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54e8d504e8
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Dave Cheney 54e8d504e8 cmd/5g: use MOVB for fixed array nil check 
Fixes #4396.

For fixed arrays larger than the unmapped page, agenr would general a nil check by loading the first word of the array. However there is no requirement for the first element of a byte array to be word aligned, so this check causes a trap on ARMv5 hardware (ARMv6 since relaxed that restriction, but it probably still comes at a cost).

Switching the check to MOVB ensures alignment is not an issue. This check is only invoked in a few places in the code where large fixed arrays are embedded into structs, compress/lzw is the biggest offender, and switching to MOVB has no observable performance penalty.

Thanks to Rémy and Daniel Morsing for helping me debug this on IRC last night.

R=remyoudompheng, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/6854063
2012-12-06 08:01:33 +11:00
api api: refresh next.txt 2012-11-07 15:26:41 -05:00
doc spec: BuiltinCall syntax must permit "..." for append 2012-12-04 13:09:02 -08:00
include lib9: remove unreferenced externs and getuser() 2012-11-08 09:39:24 -05:00
lib codereview: always use HTTPS 2012-11-29 11:19:55 -08:00
misc misc/emacs: fix go-mode hang 2012-11-27 12:21:10 -05:00
src cmd/5g: use MOVB for fixed array nil check 2012-12-06 08:01:33 +11:00
test cmd/5g: use MOVB for fixed array nil check 2012-12-06 08:01:33 +11:00
.hgignore build: update Makefile to track source code dependencies better 2012-03-13 03:31:11 +08:00
.hgtags tag go1.0.3 2012-09-24 13:15:33 -05:00
AUTHORS A+C: adding Frithjof Schulze (individual CLA) 2012-12-04 14:11:22 -08:00
CONTRIBUTORS A+C: adding Frithjof Schulze (individual CLA) 2012-12-04 14:11:22 -08:00
favicon.ico godoc: update favicon 2012-10-11 17:02:36 +11:00
LICENSE doc: update licensing text one more time 2012-03-27 15:09:13 +11:00
PATENTS LICENSE: separate, change PATENTS text 2010-12-06 16:31:59 -05:00
README build: update, streamline documentation for new $GOBIN 2010-08-24 20:00:50 -04:00
robots.txt godoc: serve robots.txt raw 2011-02-19 05:46:20 +11:00

README 

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.