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Support NBAs in initial blocks (#7754)

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This commit is contained in:
Igor Zaworski
2026-06-20 17:23:05 -04:00
committed by GitHub
parent 047d6e03d9
commit e269b914b2
20 changed files with 207 additions and 55 deletions
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src/V3Delayed.cpp
+34 -3
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@@ -275,6 +275,7 @@ class DelayedVisitor final : public VNVisitor {
bool m_inSuspendableOrFork = false; // True in suspendable processes and forks
bool m_ignoreBlkAndNBlk = false; // Suppress delayed assignment BLKANDNBLK
bool m_inNonCombLogic = false; // We are in non-combinational logic
bool m_needsInitialTrigger = false; // Whether a NodeProcedure needs a initial trigger
AstVarRef* m_currNbaLhsRefp = nullptr; // Current NBA LHS variable reference
// STATE - during NBA conversion (after visit)
@@ -291,6 +292,7 @@ class DelayedVisitor final : public VNVisitor {
VDouble0 m_nSchemeValueQueuesWhole; // Number of variables using Scheme::ValueQueueWhole
VDouble0 m_nSchemeValueQueuesPartial; // Number of variables using Scheme::ValueQueuePartial
VDouble0 m_nSharedSetFlags; // "Set" flags actually shared by Scheme::FlagShared variables
VDouble0 m_nInitialNBA; // Number of procedural blocks with initial NBA
// METHODS
@@ -999,6 +1001,12 @@ class DelayedVisitor final : public VNVisitor {
m_writeRefs(nodep->varScopep()).emplace_back(nodep, nonBlocking, m_inNonCombLogic);
}
template <typename Procedure_T>
static bool isProcedureWithSentreep(const AstNodeProcedure* const nodep) {
const Procedure_T* const procedurep = AstNode::cast<Procedure_T>(nodep);
return procedurep && procedurep->sentreep();
}
// VISITORS
void visit(AstNetlist* nodep) override {
iterateChildren(nodep);
@@ -1112,21 +1120,36 @@ class DelayedVisitor final : public VNVisitor {
iterateChildren(nodep);
}
void visit(AstNodeProcedure* nodep) override {
VL_RESTORER(m_needsInitialTrigger);
const size_t firstNBAAddedIndex = m_nbas.size();
{
VL_RESTORER(m_inSuspendableOrFork);
VL_RESTORER(m_procp);
VL_RESTORER(m_ignoreBlkAndNBlk);
VL_RESTORER(m_inNonCombLogic);
m_inSuspendableOrFork = nodep->isSuspendable();
// When we are dealing with initial block we need to
// treat it as suspendable when we meet a NBA
m_inSuspendableOrFork = nodep->isSuspendable() || VN_IS(nodep, Initial);
m_procp = nodep;
if (m_inSuspendableOrFork) {
if (nodep->isSuspendable()) {
m_ignoreBlkAndNBlk = false;
m_inNonCombLogic = true;
}
iterateChildren(nodep);
}
if (m_timingDomains.empty()) return;
auto containsClocled = [](const AstSenItem* itemp) {
while (itemp) {
if (itemp->edgeType().clockedStmt()) return true;
itemp = VN_AS(itemp->nextp(), SenItem);
}
return false;
};
const bool addInitialTrigger = m_needsInitialTrigger
&& !(isProcedureWithSentreep<AstAlways>(nodep)
|| isProcedureWithSentreep<AstAlwaysObserved>(nodep)
|| isProcedureWithSentreep<AstAlwaysReactive>(nodep))
&& !containsClocled(m_activep->sentreep()->sensesp());
if (m_timingDomains.empty() && !addInitialTrigger) return;
// There were some timing domains involved in the process. Add all of them as sensitivities
// of all NBA targets in this process. Note this is a bit of a sledgehammer, we should only
@@ -1135,6 +1158,11 @@ class DelayedVisitor final : public VNVisitor {
// First gather all senItems
AstSenItem* senItemp = nullptr;
if (addInitialTrigger) {
senItemp = new AstSenItem{nodep->fileline(), AstSenItem::InitialNBA{}};
++m_nInitialNBA;
}
for (const AstSenTree* const domainp : m_timingDomains) {
if (domainp->sensesp())
senItemp = AstNode::addNext(senItemp, domainp->sensesp()->cloneTree(true));
@@ -1218,6 +1246,8 @@ class DelayedVisitor final : public VNVisitor {
UASSERT_OBJ(m_inSuspendableOrFork || m_activep->hasClocked(), nodep,
"<= assignment in non-clocked block, should have been converted in V3Active");
m_needsInitialTrigger |= m_timingDomains.empty();
// Record scope of this NBA
nodep->user2p(m_scopep);
@@ -1327,6 +1357,7 @@ public:
V3Stats::addStat("NBA, variables using ValueQueuePartial scheme",
m_nSchemeValueQueuesPartial);
V3Stats::addStat("Optimizations, NBA flags shared", m_nSharedSetFlags);
V3Stats::addStat("Procedures needing initial NBA trigger", m_nInitialNBA);
}
};