ASLR-dependent ConstEval seeding let E4 miss OOR counterexamples; use a
deterministic seed and force OOR key collisions. Add I9 (NB=12) for the
thermometer fallback path Greptile flagged.
Co-authored-by: Cursor <cursoragent@cursor.com>
Prove the three pattern detectors work on unseen inputs, not just the RTL
they were derived from. Because detection is functional (ConstEval
fingerprinting over the reachable input space), correctness is established
per case with equiv_opt -assert (full) or a SAT miter clamped to the
reachable range (non-power-of-two), and detection is confirmed with a
w:*tag* probe.
opt_priokey:
D1-D3 spelling variants (explicit shift-or set, compound derived guard,
accumulator also exported) -- all fire and prove equivalent.
E1-E2 parameter sweep P=2..8, S=4..32.
E3 non-power-of-two S=12 reachable-range equivalence via SAT miter.
E4 same shape under -strict declines to rewrite (formal-flow safety).
F1-F2 near-miss negatives (clear accumulator, multi-hot set) -> no rewrite.
opt_prienc (round-robin):
RR4-RR5 DEPTH sweep 8/32, full sequential equivalence.
RR6 non-power-of-two DEPTH=7 reachable-range equivalence (SAT miter).
RR7 an entirely different spelling (upward wrap-scan, first-hit) of the
same arbiter -- fires and proves equivalent.
RR8 fixed-priority (no rotating pointer) negative.
opt_first_fit_alloc (coalesce):
H1 inline same-category compare (no precomputed matrix) spelling.
H2 different slot/field shape (N=8, NB=8, W=3).
All new cases pass locally; they avoid brittle exact cell-count asserts so
they are robust to upstream optimization drift.
Co-authored-by: Cursor <cursoragent@cursor.com>
Extend two existing opt passes and add one new pass to collapse
serial/dynamic-index structures that were leaving high logic depth:
- opt_first_fit_alloc: recognize the "coalesce-matrix" first-fit
allocator variant (same_cat[i][k] coalescing gated on the leader's
enable, driven from a raw input enable). Rewrite both the lane_slot
allocation and the xbar field gather from one shared log-depth scan.
- opt_prienc: detect round-robin / rotated-priority scans (req scanned
from idx_last downward with wraparound) and rewrite the depth-N
idx--/req[idx] mux chain to rotate -> log-depth priority-encode ->
unrotate.
- opt_priokey (new): recognize priority-by-key one-hot accumulators and
replace each dynamic taken[key] read ($shiftx/$bmux) with the
equivalent pairwise-key-compare reduction, dropping the wide dynamic
indexing. Supports -strict for full-key-range formal validation.
Each includes self-contained tests (equiv_opt / sat -prove-asserts,
mux-bound and negative cases) in tests/opt/.
Co-authored-by: Cursor <cursoragent@cursor.com>
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.
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
