• Alessandro Arzilli's avatar
    cmd/link: fix up debug_range for dsymutil (revert CL 72371) · eca41af0
    Alessandro Arzilli authored
    Dsymutil, an utility used on macOS when externally linking executables,
    does not support base address selector entries in debug_ranges.
    
    CL 73271 worked around this problem by removing base address selectors
    and emitting CU-relative relocations for each list entry.
    
    This commit, as an optimization, reintroduces the base address
    selectors and changes the linker to remove them again, but only when it
    knows that it will have to invoke the external linker on macOS.
    
    Compilecmp comparing master with a branch that has scope tracking
    always enabled:
    
    completed   15 of   15, estimated time remaining 0s (eta 2:43PM)
    name        old time/op       new time/op       delta
    Template          272ms ± 8%        257ms ± 5%  -5.33%  (p=0.000 n=15+14)
    Unicode           124ms ± 7%        122ms ± 5%    ~     (p=0.210 n=14+14)
    GoTypes           873ms ± 3%        870ms ± 5%    ~     (p=0.856 n=15+13)
    Compiler          4.49s ± 2%        4.49s ± 5%    ~     (p=0.982 n=14+14)
    SSA               11.8s ± 4%        11.8s ± 3%    ~     (p=0.653 n=15+15)
    Flate             163ms ± 6%        164ms ± 9%    ~     (p=0.914 n=14+15)
    GoParser          203ms ± 6%        202ms ±10%    ~     (p=0.571 n=14+14)
    Reflect           547ms ± 7%        542ms ± 4%    ~     (p=0.914 n=15+14)
    Tar               244ms ± 7%        237ms ± 3%  -2.80%  (p=0.002 n=14+13)
    XML               289ms ± 6%        289ms ± 5%    ~     (p=0.839 n=14+14)
    [Geo mean]        537ms             531ms       -1.10%
    
    name        old user-time/op  new user-time/op  delta
    Template          360ms ± 4%        341ms ± 7%  -5.16%  (p=0.000 n=14+14)
    Unicode           189ms ±11%        190ms ± 8%    ~     (p=0.844 n=15+15)
    GoTypes           1.13s ± 4%        1.14s ± 7%    ~     (p=0.582 n=15+14)
    Compiler          5.34s ± 2%        5.40s ± 4%  +1.19%  (p=0.036 n=11+13)
    SSA               14.7s ± 2%        14.7s ± 3%    ~     (p=0.602 n=15+15)
    Flate             211ms ± 7%        214ms ± 8%    ~     (p=0.252 n=14+14)
    GoParser          267ms ±12%        266ms ± 2%    ~     (p=0.837 n=15+11)
    Reflect           706ms ± 4%        701ms ± 3%    ~     (p=0.213 n=14+12)
    Tar               331ms ± 9%        320ms ± 5%  -3.30%  (p=0.025 n=15+14)
    XML               378ms ± 4%        373ms ± 6%    ~     (p=0.253 n=14+15)
    [Geo mean]        704ms             700ms       -0.58%
    
    name        old alloc/op      new alloc/op      delta
    Template         38.0MB ± 0%       38.4MB ± 0%  +1.12%  (p=0.000 n=15+15)
    Unicode          28.8MB ± 0%       28.8MB ± 0%  +0.17%  (p=0.000 n=15+15)
    GoTypes           112MB ± 0%        114MB ± 0%  +1.47%  (p=0.000 n=15+15)
    Compiler          465MB ± 0%        473MB ± 0%  +1.71%  (p=0.000 n=15+15)
    SSA              1.48GB ± 0%       1.53GB ± 0%  +3.07%  (p=0.000 n=15+15)
    Flate            24.3MB ± 0%       24.7MB ± 0%  +1.67%  (p=0.000 n=15+15)
    GoParser         30.7MB ± 0%       31.0MB ± 0%  +1.15%  (p=0.000 n=12+15)
    Reflect          76.3MB ± 0%       77.1MB ± 0%  +0.97%  (p=0.000 n=15+15)
    Tar              39.2MB ± 0%       39.6MB ± 0%  +0.91%  (p=0.000 n=15+15)
    XML              41.5MB ± 0%       42.0MB ± 0%  +1.29%  (p=0.000 n=15+15)
    [Geo mean]       77.5MB            78.6MB       +1.35%
    
    name        old allocs/op     new allocs/op     delta
    Template           385k ± 0%         387k ± 0%  +0.51%  (p=0.000 n=15+15)
    Unicode            342k ± 0%         343k ± 0%  +0.10%  (p=0.000 n=14+15)
    GoTypes           1.19M ± 0%        1.19M ± 0%  +0.62%  (p=0.000 n=15+15)
    Compiler          4.51M ± 0%        4.54M ± 0%  +0.50%  (p=0.000 n=14+15)
    SSA               12.2M ± 0%        12.4M ± 0%  +1.12%  (p=0.000 n=14+15)
    Flate              234k ± 0%         236k ± 0%  +0.60%  (p=0.000 n=15+15)
    GoParser           318k ± 0%         320k ± 0%  +0.60%  (p=0.000 n=15+15)
    Reflect            974k ± 0%         977k ± 0%  +0.27%  (p=0.000 n=15+15)
    Tar                395k ± 0%         397k ± 0%  +0.37%  (p=0.000 n=14+15)
    XML                404k ± 0%         407k ± 0%  +0.53%  (p=0.000 n=15+15)
    [Geo mean]         794k              798k       +0.52%
    
    name        old text-bytes    new text-bytes    delta
    HelloSize         680kB ± 0%        680kB ± 0%    ~     (all equal)
    
    name        old data-bytes    new data-bytes    delta
    HelloSize        9.62kB ± 0%       9.62kB ± 0%    ~     (all equal)
    
    name        old bss-bytes     new bss-bytes     delta
    HelloSize         125kB ± 0%        125kB ± 0%    ~     (all equal)
    
    name        old exe-bytes     new exe-bytes     delta
    HelloSize        1.11MB ± 0%       1.13MB ± 0%  +1.85%  (p=0.000 n=15+15)
    
    Change-Id: I61c98ba0340cb798034b2bb55e3ab3a58ac1cf23
    Reviewed-on: https://go-review.googlesource.com/98075Reviewed-by: 's avatarHeschi Kreinick <heschi@google.com>
    eca41af0
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