• Austin Clements's avatar
    cmd/compile: disable various write barrier optimizations · c39918a0
    Austin Clements authored
    Several of our current write barrier elision optimizations are invalid
    with the hybrid barrier. Eliding the hybrid barrier requires that
    *both* the current and new pointer be already shaded and, since we
    don't have the flow analysis to figure out anything about the slot's
    current value, for now we have to just disable several of these
    optimizations.
    
    This has a slight impact on binary size. On linux/amd64, the go tool
    binary increases by 0.7% and the compile binary increases by 1.5%.
    
    It also has a slight impact on performance, as one would expect. We'll
    win some of this back in subsequent commits.
    
    name                      old time/op    new time/op    delta
    BinaryTree17-12              2.38s ± 1%     2.40s ± 1%  +0.82%  (p=0.000 n=18+20)
    Fannkuch11-12                2.84s ± 1%     2.70s ± 0%  -4.97%  (p=0.000 n=18+18)
    FmtFprintfEmpty-12          44.2ns ± 1%    46.4ns ± 2%  +4.89%  (p=0.000 n=16+18)
    FmtFprintfString-12          131ns ± 0%     134ns ± 1%  +2.05%  (p=0.000 n=12+19)
    FmtFprintfInt-12             114ns ± 1%     117ns ± 1%  +3.26%  (p=0.000 n=19+20)
    FmtFprintfIntInt-12          176ns ± 1%     181ns ± 1%  +3.25%  (p=0.000 n=20+20)
    FmtFprintfPrefixedInt-12     185ns ± 1%     190ns ± 1%  +2.77%  (p=0.000 n=19+18)
    FmtFprintfFloat-12           249ns ± 1%     254ns ± 1%  +1.71%  (p=0.000 n=18+20)
    FmtManyArgs-12               747ns ± 1%     743ns ± 1%  -0.58%  (p=0.000 n=19+18)
    GobDecode-12                6.57ms ± 1%    6.61ms ± 0%  +0.73%  (p=0.000 n=19+20)
    GobEncode-12                5.58ms ± 1%    5.60ms ± 0%  +0.27%  (p=0.001 n=18+18)
    Gzip-12                      223ms ± 1%     223ms ± 1%    ~     (p=0.351 n=19+20)
    Gunzip-12                   37.9ms ± 0%    37.9ms ± 1%    ~     (p=0.095 n=16+20)
    HTTPClientServer-12         77.8µs ± 1%    78.5µs ± 1%  +0.97%  (p=0.000 n=19+20)
    JSONEncode-12               14.8ms ± 1%    14.8ms ± 1%    ~     (p=0.079 n=20+19)
    JSONDecode-12               53.7ms ± 1%    54.2ms ± 1%  +0.92%  (p=0.000 n=20+19)
    Mandelbrot200-12            3.81ms ± 1%    3.81ms ± 0%    ~     (p=0.916 n=19+18)
    GoParse-12                  3.19ms ± 1%    3.19ms ± 1%    ~     (p=0.175 n=20+19)
    RegexpMatchEasy0_32-12      71.9ns ± 1%    70.6ns ± 1%  -1.87%  (p=0.000 n=19+20)
    RegexpMatchEasy0_1K-12       946ns ± 0%     944ns ± 0%  -0.22%  (p=0.000 n=19+16)
    RegexpMatchEasy1_32-12      67.3ns ± 2%    66.8ns ± 1%  -0.72%  (p=0.008 n=20+20)
    RegexpMatchEasy1_1K-12       374ns ± 1%     384ns ± 1%  +2.69%  (p=0.000 n=18+20)
    RegexpMatchMedium_32-12      107ns ± 1%     107ns ± 1%    ~     (p=1.000 n=20+20)
    RegexpMatchMedium_1K-12     34.3µs ± 1%    34.6µs ± 1%  +0.90%  (p=0.000 n=20+20)
    RegexpMatchHard_32-12       1.78µs ± 1%    1.80µs ± 1%  +1.45%  (p=0.000 n=20+19)
    RegexpMatchHard_1K-12       53.6µs ± 0%    54.5µs ± 1%  +1.52%  (p=0.000 n=19+18)
    Revcomp-12                   417ms ± 5%     391ms ± 1%  -6.42%  (p=0.000 n=16+19)
    Template-12                 61.1ms ± 1%    64.2ms ± 0%  +5.07%  (p=0.000 n=19+20)
    TimeParse-12                 302ns ± 1%     305ns ± 1%  +0.90%  (p=0.000 n=18+18)
    TimeFormat-12                319ns ± 1%     315ns ± 1%  -1.25%  (p=0.000 n=18+18)
    [Geo mean]                  54.0µs         54.3µs       +0.58%
    
    name         old time/op  new time/op  delta
    XGarbage-12  2.24ms ± 2%  2.28ms ± 1%  +1.68%  (p=0.000 n=18+17)
    XHTTP-12     11.4µs ± 1%  11.6µs ± 2%  +1.63%  (p=0.000 n=18+18)
    XJSON-12     11.6ms ± 0%  12.5ms ± 0%  +7.84%  (p=0.000 n=18+17)
    
    Updates #17503.
    
    Change-Id: I1899f8e35662971e24bf692b517dfbe2b533c00c
    Reviewed-on: https://go-review.googlesource.com/31572Reviewed-by: 's avatarKeith Randall <khr@golang.org>
    c39918a0
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