Add error on soft constraints of randc

Changes

@@ -20,7 +20,7 @@ Verilator 5.031 devel
 * Add error on `wait` with missing `.triggered` (#4457).
 * Add error when improperly storing to parameter (#5147). [Gökçe Aydos]
 * Add coverage point hierarchy to coverage reports (#5575) (#5576). [Andrew Nolte]
-* Add error on `solve before` of `randc` variable.
+* Add error on `solve before` or soft constraints of `randc` variable.
 * Fix can't locate scope error in interface task delayed assignment (#5462) (#5568). [Zhou Shen]
 * Fix BLKANDNBLK for for VARXREFs (#5569). [Todd Strader]
 * Fix VPI error instead of fatal for vpi_get_value() on large signals (#5571). [Todd Strader]

src/V3AstNodeOther.h

@@ -2763,14 +2763,16 @@ public:
 class AstConstraintExpr final : public AstNodeStmt {
     // Constraint expression
     // @astgen op1 := exprp : AstNodeExpr
-    bool m_isSoft = false;  // Soft constraint expression
     bool m_isDisableSoft = false;  // Disable soft constraint expression
+    bool m_isSoft = false;  // Soft constraint expression
 public:
     AstConstraintExpr(FileLine* fl, AstNodeExpr* exprp)
         : ASTGEN_SUPER_ConstraintExpr(fl) {
         this->exprp(exprp);
     }
     ASTGEN_MEMBERS_AstConstraintExpr;
+    void dump(std::ostream& str) const override;
+    void dumpJson(std::ostream& str) const override;
     bool isGateOptimizable() const override { return false; }
     bool isPredictOptimizable() const override { return false; }
     bool same(const AstNode* /*samep*/) const override { return true; }

src/V3AstNodes.cpp

@@ -376,6 +376,16 @@ void AstConstraint::dumpJson(std::ostream& str) const {
     dumpJsonBoolFunc(str, isStatic);
     dumpJsonGen(str);
 }
+void AstConstraintExpr::dump(std::ostream& str) const {
+    this->AstNode::dump(str);
+    if (isDisableSoft()) str << " [DISSOFT]";
+    if (isSoft()) str << " [SOFT]";
+}
+void AstConstraintExpr::dumpJson(std::ostream& str) const {
+    dumpJsonBoolFunc(str, isDisableSoft);
+    dumpJsonBoolFunc(str, isSoft);
+    dumpJsonGen(str);
+}
 AstConst* AstConst::parseParamLiteral(FileLine* fl, const string& literal) {
     bool success = false;
     if (literal[0] == '"') {

src/V3Randomize.cpp

@@ -131,7 +131,9 @@ class RandomizeMarkVisitor final : public VNVisitor {
 
     BaseToDerivedMap m_baseToDerivedMap;  // Mapping from base classes to classes that extend them
     AstClass* m_classp = nullptr;  // Current class
-    AstNode* m_constraintExprp = nullptr;  // Current constraint expression
+    AstConstraintBefore* m_constraintBeforep = nullptr;  // Current before constraint
+    AstConstraintExpr* m_constraintExprp = nullptr;  // Current constraint expression
+    AstNode* m_constraintExprGenp = nullptr;  // Current constraint or constraint if expression
     AstNodeModule* m_modp;  // Current module
     AstNodeStmt* m_stmtp = nullptr;  // Current statement
     std::set<AstNodeVarRef*> m_staticRefs;  // References to static variables under `with` clauses
@@ -402,50 +404,57 @@ class RandomizeMarkVisitor final : public VNVisitor {
         }
     }
     void visit(AstConstraintBefore* nodep) override {
-        nodep->foreach([&](AstVarRef* const refp) {
-            if (refp->varp() && refp->varp()->isRandC()) {
-                nodep->v3error(
-                    "Randc variables not allowed in 'solve before' (IEEE 1800-2023 18.5.9)");
-            }
-        });
+        VL_RESTORER(m_constraintBeforep);
+        m_constraintBeforep = nodep;
         iterateChildrenConst(nodep);
     }
     void visit(AstConstraintExpr* nodep) override {
         VL_RESTORER(m_constraintExprp);
         m_constraintExprp = nodep;
+        VL_RESTORER(m_constraintExprGenp);
+        m_constraintExprGenp = nodep;
         iterateChildrenConst(nodep);
     }
     void visit(AstConstraintIf* nodep) override {
         {
-            VL_RESTORER(m_constraintExprp);
-            m_constraintExprp = nodep;
+            VL_RESTORER(m_constraintExprGenp);
+            m_constraintExprGenp = nodep;
             iterateConst(nodep->condp());
         }
         iterateAndNextConstNull(nodep->thensp());
         iterateAndNextConstNull(nodep->elsesp());
     }
     void visit(AstNodeVarRef* nodep) override {
-        if (!m_constraintExprp) return;
+        if (nodep->varp()->isRandC()) {
+            if (m_constraintExprp && m_constraintExprp->isSoft()) {
+                nodep->v3error(
+                    "Randc variables not allowed in 'constraint soft' (IEEE 1800-2023 18.5.13.1)");
+            } else if (m_constraintBeforep) {
+                nodep->v3error(
+                    "Randc variables not allowed in 'solve before' (IEEE 1800-2023 18.5.9)");
+            }
+        }
+        if (!m_constraintExprGenp) return;
 
