c9fd997524
Unroll s == "ab" to len(s) == 2 && s[0] == 'a' && s[1] == 'b' This generates faster and shorter code by avoiding a runtime call. Do something similar for !=. The cutoff length is 6. This was chosen empirically by examining binary sizes on arm, arm64, 386, and amd64 using the SSA backend. For all architectures examined, 4, 5, and 6 were the ideal cutoff, with identical binary sizes. The distribution of constant string equality sizes during 'go build -a std' is: 40.81% 622 len 0 14.11% 215 len 4 9.45% 144 len 1 7.81% 119 len 3 7.48% 114 len 5 5.12% 78 len 7 4.13% 63 len 2 3.54% 54 len 8 2.69% 41 len 6 1.18% 18 len 10 0.85% 13 len 9 0.66% 10 len 14 0.59% 9 len 17 0.46% 7 len 11 0.26% 4 len 12 0.20% 3 len 19 0.13% 2 len 13 0.13% 2 len 15 0.13% 2 len 16 0.07% 1 len 20 0.07% 1 len 23 0.07% 1 len 33 0.07% 1 len 36 A cutoff of length 6 covers most of the cases. Benchmarks on amd64 comparing a string to a constant of length 3: Cmp/1same-8 4.78ns ± 6% 0.94ns ± 9% -80.26% (p=0.000 n=20+20) Cmp/1diffbytes-8 6.43ns ± 6% 0.96ns ±11% -85.13% (p=0.000 n=20+20) Cmp/3same-8 4.71ns ± 5% 1.28ns ± 5% -72.90% (p=0.000 n=20+20) Cmp/3difffirstbyte-8 6.33ns ± 7% 1.27ns ± 7% -79.90% (p=0.000 n=20+20) Cmp/3difflastbyte-8 6.34ns ± 8% 1.26ns ± 9% -80.13% (p=0.000 n=20+20) The change to the prove test preserves the existing intent of the test. When the string was short, there was a new "proved in bounds" report that referred to individual byte comparisons. Change-Id: I593ac303b0d11f275672090c5c786ea0c6b8da13 Reviewed-on: https://go-review.googlesource.com/26758 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> |
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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.
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.