Fix COVERIGN on SVA goto repetition (#8118)

Signed-off-by: Artur Bieniek <[email protected]>

src/V3AssertNfa.cpp

@@ -912,12 +912,10 @@ class SvaNfaBuilder final {
         UASSERT_OBJ(maxN >= minN, repp, "GotoRep range max < min (V3Width invariant)");
         if (exceedsAssertUnrollLimit(repp, maxN)) return BuildResult::failWithError();
 
-        // IEEE 1800-2023 16.14.3: a ranged goto repetition b[->M:N] ends at every
-        // M..N-th match, but only the shared merge vertex below reaches the
-        // terminal, so a cover sequence would under-count. Reject the ranged form
-        // (the single-count b[->N] has one end and is enumerated correctly).
-        if (m_isCoverSeq && hasMax && maxN > minN) {
-            warnEndpointUnsupported(flp, "a ranged goto repetition");
+        if (m_isCoverSeq) {
+            // Several matches may wait across false cycles, but the NFA stores only one bit for
+            // them, so a cover sequence action block could run too few times.
+            warnEndpointUnsupported(flp, "a goto repetition");
             return BuildResult::failWithError();
         }
 

test_regress/t/t_cover_sequence_unsup.out

@@ -12,7 +12,10 @@
 %Warning-COVERIGN: t/t_cover_sequence_unsup.v:30:21: Ignoring unsupported: cover sequence with this ranged cycle delay
    30 |   cover sequence (a ##[1:300] b);
       |                     ^~
-%Warning-COVERIGN: t/t_cover_sequence_unsup.v:33:21: Ignoring unsupported: cover sequence with a ranged goto repetition
-   33 |   cover sequence (a [-> 2: 3]);
+%Warning-COVERIGN: t/t_cover_sequence_unsup.v:33:21: Ignoring unsupported: cover sequence with a goto repetition
+   33 |   cover sequence (a [-> 2]);
+      |                     ^~~
+%Warning-COVERIGN: t/t_cover_sequence_unsup.v:34:21: Ignoring unsupported: cover sequence with a goto repetition
+   34 |   cover sequence (a [-> 2: 3]);
       |                     ^~~
 %Error: Exiting due to

test_regress/t/t_cover_sequence_unsup.v

@@ -29,7 +29,8 @@ module t (
   // Ranged cycle delay wide enough to use the counter FSM.
   cover sequence (a ##[1:300] b);
 
-  // Ranged goto repetition (every M..N-th match is a separate end).
+  // Goto repetition coalesces multiple live attempts into one NFA state.
+  cover sequence (a [-> 2]);
   cover sequence (a [-> 2: 3]);
 
 endmodule