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verilator/src/V3Timing.cpp

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// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Prepare AST for timing features
//
// Code available from: https://verilator.org
//
//*************************************************************************
//
// Copyright 2003-2023 by Wilson Snyder. This program is free software; you
// can redistribute it and/or modify it under the terms of either the GNU
// Lesser General Public License Version 3 or the Perl Artistic License
// Version 2.0.
// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
//
// TimingVisitor transformations:
// - for each intra-assignment timing control:
// - if it's a continuous assignment, transform it into an always
// - introduce an intermediate variable
// - write the original RHS to the intermediate variable before the timing control
// - write the intermediate variable to the original LHS after the timing control
// - for each delay:
// - scale it according to the module's timescale
// - replace it with a CAwait statement waiting on the global delay scheduler (with the
// specified delay value)
// - if there is no global delay scheduler (see verilated_timing.{h,cpp}), create it
// - for each event control:
// - if there is no corresponding trigger scheduler (see verilated_timing.{h,cpp}), create it
// - replace with a CAwait statement waiting on the corresponding trigger scheduler
// - for each wait(cond) statement:
// - replace it with a loop like: while (!cond) @(<vars from cond>)
// - for each fork:
// - put each statement in a begin if it isn't in one already
// - if it's not a fork..join_none:
// - create a join sync variable
// - create statements that sync the main process with its children
// - for each process or C++ function, if it has CAwait statements, mark it as suspendable
// - if we mark a virtual function as suspendable, mark all overriding and overridden functions
// as suspendable, as well as calling processes
//
// See the internals documentation docs/internals.rst for more details.
//
//*************************************************************************
#include "config_build.h"
#include "verilatedos.h"
#include "V3Timing.h"
#include "V3Ast.h"
#include "V3Const.h"
#include "V3EmitV.h"
#include "V3Graph.h"
#include "V3SenExprBuilder.h"
#include "V3SenTree.h"
#include "V3UniqueNames.h"
VL_DEFINE_DEBUG_FUNCTIONS;
// ######################################################################
// Transform nodes affected by timing
class TimingVisitor final : public VNVisitor {
private:
// TYPES
// Vertex of a dependency graph of suspendable nodes, e.g. if a node (process or task) is
// suspendable, all its dependents should also be suspendable
class DependencyVertex final : public V3GraphVertex {
AstNode* const m_nodep; // AST node represented by this graph vertex
// ACCESSORS
string name() const override {
return cvtToHex(nodep()) + ' ' + nodep()->prettyTypeName();
}
FileLine* fileline() const override { return nodep()->fileline(); }
string dotColor() const override { return nodep()->user2() ? "red" : "black"; }
public:
// CONSTRUCTORS
DependencyVertex(V3Graph* graphp, AstNode* nodep)
: V3GraphVertex{graphp}
, m_nodep{nodep} {}
~DependencyVertex() override = default;
// ACCESSORS
virtual AstNode* nodep() const { return m_nodep; }
};
// NODE STATE
// AstNode::user1() -> bool. Set true if the node has been
// processed.
