• Tobias Tebbi's avatar
    Revert "[compiler] improve inlining heuristics: call frequency per executed bytecodes" · eb443e1f
    Tobias Tebbi authored
    This reverts commit 352a154e.
    
    Reason for revert: https://crbug.com/999972
    
    Original change's description:
    > [compiler] improve inlining heuristics: call frequency per executed bytecodes
    > 
    > TLDR: Inline less, but more where it matters. ~10% decrease in Turbofan
    > compile time including off-thread, while improving Octane scores by ~2%.
    > 
    > How things used to work:
    > 
    > There is a flag FLAG_min_inlining_frequency that limits inlining by
    > the callsite being sufficiently frequently executed. This call frequency
    > was measured relative to invocations of the parent (= the function we
    > originally optimize). At the same time, the limit was very low (0.15),
    > meaning we mostly relied on the total amount of inlined code
    > (FLAG_max_inlined_bytecode_size_cumulative) to limit inlining.
    > 
    > How things work now:
    > 
    > Instead of measuring call frequency relative to parent invocations, we
    > should have a measure that predicts how often the callsite in question
    > will be executed in the future. An obvious attempt at that would be to
    > measure how often the callsite was executed in absolute numbers in the
    > past. But depending on how fast feedback stabilizes, it can take more
    > or less time until we optimize a function. If we just take the absolute
    > call frequency up to the point in time when we optimize, we would
    > inline more for functions that stabilize slowly, which doesn't make
    > sense. So instead, we measure absolute call count per KB of executed
    > bytecodes of the parent function.
    > Since inlining big functions is more expensive, this threshold is
    > additionally scaled linearly with the bytecode-size of the inlinee.
    > The resulting formula is:
    > call_frequency >
    > FLAG_min_inlining_frequency *
    >   (bytecode.length() - FLAG_max_inlined_bytecode_size_small) /
    >   (FLAG_max_inlined_bytecode_size - FLAG_max_inlined_bytecode_size_small)
    > 
    > The new threshold is chosen in a way that it effectively limits
    > inlining, which allows us to increase
    > FLAG_max_inlined_bytecode_size_cumulative without increasing inlining
    > in general.
    > 
    > The reduction in compile time (x64 build) of ~10% was observed in Octane,
    > ARES-6, web-tooling-benchmark, and the standalone TypeScript benchmark.
    > The hope is that this will reduce CPU-time in real-world situations
    > too.
    > The Octane improvements come from inlining more in places where it
    > matters.
    > 
    > Bug: v8:6682
    > 
    > Change-Id: I99baa17dec85b71616a3ab3414d7e055beca39a0
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1768366
    > Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
    > Reviewed-by: Jakob Gruber <jgruber@chromium.org>
    > Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
    > Reviewed-by: Georg Neis <neis@chromium.org>
    > Reviewed-by: Maya Lekova <mslekova@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#63449}
    
    TBR=rmcilroy@chromium.org,neis@chromium.org,jgruber@chromium.org,tebbi@chromium.org,mslekova@chromium.org
    
    # Not skipping CQ checks because original CL landed > 1 day ago.
    
    Bug: v8:6682 chromium:999972
    Change-Id: Iffca63d4bef81afa0f66e34d35fb72f3b5baf517
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1784281Reviewed-by: 's avatarTobias Tebbi <tebbi@chromium.org>
    Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#63554}
    eb443e1f
Name
Last commit
Last update
..
arm Loading commit data...
arm64 Loading commit data...
ia32 Loading commit data...
mips Loading commit data...
mips64 Loading commit data...
ppc Loading commit data...
s390 Loading commit data...
x64 Loading commit data...
DEPS Loading commit data...
OWNERS Loading commit data...
assembler-arch.h Loading commit data...
assembler-inl.h Loading commit data...
assembler.cc Loading commit data...
assembler.h Loading commit data...
bailout-reason.cc Loading commit data...
bailout-reason.h Loading commit data...
callable.h Loading commit data...
code-comments.cc Loading commit data...
code-comments.h Loading commit data...
code-desc.cc Loading commit data...
code-desc.h Loading commit data...
code-factory.cc Loading commit data...
code-factory.h Loading commit data...
code-reference.cc Loading commit data...
code-reference.h Loading commit data...
code-stub-assembler.cc Loading commit data...
code-stub-assembler.h Loading commit data...
compilation-cache.cc Loading commit data...
compilation-cache.h Loading commit data...
compiler.cc Loading commit data...
compiler.h Loading commit data...
constant-pool.cc Loading commit data...
constant-pool.h Loading commit data...
constants-arch.h Loading commit data...
cpu-features.h Loading commit data...
external-reference-table.cc Loading commit data...
external-reference-table.h Loading commit data...
external-reference.cc Loading commit data...
external-reference.h Loading commit data...
flush-instruction-cache.cc Loading commit data...
flush-instruction-cache.h Loading commit data...
handler-table.cc Loading commit data...
handler-table.h Loading commit data...
interface-descriptors.cc Loading commit data...
interface-descriptors.h Loading commit data...
label.h Loading commit data...
machine-type.cc Loading commit data...
machine-type.h Loading commit data...
macro-assembler-inl.h Loading commit data...
macro-assembler.h Loading commit data...
optimized-compilation-info.cc Loading commit data...
optimized-compilation-info.h Loading commit data...
pending-optimization-table.cc Loading commit data...
pending-optimization-table.h Loading commit data...
register-arch.h Loading commit data...
register-configuration.cc Loading commit data...
register-configuration.h Loading commit data...
register.cc Loading commit data...
register.h Loading commit data...
reglist.h Loading commit data...
reloc-info.cc Loading commit data...
reloc-info.h Loading commit data...
safepoint-table.cc Loading commit data...
safepoint-table.h Loading commit data...
signature.h Loading commit data...
source-position-table.cc Loading commit data...
source-position-table.h Loading commit data...
source-position.cc Loading commit data...
source-position.h Loading commit data...
string-constants.cc Loading commit data...
string-constants.h Loading commit data...
tick-counter.cc Loading commit data...
tick-counter.h Loading commit data...
turbo-assembler.cc Loading commit data...
turbo-assembler.h Loading commit data...
unoptimized-compilation-info.cc Loading commit data...
unoptimized-compilation-info.h Loading commit data...