Allow the formal engine to perform a same-cycle result in the ALU

This adds an exception to holding o_valid low, when the ALU is idle.
If a write to the ALU just occurred, allow o_valid to become high, in
the same cycle.

diff --git a/src/soc/experiment/formal/proof_compalu_multi.py b/src/soc/experiment/formal/proof_compalu_multi.py
index bf6d2615b8142c15561cc63ca946ce718547e227..96b61a2b6a0375d37347a5ba19d675900ef97a40 100644 (file)
--- a/src/soc/experiment/formal/proof_compalu_multi.py
+++ b/src/soc/experiment/formal/proof_compalu_multi.py
@@ -153,7 +153,7 @@ class CompALUMultiTestCase(FHDLTestCase):
             m.d.sync += cnt.eq(cnt + do_masked_read[i])
             cnt_masked_read.append(cnt)
         # If the ALU is idle, do not assert valid
-        with m.If(cnt_alu_read == cnt_alu_write):
+        with m.If((cnt_alu_read == cnt_alu_write) & ~do_alu_write):
             m.d.comb += Assume(~alu.n.o_valid)
         # Keep ALU valid high, until read
         last_alu_valid = Signal()