// AstSenTree::user1() -> AstVarScope*. Trigger scheduler assigned
// to this sentree
// Ast{NodeProcedure,CFunc,Begin}::user2() -> bool. Set true if process/task is
// suspendable
// AstSenTree::user2() -> AstCExpr*. Debug info passed to the
// timing schedulers
// Ast{NodeProcedure,CFunc,Begin}::user3() -> DependencyVertex*. Vertex in m_depGraph
const VNUser1InUse m_user1InUse;
const VNUser2InUse m_user2InUse;
const VNUser3InUse m_user3InUse;
// STATE
// Current context
AstNetlist* const m_netlistp; // Root node
AstScope* const m_scopeTopp = m_netlistp->topScopep()->scopep(); // Scope at the top
AstClass* m_classp = nullptr; // Current class
AstScope* m_scopep = nullptr; // Current scope
AstActive* m_activep = nullptr; // Current active
AstNode* m_procp = nullptr; // NodeProcedure/CFunc/Fork we're under
double m_timescaleFactor = 1.0; // Factor to scale delays by
// Unique names
V3UniqueNames m_contAssignVarNames{"__VassignWtmp"}; // Names for temp AssignW vars
V3UniqueNames m_intraValueNames{"__Vintraval"}; // Intra assign delay value var names
V3UniqueNames m_intraIndexNames{"__Vintraidx"}; // Intra assign delay index var names
V3UniqueNames m_intraLsbNames{"__Vintralsb"}; // Intra assign delay LSB var names
V3UniqueNames m_forkNames{"__Vfork"}; // Fork name generator
V3UniqueNames m_trigSchedNames{"__VtrigSched"}; // Trigger scheduler name generator
V3UniqueNames m_dynTrigNames{"__VdynTrigger"}; // Dynamic trigger name generator
// DTypes
AstBasicDType* m_forkDtp = nullptr; // Fork variable type
AstBasicDType* m_trigSchedDtp = nullptr; // Trigger scheduler type
// Timing-related globals
AstVarScope* m_delaySchedp = nullptr; // Global delay scheduler
AstVarScope* m_dynamicSchedp = nullptr; // Global dynamic trigger scheduler
AstSenTree* m_delaySensesp = nullptr; // Domain to trigger if a delayed coroutine is resumed
AstSenTree* m_dynamicSensesp = nullptr; // Domain to trigger if a dynamic trigger is set
// Other
V3Graph m_depGraph; // Dependency graph where a node is a dependency of another if it being
// suspendable makes the other node suspendable
SenTreeFinder m_finder{m_netlistp}; // Sentree finder and uniquifier
// METHODS
// Get or create the dependency vertex for the given node
DependencyVertex* getDependencyVertex(AstNode* const nodep) {
if (!nodep->user3p()) nodep->user3p(new DependencyVertex{&m_depGraph, nodep});
return nodep->user3u().to<DependencyVertex*>();
}
// Find net delay on the LHS of an assignment
AstDelay* getLhsNetDelay(AstNodeAssign* nodep) const {
bool foundWrite = false;
AstDelay* delayp = nullptr;
nodep->lhsp()->foreach([&](const AstNodeVarRef* const refp) {
if (!refp->access().isWriteOrRW()) return;
UASSERT_OBJ(!foundWrite, nodep, "Should only be one variable written to on the LHS");
foundWrite = true;
if (refp->varp()->delayp()) {
delayp = refp->varp()->delayp();
delayp->unlinkFrBack();
}
});
return delayp;
}
// Transform an assignment with an intra timing control into a timing control with the
// assignment under it
AstNode* factorOutTimingControl(AstNodeAssign* nodep) const {
AstNode* stmtp = nodep;
AstDelay* delayp = getLhsNetDelay(nodep);
FileLine* const flp = nodep->fileline();
AstNode* const controlp = nodep->timingControlp();
if (controlp) {
controlp->unlinkFrBack();
if (auto* const assignDelayp = VN_CAST(controlp, Delay)) {
if (delayp) {
delayp->lhsp(new AstAdd{flp, delayp->lhsp()->unlinkFrBack(),
assignDelayp->lhsp()->unlinkFrBack()});
VL_DO_DANGLING(assignDelayp->deleteTree(), nodep);
} else {
delayp = assignDelayp;
}
}
}
if (delayp) {
stmtp->replaceWith(delayp);
delayp->addStmtsp(stmtp);
