cmd/link: use BestSpeed for DWARF compression
DWARF compression accounts for roughly 30% of the linker's time. This
CL switches from DefaultCompression to BestSpeed, which virtually
eliminates this time. This roughly halves the overhead of handling
DWARF in the linker:
name \ time/op nodwarf dwarf dwarf-speed
BuildCmdGoAll 10.0s ±11% 10.6s ± 5% 10.8s ± 5%
nodwarf +6.41% +8.03%
dwarf ~
LinkCmdGo 626ms ± 5% 1096ms ± 2% 860ms ± 2%
nodwarf +75.17% +37.36%
dwarf -21.59%
Previously, enabling DWARF had a 75% overhead in link time for cmd/go.
This change reduces this overhead to 37% (a 22% reduction).
The effect on binary size is minimal compared to DefaultCompression,
and still substantially better than no compression:
cmd/go bytes
nodwarf
10106953
dwarf
12159049 nodwarf+20%
dwarf-speed
12408905 nodwarf+23%
dwarf-nozlib
17766473 nodwarf+76%
Updates #26318.
Change-Id: I33bb7caa038a2753c29104501663daf4839e7054
Reviewed-on: https://go-review.googlesource.com/123356
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>