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Due the compute unit pipeline being executed in reverse order, there exists a scenario where a compute unit will execute an extra instruction when it's supposed to be stopped at a barrier. It occurs as follows: * The ScheduleStage sets a barrier instruction ready to execute. * The ScoreboardCheckStage adds another instruction to the readyList. This is where the barrier is checked, but because the barrier isn't executing yet, the instruction can be passed along to ScheduleStage * The barrier executes, and stalls * The ScheduleStage sees that there's a new instruction and schedules it to be executed. * Only now will the ScoreboardCheckStage realize a barrier is active and stall accordingly * The subsequent instruction executes This patch sets the wavefront status to be S_BARRIER in ScheduleStage instead of in the barrier instruction execution in order to have ScoreboardCheckStage realize that we're going to execute a barrier, preventing it from marking another instruciton as ready. Change-Id: Ib683e2c68f361d7ee60a3beaf53b4b6c888c9f8d Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41573 Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com> Reviewed-by: Alexandru Duțu <alexandru.dutu@amd.com> Maintainer: Matt Sinclair <mattdsinclair@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.