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Peter Kümmel 814f63ec32 toolchain: add link-time-optimization support
Add a new option BR2_GCC_ENABLE_LTO that builds gcc and binutils with
LTO support.

Individual packages still have to enable LTO explicitly by passing '-flto' to
GCC, which passes it on to the linker. This option does not add that flag
globally. Some packages detect if the compiler supports LTO and enable the flag
if it does.

To support LTO, ar and ranlib must be called with an argument which triggers the
usage of the LTO plugin. Since GCC doesn't call these tools itself, it instead
provides wrappers for ar and ranlib that pass the LTO arguments. This way
existing Makefiles don't need to be changed for LTO support. However, these
wrappers are called <tuple>-gcc-ar which matches the pattern to link to the
buildroot wrapper in the external toolchain logic. So the external toolchain
logic is updated to provide the correct symlink.

[Thomas:
  - Add a separate BR2_BINUTILS_ENABLE_LTO option to enable LTO
    support in binutils. This is a blind option, selected by
    BR2_GCC_ENABLE_LTO. It just avoids having binutils.mk poke
    directly into gcc Config.in options.
  - Remove the check on the AVR32 special gcc version, which we don't
    support anymore.
  - Adapt the help text of the LTO Config.in option to no longer
    mention "Since version 4.5", since we only support gcc >= 4.5 in
    Buildroot anyway.
  - Fix typo in toolchain-external.mk comment.]

Signed-off-by: Peter Kümmel <syntheticpp@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
2015-03-07 15:01:53 +01:00
arch arch: add support for AMD steamroller 2015-03-04 22:16:41 +01:00
board board: add support for RIoTboard 2015-03-06 23:52:01 +01:00
boot boot/syslinux: bump version to 6.03 2015-03-04 23:02:53 +01:00
configs board: add support for RIoTboard 2015-03-06 23:52:01 +01:00
docs website/news.html: add 2015.02 announcement link 2015-03-02 21:05:32 +01:00
fs fs/tar: only store numeric uid/gid 2015-02-19 22:02:59 +01:00
linux linux: clarify kernel configuration entries 2015-03-05 21:18:35 +01:00
package toolchain: add link-time-optimization support 2015-03-07 15:01:53 +01:00
support pkg-stats: ignore linux-ext-fbtft.mk and doc-asciidoc.mk 2015-02-15 23:28:55 +01:00
system system: Defaulting TZ_LOCALTIME to UTC 2015-02-21 23:47:07 +01:00
toolchain toolchain: add link-time-optimization support 2015-03-07 15:01:53 +01:00
.defconfig arch: kill avr32 2015-02-14 17:39:50 +01:00
.gitignore update gitignore 2013-05-04 12:41:55 +02:00
CHANGES Update for 2015.02 2015-03-01 22:26:12 +01:00
Config.in Config.in: remove BR2_DEPRECATED_SINCE_2014_02 2015-03-04 22:13:40 +01:00
Config.in.legacy valgrind: rename ptrcheck to sgcheck like upstream 2015-03-07 14:48:12 +01:00
COPYING clarify license and fix website license link 2009-05-08 09:29:41 +02:00
Makefile Kickoff 2015.05 cycle 2015-03-02 21:03:01 +01:00
Makefile.legacy Makefile.legacy: fix recursive invocation with BUILDROOT_DL_DIR and _CONFIG 2014-02-11 08:14:57 +01:00
README docs: Move README file to root 2014-03-03 21:28:39 +01:00

To build and use the buildroot stuff, do the following:

1) run 'make menuconfig'
2) select the packages you wish to compile
3) run 'make'
4) wait while it compiles
5) Use your shiny new root filesystem. Depending on which sort of
    root filesystem you selected, you may want to loop mount it,
    chroot into it, nfs mount it on your target device, burn it
    to flash, or whatever is appropriate for your target system.

You do not need to be root to build or run buildroot.  Have fun!

Offline build:
==============

In order to do an offline-build (not connected to the net), fetch all
selected source by issuing a
$ make source

before you disconnect.
If your build-host is never connected, then you have to copy buildroot
and your toplevel .config to a machine that has an internet-connection
and issue "make source" there, then copy the content of your dl/ dir to
the build-host.

Building out-of-tree:
=====================

Buildroot supports building out of tree with a syntax similar
to the Linux kernel. To use it, add O=<directory> to the
make command line, E.G.:

$ make O=/tmp/build

And all the output files (including .config) will be located under /tmp/build.

More finegrained configuration:
===============================

You can specify a config-file for uClibc:
$ make UCLIBC_CONFIG_FILE=/my/uClibc.config

And you can specify a config-file for busybox:
$ make BUSYBOX_CONFIG_FILE=/my/busybox.config

To use a non-standard host-compiler (if you do not have 'gcc'),
make sure that the compiler is in your PATH and that the library paths are
setup properly, if your compiler is built dynamically:
$ make HOSTCC=gcc-4.3.orig HOSTCXX=gcc-4.3-mine

Depending on your configuration, there are some targets you can use to
use menuconfig of certain packages. This includes:
$ make HOSTCC=gcc-4.3 linux-menuconfig
$ make HOSTCC=gcc-4.3 uclibc-menuconfig
$ make HOSTCC=gcc-4.3 busybox-menuconfig

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