Fix mixed-width inside and dist range bounds failing randomization (#7875)

src/V3Randomize.cpp

@@ -4453,6 +4453,39 @@ class RandomizeVisitor final : public VNVisitor {
         return new AstConstraintIf{fl, condp, thenBodyp, nullptr};
     }
 
+    static bool distBoundRefsRandVar(const AstNode* boundp) {
+        bool found = false;
+        boundp->foreach([&](const AstVarRef* vrefp) {
+            if (vrefp->varp()->rand().isRandomizable()) found = true;
+        });
+        return found;
+    }
+
+    // (distExpr >= lo) && (distExpr <= hi); signed comparisons for signed vars
+    static AstNodeExpr* newDistRangeMembership(AstDist* distp, const AstInsideRange* irp) {
+        FileLine* const fl = distp->fileline();
+        const bool isSigned = distp->exprp()->isSigned();
+        AstNodeExpr* const distExprGtep = distp->exprp()->cloneTreePure(false);
+        AstNodeExpr* const distExprLtep = distp->exprp()->cloneTreePure(false);
+        distExprGtep->user1(true);
+        distExprLtep->user1(true);
+        AstNodeExpr* const gep
+            = isSigned ? static_cast<AstNodeExpr*>(
+                             new AstGteS{fl, distExprGtep, irp->lhsp()->cloneTreePure(false)})
+                       : static_cast<AstNodeExpr*>(
+                             new AstGte{fl, distExprGtep, irp->lhsp()->cloneTreePure(false)});
+        AstNodeExpr* const lep
+            = isSigned ? static_cast<AstNodeExpr*>(
+                             new AstLteS{fl, distExprLtep, irp->rhsp()->cloneTreePure(false)})
+                       : static_cast<AstNodeExpr*>(
+                             new AstLte{fl, distExprLtep, irp->rhsp()->cloneTreePure(false)});
+        gep->user1(true);
+        lep->user1(true);
+        AstNodeExpr* const andp = new AstLogAnd{fl, gep, lep};
+        andp->user1(true);
+        return andp;
+    }
+
     // Replace AstDist with weighted bucket selection via AstConstraintIf chain.
     // Supports both constant and variable weight expressions.
     void lowerDistConstraints(AstTask* taskp, AstNode* constrItemsp,
@@ -4577,25 +4610,7 @@ class RandomizeVisitor final : public VNVisitor {
             for (const auto& bucket : buckets) {
                 AstNodeExpr* memberp;
                 if (const AstInsideRange* const irp = VN_CAST(bucket.rangep, InsideRange)) {
-                    // (distExpr >= lo) && (distExpr <= hi); signed comparisons for signed vars
+                    memberp = newDistRangeMembership(distp, irp);
-                    const bool isSigned = distp->exprp()->isSigned();
-                    AstNodeExpr* const distExprGtep = distp->exprp()->cloneTreePure(false);
-                    AstNodeExpr* const distExprLtep = distp->exprp()->cloneTreePure(false);
-                    distExprGtep->user1(true);
-                    distExprLtep->user1(true);
-                    AstNodeExpr* const gep
-                        = isSigned ? static_cast<AstNodeExpr*>(new AstGteS{
-                                         fl, distExprGtep, irp->lhsp()->cloneTreePure(false)})
-                                   : static_cast<AstNodeExpr*>(new AstGte{
-                                         fl, distExprGtep, irp->lhsp()->cloneTreePure(false)});
-                    AstNodeExpr* const lep
-                        = isSigned ? static_cast<AstNodeExpr*>(new AstLteS{
-                                         fl, distExprLtep, irp->rhsp()->cloneTreePure(false)})
-                                   : static_cast<AstNodeExpr*>(new AstLte{
-                                         fl, distExprLtep, irp->rhsp()->cloneTreePure(false)});
-                    gep->user1(true);
-                    lep->user1(true);
-                    memberp = new AstLogAnd{fl, gep, lep};
                 } else {
                     // distExpr == val
                     AstNodeExpr* const distExprCopyp = distp->exprp()->cloneTreePure(false);
@@ -4673,7 +4688,13 @@ class RandomizeVisitor final : public VNVisitor {
             AstNode* chainp = nullptr;
             for (int i = static_cast<int>(buckets.size()) - 1; i >= 0; --i) {
                 AstNodeExpr* constraintExprp;
-                if (const AstInsideRange* const irp = VN_CAST(buckets[i].rangep, InsideRange)) {
+                const AstInsideRange* const irp = VN_CAST(buckets[i].rangep, InsideRange);
+                if (irp
+                    && (distBoundRefsRandVar(irp->lhsp()) || distBoundRefsRandVar(irp->rhsp()))) {
+                    // Bounds solved concurrently cannot pin a pre-solve value; softly
+                    // prefer the symbolic range so the hard membership stays satisfiable
+                    constraintExprp = newDistRangeMembership(distp, irp);
+                } else if (irp) {
                     // Pick distExpr = lo + rand64() % (hi - lo + 1) for a uniform value in range
                     AstNodeExpr* const distExprCopyp = distp->exprp()->cloneTreePure(false);
                     distExprCopyp->user1(true);

