The CpuModel class looks like it was originally intended to hold a lot
more information that it does now, which is just the name of a CPU, and
whether it should be enabled by default. All the built in configs in
build_opts already explicitly list a set of CPUs, and CPUs should not,
generally speaking, be enabled by default, since they almost always need
to be specifically supported by an ISA. This is mutual, since usually
ISAs definitions are not quite correct or complete, and this is often
exposed by plugging them into different, and/or more complex CPU models
which stress those short comings.
This change drops the idea of a "default" CPU, and since the only thing
being tracked at this point is a list of CPUs, it turns CpuModel() into
a simple function which adds a name to a set of supported CPUs.
Change-Id: Id7475d5dc8548802b5253f79839da8c76ef4d165
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48963
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
We currently generate and compile one version of the ISA code per CPU
model. This is obviously wasting a lot of resources at compile
time. This changeset factors out the interface into a separate
ExecContext class, which also serves as documentation for the
interface between CPUs and the ISA code. While doing so, this
changeset also fixes up interface inconsistencies between the
different CPU models.
The main argument for using one set of ISA code per CPU model has
always been performance as this avoid indirect branches in the
generated code. However, this argument does not hold water. Booting
Linux on a simulated ARM system running in atomic mode
(opt/10.linux-boot/realview-simple-atomic) is actually 2% faster
(compiled using clang 3.4) after applying this patch. Additionally,
compilation time is decreased by 35%.
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.
--HG--
extra : convert_revision : 103f6b490d2eb224436688c89cdc015211c4fd30
