Support disable soft constraint

include/verilated_random.cpp

@@ -746,6 +746,12 @@ void VlRandomizer::soft(std::string&& constraint, const char* /*filename*/, uint
     m_softConstraints.emplace_back(std::move(constraint));
 }
 
+void VlRandomizer::disable_soft(std::string&& constraint) {
+    m_softConstraints.erase(
+        std::remove(m_softConstraints.begin(), m_softConstraints.end(), constraint),
+        m_softConstraints.end());
+}
+
 void VlRandomizer::clearConstraints() {
     m_constraints.clear();
     m_constraints_line.clear();

include/verilated_random.h

@@ -596,6 +596,7 @@ public:
               const char* source = "");
     void soft(std::string&& constraint, const char* filename = "", uint32_t linenum = 0,
               const char* source = "");
+    void disable_soft(std::string&& constraint);
     void clearConstraints();
     void clearAll();  // Clear both constraints and variables
     void markRandc(const char* name);  // Mark variable as randc for cyclic tracking

src/V3AstAttr.h

@@ -814,6 +814,7 @@ public:
         RANDOMIZER_BASIC_STD_RANDOMIZATION,
         RANDOMIZER_CLEARCONSTRAINTS,
         RANDOMIZER_CLEARALL,
+        RANDOMIZER_DISABLE_SOFT,
         RANDOMIZER_HARD,
         RANDOMIZER_SOFT,
         RANDOMIZER_UNIQUE,
@@ -951,6 +952,7 @@ inline std::ostream& operator<<(std::ostream& os, const VCMethod& rhs) {
            {RANDOMIZER_BASIC_STD_RANDOMIZATION, "basicStdRandomization", false}, \
            {RANDOMIZER_CLEARCONSTRAINTS, "clearConstraints", false}, \
            {RANDOMIZER_CLEARALL, "clearAll", false}, \
+           {RANDOMIZER_DISABLE_SOFT, "disable_soft", false}, \
            {RANDOMIZER_HARD, "hard", false}, \
            {RANDOMIZER_SOFT, "soft", false}, \
            {RANDOMIZER_UNIQUE, "rand_unique", false}, \

src/V3Randomize.cpp

@@ -1920,35 +1920,38 @@ class ConstraintExprVisitor final : public VNVisitor {
             VL_DO_DANGLING(nodep->deleteTree(), nodep);
             return;
         }
-        // Emit as soft or hard constraint per IEEE 1800-2017 18.5.13
-        const VCMethod method
-            = nodep->isSoft() ? VCMethod::RANDOMIZER_SOFT : VCMethod::RANDOMIZER_HARD;
+        // Emit as soft, hard, or disable_soft per IEEE 1800-2017 18.5.13
+        const VCMethod method = nodep->isDisableSoft() ? VCMethod::RANDOMIZER_DISABLE_SOFT
+                                : nodep->isSoft()      ? VCMethod::RANDOMIZER_SOFT
+                                                        : VCMethod::RANDOMIZER_HARD;
         AstCMethodHard* const callp = new AstCMethodHard{
             nodep->fileline(),
             new AstVarRef{nodep->fileline(), VN_AS(m_genp->user2p(), NodeModule), m_genp,
                           VAccess::READWRITE},
             method, nodep->exprp()->unlinkFrBack()};
         callp->dtypeSetVoid();
-        // Pass filename, lineno, and source as separate arguments
-        // This allows EmitC to call protect() on filename, similar to VL_STOP
-        // Add filename parameter
-        callp->addPinsp(new AstCExpr{nodep->fileline(), AstCExpr::Pure{},
-                                     "\"" + nodep->fileline()->filename() + "\""});
-        // Add line number parameter
-        const uint32_t lineno = static_cast<uint32_t>(nodep->fileline()->lineno());
-        callp->addPinsp(new AstConst{nodep->fileline(), lineno});
-        // Add source text parameter (empty if --protect-ids to avoid source leakage)
-        std::string prettyText;
-        if (!v3Global.opt.protectIds()) {
-            prettyText = nodep->fileline()->prettySource();
-            size_t pos = 0;
-            while ((pos = prettyText.find('"', pos)) != std::string::npos) {
-                prettyText.insert(pos, "\\");
-                pos += std::strlen("\\\"");
+        if (!nodep->isDisableSoft()) {
+            // Pass filename, lineno, and source as separate arguments
+            // This allows EmitC to call protect() on filename, similar to VL_STOP
+            // Add filename parameter
+            callp->addPinsp(new AstCExpr{nodep->fileline(), AstCExpr::Pure{},
+                                         "\"" + nodep->fileline()->filename() + "\""});
+            // Add line number parameter
+            const uint32_t lineno = static_cast<uint32_t>(nodep->fileline()->lineno());
+            callp->addPinsp(new AstConst{nodep->fileline(), lineno});
+            // Add source text parameter (empty if --protect-ids to avoid source leakage)
+            std::string prettyText;
+            if (!v3Global.opt.protectIds()) {
+                prettyText = nodep->fileline()->prettySource();
+                size_t pos = 0;
+                while ((pos = prettyText.find('"', pos)) != std::string::npos) {
+                    prettyText.insert(pos, "\\");
+                    pos += std::strlen("\\\"");
+                }
             }
+            callp->addPinsp(
+                new AstCExpr{nodep->fileline(), AstCExpr::Pure{}, "\"" + prettyText + "\""});
         }
-        callp->addPinsp(
-            new AstCExpr{nodep->fileline(), AstCExpr::Pure{}, "\"" + prettyText + "\""});
         nodep->replaceWith(callp->makeStmt());
         VL_DO_DANGLING(nodep->deleteTree(), nodep);
     }

test_regress/t/t_randomize.v

@@ -44,8 +44,7 @@ class Packet;
 
    constraint dis {
       soft sublength;
-      // TODO: disable soft not yet supported, treated as hard constraint
-      // disable soft sublength;
+      disable soft sublength;
       sublength <= length;
    }