stmtp = delayp;
}
if (auto* const sensesp = VN_CAST(controlp, SenTree)) {
auto* const eventControlp = new AstEventControl{flp, sensesp, nullptr};
stmtp->replaceWith(eventControlp);
eventControlp->addStmtsp(stmtp);
stmtp = eventControlp;
} else if (auto* const beginp = VN_CAST(controlp, Begin)) {
// Begin from V3AssertPre
stmtp->replaceWith(beginp);
beginp->addStmtsp(stmtp);
stmtp = beginp;
}
return stmtp == nodep ? nullptr : stmtp;
}
// Calculate the factor to scale delays by
double calculateTimescaleFactor(VTimescale timeunit) const {
int scalePowerOfTen = timeunit.powerOfTen() - m_netlistp->timeprecision().powerOfTen();
return std::pow(10.0, scalePowerOfTen);
}
// Construct SenItems from VarRefs in an expression
AstSenItem* varRefpsToSenItemsp(AstNode* const nodep) const {
AstNode* senItemsp = nullptr;
const VNUser4InUse user4InUse;
nodep->foreach([&](AstNodeVarRef* refp) {
if (refp->access().isWriteOnly()) return;
AstVarScope* const vscp = refp->varScopep();
if (vscp->user4SetOnce()) return;
const bool isEvent = vscp->dtypep() && vscp->dtypep()->basicp()
&& vscp->dtypep()->basicp()->isEvent();
const auto edgeType = isEvent ? VEdgeType::ET_EVENT : VEdgeType::ET_CHANGED;
senItemsp = AstNode::addNext(
senItemsp, new AstSenItem{refp->fileline(), edgeType,
new AstVarRef{refp->fileline(), vscp, VAccess::READ}});
});
return VN_AS(senItemsp, SenItem);
}
// Creates the global delay scheduler variable
AstVarScope* getCreateDelayScheduler() {
if (m_delaySchedp) return m_delaySchedp;
auto* const dlySchedDtp = new AstBasicDType{
m_scopeTopp->fileline(), VBasicDTypeKwd::DELAY_SCHEDULER, VSigning::UNSIGNED};
m_netlistp->typeTablep()->addTypesp(dlySchedDtp);
m_delaySchedp = m_scopeTopp->createTemp("__VdlySched", dlySchedDtp);
// Delay scheduler has to be accessible from top
m_delaySchedp->varp()->sigPublic(true);
m_netlistp->delaySchedulerp(m_delaySchedp->varp());
return m_delaySchedp;
}
// Creates the delay sentree
AstSenTree* getCreateDelaySenTree() {
if (m_delaySensesp) return m_delaySensesp;
FileLine* const flp = m_scopeTopp->fileline();
auto* const awaitingCurrentTimep
= new AstCMethodHard{flp, new AstVarRef{flp, getCreateDelayScheduler(), VAccess::READ},
"awaitingCurrentTime"};
awaitingCurrentTimep->dtypeSetBit();
m_delaySensesp
= new AstSenTree{flp, new AstSenItem{flp, VEdgeType::ET_TRUE, awaitingCurrentTimep}};
m_netlistp->topScopep()->addSenTreesp(m_delaySensesp);
return m_delaySensesp;
}
// Creates the global dynamic trigger scheduler variable
AstVarScope* getCreateDynamicTriggerScheduler() {
if (m_dynamicSchedp) return m_dynamicSchedp;
auto* const dynSchedDtp
= new AstBasicDType{m_scopeTopp->fileline(), VBasicDTypeKwd::DYNAMIC_TRIGGER_SCHEDULER,
VSigning::UNSIGNED};
m_netlistp->typeTablep()->addTypesp(dynSchedDtp);
m_dynamicSchedp = m_scopeTopp->createTemp("__VdynSched", dynSchedDtp);
return m_dynamicSchedp;
}
// Creates the dynamic trigger sentree
AstSenTree* getCreateDynamicTriggerSenTree() {
if (m_dynamicSensesp) return m_dynamicSensesp;
FileLine* const flp = m_scopeTopp->fileline();
auto* const awaitingCurrentTimep = new AstCMethodHard{
flp, new AstVarRef{flp, getCreateDynamicTriggerScheduler(), VAccess::READ},
"evaluate"};
awaitingCurrentTimep->dtypeSetBit();
m_dynamicSensesp
= new AstSenTree{flp, new AstSenItem{flp, VEdgeType::ET_TRUE, awaitingCurrentTimep}};
m_netlistp->topScopep()->addSenTreesp(m_dynamicSensesp);
return m_dynamicSensesp;
}
// Returns true if we are under a class or the given tree has any references to locals. These
// are cases where static, globally-evaluated triggers are not suitable.
