commit-Queue: Jakob Gruber <jgruber@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#70655}
    
    Tbr: ulan@chromium.org, tebbi@chromium.org, rmcilroy@chromium.org
    Bug: v8:8661
    Bug: v8:8768
    Bug: chromium:1140165
    Change-Id: I471cc94fc085e527dc9bfb5a84b96bd907c2333f
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2488682Reviewed-by: 's avatarJakob Gruber <jgruber@chromium.org>
    Commit-Queue: Jakob Gruber <jgruber@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#70672}
    c7cb9bec
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