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The previous implementation left the registers unmodified which is technically correct since there is no defined behavior in that case or a fault to raise. That would make what happened when the following code consumed the result unpredictable because it would depend on what junk values were left in the registers. This was originally not a problem since the space of supported functions were tightly packed, but someone added a new function with a gap without adjusting this behavior. This change makes CPUID zero out RAX, RBX, RCX, and RDX when it fails. That should be more predictable and cause less flakey failures. Change-Id: If6ffb17c2969d34aff1600c0ffc32333d0b9be44 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20168 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Pouya Fotouhi <pfotouhi@ucdavis.edu> 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/Introduction, and for more information about building the simulator and getting started please see http://www.gem5.org/Documentation and http://www.gem5.org/Tutorials. 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/Dependencies 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 ALPHA, 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/Build_System for more details and options. With the simulator built, have a look at http://www.gem5.org/Running_gem5 for more information on how to use gem5. 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. Please see the gem5 download page for these items at http://www.gem5.org/Download If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.