Add CI pipeline for formal verification

* Add formal verification tests with sby to CI
* Fix reviewdog having insufficient API permissions

See-also: #15
Signed-off-by: Warrick Lo <wlo@warricklo.net>

1 files changed, 23 insertions, 0 deletions

diff --git a/dv/formal/simple_alu/README.md b/dv/formal/simple_alu/README.md
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+# simple_alu Formal Verification
+
+Run with: `sby -f simple_alu.sby` from this directory.
+
+Reference: https://yosyshq.readthedocs.io/projects/sby/en/latest/reference.html
+
+## Mode
+
+Bounded Model Check (BMC, depth=100): proves assertions hold for the first 100 clock cycles.
+A counterexample waveform is generated on failure.
+
+Prove mode (k-induction): proves assertions hold for infinite time. Much stronger guarantee but harder to converge. Change `mode bmc` to `mode prove` in the `.sby` to use it.
+
+## Properties
+
+| Name              | Status      | Description                              |
+|-------------------|-------------|------------------------------------------|
+| `a_rst_check`     | implemented | y == 0 one cycle after reset asserts     |
+| `a_rst_overflow`  | planned     | overflow == 0 one cycle after reset      |
+| `a_add`           | planned     | y == a+b one cycle after sel=0           |
+| `a_sub`           | planned     | y == a-b one cycle after sel=1           |
+| `a_overflow_add`  | planned     | overflow correct for addition            |
+| `a_overflow_sub`  | planned     | overflow correct for subtraction         |
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