From dda0405fce36d4f3fba964ee4194e36af69450b3 Mon Sep 17 00:00:00 2001
From: Matthew Ballance <matt.ballance@gmail.com>
Date: Thu, 5 Mar 2026 14:28:20 +0000
Subject: [PATCH] V3Covergroup: initialize bin counters to 0, not random

Coverage bin counters (__Vcov_* member variables) were being initialized
with VL_SCOPED_RAND_RESET_I because they are plain uint32 members with no
explicit initial value. This caused 0% coverage readings at runtime when
randReset != 0 (as used in CI).

Fix all 5 bin counter AstVar creation sites to set an explicit valuep of
AstConst(0), so V3EmitCFunc emits '= 0U' instead of VL_SCOPED_RAND_RESET_I.

Affects: regular bins, default bins, array bins, transition array bins,
and cross bins.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 src/V3Covergroup.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/V3Covergroup.cpp b/src/V3Covergroup.cpp
index de6a68a52..2bef975c6 100644
--- a/src/V3Covergroup.cpp
+++ b/src/V3Covergroup.cpp
@@ -531,6 +531,7 @@ class FunctionalCoverageVisitor final : public VNVisitor {
             AstVar* const varp = new AstVar{cbinp->fileline(), VVarType::MEMBER, varName,
                                             cbinp->findUInt32DType()};
             varp->isStatic(false);
+            varp->valuep(new AstConst{cbinp->fileline(), AstConst::WidthedValue{}, 32, 0});
             m_covergroupp->addMembersp(varp);
             UINFO(4, "    Created member variable: "
                          << varName << " type=" << static_cast<int>(cbinp->binsType())
@@ -566,6 +567,7 @@ class FunctionalCoverageVisitor final : public VNVisitor {
             AstVar* const varp = new AstVar{defBinp->fileline(), VVarType::MEMBER, varName,
                                             defBinp->findUInt32DType()};
             varp->isStatic(false);
+            varp->valuep(new AstConst{defBinp->fileline(), AstConst::WidthedValue{}, 32, 0});
             m_covergroupp->addMembersp(varp);
             UINFO(4, "    Created default bin variable: " << varName << endl);
 
@@ -1031,6 +1033,7 @@ class FunctionalCoverageVisitor final : public VNVisitor {
             AstVar* const varp = new AstVar{arrayBinp->fileline(), VVarType::MEMBER, varName,
                                             arrayBinp->findUInt32DType()};
             varp->isStatic(false);
+            varp->valuep(new AstConst{arrayBinp->fileline(), AstConst::WidthedValue{}, 32, 0});
             m_covergroupp->addMembersp(varp);
             UINFO(4, "    Created array bin [" << index << "]: " << varName << endl);
 
@@ -1113,6 +1116,7 @@ class FunctionalCoverageVisitor final : public VNVisitor {
             AstVar* const varp = new AstVar{arrayBinp->fileline(), VVarType::MEMBER, varName,
                                             arrayBinp->findUInt32DType()};
             varp->isStatic(false);
+            varp->valuep(new AstConst{arrayBinp->fileline(), AstConst::WidthedValue{}, 32, 0});
             m_covergroupp->addMembersp(varp);
             UINFO(4, "      Created transition array bin [" << index << "]: " << varName << endl);
 
@@ -1267,6 +1271,7 @@ class FunctionalCoverageVisitor final : public VNVisitor {
         AstVar* const varp = new AstVar{crossp->fileline(), VVarType::MEMBER, varName,
                                         bins[0]->findUInt32DType()};
         varp->isStatic(false);
+        varp->valuep(new AstConst{crossp->fileline(), AstConst::WidthedValue{}, 32, 0});
         m_covergroupp->addMembersp(varp);
 
         UINFO(4, "      Created cross bin variable: " << varName << endl);