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The Go programming language
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The loop recognizer uses the standard dominance frontiers but gets confused by dead code, which has a (not explicitly set) rpo number of 0, meaning it looks like the head of the function, so it dominates everything. If the loop recognizer encounters dead code while tracking backward through the graph it fails to recognize where it started as a loop, and then the optimizer does not registerize values loaded inside that loop. Fix by checking rpo against rpo2r. Separately, run a quick pass over the generated code to squash JMPs to JMP instructions, which are convenient to emit during code generation but difficult to read when debugging the -S output. A side effect of this pass is to eliminate dead code, so the output files may be slightly smaller and the optimizer may have less work to do. There is no semantic effect, because the linkers flatten JMP chains and delete dead instructions when laying out the final code. Doing it here too just makes the -S output easier to read and more like what the final binary will contain. The "dead code breaks loop finding" bug is thus fixed twice over. It seemed prudent to fix loopit separately just in case dead code ever sneaks back in for one reason or another. R=ken2 CC=golang-dev https://golang.org/cl/5190043 |
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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.