configs: Use absolute import paths

Use absoluate import paths to be Python 3 compatible. This also
imports absolute_import from __future__ to ensure that Python 2.7
behaves the same way as Python 3.

Change-Id: Ica06ed95814e9cd3e768b3e1785075e36f6e56d0
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/16708
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

configs: Fix Python 3 iterator and exec compatibility issues

Python 2.7 used to return lists for operations such as map and range,
this has changed in Python 3. To make the configs Python 3 compliant,
add explicit conversions from iterators to lists where needed, replace
xrange with range, and fix changes to exec syntax.

This change doesn't fix import paths since that might require us to
restructure the configs slightly.

Change-Id: Idcea8482b286779fc98b4e144ca8f54069c08024
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/16002
Reviewed-by: Gabe Black <gabeblack@google.com>

config: Fix the "script" SysPath functor.

This particular functor looks in the config root, not in the path
specified by M5_ROOT like binary and disk.

Change-Id: Ib007c36934c65ca9f808e995a2e0c71f0b338788
Reviewed-on: https://gem5-review.googlesource.com/5641
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

config: Rework the SysPaths functions into functors.

These functions were already being treated as psuedo objects and had
properties assigned to them setting what their paths were. That's a bit
unusual and made it less obvious what the code was doing, but also
forced the "system" function to know what all the possible path
searching functions were so that they'd have their "path" property
initialized properly in a central location.

This change introduces a PathSearcFunc class which encapsulates the
mechanisms of the old code and makes it implicitly extensible so that
other path searching functions which might look in other directories
can be added in other places.

Change-Id: I7be28e51481a06ec83997677af99927709b18003
Reviewed-on: https://gem5-review.googlesource.com/5341
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

config: expand '~' and '~user' in paths

config: rename 'file' var

Rename uses of 'file' as a local variable to avoid conflict
with the built-in type of the same name.

config: make M5_PATH a real search path

Although you can put a list of colon-separated directory names
in M5_PATH, the current code just takes the first one that
exists and assumes all files must live there. This change
makes the code search the specified list of directories
for each individual binary or disk image that's requested.

The main motivation is that the x86/Alpha binaries and the
ARM binaries are in separate downloads, and thus naturally
end up in separate directories. With this change, you can
have M5_PATH point to those two directories, then run any
FS regression test without changing M5_PATH. Currently,
you either have to merge the two download directories
or change M5_PATH (or do something else I haven't figured out).

make rcS files read from the m5 source directory, not /dist.

Two minor fixes.

configs/common/SysPaths.py:
Undo accidental change.
src/SConscript:
Fix.

Clean up configs.

configs/common/FSConfig.py:
configs/common/SysPaths.py:
configs/example/fs.py:
configs/example/se.py:
tests/configs/o3-timing-mp.py:
tests/configs/o3-timing.py:
Clean up configs by removing FullO3Config and instead using default values.
src/python/m5/objects/FUPool.py:
Add in default FUPool.
src/python/m5/objects/O3CPU.py:
Use defaults better. Also set checker parameters, and fix up a config bug.

Some reorganization. Options are all handled at the user level script. Move createCpus function (now called connectCpu) to Util.py, where it can be used by other configs.