Support soft foreach in constraint (#8174)

src/V3AstNodeStmt.h

@@ -1675,10 +1675,16 @@ public:
 // === AstNodeForeach ===
 class AstConstraintForeach final : public AstNodeForeach {
     // Constraint foreach statement
+    bool m_soft;  // is soft foreach, non-standard extension
 public:
-    AstConstraintForeach(FileLine* fl, AstForeachHeader* headerp, AstNode* bodyp)
-        : ASTGEN_SUPER_ConstraintForeach(fl, headerp, bodyp) {}
+    AstConstraintForeach(FileLine* fl, AstForeachHeader* headerp, AstNode* bodyp,
+                         bool soft = false)
+        : ASTGEN_SUPER_ConstraintForeach(fl, headerp, bodyp)
+        , m_soft{soft} {}
     ASTGEN_MEMBERS_AstConstraintForeach;
+    bool isSoft() const { return m_soft; }
+    void dump(std::ostream& str) const override;
+    void dumpJson(std::ostream& str) const override;
 };
 class AstForeach final : public AstNodeForeach {
 public:

src/V3AstNodes.cpp

@@ -2307,6 +2307,14 @@ void AstCover::dumpJson(std::ostream& str) const {
     dumpJsonBoolFuncIf(str, isSeqEvent);
     this->AstNodeCoverOrAssert::dumpJson(str);
 }
+void AstConstraintForeach::dump(std::ostream& str) const {
+    this->AstNodeForeach::dump(str);
+    if (isSoft()) str << "[SOFT]";
+}
+void AstConstraintForeach::dumpJson(std::ostream& str) const {
+    dumpJsonBoolFuncIf(str, isSoft);
+    dumpJsonGen(str);
+}
 void AstClocking::dump(std::ostream& str) const {
     this->AstNode::dump(str);
     if (isDefault()) str << " [DEFAULT]";

src/V3LinkParse.cpp

@@ -298,6 +298,12 @@ class LinkParseVisitor final : public VNVisitor {
         v3Global.useRandomizeMethods(true);
         iterateChildren(nodep);
     }
+    void visit(AstConstraintForeach* nodep) override {
+        if (nodep->isSoft()) {
+            nodep->v3warn(NONSTD, "Non-standard soft foreach");
+            nodep->foreach([](AstConstraintExpr* exprp) { exprp->isSoft(true); });
+        }
+    }
     void visit(AstEnumDType* nodep) override {
         if (nodep->name() == "") {
             nodep->name(nameFromTypedef(nodep));  // Might still remain ""

src/verilog.y

@@ -8166,6 +8166,9 @@ constraint_expression<nodep>:  // ==IEEE: constraint_expression
         //                      // IEEE says array_identifier here, but dotted accepted in VMM + 1800-2009
         |       yFOREACH '(' idClassSelForeach ')' constraint_set
                         { $$ = new AstConstraintForeach{$1, $3, $5}; }
+        //                      // Non-IEEE extension, soft foreach
+        |       ySOFT yFOREACH '(' idClassSelForeach ')' constraint_set
+                        { $$ = new AstConstraintForeach{$2, $4, $6, true}; }
         //                      // soft is 1800-2012
         |       yDISABLE ySOFT constraint_primary ';'
                         { AstConstraintExpr* const newp = new AstConstraintExpr{$1, $3};