         if (nodep->varp()->lifetime().isStatic()) m_staticRefs.emplace(nodep);
 
         if (!nodep->varp()->rand().isRandomizable()) return;
-        for (AstNode* backp = nodep; backp != m_constraintExprp && !backp->user1();
+        for (AstNode* backp = nodep; backp != m_constraintExprGenp && !backp->user1();
              backp = backp->backp())
             backp->user1(true);
     }
     void visit(AstMemberSel* nodep) override {
-        if (!m_constraintExprp) return;
+        if (!m_constraintExprGenp) return;
         if (VN_IS(nodep->fromp(), LambdaArgRef)) {
             if (!nodep->varp()->rand().isRandomizable()) return;
-            for (AstNode* backp = nodep; backp != m_constraintExprp && !backp->user1();
+            for (AstNode* backp = nodep; backp != m_constraintExprGenp && !backp->user1();
                  backp = backp->backp())
                 backp->user1(true);
         }
     }
     void visit(AstArraySel* nodep) override {
-        if (!m_constraintExprp) return;
-        for (AstNode* backp = nodep; backp != m_constraintExprp && !backp->user1();
+        if (!m_constraintExprGenp) return;
+        for (AstNode* backp = nodep; backp != m_constraintExprGenp && !backp->user1();
              backp = backp->backp())
             backp->user1(true);
         iterateChildrenConst(nodep);

test_regress/t/t_randomize_before_randc_bad.out

@@ -1,5 +1,5 @@
-%Error: t/t_randomize_before_randc_bad.v:11:29: Randc variables not allowed in 'solve before' (IEEE 1800-2023 18.5.9)
+%Error: t/t_randomize_before_randc_bad.v:11:45: Randc variables not allowed in 'solve before' (IEEE 1800-2023 18.5.9)
                                               : ... note: In instance 't'
    11 |     constraint raint2_bad { solve b1 before b2; }   
-      |                             ^~~~~
+      |                                             ^~
 %Error: Exiting due to

test_regress/t/t_randomize_soft_randc_bad.out

@@ -0,0 +1,5 @@
+%Error: t/t_randomize_soft_randc_bad.v:10:28: Randc variables not allowed in 'constraint soft' (IEEE 1800-2023 18.5.13.1)
+                                            : ... note: In instance 't'
+   10 |    constraint c_bad { soft rc > 4; }   
+      |                            ^~
+%Error: Exiting due to

test_regress/t/t_randomize_soft_randc_bad.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2024 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('linter')
+
+test.lint(fails=test.vlt_all, expect_filename=test.golden_filename)
+
+test.passes()

test_regress/t/t_randomize_soft_randc_bad.v

@@ -0,0 +1,14 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+class Cls1;
+   randc int rc;
+
+   constraint c_bad { soft rc > 4; }  // Bad, no soft on randc
+endclass
+
+module t (/*AUTOARG*/);
+endmodule