The aiger2 backend checks for unsupported cells during indexing. This
causes it to fail when `$connect` or `$tribuf` (as workaround for
missing 'z-$buf support) cells are present in the module.
Since bufnorm adds these cells automatically, it is very easy to end up
with them due to unconnected wires or e.g. `$specify` cells, which do
not pose an actual problem for the backend, since it will never
encounter those during a traversal.
With this, we ignore them during indexing and only produce an actual error
message if we reach such a cell during the traversal.
This makes the Verilog backend handle the $connect and $input_port
cells. This represents the undirected $connect cell using the `tran`
primitive, so we also extend the frontend to support this.
The $input_port cell is added by the bufnorm code to simplify handling
of input ports for new code that uses bufnorm, but the aiger2 backend
does already handle input ports separately, so we just ignore those.
With the previous bufnorm implementation inout ports were not supported
at all, so this didn't matter, but with the new bufnorm implementation
they need to be treated as output ports.
Checking only happens at compile time if -std=c++20 (or greater) is enabled. Otherwise
the checking happens at run time.
This requires the format string to be a compile-time constant (when compiling with
C++20), so fix a few places where that isn't true.
The format string behavior is a bit more lenient than C printf. For %d/%u
you can pass any integer type and it will be converted and output without
truncating bits, i.e. any length specifier is ignored and the conversion is
always treated as 'll'. Any truncation needs to be done by casting the argument itself.
For %f/%g you can pass anything that converts to double, including integers.
Performance results with clang 19 -O3 on Linux:
```
hyperfine './yosys -dp "read_rtlil /usr/local/google/home/rocallahan/Downloads/jpeg.synth.il; dump"'
```
C++17 before: Time (mean ± σ): 101.3 ms ± 0.8 ms [User: 85.6 ms, System: 15.6 ms]
C++17 after: Time (mean ± σ): 98.4 ms ± 1.2 ms [User: 82.1 ms, System: 16.1 ms]
C++20 before: Time (mean ± σ): 100.9 ms ± 1.1 ms [User: 87.0 ms, System: 13.8 ms]
C++20 after: Time (mean ± σ): 97.8 ms ± 1.4 ms [User: 83.1 ms, System: 14.7 ms]
The generated code is reasonably efficient. E.g. with clang 19, `stringf()` with a format
with no %% escapes and no other parameters (a weirdly common case) often compiles to a fully
inlined `std::string` construction. In general the format string parsing is often (not always)
compiled away.
If you have a large design with a lot of modules and you use the Verilog
backend to emit modules one at a time to separate files, performance is
very low. The problem is that the Verilog backend calls `design->sort()`
every time, which sorts the contents of all modules, and this is slow
even when everything is already sorted.
We can easily fix this by only sorting the contents of modules that
we're actually going to emit.
Update experimental pass warnings to use a shared function. Reduces repetition, and also allows all of the warning flags to be combined (which at present is just experimental and the new internal).
Update `test_*` passes to call `internal()` in their constructors.
Akash Levy
Jannis Harder
Robert O'Callahan
Akash Levy
Emil J
Hongce Zhang
Krystine Sherwin
Miodrag Milanović
N. Engelhardt
George Rennie