Support assert property statement-else-statement

src/V3Assert.cpp

@@ -182,7 +182,7 @@ private:
             const bool force = VN_IS(nodep, AssertIntrinsic);
             if (passsp) passsp = newIfAssertOn(passsp, force);
             if (failsp) failsp = newIfAssertOn(failsp, force);
-            if (!failsp) failsp = newFireAssertUnchecked(nodep, "'assert' failed.");
+            if (!passsp && !failsp) failsp = newFireAssertUnchecked(nodep, "'assert' failed.");
             ifp = new AstIf{nodep->fileline(), propp, passsp, failsp};
             ifp->isBoundsCheck(true);  // To avoid LATCH warning
             // It's more LIKELY that we'll take the nullptr if clause

src/verilog.y

@@ -5772,14 +5772,13 @@ concurrent_assertion_item<nodep>:       // IEEE: concurrent_assertion_item
 concurrent_assertion_statement<nodep>:  // ==IEEE: concurrent_assertion_statement
         //                      // IEEE: assert_property_statement
         //                      // IEEE: assume_property_statement
-        //UNSUP remove below:
-                assertOrAssume yPROPERTY '(' property_spec ')' elseStmtBlock
-                        { $$ = new AstAssert{$1, new AstSampled{$1, $4}, nullptr, $6, false}; }
-        //UNSUP remove above:
         //                      // action_block expanded here
-        //UNSUP assertOrAssume yPROPERTY '(' property_spec ')' stmt %prec prLOWER_THAN_ELSE  {}
+                assertOrAssume yPROPERTY '(' property_spec ')' stmt %prec prLOWER_THAN_ELSE
-        //UNSUP assertOrAssume yPROPERTY '(' property_spec ')' stmt yELSE stmt  {}
+                        { $$ = new AstAssert{$1, new AstSampled{$1, $4}, $6, nullptr, false}; }
-        //UNSUP assertOrAssume yPROPERTY '(' property_spec ')' yELSE stmt  {}
+        |       assertOrAssume yPROPERTY '(' property_spec ')' stmt yELSE stmt
+                        { $$ = new AstAssert{$1, new AstSampled{$1, $4}, $6, $8, false}; }
+        |       assertOrAssume yPROPERTY '(' property_spec ')' yELSE stmt
+                        { $$ = new AstAssert{$1, new AstSampled{$1, $4}, nullptr, $7, false}; }
         //                      // IEEE: cover_property_statement
         |       yCOVER yPROPERTY '(' property_spec ')' stmtBlock
                         { $$ = new AstCover{$1, $4, $6, false}; }
@@ -5797,11 +5796,6 @@ concurrent_assertion_statement<nodep>:  // ==IEEE: concurrent_assertion_statemen
                         { $$ = new AstRestrict{$1, $4}; }
         ;
 
-elseStmtBlock<nodep>:   // Part of concurrent_assertion_statement
-                ';'                                     { $$ = nullptr; }
-        |       yELSE stmtBlock                         { $$ = $2; }
-        ;
-
 property_declaration<nodeFTaskp>:  // ==IEEE: property_declaration
                 property_declarationFront property_port_listE ';' property_declarationBody
                         yENDPROPERTY endLabelE

test_regress/t/t_assert_sampled.v

@@ -4,6 +4,8 @@
 // any use, without warranty, 2022 by Antmicro Ltd.
 // SPDX-License-Identifier: CC0-1.0
 
+`define checkd(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%0d exp=%0d\n", `__FILE__,`__LINE__, (gotv), (expv)); $stop; end while(0);
+
 module t (/*AUTOARG*/
    // Inputs
    clk
@@ -14,6 +16,7 @@ module t (/*AUTOARG*/
 
    Test1 t1(clk, a, b);
    Test2 t2(clk, a, b);
+   Test3 t3(clk, a, b);
 
    initial begin
       a = 0;
@@ -54,3 +57,33 @@ module Test2(
    assert property (@(posedge clk) a == b);
 
 endmodule
+
+module Test3(
+   clk, a, b
+   );
+
+   input clk;
+   input [3:0] a, b;
+
+   int         hits[10];
+
+   assert property (@(posedge clk) a == b) hits[1]=1;
+   assert property (@(posedge clk) a == b) else hits[2]=1;
+   assert property (@(posedge clk) a == b) hits[3]=1; else hits[4]=1;
+
+   assert property (@(posedge clk) a != b) hits[5]=1;
+   assert property (@(posedge clk) a != b) else hits[6]=1;
+   assert property (@(posedge clk) a != b) hits[7]=1; else hits[8]=1;
+
+   final begin
+      `checkd(hits[1], 1);
+      `checkd(hits[2], 0);
+      `checkd(hits[3], 1);
+      `checkd(hits[4], 0);
+      `checkd(hits[5], 0);
+      `checkd(hits[6], 1);
+      `checkd(hits[7], 0);
+      `checkd(hits[8], 1);
+   end
+
+endmodule