bool needDynamicTrigger(AstNode* const nodep) const {
return m_classp || nodep->exists([](const AstNodeVarRef* const refp) {
return refp->varp()->isFuncLocal();
});
}
// Returns true if the given trigger expression needs a destructive post update after trigger
// evaluation. Currently this only applies to named events.
bool destructivePostUpdate(AstNode* const exprp) const {
return exprp->exists([](const AstNodeVarRef* const refp) {
AstBasicDType* const dtypep = refp->dtypep()->basicp();
return dtypep && dtypep->isEvent();
});
}
// Creates a trigger scheduler variable
AstVarScope* getCreateTriggerSchedulerp(AstSenTree* const sensesp) {
if (!sensesp->user1p()) {
if (!m_trigSchedDtp) {
m_trigSchedDtp
= new AstBasicDType{m_scopeTopp->fileline(), VBasicDTypeKwd::TRIGGER_SCHEDULER,
VSigning::UNSIGNED};
m_netlistp->typeTablep()->addTypesp(m_trigSchedDtp);
}
AstVarScope* const trigSchedp
= m_scopeTopp->createTemp(m_trigSchedNames.get(sensesp), m_trigSchedDtp);
sensesp->user1p(trigSchedp);
}
return VN_AS(sensesp->user1p(), VarScope);
}
// Creates a string describing the sentree
AstCExpr* createEventDescription(AstSenTree* const sensesp) const {
if (!sensesp->user2p()) {
std::stringstream ss;
ss << '"';
V3EmitV::verilogForTree(sensesp, ss);
ss << '"';
auto* const commentp = new AstCExpr{sensesp->fileline(), ss.str(), 0};
commentp->dtypeSetString();
sensesp->user2p(commentp);
return commentp;
}
return VN_AS(sensesp->user2p(), CExpr)->cloneTree(false);
}
// Adds debug info to a hardcoded method call
void addDebugInfo(AstCMethodHard* const methodp) const {
if (v3Global.opt.protectIds()) return;
FileLine* const flp = methodp->fileline();
AstCExpr* const ap = new AstCExpr{flp, '"' + flp->filename() + '"', 0};
ap->dtypeSetString();
methodp->addPinsp(ap);
AstCExpr* const bp = new AstCExpr{flp, cvtToStr(flp->lineno()), 0};
bp->dtypeSetString();
methodp->addPinsp(bp);
}
// Adds debug info to a trigSched.trigger() call
void addEventDebugInfo(AstCMethodHard* const methodp, AstSenTree* const sensesp) const {
if (v3Global.opt.protectIds()) return;
methodp->addPinsp(createEventDescription(sensesp));
addDebugInfo(methodp);
}
// Creates the fork handle type and returns it
AstBasicDType* getCreateForkSyncDTypep() {
if (m_forkDtp) return m_forkDtp;
m_forkDtp = new AstBasicDType{m_scopeTopp->fileline(), VBasicDTypeKwd::FORK_SYNC,
VSigning::UNSIGNED};
m_netlistp->typeTablep()->addTypesp(m_forkDtp);
return m_forkDtp;
}
// Create a temp variable and optionally put it before the specified node (mark local if so)
AstVarScope* createTemp(FileLine* const flp, const std::string& name,
AstNodeDType* const dtypep, AstNode* const insertBeforep = nullptr) {
AstVar* varp;
if (insertBeforep) {
varp = new AstVar{flp, VVarType::BLOCKTEMP, name, dtypep};
varp->funcLocal(true);
insertBeforep->addHereThisAsNext(varp);
} else {
varp = new AstVar{flp, VVarType::MODULETEMP, name, dtypep};
m_scopep->modp()->addStmtsp(varp);
}
AstVarScope* vscp = new AstVarScope{flp, m_scopep, varp};
m_scopep->addVarsp(vscp);
return vscp;
}
// Add a done() call on the fork sync
