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Daniel Martí e6ad619ad6 cmd/go: further reduce init work
The first biggest offender was crypto/des.init at ~1%. It's
cryptographically broken and the init function is relatively expensive,
which is unfortunate as both crypto/tls and crypto/x509 (and by
extension, cmd/go) import it. Hide the work behind sync.Once.

The second biggest offender was flag.sortFlags at just under 1%, used by
the Visit flagset methods. It allocated two slices, which made a
difference as cmd/go iterates over multiple flagsets during init.
Use a single slice with a direct sort.Interface implementation.

Another big offender is initializing global maps. Reducing this work in
cmd/go/internal/imports and net/textproto gives us close to another
whole 1% in saved work. The former can use map literals, and the latter
can hide the work behind sync.Once.

Finally, compress/flate used newHuffmanBitWriter as part of init, which
allocates many objects and slices. Yet it only used one of the slice
fields. Allocating just that slice saves a surprising ~0.3%, since we
generated a lot of unnecessary garbage.

All in all, these little pieces amount to just over 3% saved CPU time.

name         old time/op  new time/op  delta
ExecGoEnv-8  3.61ms ± 1%  3.50ms ± 0%  -3.02%  (p=0.000 n=10+10)

Updates #26775.
Updates #29382.

Change-Id: I915416e88a874c63235ba512617c8aef35c0ca8b
Reviewed-on: https://go-review.googlesource.com/c/go/+/166459
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2019-03-31 10:49:55 +00:00
.github .github: don't render author-facing text in ISSUE_TEMPLATE 2018-11-02 04:47:34 +00:00
api text/scanner: don't liberally consume (invalid) floats or underbars 2019-02-20 20:23:28 +00:00
doc cmd/compile: add sign-extension operators on wasm 2019-03-28 20:23:05 +00:00
lib/time time: read 64-bit data if available 2019-02-26 23:10:35 +00:00
misc cmd/link: permit duplicate weak symbols 2019-03-29 17:46:01 +00:00
src cmd/go: further reduce init work 2019-03-31 10:49:55 +00:00
test cmd/compile: make prove learn index >= 0 from successful bounds checks 2019-03-30 23:22:02 +00:00
.gitattributes
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A+C: change email address for Elias Naur 2019-01-23 15:05:26 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
CONTRIBUTORS CONTRIBUTORS: second round of updates for Go 1.12 2019-01-30 18:01:19 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md README: linkify some paths 2018-06-06 18:07:01 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
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README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

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