These updates should not be necessary. In fact, if they were necessary, this code
would be buggy, because the results would depend on the order in which wires are traversed:
If wire A is retained, which causes an update to `used_signals`, which then causes wire B
to be retained when it otherwise wouldn't be, then we would get different results depending
on whether A is visited before B.
These updates will also make it difficult to process these wires in parallel.
The negation here is confusing. The intent of the code is "if `s1` is preferred
over `s2` as the canonical `SigBit` for this signal, make `s1` the canonical `SigBit`
in `assign_map`", so write the code that way instead of "if `s2` is not preferred
over `s1` ...".
This doesn't change any behavior now that `compare_signals()` is a total order,
i.e. `s1` is preferred over `s2`, `s2` is preferred over `s1`, or `s1` and `s2` are equal.
Now, when `s1` and `s2` are equal, we don't call `assign_map.add(s1)`, but that's
already a noop in that case.
Currently when `s1` and `s2` are different bits of the same wire,
it is possible for both `compare_signals(s1, s2)` and `compare_signals(s2, s1)` to
return false. This means the calling code will call `assign_map.add()` for
both `s1` and `s2`, which doesn't make much sense --- one of `s1` or `s2`
should be consistently preferred.
So fix that by preferring the `SigBit` with the smaller bit offset.
Change from equality check to >= to allow cells where output
is wider than natural width (zero-extended). Only reject cells
with Y_WIDTH < natural width (truncated).
This fixes test failures while still preventing the truncation
issue identified in widlarizer's feedback.
Only allow rebalancing of cells with "natural" output widths (no truncation).
This prevents equivalence failures when moving operands between adders
with different intermediate truncation points.
For each operation type, the natural width is:
- Addition: max(A_WIDTH, B_WIDTH) + 1 (for carry bit)
- Multiplication: A_WIDTH + B_WIDTH
- Logic ops: max(A_WIDTH, B_WIDTH)
Fixes widlarizer's counterexample in YosysHQ/yosys#5605 where an 8-bit
intermediate wire was intentionally truncating adder results, and
rebalancing would change where that truncation occurred.
This pass converts cascaded chains of arithmetic and logic cells ($add,
$mul, $and, $or, $xor) into balanced binary trees to improve timing
performance in hardware synthesis.
The optimization uses a breadth-first search approach to identify chains
of compatible cells, then recursively constructs balanced trees that
reduce the critical path depth.
Features:
- Supports arithmetic cells: $add, $mul
- Supports logic cells: $and, $or, $xor
- Command-line options: -arith (arithmetic only), -logic (logic only)
- Preserves signed/unsigned semantics
- Comprehensive test suite with 30 test cases
Original implementation by Akash Levy <akash@silimate.com> for Silimate.
Upstreamed from https://github.com/Silimate/yosys
I am getting weird crashes on `main` in `tests/sdc/alu_sub.ys` which I traced to a null `Wire*`
in `SdcObjects::constrained_ports`. The null `Wire*` is being set in the `SdcObjects`
constructor. I don't understand what's going on here, so I added this check to detect the
missing wire early ... and that made the crash go away. Compiler bug maybe? I have
`Debian clang version 19.1.7 (3+build5)`, default build configuration.
Anyway this code seems fine to have.
I'm not sure why but this is actually faster than existing `opt_merge` even with
YOSYS_MAX_THREADS=1, for the jpeg synthesis test. 16.0s before, 15.5s after for
end-to-end synthesis.
This avoids changing `assign_map` and `initvals`, which are inputs to the hash function for `known_cells`,
while `known_cells` exists. Changing the hash function for a hashtable while it exists leads to
confusing behavior. That also means the exact behavior of `opt_merge` cannot be reproduced by a
parallel implementation.
When IdString refcounting was expensive, it made sense to pass it by const reference
instead of by value, to avoid refcount churn. Now that IdString is not refcounted,
it's slightly more efficient to pass it by value.
Some cells (e.g. $macc_v2) are marked evaluable, but will raise an abort if called with `CellTypes::eval()`.
Instead of falling through to the abort, we can pass a pointer to a boolean to check for errors.
Use said check to catch `CellTypes::eval()` errors and treat them as unevaluable but otherwise continue.
Reflows the series of if checks into `if ... else if ... else` so that we can check for errors and set state in one place.
Fixes these build errors I'm getting locally with `tcl-devel-9.0.0-7.fc42.x86_64`.
I guess Tcl 9 broke this.
```
passes/cmds/sdc/sdc.cc:438:6: error: no matching function for call to 'Tcl_ListObjLength'
438 | if (Tcl_ListObjLength(interp, listObj, &listLength) == TCL_OK) {
| ^~~~~~~~~~~~~~~~~
/usr/include/tclDecls.h:1788:13: note: candidate function not viable: no known conversion from 'int *' to 'Tcl_Size *' (aka 'long *') for 3rd argument
1788 | EXTERN int Tcl_ListObjLength(Tcl_Interp *interp,
| ^
1789 | Tcl_Obj *listPtr, Tcl_Size *lengthPtr);
| ~~~~~~~~~~~~~~~~~~~
passes/cmds/sdc/sdc.cc:446:8: error: no matching function for call to 'Tcl_ListObjLength'
446 | if (Tcl_ListObjLength(interp, subListObj, &subListLength) == TCL_OK) {
| ^~~~~~~~~~~~~~~~~
/usr/include/tclDecls.h:1788:13: note: candidate function not viable: no known conversion from 'int *' to 'Tcl_Size *' (aka 'long *') for 3rd argument
1788 | EXTERN int Tcl_ListObjLength(Tcl_Interp *interp,
| ^
1789 | Tcl_Obj *listPtr, Tcl_Size *lengthPtr);
| ~~~~~~~~~~~~~~~~~~~
```
This uses the environment variable `YOSYS_PLUGIN_PATH` to provide multiple colon-delimited search paths for native plugins in a similar manner to `PATH` for executables and `PYTHONPATH` for Python modules.
This addresses https://github.com/YosysHQ/yosys/issues/2545, allowing Yosys to be better packaged in non-FHS environments such as Nix.
We were performing the helper passes `abc9_ops -replace_zbufs` and
`abc9_ops -restore_zbufs` for every module, but those passes act on the
full design (and can't be applied entirely selectively due to entering
and leaving bufnorm).
This lead to an explosive creation of a lot of redundant bufnorm helper
cells that would have been cleaned up by `clean` but that never ran.
Instead we now run each helper pass once, one before and one after
iterating over the selected modules. This limits the number of bufnorm
helper cells.
For consistency.
Also trying a new thing: only rebuilding objects that use the pybind11 library. The idea is these are the only objects that include the Python/pybind headers and thus the only ones that depend on the Python ABI in any capacity, so other objects can be reused across wheel builds. This has the potential to cut down build times.
- Rewrite all Python features to use the pybind11 library instead of boost::python.
Unlike boost::python, pybind11 is a header-only library that is just included by Pyosys code, saving a lot of compile time on wheels.
- Factor out as much "translation" code from the generator into proper C++ files
- Fix running the embedded interpreter not supporting "from pyosys import libyosys as ys" like wheels
- Move Python-related elements to `pyosys` directory at the root of the repo
- Slight shift in bridging semantics:
- Containers are declared as "opaque types" and are passed by reference to Python - many methods have been implemented to make them feel right at home without the overhead/ambiguity of copying to Python and then copying back after mutation
- Monitor/Pass use "trampoline" pattern to support virual methods overridable in Python: virtual methods no longer require `py_` prefix
- Create really short test set for pyosys that just exercises basic functionality