systemc: Separate and conditionalize exposing sc_main to python.

Change-Id: Ib39dd79c607b277ba94f90dee41c09c1b3b66481
Reviewed-on: https://gem5-review.googlesource.com/c/13978
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

systemc: Seperate out the sc_main fiber and its bookkeeping.

By pulling out the sc_main fiber (scMainFiber), we can make it
available to different entities in the simulator and avoid having to
have parallel bookkeeping.

Also this will make it possible to hook into sc_main without putting
the code in sc_main.cc.

Change-Id: I7689441424238e9b2e4d2b48e945dea35fd8cc5d
Reviewed-on: https://gem5-review.googlesource.com/c/13977
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Switch to using predefined messages for core.

Create and use predefined messages for core which match the ones
Accellera uses.

Change-Id: I05b1398933f753946d5917f39d0f39c7cb45ed9f
Reviewed-on: https://gem5-review.googlesource.com/c/13323
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Refactor reporting to prep for int based messages.

There's a deprecated reporting mechanism based on integer message ids,
and the reporting mechanism needs to be refactored a bit to make it
easier to support.

Some bookkeeping data structures were moved out to somewhere they
can be accessed by other code, obviating the non-standard get_handler
function.

Change-Id: Id427cd79be9ef0f3275fbac39ff047ab672fb3e0
Reviewed-on: https://gem5-review.googlesource.com/c/13318
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Use the "catch action" and the handler func outside sc_main.

If an exception escapes sc_main, Accellera catches it and feeds it
into the report handler, telling it to run the catch actions. This
seems like it sets up lots of dangerous scenarios, and also makes a
vital error detecting path more complex and error prone.

On the other hand, it makes one of the tests pass.

Change-Id: I7f9d07e01e63c7abeee903febe2e434041ec49a4
Reviewed-on: https://gem5-review.googlesource.com/c/13307
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Modify reportifyException to keep sc_reports in scope.

reportifyException was sometimes indirectly creating temporary
sc_report objects which would go out of scope when they were
returned. The later code which tried to print them would then read
garbage.

Change-Id: I0a744eb029c62bf2ffee83db0a0e6dcbe3e60f7d
Reviewed-on: https://gem5-review.googlesource.com/c/13190
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Simplify sc_time_stamp().

sc_time is now inherently based on properly scaled Ticks, so there's no
reason to try to scale it to be in picoseconds, especially since the
scaling factor may be unreliable if the timescale hasn't been fixed
yet.

Change-Id: I28baeb9792e81e1d00f6f37672df435766311864
Reviewed-on: https://gem5-review.googlesource.com/c/12974
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Warn if sc_stop is called more than once.

Change-Id: Ief88b9af0119ba4b007f79905db2522b5f95b820
Reviewed-on: https://gem5-review.googlesource.com/c/12811
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Fortify how exceptions are caught and passed around.

This change tightens up exception catching and makes gem5's systemc
code react to exceptions more in line with the Accellera
implementation. This prevents exceptions from being caught by the
pybind11 integration which makes it very difficult to see where an
exception came from, and makes the output differ by including a
(mostly useless) backtrace.

Change-Id: I7130d53a98fadd137073d1718f780f32f57c658c
Reviewed-on: https://gem5-review.googlesource.com/c/12601
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Handle sc_stop called from sc_main correctly.

When in sc_main, sc_is_running will return true but we're not going
to run any gem5 events since we're currently in the sc_main Fiber. In
that case, we need to do the sc_stop work inline.

If we're actually running and not just paused, then we do still want to
schedule the work of sc_stop to happen as its own event since that will
happen before returning to sc_main, and actually will likely be the
mechanism by which sc_main starts executing again.

Change-Id: If9ffafc4f240af0f3d9c726b36a0950b5219dc00
Reviewed-on: https://gem5-review.googlesource.com/12269
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Check for time overflow in sc_start.

A regression tests checks this situation.

Change-Id: I7716bf7c8cf219c372ab9722fc0ad52e7e674b17
Reviewed-on: https://gem5-review.googlesource.com/12256
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Handle sc_time_stamp before any sc_time is constructed.

The time resolution won't yet be fixed, so the scaling factor will
still be set to zero.

Change-Id: I1d1e58316ee05cc477a31ce90e2bbf56dcbc65c3
Reviewed-on: https://gem5-review.googlesource.com/12255
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Keep track of how sc_main completes and expose that to python.

That makes it possible for the config script to retrieve the result of
running sc_main. sc_main (or at least the python front end for it)
can't return results directly since it usually doesn't run to
completion when it's first called.

Change-Id: I9740e9688571e2ca824a684be70480f1eadddcdb
Reviewed-on: https://gem5-review.googlesource.com/12253
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: If sc_main returns, don't do any more systemc stuff.

When sc_main returns, clear out any pending work in the scheduler and
also block the systemc kernel from doing actions which correspond with
the start of simulation.

It's most likely that work like oustanding timeouts might survive past
the end of sc_main, especially if it never officially called sc_stop.
It's also possible for sc_main to return and never actually call
sc_start. In that case, the kernel should not call callbacks of the
various objects (which may no longer even exist), or go through the
initialization phase.

If sc_main is never called at all, then the kernel's actions aren't
gated.

Change-Id: I49bf094be3283a92d846d2f3da224950bd893a5c
Reviewed-on: https://gem5-review.googlesource.com/12249
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: When sc_start is told to run zero time, do one delta cycle.

