follow comments and refine

src/V3Randomize.cpp

@@ -3534,7 +3534,14 @@ class RandomizeVisitor final : public VNVisitor {
                 buckets.push_back({ditemp->rangep(), weightExprp});
             }
 
-            if (buckets.empty()) continue;
+            if (buckets.empty()) {
+                // All weights are zero: dist is vacuously true (unconstrained)
+                AstConstraintExpr* const truep
+                    = new AstConstraintExpr{fl, new AstConst{fl, AstConst::BitTrue{}}};
+                constrExprp->replaceWith(truep);
+                VL_DO_DANGLING(pushDeletep(constrExprp), constrExprp);
+                continue;
+            }
 
             // Build totalWeight expression: w[0] + w[1] + ... + w[N-1]
             AstNodeExpr* totalWeightExprp = nullptr;
@@ -3556,6 +3563,7 @@ class RandomizeVisitor final : public VNVisitor {
             totalVarp->noSubst(true);
             totalVarp->lifetime(VLifetime::AUTOMATIC_EXPLICIT);
             totalVarp->funcLocal(true);
+            totalVarp->isInternal(true);
             taskp->addStmtsp(totalVarp);
             taskp->addStmtsp(
                 new AstAssign{fl, new AstVarRef{fl, totalVarp, VAccess::WRITE}, totalWeightExprp});
@@ -3567,6 +3575,7 @@ class RandomizeVisitor final : public VNVisitor {
             bucketVarp->noSubst(true);
             bucketVarp->lifetime(VLifetime::AUTOMATIC_EXPLICIT);
             bucketVarp->funcLocal(true);
+            bucketVarp->isInternal(true);
             taskp->addStmtsp(bucketVarp);
 
             AstNodeExpr* randp = new AstRand{fl, nullptr, false};
@@ -3629,16 +3638,16 @@ class RandomizeVisitor final : public VNVisitor {
 
             if (chainp) {
                 constrExprp->replaceWith(chainp);
-                VL_DO_DANGLING(constrExprp->deleteTree(), constrExprp);
+                VL_DO_DANGLING(pushDeletep(constrExprp), constrExprp);
             }
 
             // Clean up nodes used only as clone templates (never inserted into tree)
             for (auto& bucket : buckets) {
-                VL_DO_DANGLING(bucket.weightExprp->deleteTree(), bucket.weightExprp);
+                VL_DO_DANGLING(pushDeletep(bucket.weightExprp), bucket.weightExprp);
             }
-            VL_DO_DANGLING(runningSump->deleteTree(), runningSump);
+            VL_DO_DANGLING(pushDeletep(runningSump), runningSump);
             // Last cumSum is unused (last bucket is unconditional default)
-            VL_DO_DANGLING(cumSums.back()->deleteTree(), cumSums.back());
+            pushDeletep(cumSums.back());
         }
     }
 
@@ -3658,6 +3667,7 @@ class RandomizeVisitor final : public VNVisitor {
     void visit(AstClass* nodep) override {
         VL_RESTORER(m_modp);
         VL_RESTORER(m_randCaseNum);
+        VL_RESTORER(m_distNum);
         m_modp = nodep;
         m_randCaseNum = 0;
         m_distNum = 0;

test_regress/t/t_constraint_dist_weight.v

@@ -25,6 +25,11 @@ class DistZeroWeight;
   constraint c { x dist { 8'd0 := 0, 8'd1 := 1, 8'd2 := 1 }; }
 endclass
 
+class DistAllZeroWeight;
+  rand bit [7:0] x;
+  constraint c { x dist { 8'd0 := 0, 8'd1 := 0, 8'd2 := 0 }; }
+endclass
+
 class DistVarWeight;
   rand bit [7:0] x;
   int w1, w2;
@@ -42,6 +47,7 @@ module t;
     DistScalar sc;
     DistRange rg;
     DistZeroWeight zw;
+    DistAllZeroWeight azw;
     DistVarWeight vw;
     DistVarWeightRange vwr;
     int count_high;
@@ -58,7 +64,7 @@ module t;
       if (sc.x == 8'd255) count_high++;
       else `checkd(sc.x, 0);
     end
-    `check_range(count_high, 1200, 1800);
+    `check_range(count_high, total * 60 / 100, total * 90 / 100);
 
     // :/ range weights: expect ~75% in [10:19]
     rg = new;
@@ -71,7 +77,7 @@ module t;
         `stop;
       end
     end
-    `check_range(count_range_high, 1200, 1800);
+    `check_range(count_range_high, total * 60 / 100, total * 90 / 100);
 
     // Zero weight: value 0 must never appear
     zw = new;
@@ -84,6 +90,12 @@ module t;
       `check_range(zw.x, 1, 2);
     end
 
+    // All-zero weights: dist constraint is effectively unconstrained, randomize succeeds
+    azw = new;
+    repeat (20) begin
+      `checkd(azw.randomize(), 1);
+    end
+
     // Variable := scalar weights: w1=1, w2=3 => expect ~75% for value 255
     vw = new;
     vw.w1 = 1;
@@ -94,7 +106,7 @@ module t;
       if (vw.x == 8'd255) count_high++;
       else `checkd(vw.x, 0);
     end
-    `check_range(count_high, 1200, 1800);
+    `check_range(count_high, total * 60 / 100, total * 90 / 100);
 
     // Variable :/ range weights: w1=1, w2=3 => expect ~75% in [10:19]
     vwr = new;
@@ -109,7 +121,7 @@ module t;
         `stop;
       end
     end
-    `check_range(count_range_high, 1200, 1800);
+    `check_range(count_range_high, total * 60 / 100, total * 90 / 100);
 
     $write("*-* All Finished *-*\n");
     $finish;

test_regress/t/t_randomize.py

@@ -9,8 +9,13 @@
 
 import vltest_bootstrap
 
-test.scenarios('vlt')
+test.scenarios('simulator')
 
-test.lint()
+if not test.have_solver:
+    test.skip("No constraint solver installed")
+
+test.compile()
+
+test.execute()
 
 test.passes()

test_regress/t/t_randomize.v

@@ -11,7 +11,7 @@ class Packet;
    rand bit if_4;
    rand bit iff_5_6;
 
-   /*rand*/ int array[2];  // 2,4,6  // TODO: add rand when supported
+   rand int array[2];  // 2,4,6
 
    constraint empty {}
 
@@ -58,7 +58,7 @@ module t;
 
       automatic int v;
       automatic bit if_4 = '0;
-      // TODO not testing constrained values
+      p = new;
       v = p.randomize();
       if (v != 1) $stop;
       v = p.randomize() with {};