Adds timing support to Verilator. It makes it possible to use delays,
event controls within processes (not just at the start), wait
statements, and forks.
Building a design with those constructs requires a compiler that
supports C++20 coroutines (GCC 10, Clang 5).
The basic idea is to have processes and tasks with delays/event controls
implemented as C++20 coroutines. This allows us to suspend and resume
them at any time.
There are five main runtime classes responsible for managing suspended
coroutines:
* `VlCoroutineHandle`, a wrapper over C++20's `std::coroutine_handle`
with move semantics and automatic cleanup.
* `VlDelayScheduler`, for coroutines suspended by delays. It resumes
them at a proper simulation time.
* `VlTriggerScheduler`, for coroutines suspended by event controls. It
resumes them if its corresponding trigger was set.
* `VlForkSync`, used for syncing `fork..join` and `fork..join_any`
blocks.
* `VlCoroutine`, the return type of all verilated coroutines. It allows
for suspending a stack of coroutines (normally, C++ coroutines are
stackless).
There is a new visitor in `V3Timing.cpp` which:
* scales delays according to the timescale,
* simplifies intra-assignment timing controls and net delays into
regular timing controls and assignments,
* simplifies wait statements into loops with event controls,
* marks processes and tasks with timing controls in them as
suspendable,
* creates delay, trigger scheduler, and fork sync variables,
* transforms timing controls and fork joins into C++ awaits
There are new functions in `V3SchedTiming.cpp` (used by `V3Sched.cpp`)
that integrate static scheduling with timing. This involves providing
external domains for variables, so that the necessary combinational
logic gets triggered after coroutine resumption, as well as statements
that need to be injected into the design eval function to perform this
resumption at the correct time.
There is also a function that transforms forked processes into separate
functions.
See the comments in `verilated_timing.h`, `verilated_timing.cpp`,
`V3Timing.cpp`, and `V3SchedTiming.cpp`, as well as the internals
documentation for more details.
Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>
Fix compile error for queue method usage, if it is the
first statement in a block of code, and the return
value is not used. Example:
> if (foo)
> void'(bar.pop_front());
* Tests: Add a test to reproduce #3399
* Fix#3399. When reading an inout port in a module, it should refer the
original inout port, not the generated MODTEMP.
vcddiff is a bit broken, and sometimes 'vcddiff a b' fails while the
files are indeed equivalent. There is a chance however that 'vcddif b a'
will succeed in this case, so compare trace files both ways when
checking test results and claim success if vcddiff succeeds in at least
one direction.
* Tests: Add a test to reproduce #3509
* Tests: Compile without tautological-compare check because bit op tree optimization is disabled in the test.
* Internals: Dedup code. No functional change is intended.
* Fix#3509.
"2'b10 == (2'b11 & {1'b0, val[0]})" and "2'b10 != (2'b11 & {1'b0, val[0]})" were
wrongly optimized to "!val[0]" and "val[0]" respectively.
Now properly optimize them to 1'b0 and 1'b1.
* Commentary
* Commentary: Update Changes
These have been 'deprecated' for 2 years and are otherwise unused except
for using a temporary placeholder value, which I have inlined with the
default value.
Also remove the now VL_TIME_STR_CONVERT utility function (and
corresponding unit tests), which have no references in any project on
GitHub.
Associative arrays that specify a wildcard index type may be indexed by
integral expressions of any size, with leading zeros removed
automatically. A natural representation for such expressions is a
string, especially that the standard explicitly specifies automatic
casts from string indices to bit vectors of equivalent size.
The automatic cast part is done implicitly by the existing type system.
A simpler way to just make this work would be to convert wildcard index
type to a string type directly in the parser code, but several new AST
classes are needed to make sure illegal method calls are detected.
The verilated data structure implementation is reused, because there is
no need for differentiating the behavior on C++ side.
Step towards a proper run-time library. Reduce the amount of ifdefs in
the implementation of offloaded tracing. There are still a very small
number of ifdefs left, which will need more careful changes in order to
keep user API compatibility.
