60fd32a47f
mapaccess{1,2} returns a pointer to the value. When the key
is not in the map, it returns a pointer to zeroed memory.
Currently, for large map values we have a complicated scheme which
dynamically allocates zeroed memory for this purpose. It is ugly
code and requires an atomic.Load in a bunch of places we'd rather
not have it.
Switch to a scheme where callsites of mapaccess{1,2} which expect
large return values pass in a pointer to zeroed memory that
mapaccess can return if the key is not found. This avoids the
atomic.Load on all map accesses with a few extra instructions only
for the large value acccesses, plus a bit of bss space.
There was a time (1.4 & 1.5?) where we did something like this but
all the tricks to make the right size zero value were done by the
linker. That scheme broke in the presence of dyamic linking.
The scheme in this CL works even when dynamic linking.
Fixes #12337
Change-Id: Ic2d0319944af33bbb59785938d9ab80958d1b4b1
Reviewed-on: https://go-review.googlesource.com/22221
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
|
||
|---|---|---|
| .github | ||
| api | ||
| doc | ||
| lib/time | ||
| misc | ||
| src | ||
| test | ||
| .gitattributes | ||
| .gitignore | ||
| AUTHORS | ||
| CONTRIBUTING.md | ||
| CONTRIBUTORS | ||
| favicon.ico | ||
| LICENSE | ||
| PATENTS | ||
| README.md | ||
| robots.txt | ||
The Go Programming Language
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.
Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.
Go is the work of hundreds of contributors. We appreciate your help!
To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html
Note that we do not accept pull requests and that we use the issue tracker for bug reports and proposals only. Please ask questions on https://forum.golangbridge.org or https://groups.google.com/forum/#!forum/golang-nuts.
Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.
--
Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See https://golang.org/doc/install or doc/install.html for more details.