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Sometimes when using the GuestABI mechanism, gem5 wants to know that a function was called and with what arguments to do its own processing, but doesn't want to return its own value since it will still let the simulated system execute its own function. There are also situations where gem5 wants to return a value, but not through the normal mechanism. That happens when, for instance, a gem5 op is triggered by a memory access, and that access is what should return the value, not a particular fixed register. This option is a template parameter rather than a function argument so that if it's not going to be used, no "Return" type needs to be defined since it's not present at all in the chain of functions invokeSimcall expands to. This will also make it easier to reuse generic ABIs in those situations without having to make custom wrappers. Change-Id: I969e78495c8f4e73f4de1a3dfb4d74c9b30f5af5 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28288 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Gabe Black <gabeblack@google.com> Tested-by: kokoro <noreply+kokoro@google.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, SWIG, 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 the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/documentation/general_docs/building for more details and options. The basic source release includes these subdirectories: - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - 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 will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.