This patch addresses two issues with NBAs in non-inlined functions/tasks:
- If the NBA writes to a local automatic var, the var could cease to exist before the NBA executes. This is normally addressed by fork dynscopes (#4356), but NBA-to-fork transformation happens way after `V3Fork` (in `V3Timing`). To solve this, we put NBAs that write to locals under forks in `V3Fork` already. This way, such locals will be put in dynscopes, and will still exist after the task containing the NBA exits.
- The above change means that any writes in forks other than `fork..join` should be handled by `V3Fork`. Thus, in `V3SchedTiming`, we only have to worry about read references, so we can simply copy all remaining locals. Because we copy, lifetimes are not an issue. This fixes a bug that allowed assignment intravals to be overwritten if they go out of scope in the containing function.
This saves about 5% memory. V3AstUserAllocator is appropriate for most use
cases, performance is marginally up as we are mostly D-cache bound on
large designs.
Multiple edge timing controls in class methods would cause compilation errors on
the generated C++ code. This is because the `SenExprBuilder` used for these
would get recreated per timing control, resulting in duplicate variable names.
The fix is to have a single `SenExprBuilder` per scope.
Multiple edge timing controls in class methods would cause compilation errors on the generated C++ code. This is because the `SenExprBuilder` used for these would get recreated per timing control, resulting in duplicate variable names. The fix is to have a single `SenExprBuilder` per scope.
Event-triggered coroutines live in two stages: 'uncommitted' and 'ready'. First
they land in 'uncommitted', meaning they can't be resumed yet. Only after
coroutines from the 'ready' queue are resumed, the 'uncommitted' ones are moved
to the 'ready' queue, and can be resumed. This is to avoid self-triggering in
situations like waiting for an event immediately after triggering it.
However, there is an issue with `wait` statements. If you have a `wait(b)`, it's
being translated into a loop that awaits a change in `b` as long as `b` is
false. If `b` is false at first, the coroutine is put into the `uncommitted`
queue. If `b` is set to true before it's committed, the coroutine won't get
resumed.
This patch fixes that by immediately committing event controls created from
`wait` statements. That means the coroutine from the example above will get
resumed from now on.
This makes the implementation of the detection and propagation of the
suspendable property simpler and easier to read. More importantly, there are no
more jumps around the AST with the `visit` functions, which in some cases could
result in incorrect visitor context while in the `visit` function. See the added
test, which would cause Verilator to segfault before this patch.
In testing, verilation performance was not shown to be affected by this change.
Though there is a slight performance improvement from this patch, due to adding
one more check before refreshing class member cache.
Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>
Wilson Snyder
Geza Lore
Krzysztof Bieganski
Arkadiusz Kozdra
Szymon Gizler
Krzysztof Boroński
Aleksander Kiryk
github action
Mariusz Glebocki
Ryszard Rozak