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Alec Roelke ee0c261e10 riscv: [Patch 7/5] Corrected LRSC semantics 
RISC-V makes use of load-reserved and store-conditional instructions to
enable creation of lock-free concurrent data manipulation as well as
ACQUIRE and RELEASE semantics for memory ordering of LR, SC, and AMO
instructions (the latter of which do not follow LR/SC semantics). This
patch is a correction to patch 4, which added these instructions to the
implementation of RISC-V. It modifies locked_mem.hh and the
implementations of lr.w, sc.w, lr.d, and sc.d to apply the proper gem5
flags and return the proper values.

An important difference between gem5's LLSC semantics and RISC-V's LR/SC
ones, beyond the name, is that gem5 uses 0 to indicate failure and 1 to
indicate success, while RISC-V is the opposite. Strictly speaking, RISC-V
uses 0 to indicate success and nonzero to indicate failure where the
value would indicate the error, but currently only 1 is reserved as a
failure code by the ISA reference.

This is the seventh patch in the series which originally consisted of five
patches that added the RISC-V ISA to gem5. The original five patches added
all of the instructions and added support for more detailed CPU models and
the sixth patch corrected the implementations of Linux constants and
structs. There will be an eighth patch that adds some regression tests
for the instructions.

[Removed some commented-out code from locked_mem.hh.]
Signed-off by: Alec Roelke

Signed-off by: Jason Lowe-Power <jason@lowepower.com>
2016-11-30 17:10:28 -05:00
build_opts riscv: [Patch 5/5] Added missing support for timing CPU models 2016-11-30 17:10:28 -05:00
configs mem: Split the hit_latency into tag_latency and data_latency 2016-11-30 17:10:27 -05:00
ext arch: [Patch 1/5] Added RISC-V base instruction set RV64I 2016-11-30 17:10:28 -05:00
src riscv: [Patch 7/5] Corrected LRSC semantics 2016-11-30 17:10:28 -05:00
system arm, config: Add an example ARM big.LITTLE(tm) configuration script 2016-07-21 17:19:16 +01:00
tests tests: Check for TrafficGen as part of memcheck regression 2016-11-30 11:15:21 -05:00
util style: Add options to select checkers and apply fixes 2016-11-25 10:33:15 +00:00
.gitignore misc: Add a gitignore file based on the current hgignore 2016-03-16 17:20:00 +00:00
.hgignore misc: ignore object files and static libs in util/m5 2015-11-13 17:03:48 -05:00
.hgtags Added tag stable_2015_09_03 for changeset 60eb3fef9c2d 2015-09-03 15:38:46 -05:00
COPYING copyright: Add code for finding all copyright blocks and create a COPYING file 2011-06-02 17:36:07 -07:00
LICENSE copyright: Add code for finding all copyright blocks and create a COPYING file 2011-06-02 17:36:07 -07:00
README misc: README direct to website for dependencies 2014-08-26 10:12:04 -04:00
SConstruct scons: Bump minimum gcc version to 4.8 2016-05-30 02:10:48 -04:00

README 

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.