Fix `disable iff` in simple properties (#6890)

src/V3Assert.cpp

@@ -697,7 +697,11 @@ class AssertVisitor final : public VNVisitor {
             m_inSampled = true;
             iterateChildren(nodep);
         }
-        nodep->replaceWith(nodep->exprp()->unlinkFrBack());
+        if (nodep->exprp()) {
+            nodep->replaceWith(nodep->exprp()->unlinkFrBack());
+        } else {
+            nodep->unlinkFrBack();
+        }
         VL_DO_DANGLING(pushDeletep(nodep), nodep);
     }
     void visit(AstVarRef* nodep) override {

src/V3AssertPre.cpp

@@ -632,6 +632,11 @@ private:
         // Unlink and just keep a pointer to it, convert to sentree as needed
         m_senip = nodep->sensesp();
         iterateNull(nodep->disablep());
+        if (VN_AS(nodep->backp(), NodeCoverOrAssert)->type() == VAssertType::CONCURRENT) {
+            const AstNodeDType* const propDtp = nodep->propp()->dtypep();
+            nodep->propp(new AstSampled{nodep->fileline(), nodep->propp()->unlinkFrBack()});
+            nodep->propp()->dtypeFrom(propDtp);
+        }
         iterate(nodep->propp());
     }
     void visit(AstPExpr* nodep) override {

src/verilog.y

@@ -6353,11 +6353,11 @@ concurrent_assertion_statement<nodeStmtp>:  // ==IEEE: concurrent_assertion_stat
         //                      // IEEE: assume_property_statement
         //                      // action_block expanded here
                 assertOrAssume yPROPERTY '(' property_spec ')' stmt %prec prLOWER_THAN_ELSE
-                        { $$ = new AstAssert{$<fl>1, new AstSampled{$<fl>1, $4}, $6, nullptr, VAssertType::CONCURRENT, $1}; }
+                        { $$ = new AstAssert{$<fl>1, $4, $6, nullptr, VAssertType::CONCURRENT, $1}; }
         |       assertOrAssume yPROPERTY '(' property_spec ')' stmt yELSE stmt
-                        { $$ = new AstAssert{$<fl>1, new AstSampled{$<fl>1, $4}, $6, $8, VAssertType::CONCURRENT, $1}; }
+                        { $$ = new AstAssert{$<fl>1, $4, $6, $8, VAssertType::CONCURRENT, $1}; }
         |       assertOrAssume yPROPERTY '(' property_spec ')' yELSE stmt
-                        { $$ = new AstAssert{$<fl>1, new AstSampled{$<fl>1, $4}, nullptr, $7, VAssertType::CONCURRENT, $1}; }
+                        { $$ = new AstAssert{$<fl>1, $4, nullptr, $7, VAssertType::CONCURRENT, $1}; }
         //                      // IEEE: cover_property_statement
         |       yCOVER yPROPERTY '(' property_spec ')' stmt
                         { $$ = new AstCover{$1, $4, $6, VAssertType::CONCURRENT}; }

test_regress/t/t_assert_disable_iff.v

@@ -4,55 +4,61 @@
 // without warranty, 2019 by Peter Monsson.
 // SPDX-License-Identifier: CC0-1.0
 
-module t (/*AUTOARG*/
-   // Inputs
-   clk
-   );
+module t (  /*AUTOARG*/
+    // Inputs
+    clk
+);
 
-   input clk;
-   int cyc;
+  input clk;
+  int cyc;
 
-   Test test (/*AUTOINST*/
-              // Inputs
-              .clk                      (clk));
+  Test test (  /*AUTOINST*/
+      // Inputs
+      .clk(clk),
+      .cyc(cyc)
+  );
 
-   always @(posedge clk) begin
-      cyc <= cyc + 1;
-      if (cyc == 10) begin
-         $write("*-* All Finished *-*\n");
-         $finish;
-      end
-   end
+  always @(posedge clk) begin
+    cyc <= cyc + 1;
+    if (cyc == 10) begin
+      $write("*-* All Finished *-*\n");
+      $finish;
+    end
+  end
 
 endmodule
 
 module Test (
-    input clk
+    input clk,
+    input int cyc
 );
 
 `ifdef FAIL_ASSERT_1
-   assert property (@(posedge clk) disable iff (0) 0)
-   else $display("wrong disable");
+  assert property (@(posedge clk) disable iff (0) 0)
+  else $display("wrong disable");
 `endif
 
-   assert property (@(posedge clk) disable iff (1) 0) $stop;
-   else $stop;
+  assert property (@(posedge clk) disable iff (1) 0) $stop;
+  else $stop;
 
-   assert property (@(posedge clk) disable iff (1) 1) $stop;
-   else $stop;
+  assert property (@(posedge clk) disable iff (1) 1) $stop;
+  else $stop;
 
-   assert property (@(posedge clk) disable iff (0) 1);
+  assert property (@(posedge clk) disable iff (0) 1);
 
-   //
-   // Cover properties behave differently
-   //
+  // Pass 1st cycle
+  assert property (@(cyc) disable iff (cyc != $sampled(cyc)) cyc == 0);
 
-   cover property (@(posedge clk) disable iff (1) 1) $stop;
+  //
+  // Cover properties behave differently
+  //
 
-   cover property (@(posedge clk) disable iff (1) 0) $stop;
+  cover property (@(posedge clk) disable iff (1) 1) $stop;
 
-   cover property (@(posedge clk) disable iff (0) 1) $display("*COVER: ok");
+  cover property (@(posedge clk) disable iff (1) 0) $stop;
 
-   cover property (@(posedge clk) disable iff (0) 0) $stop;
+  cover property (@(posedge clk) disable iff (0) 1) $display("*COVER: ok");
+
+  cover property (@(posedge clk) disable iff (0) 0) $stop;
 
 endmodule