dda149ecf8
There is currently a "--gold-linker" option, which tells SCons to use
the gold linker. This puts the gold linker in a special position where
it has its own command line option, and makes it impossible to
explicitly select any other linker.
This change adds a --linker option which can be set to "bfd" (the
default gnu linker), "gold" (the gnu gold linker), or "lld" which is the
clang linker. If none is specified, SCons will let the compiler fall
back to whatever its default is.
The --gold-linker option is modified so that it just sets the --linker
option for you. Because of how SCons handles adding command line
options, there isn't a good way to complain if both it and --linker is
used, nor is there a good way to warn that the user is using a
deprecated command line option. A warning is in the help text for that
option now, though.
If the gold linker is selected, this change also sets the --threads
option, and sets the --thread-count option. This tells the gold linker
to run multi-threaded to speed up linking. Apparently the gold linker
must have been built with an option that enables threading for these
options to have any effect. If threads and LTO are both enabled, the
gold linker segfaults. To avoid that problem, we don't add --threads if
LTO has been enabled.
This change also enables a new configuration, where lld, the clang
linker, can be used with gcc. Unfortunately the format of LTO
information gcc/g++ generates is not compatible with lld, and so if you
set the linker to lld and enable LTO, you'll probably get errors like
not being able to find the symbol "main".
This change also allows you to select the default gnu linker ("bfd")
when using clang, although it's not clear why you would want to do that.
Change-Id: Ib37030431527f5d0bc626e9594b2e1142df889be
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49003
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of these tools. Once you have all dependencies resolved, type 'scons build/<CONFIG>/gem5.opt' where CONFIG is one of the options in build_opts like ARM, NULL, MIPS, POWER, SPARC, X86, Garnet_standalone, etc. This will build an optimized version of the gem5 binary (gem5.opt) with the the specified configuration. See http://www.gem5.org/documentation/general_docs/building for more details and options. The main source tree includes these subdirectories: - build_opts: pre-made default configurations for gem5 - build_tools: tools used internally by gem5's build process. - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - include: include files for use in other programs - site_scons: modular components of the build system - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of those resources can be downloaded from http://resources.gem5.org, and/or from the git repository here: https://gem5.googlesource.com/public/gem5-resources/ If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.