128 lines
4.9 KiB
C++
128 lines
4.9 KiB
C++
// -*- mode: C++; c-file-style: "cc-mode" -*-
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//*************************************************************************
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// DESCRIPTION: Verilator: Create triggers necessary for scheduling across
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// virtual interfaces
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//
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// Code available from: https://verilator.org
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//
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//*************************************************************************
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//
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// This program is free software; you can redistribute it and/or modify it
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// under the terms of either the GNU Lesser General Public License Version 3
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// or the Perl Artistic License Version 2.0.
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// SPDX-FileCopyrightText: 2003-2026 Wilson Snyder
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// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
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//
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//*************************************************************************
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// V3SchedVirtIface's Transformations:
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//
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// Identify interface members written through virtual interface variables (VIF writes).
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// For each such member, collect all VarScopes across all instantiations of that
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// interface type. Each VarScope gets its own value-change trigger in the scheduler.
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//
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// Also disables lifetime optimization for variables in AlwaysPost blocks that
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// write through virtual interfaces.
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//
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//*************************************************************************
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#include "V3PchAstNoMT.h" // VL_MT_DISABLED_CODE_UNIT
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#include "V3AstNodeExpr.h"
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#include "V3Sched.h"
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VL_DEFINE_DEBUG_FUNCTIONS;
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namespace V3Sched {
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namespace {
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class VirtIfaceVisitor final : public VNVisitor {
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private:
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// STATE
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// Set of (iface, member) pairs written through VIF -- defines which members need triggers
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std::set<std::pair<const AstIface*, const std::string>> m_vifWrittenMembers;
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// All candidate VarScopes of interface members (keyed by interface type + member name)
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std::map<std::pair<const AstIface*, const std::string>, std::vector<AstVarScope*>>
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m_candidateVscps;
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VirtIfaceTriggers m_triggers;
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// METHODS
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// Returns true if statement writes across a virtual interface boundary
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static bool writesToVirtIface(const AstNode* const nodep) {
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return nodep->exists([](const AstMemberSel* const memberSelp) {
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if (!memberSelp->access().isWriteOrRW()) return false;
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AstIfaceRefDType* const dtypep
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= VN_CAST(memberSelp->fromp()->dtypep()->skipRefp(), IfaceRefDType);
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return dtypep && dtypep->isVirtual();
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});
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}
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// VISITORS
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void visit(AstMemberSel* nodep) override {
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// Detect writes through VIF: the MemberSel's fromp resolves to a virtual interface type.
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// Handles both direct VIF access (vif.member) and class chain (obj.vif.member).
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if (nodep->access().isWriteOrRW()) {
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AstIfaceRefDType* const dtypep
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= VN_CAST(nodep->fromp()->dtypep()->skipRefp(), IfaceRefDType);
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if (dtypep && dtypep->isVirtual()) {
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m_vifWrittenMembers.emplace(dtypep->ifacep(), nodep->varp()->name());
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}
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}
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iterateChildren(nodep);
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}
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void visit(AstVarScope* nodep) override {
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// Collect candidate VarScopes. sensIfacep() is set on interface members
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// accessed via any MemberSel (virtual or non-virtual).
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if (const AstIface* const ifacep = nodep->varp()->sensIfacep()) {
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m_candidateVscps[{ifacep, nodep->varp()->name()}].push_back(nodep);
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}
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}
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void visit(AstNodeProcedure* nodep) override {
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// Disable lifetime optimization for variables in AlwaysPost blocks
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// that write to virtual interface members, as VIF reads may observe them
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if (VN_IS(nodep, AlwaysPost) && writesToVirtIface(nodep)) {
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nodep->foreach([](AstVarRef* refp) { refp->varScopep()->optimizeLifePost(false); });
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}
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iterateChildren(nodep);
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}
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void visit(AstNode* nodep) override { iterateChildren(nodep); }
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// Build final trigger list by intersecting VIF writes with candidate VarScopes
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void buildTriggers() {
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for (const auto& written : m_vifWrittenMembers) {
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const auto it = m_candidateVscps.find(written);
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if (it == m_candidateVscps.end()) continue;
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for (AstVarScope* const vscp : it->second) {
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const AstIface* const ifacep = written.first;
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m_triggers.addTrigger(ifacep, vscp->varp(), vscp);
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}
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}
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}
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public:
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// CONSTRUCTORS
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explicit VirtIfaceVisitor(AstNetlist* nodep) {
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iterate(nodep);
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buildTriggers();
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}
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~VirtIfaceVisitor() override = default;
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// METHODS
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VirtIfaceTriggers take_triggers() { return std::move(m_triggers); }
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};
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} //namespace
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VirtIfaceTriggers makeVirtIfaceTriggers(AstNetlist* nodep) {
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UINFO(2, __FUNCTION__ << ":");
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VirtIfaceTriggers triggers{};
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if (v3Global.hasVirtIfaces()) {
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triggers = VirtIfaceVisitor{nodep}.take_triggers();
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// Dump after destructor so VNDeleter runs
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V3Global::dumpCheckGlobalTree("sched_vif", 0, dumpTreeEitherLevel() >= 6);
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}
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return triggers;
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}
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} //namespace V3Sched
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