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Fix cross-interface tristate enable propagation/lowering

This commit is contained in:
Nick Brereton 2026-03-26 08:04:30 -04:00
parent 728ddf3331
commit 8ce2784f1d
1 changed files with 22 additions and 7 deletions
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29
src/V3Tristate.cpp
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@ -637,6 +637,8 @@ class TristateVisitor final : public TristateBaseVisitor {
return newp;
}
bool hasResolvedTriEnable(const AstVar* varp) const { return VN_IS(varp->user1p(), Var); }
void setPullDirection(AstVar* varp, AstPull* pullp) {
const AstPull* const oldpullp = m_varAux(varp).pullp;
if (!oldpullp) {
@ -695,13 +697,20 @@ class TristateVisitor final : public TristateBaseVisitor {
// Now go through the lhs driver map and generate the output
// enable logic for any tristates.
// Note there might not be any drivers.
for (AstVar* varp : vars) { // Use vector instead of m_lhsmap iteration for stability
// Include vars that are tristate in this module's graph and vars that already
// have a resolved __en from lower-level/interface processing.
std::vector<AstVar*> varsToProcess = vars;
for (const auto& lhsEnt : m_lhsmap) {
AstVar* const varp = lhsEnt.first;
if (!m_tgraph.isTristate(varp) && hasResolvedTriEnable(varp)) varsToProcess.push_back(varp);
}
for (AstVar* varp : varsToProcess) { // Use vector instead of m_lhsmap iteration for stability
const std::map<AstVar*, RefStrengthVec*>::iterator it = m_lhsmap.find(varp);
if (it == m_lhsmap.end()) continue;
AstVar* const invarp = it->first;
RefStrengthVec* refsp = it->second;
// Figure out if this var needs tristate expanded.
if (m_tgraph.isTristate(invarp)) {
if (m_tgraph.isTristate(invarp) || hasResolvedTriEnable(invarp)) {
// Check if the var is owned by a different module (cross-module reference).
// For interface vars this is expected; for regular modules it's unsupported.
AstNodeModule* const ownerModp = findParentModule(invarp);
@ -945,6 +954,10 @@ class TristateVisitor final : public TristateBaseVisitor {
// This net intentionally has multiple contributors; DFG should not emit
// MULTIDRIVEN warnings for this lowered tristate pattern.
invarp->setDfgAllowMultidriveTri();
// Create the canonical interface __en early so parent modules processed
// later in this pass can recognize this signal as tristate-resolved and
// lower their own cross-interface drivers as contributions too.
getCreateEnVarp(invarp, false)->setDfgTriLowered();
AstNodeModule* const ifaceModp = findParentModule(invarp);
UASSERT_OBJ(ifaceModp, invarp, "Interface tristate var has no parent module");
const int contribIdx = static_cast<int>(m_ifaceContribs[invarp].size());
@ -1971,7 +1984,8 @@ class TristateVisitor final : public TristateBaseVisitor {
// Detect all var lhs drivers and adds them to the
// VarMap so that after the walk through the module we can expand
// any tristate logic on the driver.
if (nodep->access().isWriteOrRW() && m_tgraph.isTristate(nodep->varp())) {
if (nodep->access().isWriteOrRW()
&& (m_tgraph.isTristate(nodep->varp()) || hasResolvedTriEnable(nodep->varp()))) {
UINFO(9, " Ref-to-lvalue " << nodep);
if (m_inAlias) {
if (nodep->varp()->direction().isAny()) {
@ -1990,10 +2004,11 @@ class TristateVisitor final : public TristateBaseVisitor {
} else if (nodep->access().isReadOnly()
// Not already processed, nor varref from visit(AstPin) creation
&& !nodep->user1p()
// Reference to another tristate variable
&& m_tgraph.isTristate(nodep->varp())
// and in a position where it feeds upstream to another tristate
&& m_tgraph.feedsTri(nodep)) {
// Reference to another tristate variable in this module context
&& ((m_tgraph.isTristate(nodep->varp()) && m_tgraph.feedsTri(nodep))
// Or a cross-module/interface reference whose target already has
// a resolved tristate-enable signal from prior processing.
|| (VN_IS(nodep, VarXRef) && VN_IS(nodep->varp()->user1p(), Var)))) {
// Then propagate the enable from the original variable
UINFO(9, " Ref-to-tri " << nodep);
FileLine* const fl = nodep->fileline();