void addForkDone(AstBegin* const beginp, AstVarScope* const forkVscp) const {
FileLine* const flp = beginp->fileline();
auto* const donep = new AstCMethodHard{
beginp->fileline(), new AstVarRef{flp, forkVscp, VAccess::WRITE}, "done"};
donep->dtypeSetVoid();
addDebugInfo(donep);
beginp->addStmtsp(donep->makeStmt());
}
// Handle the 'join' part of a fork..join
void makeForkJoin(AstFork* const forkp) {
// Create a fork sync var
FileLine* const flp = forkp->fileline();
// If we're in a function, insert the sync var directly before the fork
AstNode* const insertBeforep = VN_IS(m_procp, CFunc) ? forkp : nullptr;
AstVarScope* forkVscp
= createTemp(flp, forkp->name() + "__sync", getCreateForkSyncDTypep(), insertBeforep);
unsigned joinCount = 0; // Needed for join counter
// Add a <fork sync>.done() to each begin
for (AstNode* beginp = forkp->stmtsp(); beginp; beginp = beginp->nextp()) {
addForkDone(VN_AS(beginp, Begin), forkVscp);
joinCount++;
}
if (forkp->joinType().joinAny()) joinCount = 1;
// Set the join counter
auto* const initp = new AstCMethodHard{flp, new AstVarRef{flp, forkVscp, VAccess::WRITE},
"init", new AstConst{flp, joinCount}};
initp->dtypeSetVoid();
forkp->addHereThisAsNext(initp->makeStmt());
// Await the join at the end
auto* const joinp
= new AstCMethodHard{flp, new AstVarRef{flp, forkVscp, VAccess::WRITE}, "join"};
joinp->dtypeSetVoid();
addDebugInfo(joinp);
AstCAwait* const awaitp = new AstCAwait{flp, joinp};
awaitp->dtypeSetVoid();
forkp->addNextHere(awaitp->makeStmt());
}
// VISITORS
void visit(AstNodeModule* nodep) override {
UASSERT(!m_classp, "Module or class under class");
VL_RESTORER(m_classp);
m_classp = VN_CAST(nodep, Class);
VL_RESTORER(m_timescaleFactor);
m_timescaleFactor = calculateTimescaleFactor(nodep->timeunit());
iterateChildren(nodep);
}
void visit(AstScope* nodep) override {
VL_RESTORER(m_scopep);
m_scopep = nodep;
iterateChildren(nodep);
}
void visit(AstActive* nodep) override {
m_activep = nodep;
iterateChildren(nodep);
m_activep = nullptr;
}
void visit(AstNodeProcedure* nodep) override {
VL_RESTORER(m_procp);
m_procp = nodep;
iterateChildren(nodep);
if (nodep->user2()) nodep->setSuspendable();
}
void visit(AstAlways* nodep) override {
visit(static_cast<AstNodeProcedure*>(nodep));
if (nodep->isSuspendable() && !nodep->user1SetOnce()) {
FileLine* const flp = nodep->fileline();
AstSenTree* const sensesp = m_activep->sensesp();
if (sensesp->hasClocked()) {
AstNode* bodysp = nodep->stmtsp()->unlinkFrBackWithNext();
auto* const controlp = new AstEventControl{flp, sensesp->cloneTree(false), bodysp};
nodep->addStmtsp(controlp);
iterate(controlp);
}
// Note: The 'while (true)' outer loop will be added in V3Sched
auto* const activep = new AstActive{
flp, "", new AstSenTree{flp, new AstSenItem{flp, AstSenItem::Initial{}}}};
activep->sensesStorep(activep->sensesp());
activep->addStmtsp(nodep->unlinkFrBack());
m_activep->addNextHere(activep);
}
}
void visit(AstCFunc* nodep) override {
VL_RESTORER(m_procp);
m_procp = nodep;
iterateChildren(nodep);
DependencyVertex* const vxp = getDependencyVertex(nodep);
if (m_classp && nodep->isVirtual()
