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 <[email protected]>
* EmitXml: Added <ccall>, <constpool>, <initarray>/<inititem>, wrapped children of <if> and <while> with <begin> elements to prevent ambiguity
* EmitXml: added signed="true" to signed basicdtypes
When using a "if" statement inside an always block, part of the code may
be unreachable. This can be used to avoid errors, but it generated an
error, this commit demotes this to a warning. Partly fixes#2625.
Wilson Snyder
Aleksander Kiryk
Varun Koyyalagunta
Krzysztof Bieganski
Ryszard Rozak
Mostafa Gamal
Gustav Svensk
William D. Jones
Arkadiusz Kozdra
Mariusz Glebocki
Huanghuang Zhou
Martin Stadler
Kamil Rakoczy
Yoda Lee
Aliaksei Chapyzhenka
Xi Zhang
Drew Ranck
Chuxuan Wang
Larry Doolittle
Jamie Iles
Raynard Qiao
Guokai Chen
HungMingWu
Adrien Le Masle
Michaël Lefebvre
Julie Schwartz
Teng Huang
Zhanglei Wang
Keith Colbert
Iru Cai
Daniel Bates
Ivan Vnučec
Steven Hugg
Felix Yan
Martin Schmidt
Miodrag Milanović
Ameya Vikram Singh
Jonathan Drolet
Graham Rushton
David Metz
Udi Finkelstein
Drew Taussig
David Turner
Andreas Kuster
Àlex Torregrosa
Morten Borup Petersen
Samuel Riedel
Pierre-Henri Horrein
Paul Wright