VCD tracing is now parallelized using the same thread pool as the model.
We achieve this by breaking the top level trace functions into multiple
top level functions (as many as --threads), and after emitting the time
stamp to the VCD file on the main thread, we execute the tracing
functions in parallel on the same thread pool as the model (which we
pass to the trace file during registration), tracing into a secondary
per thread buffer. The main thread will then stitch (memcpy) the buffers
together into the output file.
This makes the `--trace-threads` option redundant with `--trace`, which
now only affects `--trace-fst`. FST tracing uses the previous offloading
scheme.
This obviously helps a lot in VCD tracing performance, and I have seen
better than Amdahl speedup, namely I get 3.9x on XiangShan 4T (2.7x on
OpenTitan 4T).
This is a major re-design of the way code is scheduled in Verilator,
with the goal of properly supporting the Active and NBA regions of the
SystemVerilog scheduling model, as defined in IEEE 1800-2017 chapter 4.
With this change, all internally generated clocks should simulate
correctly, and there should be no more need for the `clock_enable` and
`clocker` attributes for correctness in the absence of Verilator
generated library models (`--lib-create`).
Details of the new scheduling model and algorithm are provided in
docs/internals.rst.
Implements #3278
The --prof-threads option has been split into two independent options:
1. --prof-exec, for collecting verilator_gantt and other execution
related profiling data, and
2. --prof-pgo, for collecting data needed for PGO
The implementation of execution profiling is extricated from
VlThreadPool and is now a separate class VlExecutionProfiler. This means
--prof-exec can now be used for single-threaded models (though it does
not measure a lot of things just yet). For consistency VerilatedProfiler
is renamed VlPgoProfiler. Both VlExecutionProfiler and VlPgoProfiler are
in verilated_profiler.{h/cpp}, but can be used completely independently.
Also re-worked the execution profile format so it now only emits events
without holding onto any temporaries. This is in preparation for some
future optimizations that would be hindered by the introduction of function
locals via AstText.
Also removed the Barrier event. Clearing the profile buffers is not
notably more expensive as the profiling records are trivially
destructible.
debug() declared by VL_DEGUB_FUNC used to cache the result of the debug
level lookup (which depends on options) in a static. This meant that if
the debug() function was called before option parsing, the default debug
level of 0 would be used for the rest of the program, even if a --debug
option was given. Fixed by not caching the debug level until after
option parsing is complete.
What previously used to be per module static constants created in
V3Table and V3Prelim are now merged globally within the whole model and
emitted as part of a separate constant pool. Members of the constant
pool are global variables which are declared lazily when used (similar to
loose methods).
Add V3OptionsParser that can suggest correct option.
Co-authored-by: Wilson Snyder <wsnyder@wsnyder.org>
Co-authored-by: github action <action@example.com>
This provides minor simulation performance benefit, but can provide
large C++ compilation time improvement, notably with Clang (4x).
This patch implements #2366 .
This adds the flag --generate-waivefile <filename>. This will generate
a verilator config file with the proper lint_off statemens to turn off
warnings emitted during this particular run.
This feature can be used to start with using Verilator as linter and
systematically capture all known lint warning for further
elimination. It hopefully helps people turning of -Wno-fatal or
-Wno-lint and gradually improve their code base.
Signed-off-by: Stefan Wallentowitz <stefan.wallentowitz@hm.edu>
Wilson Snyder
Geza Lore
Krzysztof Bieganski
Yutetsu TAKATSUKASA
Stefan Wallentowitz