This is a special case which is mentioned in the spec but hadn't yet
been given any special handling in this implementation.

Change-Id: I500d046f09d916a08e22821f8d3e2f490f8ba5bb
Reviewed-on: https://gem5-review.googlesource.com/12212
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add a nonstandard sc_status pretty printer operator.

This operator exists in the Accellera implementation, and is necessary
to make the test output match.

Change-Id: I266629d6c936d4846e88e35af36555fb392b181c
Reviewed-on: https://gem5-review.googlesource.com/12074
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Generalize working with the systemc python module from C++.

This change pulls the systemc python module creation code out of
sc_main and puts it into a more general purpose python.hh and
python.cc which can be used by other code to add other entries into
that module without having to track that in a central place.

This change also adds a mechanism for notifying C++ code that the
embedded python interpretter is up and ready to interact with in case
it needs to call some python only functionality. An example of that is
the code which tracks and then fixes the timescale for the simulator.

Change-Id: I9afcd5a089b21d23ebc1b5fdb6f643ae2f7e5f11
Reviewed-on: https://gem5-review.googlesource.com/12069
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Make some functions of the kernel static.

This makes it possible to call them without having to have a kernel
instance available. The kernel is a singleton anyway, so there should
only ever be a single instance of any of these values.

Change-Id: I3610d60cc72e9f3114997fe63db94b96ccaac3cd
Reviewed-on: https://gem5-review.googlesource.com/12041
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement the various sc_module stage callbacks.

This change also gets rid of the SystemC namespace which was
deprecated in favor of sc_gem5.

A few utility functions which check whether certain callbacks have
finished were also implemented. status tracking moved from a global
variable in sc_main.cc to a member of the kernel simobject.

Change-Id: I50967fae9c576fbe45b1faff587aaa824857a289
Reviewed-on: https://gem5-review.googlesource.com/12033
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement pending activity related functions

Track the number of notifications/timeouts that are scheduled at any
given time. This lets us implement sc_pending_activity_at_current_time,
sc_pending_activity_at_future_time, and sc_time_to_pending_activity.

Change-Id: Ia3fcd29bdbfe1a6c77eb52ce4836982d4705263c
Reviewed-on: https://gem5-review.googlesource.com/12032
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement sc_pause, sc_stop, and re-sc_start-ing.

This change further modifies the scheduler to implement the sc_pause
and sc_stop functions, and to ensure that calling sc_start again works.
Also, some small changes were made to how processes and contexts are
hooked up. Now, rather than checking whether a process is running to
determine wether it started on its own or needs to be started manually,
there's a bool which explicitly tracks whether it needs this step. The
problem was that once a thread finished, it wasn't considered running
any more. In that case it had run but finished, but that was
indistinguishable from it needing to run but not having been started.

Change-Id: I3aefb5493f91d9efa1a1382586196339b67925fe
Reviewed-on: https://gem5-review.googlesource.com/12031
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Hook up sc_time_stamp sc_delta_count.

sc_time_stamp reports the current simulation time. sc_delta_count was
hooked up to a dummy value. This change hooks it up to the scheduler so
that it returns the real value.

Change-Id: I354c4be32161eabeea86af653f5cb0a5d384645b
Reviewed-on: https://gem5-review.googlesource.com/11712
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Get sc_main to work even when dynamically linked.

Unfortunately multiply defined weak symbols don't work like they're
supposed to when the different versions are across dynamic linking
boundaries.

Fortunately, a weak symbol with no definition at all will still
consistently evaluate as 0, and a singularly defined weak symbol will
still resolve correctly.

Instead of relying on a weak version of sc_main being overridden by a
strong/non-default definition, this change leaves it as undefined and
detects at run time whether the symbol resolves to 0 or to an actual
code location.

Change-Id: I31c4ff769b0c52277c6cf4845ca3f85000009583
Reviewed-on: https://gem5-review.googlesource.com/11610
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Make sc_main run in its own fiber.

The fiber will run until either sc_main returns, or until sc_start is
called. If sc_start is called, then the fiber will only be paused and
waiting for simulation cycles to be run by gem5. Once sc_pause and
sc_stop are implemented, if those are called the sc_main fiber will
be re-entered and allowed to run further towards completion.

Change-Id: I4df94f4f6fed8d49471732619a203d734d9a13a6
Reviewed-on: https://gem5-review.googlesource.com/10849
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement some simple accessor functions in sc_main.cc.

These functions just read or write values with minimal amounts of
logic.

Change-Id: I22d5b49a2550a88a854d1619f08b0055c1312271
Reviewed-on: https://gem5-review.googlesource.com/10847
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add some missing functions which interact with the scheduler.

Change-Id: Ifc8c8d4a7bb6e941485e80f4884cfa4bb648c17c
Reviewed-on: https://gem5-review.googlesource.com/10846
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Seperate the "external" header interface.

Most (but not all) of the SystemC headers are part of the "external"
interface that an existing, standard compliant module would include
through <systemc.h> or <systemc>. Since those follow slightly different
rules (relative includes, no gem5 includes), this change separates them
out so that they're easier to identify.

Also, this change moves the other files into a "core" subdirectory,
with the intention to add a "dt", aka data type, directory some time in
the future when those standard defined types are implemented.

Change-Id: Ida63f9cc0bc0431024d4dd691cc5b22b944a99a8
Reviewed-on: https://gem5-review.googlesource.com/10835
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>