From 155dcc56585fd5c900dd1a69c151c0c4c49b0c65 Mon Sep 17 00:00:00 2001
From: Krzysztof Bieganski <kbieganski@antmicro.com>
Date: Tue, 27 Aug 2024 15:39:36 +0200
Subject: [PATCH] Fix empty `foreach` in `if` in constraints (#5408)

Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>
---
 src/V3Randomize.cpp                   | 4 +++-
 test_regress/t/t_constraint_foreach.v | 8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/V3Randomize.cpp b/src/V3Randomize.cpp
index 4a6f6160a..95e2d01c2 100644
--- a/src/V3Randomize.cpp
+++ b/src/V3Randomize.cpp
@@ -695,11 +695,13 @@ class ConstraintExprVisitor final : public VNVisitor {
             AstNode* const cstmtp = new AstText{fl, "ret += \" \" + "};
             cstmtp->addNext(itemp);
             cstmtp->addNext(new AstText{fl, ";"});
-            AstNode* const exprsp = new AstText{fl, "([&]{ std::string ret = \"(bvand\";"};
+            AstNode* const exprsp = new AstText{fl, "([&]{ std::string ret;"};
             exprsp->addNext(new AstBegin{
                 fl, "",
                 new AstForeach{fl, nodep->arrayp()->unlinkFrBack(), new AstCStmt{fl, cstmtp}},
                 false, true});
+            exprsp->addNext(
+                new AstText{fl, "return ret.empty() ? \"#b1\" : \"(bvand \" + ret + \")\";"});
             exprsp->addNext(new AstText{fl, "return ret + \")\"; })()"});
             AstNodeExpr* const newp = new AstCExpr{fl, exprsp};
             newp->dtypeSetString();
diff --git a/test_regress/t/t_constraint_foreach.v b/test_regress/t/t_constraint_foreach.v
index 6bd36c704..35ec42c69 100644
--- a/test_regress/t/t_constraint_foreach.v
+++ b/test_regress/t/t_constraint_foreach.v
@@ -32,8 +32,16 @@ endclass
 class D;
    rand bit posit;
    rand int x;
+   int o[$];  // empty
+   int p[$] = {1};
    int q[$] = {0, 0, 0, 0, 0};
    constraint fore {
+      if (posit == 1) {
+         foreach(o[i]) o[i] > 0;
+      }
+      if (posit == 1) {
+         foreach(p[i]) p[i] > 0;
+      }
       if (posit == 1) {
          x < 7;
          foreach(q[i])