disable-iff and conditional assertion expressions should not error fo…

…r constant values The error is for degenerate sequences, but disable-iff and conditional properties are not sequences, they are properties, so the error doesn't make sense. No commercial tool errors or even warns for these.
MikePopoloski · May 27, 2024 · a65d5b9 · a65d5b9
1 parent f2d2335
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Showing 3 changed files with 9 additions and 21 deletions.
diff --git a/scripts/diagnostics.txt b/scripts/diagnostics.txt
@@ -861,8 +861,6 @@ note NoteExpandedHere "expanded here"
 note SeqAdmitsEmptyMatches "sequence property admits empty matches"
 note SeqAdmitsNoMatches "sequence property can never be matched"
 note SeqAcceptsOnlyEmptyMatches "sequence property admits only empty matches"
-note SeqPropCondAlwaysFalse "condition is always false"
-note DisableIffCondAlwaysTrue "disable iff condition is always true"
 
 subsystem Types
 error InvalidEnumBase "invalid enum base type {} (must be a single dimensional integer type)"

diff --git a/source/ast/expressions/AssertionExpr.cpp b/source/ast/expressions/AssertionExpr.cpp
@@ -1345,14 +1345,6 @@ AssertionExpr& ConditionalAssertionExpr::fromSyntax(const ConditionalPropertyExp
     if (syntax.elseClause)
         elseExpr = &bind(*syntax.elseClause->expr, context);
 
-    // If condition is a constant false value then there is never a match.
-    if (!elseExpr) {
-        if (context.tryEval(cond).isFalse()) {
-            auto& diag = context.addDiag(diag::SeqPropNondegenerate, syntax.sourceRange());
-            diag.addNote(diag::SeqPropCondAlwaysFalse, cond.sourceRange);
-        }
-    }
-
     return *comp.emplace<ConditionalAssertionExpr>(cond, ifExpr, elseExpr);
 }
 
@@ -1424,12 +1416,6 @@ AssertionExpr& DisableIffAssertionExpr::fromSyntax(const DisableIffSyntax& synta
 
     checkSampledValueExpr(cond, context, false, diag::DisableIffLocalVar, diag::DisableIffMatched);
 
-    // If condition is always true then there's never a match.
-    if (context.tryEval(cond).isTrue()) {
-        auto& diag = context.addDiag(diag::SeqPropNondegenerate, syntax.sourceRange());
-        diag.addNote(diag::DisableIffCondAlwaysTrue, cond.sourceRange);
-    }
-
     if (context.assertionInstance && context.assertionInstance->isRecursive)
         context.addDiag(diag::RecursivePropDisableIff, syntax.sourceRange());
 

diff --git a/tests/unittests/ast/AssertionTests.cpp b/tests/unittests/ast/AssertionTests.cpp
@@ -2382,7 +2382,9 @@ endmodule
         }
         else if (diags.size() != 1 || diags[0].code != code) {
             FAIL_CHECK(expr);
-            CHECK(diags[0].code == *code);
+            CHECK(diags.size() == 1);
+            if (diags.size() == 1)
+                CHECK(diags[0].code == *code);
         }
     };
 
@@ -2430,7 +2432,9 @@ endmodule
         }
         else if (diags.size() != 1 || diags[0].code != code) {
             FAIL_CHECK(expr);
-            CHECK(diags[0].code == *code);
+            CHECK(diags.size() == 1);
+            if (diags.size() == 1)
+                CHECK(diags[0].code == *code);
         }
     };
 
@@ -2508,15 +2512,13 @@ endmodule
 
     test("if (b) a ##1 c else d ##1 e");
     test("if (1'b0) a ##1 c else d ##1 e");
-    test("if (1'b0) a ##1 c", diag::SeqPropNondegenerate);
     test("if (1'b1) a ##1 c else d ##1 e");
     test("if (a) b intersect ##2 b", diag::SeqPropNondegenerate);
     test("if (a) ##2 b intersect ##2 b");
     test("case (b) 1, 2, 3: 1 ##1 b; 4: a and b; default: 1 |-> b; endcase");
     test("case (b) 1, 2, 3: 1 ##1 b; 4: a and b; default: 1[*0] |-> b; endcase",
          diag::OverlapImplNondegenerate);
     test("disable iff (clk) a");
-    test("disable iff (1'b1) a", diag::SeqPropNondegenerate);
 }
 
 TEST_CASE("Sequence nondegeneracy tests 3") {
@@ -2543,7 +2545,9 @@ endmodule
         }
         else if (diags.size() != 1 || diags[0].code != code) {
             FAIL_CHECK(expr);
-            CHECK(diags[0].code == *code);
+            CHECK(diags.size() == 1);
+            if (diags.size() == 1)
+                CHECK(diags[0].code == *code);
         }
     };