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535e6c5fa4
Fourth of five patches adding RISC-V to GEM5. This patch adds the RV64A extension, which includes atomic memory instructions. These instructions atomically read a value from memory, modify it with a value contained in a source register, and store the original memory value in the destination register and modified value back into memory. Because this requires two memory accesses and GEM5 does not support two timing memory accesses in a single instruction, each of these instructions is split into two micro- ops: A "load" micro-op, which reads the memory, and a "store" micro-op, which modifies and writes it back. Each atomic memory instruction also has two bits that acquire and release a lock on its memory location. Additionally, there are atomic load and store instructions that only either load or store, but not both, and can acquire or release memory locks. Note that because the current implementation of RISC-V only supports one core and one thread, it doesn't make sense to make use of AMO instructions. However, they do form a standard extension of the RISC-V ISA, so they are included mostly as a placeholder for when multithreaded execution is implemented. As a result, any tests for their correctness in a future patch may be abbreviated. Patch 1 introduced RISC-V and implemented the base instruction set, RV64I; patch 2 implemented the integer multiply extension, RV64M; and patch 3 implemented the single- and double-precision floating point extensions, RV64FD. Patch 5 will add support for timing, minor, and detailed CPU models that isn't present in patches 1-4. [Added missing file amo.isa] [Replaced information removed from initial patch that was missed during division into multiple patches.] [Fixed some minor formatting issues.] [Fixed oversight where LR and SC didn't have both AQ and RL flags.] Signed-off by: Alec Roelke Signed-off by: Jason Lowe-Power <jason@lowepower.com> |
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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.