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The Go programming language
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It's okay to preempt at ordinary function calls because compilers arrange that there are no live registers to save on entry to the function call. The software floating point routines are function calls masquerading as individual machine instructions. They are expected to keep all the registers intact. In particular, they are expected not to clobber all the floating point registers. The floating point registers are kept per-M, because they are not live at non-preemptive goroutine scheduling events, and so keeping them per-M reduces the number of 132-byte register blocks we are keeping in memory. Because they are per-M, allowing the goroutine to be rescheduled during software floating point simulation would mean some other goroutine could overwrite the registers or perhaps the goroutine would continue running on a different M entirely. Disallow preemption during the software floating point routines to make sure that a function full of floating point instructions has the same floating point registers throughout its execution. R=golang-dev, dave CC=golang-dev https://golang.org/cl/12298043 |
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This is the source code repository for the Go programming language.
For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install.html in your web browser.
After installing Go, you can view a nicely formatted
doc/install.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install.html.
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 README). 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.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 doc/install.html for more details.