mem-cache: Add multi-prefetcher adaptor

This patch adds a meta-prefetcher that enables gem5's cache models to
connect to multiple prefetchers. Sub-prefetchers still use the
probes-based interface and training can be controlled
independently. However, when the cache requests a prefetch packet, the
adaptor traverses the priority list of prefetchers and uses the first
prefetcher that is able to generate a prefetch.

Kudos to Mitch Hayenga for the original version of this patch.

Change-Id: I25569a834997e5404c7183ec995d212912c5dcdf
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18868
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

mem-cache: Proactive Instruction Fetch Implementation

Ferdman, M., Kaynak, C., & Falsafi, B. (2011, December).
Proactive instruction fetch. In Proceedings of the 44th Annual IEEE/ACM
International Symposium on Microarchitecture (pp. 152-162). ACM.

Change-Id: I38c3ab30a94ab279f03e3d5936ce8ed118310c0e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16968
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Added the STeMS prefetcher

Reference:
Stephen Somogyi, Thomas F. Wenisch, Anastasia Ailamaki, and
Babak Falsafi. 2009. Spatio-temporal memory streaming.
In Proceedings of the 36th annual international symposium on
Computer architecture (ISCA '09). ACM, New York, NY, USA, 69-80.

Change-Id: I58cea1a7faa9391f8aa4469eb4973feabd31097a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16423
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Added the Indirect Memory Prefetcher

Reference:
Xiangyao Yu, Christopher J. Hughes, Nadathur Satish, and Srinivas Devadas.
2015. IMP: indirect memory prefetcher. In Proceedings of the 48th
International Symposium on Microarchitecture (MICRO-48). ACM,
New York, NY, USA, 178-190. DOI: https://doi.org/10.1145/2830772.2830807

Change-Id: I52790f69c13ec55b8c1c8b9396ef9a1fb1be9797
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16223
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Sandbox Based Optimal Offset Implementation

Brown, N. T., & Sendag, R. Sandbox Based Optimal Offset Estimation.

Change-Id: Ieb693b6b2c3d8bdfb6948389ca10e92c85454862
Reviewed-on: https://gem5-review.googlesource.com/c/15095
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: A Best-Offset Prefetcher

Michaud, P. (2015, June). A best-offset prefetcher.
In 2nd Data Prefetching Championship.

Change-Id: I61bb89ca5639356d54aeb04e856d5bf6e8805c22
Reviewed-on: https://gem5-review.googlesource.com/c/14820
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Added the Slim AMPM Prefetcher

Reference:
Towards Bandwidth-Efficient Prefetching with Slim AMPM.
Young, V., & Krishna, A. (2015). The 2nd Data Prefetching Championship.

Slim AMPM is composed of two prefetchers, the DPCT and the AMPM (both already
in gem5).

Change-Id: I6e868faf216e3e75231cf181d59884ed6f0d382a
Reviewed-on: https://gem5-review.googlesource.com/c/16383
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Irregular Stream Buffer Prefetcher

Based in the description of the following publication:
Akanksha Jain and Calvin Lin. 2013. Linearizing irregular memory accesses
for improved correlated prefetching. In Proceedings of the 46th Annual
IEEE/ACM International Symposium on Microarchitecture (MICRO-46). ACM,
New York, NY, USA, 247-259.

Change-Id: Ibeb6abc93ca40ad634df6ed5cf8becb0a49d1165
Reviewed-on: https://gem5-review.googlesource.com/c/15215
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>

mem-cache: Added the Delta Correlating Prediction Tables Prefetcher

Reference:
Multi-level hardware prefetching using low complexity delta correlating
prediction tables with partial matching.
Marius Grannaes, Magnus Jahre, and Lasse Natvig. 2010.
In Proceedings of the 5th international conference on High Performance
Embedded Architectures and Compilers (HiPEAC'10)
Change-Id: I7b5d7ede9284862a427cfd5693a47652a69ed49d
Reviewed-on: https://gem5-review.googlesource.com/c/16062
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

mem-cache: Updated version of the Signature Path Prefetcher

This implementation is based in the description available in:
Jinchun Kim, Seth H. Pugsley, Paul V. Gratz, A. L. Narasimha Reddy,
Chris Wilkerson, and Zeshan Chishti. 2016.
Path confidence based lookahead prefetching.
In The 49th Annual IEEE/ACM International Symposium on Microarchitecture
(MICRO-49). IEEE Press, Piscataway, NJ, USA, Article 60, 12 pages.

Change-Id: I4b8b54efef48ced7044bd535de9a69bca68d47d9
Reviewed-on: https://gem5-review.googlesource.com/c/14819
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Access Map Pattern Matching Prefetcher

Implementation of the Access Map Pattern Matching prefetcher
Based in the description of the following paper:
Access map pattern matching for high performance data cache prefetch.
Ishii, Y., Inaba, M., & Hiraki, K. (2011).
Journal of Instruction-Level Parallelism, 13, 1-24.

Change-Id: I0d4b7f7afc2ab4938bdd8755bfed26e26a28530c
Reviewed-on: https://gem5-review.googlesource.com/c/15096
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem-cache: Signature Path Prefetcher

Related paper:
Lookahead Prefetching with Signature Path
J Kim, PV Gratz, ALN Reddy
The 2nd Data Prefetching Championship (DPC2), 2015

Change-Id: I2319be2fa409f955f65e1bf1e1bb2d6d9a4fea11
Reviewed-on: https://gem5-review.googlesource.com/c/14737
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

mem: Rework the structuring of the prefetchers

Re-organizes the prefetcher class structure. Previously the
BasePrefetcher forced multiple assumptions on the prefetchers that
inherited from it. This patch makes the BasePrefetcher class truly
representative of base functionality. For example, the base class no
longer enforces FIFO order. Instead, prefetchers with FIFO requests
(like the existing stride and tagged prefetchers) now inherit from a
new QueuedPrefetcher base class.

Finally, the stride-based prefetcher now assumes a custimizable lookup table
(sets/ways) rather than the previous fully associative structure.

mem: Remove the GHB prefetcher from the source tree

There are two primary issues with this code which make it deserving of deletion.

1) GHB is a way to structure a prefetcher, not a definitive type of prefetcher
2) This prefetcher isn't even structured like a GHB prefetcher.
It's basically a worse version of the stride prefetcher.

It primarily serves to confuse new gem5 users and most functionality is already
present in the stride prefetcher.

arch: Resurrect the NOISA build target and rename it NULL

This patch makes it possible to once again build gem5 without any
ISA. The main purpose is to enable work around the interconnect and
memory system without having to build any CPU models or device models.

The regress script is updated to include the NULL ISA target. Currently
no regressions make use of it, but all the testers could (and perhaps
should) transition to it.

prefetcher: Make prefetcher a sim object instead of it being a parameter on cache

SCons: Support building without an ISA

Rename cache files for brevity and consistency with rest of tree.

Rework the way SCons recurses into subdirectories, making it
automatic. The point is that now a subdirectory can be added
to the build process just by creating a SConscript file in it.
The process has two passes. On the first pass, all subdirs
of the root of the tree are searched for SConsopts files.
These files contain any command line options that ought to be
added for a particular subdirectory. On the second pass,
all subdirs of the src directory are searched for SConscript
files. These files describe how to build any given subdirectory.
I have added a Source() function. Any file (relative to the
directory in which the SConscript resides) passed to that
function is added to the build. Clean up everything to take
advantage of Source().
function is added to the list of files to be built.