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The only way to allocate fixed sized arrays which will definitely be big enough for all source/destination registers for a given instruction is to track the maximum number of each at compile time, and then size the arrays appropriately. That creates a point of centralization which prevents breaking up decoder and instruction definitions into more modular pieces, and if multiple ISAs are ever built at once, would require coordination between all ISAs, and wasting memory for most of them. The dynamic allocation overhead is minimized by allocating the storage for all variable arrays in one chunk, and then placing the arrays there using placement new. There is still some overhead, although less than it might be otherwise. Change-Id: Id2c42869cba944deb97da01ca9e0e70186e22532 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38384 Reviewed-by: Jason Lowe-Power <power.jg@gmail.com> Maintainer: Jason Lowe-Power <power.jg@gmail.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.