src/V3Width.cpp

@@ -3464,10 +3464,12 @@ class WidthVisitor final : public VNVisitor {
         for (AstNode *nextip, *itemp = nodep->itemsp(); itemp; itemp = nextip) {
             nextip = itemp->nextp();
             itemp = VN_AS(itemp, DistItem)->rangep();
-            // InsideRange will get replaced with Lte&Gte and finalized later
+            if (VN_IS(itemp, InsideRange)) {
-            if (!VN_IS(itemp, InsideRange))
+                userIterate(itemp, WidthVP{subDTypep, FINAL}.p());
+            } else {
                 iterateCheck(nodep, "Dist Item", itemp, CONTEXT_DET, FINAL, subDTypep, EXTEND_EXP);
             }
+        }
 
         // Inside a constraint, V3Randomize handles dist lowering with proper weights,
         // but only for simple scalar/range items. Container-type items (queues, arrays)
@@ -3541,11 +3543,13 @@ class WidthVisitor final : public VNVisitor {
                      EXTEND_EXP);
         for (AstNode *nextip, *itemp = nodep->itemsp(); itemp; itemp = nextip) {
             nextip = itemp->nextp();  // iterate may cause the node to get replaced
-            // InsideRange will get replaced with Lte&Gte and finalized later
+            if (VN_IS(itemp, InsideRange)) {
-            if (!VN_IS(itemp, InsideRange) && !itemp->dtypep()->isNonPackedArray())
+                userIterate(itemp, WidthVP{expDTypep, FINAL}.p());
+            } else if (!itemp->dtypep()->isNonPackedArray()) {
                 iterateCheck(nodep, "Inside Item", itemp, CONTEXT_DET, FINAL, expDTypep,
                              EXTEND_EXP);
             }
+        }
 
         AstNodeExpr* exprp;
         AstExprStmt* exprStmtp = nullptr;
@@ -3636,9 +3640,26 @@ class WidthVisitor final : public VNVisitor {
             V3Const::constifyEdit(nodep->lhsp());  // lhsp may change
             V3Const::constifyEdit(nodep->rhsp());  // rhsp may change
         } else {
+            if (m_vup->prelim()) {
                 userIterateAndNext(nodep->lhsp(), m_vup);
                 userIterateAndNext(nodep->rhsp(), m_vup);
             }
+            if (m_vup->final()) {
+                AstNodeDType* const expDTypep = m_vup->dtypeOverridep(nodep->dtypep());
+                // Warning waivers match visit_cmp_eq_gt on the lowered Gte/Lte
+                const int expWidth = expDTypep->width();
+                const bool waiveLhs = expWidth == 32
+                                      && !(expDTypep->isSigned() && nodep->lhsp()->isSigned())
+                                      && expDTypep->widthMin() >= nodep->lhsp()->width();
+                const bool waiveRhs = expWidth == 32
+                                      && !(expDTypep->isSigned() && nodep->rhsp()->isSigned())
+                                      && expWidth >= nodep->rhsp()->widthMin();
+                iterateCheck(nodep, "Range LHS", nodep->lhsp(), CONTEXT_DET, FINAL, expDTypep,
+                             EXTEND_EXP, !waiveLhs);
+                iterateCheck(nodep, "Range RHS", nodep->rhsp(), CONTEXT_DET, FINAL, expDTypep,
+                             EXTEND_EXP, !waiveRhs);
+            }
+        }
         nodep->dtypeFrom(nodep->lhsp());
     }
 

