04540f1549
Link time optimization is a technique for whole-program optimization. Instead of doing code generation during compilation, the compiler saves its intermediate representation to the object files. During the final linking step, it will then merge all the object files together and perform optimizations on the entire program. This can often reduce the final binary size, but also may increase the total compilation time. This patch introduces a Kconfig option for enabling link time optimization in libpayload. Since libpayload does no linking of its own, its LTO archive files will contain only IR and no generated code. Downstream projects will need to use LTO-aware tools when manipulating the archives (eg. gcc-ar and gcc-nm), but otherwise do not need to use LTO themselves -- the compiler will recognize which files are LTO and which are not, so enabling this option should mostly be "drop in". For example, when building coreinfo.elf using tinycurses libpayload: binary size compilation time default 114 KiB 11.49s LTO 95 KiB 10.36s In this case the total compilation time was actually shorter -- despite the final linking step taking longer, this was offset by the shorter compilation times for each individual file (since there is no code gen until the very end). Change-Id: I048f2ff6298ed0d891098942e1e8b29d35487b91 Signed-off-by: Jacob Garber <jgarber1@ualberta.ca> Reviewed-on: https://review.coreboot.org/c/coreboot/+/38291 Reviewed-by: Nico Huber <nico.h@gmx.de> Reviewed-by: Martin Roth <martinroth@google.com> Tested-by: build bot (Jenkins) <no-reply@coreboot.org> |
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| .. | ||
| arch | ||
| bin | ||
| configs | ||
| crypto | ||
| curses | ||
| drivers | ||
| gdb | ||
| include | ||
| libc | ||
| libcbfs | ||
| liblz4 | ||
| liblzma | ||
| libpci | ||
| sample | ||
| tests | ||
| .gitignore | ||
| Doxyfile | ||
| Kconfig | ||
| LICENSES | ||
| LICENSE_GPL | ||
| Makefile | ||
| Makefile.inc | ||
| README | ||
README
-------------------------------------------------------------------------------
libpayload README
-------------------------------------------------------------------------------
libpayload is a minimal library to support standalone payloads
that can be booted with firmware like coreboot. It handles the setup
code, and provides common C library symbols such as malloc() and printf().
Note: This is _not_ a standard library for use with an operating system,
rather it's only useful for coreboot payload development!
See https://www.coreboot.org for details on coreboot.
Installation
------------
$ git clone https://review.coreboot.org/coreboot.git
$ cd coreboot/payloads/libpayload
$ make menuconfig
$ make
$ make install (optional, will install into ./install per default)
On x86 systems, libpayload will always be 32-bit even if your host OS runs
in 64-bit, so you might have to install the 32-bit libgcc version.
On Debian systems you'd do 'apt-get install gcc-multilib' for example.
Run 'make distclean' before switching boards. This command will remove
your current .config file, so you need 'make menuconfig' again or
'make defconfig' in order to set up configuration. Default configuration
is based on 'configs/defconfig'. See the configs/ directory for examples
of configuration.
Usage
-----
Here's an example of a very simple payload (hello.c) and how to build it:
#include <libpayload.h>
int main(void)
{
printf("Hello, world!\n");
return 0;
}
Building the payload using the 'lpgcc' compiler wrapper:
$ lpgcc -o hello.elf hello.c
Please see the sample/ directory for details.
Website and Mailing List
------------------------
The main website is https://www.coreboot.org/Libpayload.
For additional information, patches, and discussions, please join the
coreboot mailing list at https://www.coreboot.org/Mailinglist, where most
libpayload developers are subscribed.
Copyright and License
---------------------
See LICENSES.