test_regress/t/t_constraint_inside_impl_mixwidth.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+if not test.have_solver:
+    test.skip("No constraint solver installed")
+
+test.compile()
+
+test.execute()
+
+test.passes()

test_regress/t/t_constraint_inside_impl_mixwidth.v

@@ -0,0 +1,155 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 PlanV GmbH
+// SPDX-License-Identifier: CC0-1.0
+
+// verilog_format: off
+`define stop $stop
+`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);
+// verilog_format: on
+
+// verilator lint_off WIDTHEXPAND
+class Impl;
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    y != 0 -> x inside {[y - g : y]};
+  }
+endclass
+
+class Neg;  // inside under logical-not
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    y != 0 -> !(x inside {[y - g : y - 1]});
+  }
+endclass
+
+class LAnd;  // inside as a logical-and operand
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    (x inside {[y - g : y]}) && (x[0] == 1'b0);
+  }
+endclass
+
+class Nest;  // nested implication a -> (b -> inside)
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  rand bit a, b;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    a == 1;
+    b == 1;
+    a -> (b -> x inside {[y - g : y]});
+  }
+endclass
+
+class CondCtx;  // inside as a ?: condition
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  rand bit s;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    (x inside {[y - g : y]}) ? (s == 1'b1) : (s == 1'b0);
+  }
+endclass
+
+class Ctl;  // all-32-bit control
+  rand bit [31:0] x, y, g;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 32'h100;
+    y != 0 -> x inside {[y - g : y]};
+  }
+endclass
+
+class DistRange;  // mixed-width dist range bound
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    x dist {
+      [y - g : y] := 1,
+      5 := 1
+    };
+  }
+endclass
+
+class Bare;  // bare narrow variable as a bound
+  rand bit [63:0] x, y;
+  rand bit [31:0] g;
+  constraint c {
+    g inside {[1 : 10]};
+    y == 64'h100;
+    y != 0 -> x inside {[g : y]};
+  }
+endclass
+
+module t;
+  Impl im;
+  Neg ng;
+  LAnd la;
+  Nest ne;
+  CondCtx cx;
+  Ctl ct;
+  DistRange dr;
+  Bare br;
+  int ok;
+  initial begin
+    im = new;
+    ng = new;
+    la = new;
+    ne = new;
+    cx = new;
+    ct = new;
+    dr = new;
+    br = new;
+    for (int i = 0; i < 20; ++i) begin
+      ok = im.randomize();
+      `checkd(ok, 1);
+      if (im.x < (64'h100 - im.g) || im.x > 64'h100) `checkd(0, 1);
+
+      ok = ng.randomize();
+      `checkd(ok, 1);
+      if (ng.x >= (64'h100 - ng.g) && ng.x <= 64'hFF) `checkd(0, 1);
+
+      ok = la.randomize();
+      `checkd(ok, 1);
+      if (la.x < (64'h100 - la.g) || la.x > 64'h100 || la.x[0] !== 1'b0) `checkd(0, 1);
+
+      ok = ne.randomize();
+      `checkd(ok, 1);
+      if (ne.x < (64'h100 - ne.g) || ne.x > 64'h100) `checkd(0, 1);
+
+      ok = cx.randomize();
+      `checkd(ok, 1);
+      if (cx.s !== ((cx.x >= (64'h100 - cx.g)) && (cx.x <= 64'h100))) `checkd(0, 1);
+
+      ok = ct.randomize();
+      `checkd(ok, 1);
+      if (ct.x < (32'h100 - ct.g) || ct.x > 32'h100) `checkd(0, 1);
+
+      ok = dr.randomize();
+      `checkd(ok, 1);
+      if (dr.x != 5 && (dr.x < (64'h100 - dr.g) || dr.x > 64'h100)) `checkd(0, 1);
+
+      ok = br.randomize();
+      `checkd(ok, 1);
+      if (br.x < {32'h0, br.g} || br.x > 64'h100) `checkd(0, 1);
+    end
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule
+// verilator lint_on WIDTHEXPAND