&& !nodep->user1SetOnce()) { // If virtual (only visit once)
// Go over overridden functions
m_classp->repairCache();
for (auto* cextp = m_classp->extendsp(); cextp;
cextp = VN_AS(cextp->nextp(), ClassExtends)) {
if (auto* const overriddenp
= VN_CAST(cextp->classp()->findMember(nodep->name()), CFunc)) {
if (overriddenp->user2()) { // If suspendable
if (!nodep->user2()) {
// It should be a coroutine but it has no awaits. Add a co_return at
// the end (either that or a co_await is required in a coroutine)
nodep->addStmtsp(new AstCStmt{nodep->fileline(), "co_return;\n"});
}
nodep->user2(true);
// If it's suspendable already, no need to add it as our dependency or
// self to its dependencies
} else {
DependencyVertex* const overriddenVxp = getDependencyVertex(overriddenp);
new V3GraphEdge{&m_depGraph, vxp, overriddenVxp, 1};
new V3GraphEdge{&m_depGraph, overriddenVxp, vxp, 1};
}
}
}
}
if (nodep->user2() && !nodep->isCoroutine()) { // If first marked as suspendable
nodep->rtnType("VlCoroutine");
// If in a class, create a shared pointer to 'this'
if (m_classp) nodep->addInitsp(new AstCStmt{nodep->fileline(), "VL_KEEP_THIS;\n"});
// Revisit dependent nodes if needed
for (V3GraphEdge* edgep = vxp->inBeginp(); edgep; edgep = edgep->inNextp()) {
auto* const depVxp = static_cast<DependencyVertex*>(edgep->fromp());
AstNode* const depp = depVxp->nodep();
if (!depp->user2()) { // If dependent not suspendable
depp->user2(true);
if (auto* const funcp = VN_CAST(depp, CFunc)) {
// It's a coroutine but has no awaits (a class method that overrides/is
// overridden by a suspendable, but doesn't have any awaits itself). Add a
// co_return at the end (either that or a co_await is required in a
// coroutine)
funcp->addStmtsp(new AstCStmt{funcp->fileline(), "co_return;\n"});
}
}
iterate(depp);
}
}
}
void visit(AstNodeCCall* nodep) override {
if (nodep->funcp()->user2()) { // If suspendable
VNRelinker relinker;
nodep->unlinkFrBack(&relinker);
AstCAwait* const awaitp = new AstCAwait{nodep->fileline(), nodep};
awaitp->dtypeSetVoid();
relinker.relink(awaitp);
} else {
// Add our process/func as the CFunc's dependency as we might have to put an await here
DependencyVertex* const procVxp = getDependencyVertex(m_procp);
DependencyVertex* const funcVxp = getDependencyVertex(nodep->funcp());
new V3GraphEdge{&m_depGraph, procVxp, funcVxp, 1};
}
iterateChildren(nodep);
}
void visit(AstCAwait* nodep) override {
v3Global.setUsesTiming();
m_procp->user2(true);
}
void visit(AstDelay* nodep) override {
UASSERT_OBJ(!nodep->isCycleDelay(), nodep,
"Cycle delays should have been handled in V3AssertPre");
FileLine* const flp = nodep->fileline();
AstNodeExpr* valuep = V3Const::constifyEdit(nodep->lhsp()->unlinkFrBack());
auto* const constp = VN_CAST(valuep, Const);
if (constp && constp->isZero()) {
nodep->v3warn(ZERODLY, "Unsupported: #0 delays do not schedule process resumption in "
"the Inactive region");
} else {
// Scale the delay
if (valuep->dtypep()->isDouble()) {
valuep = new AstRToIRoundS{
flp,
new AstMulD{flp, valuep,
new AstConst{flp, AstConst::RealDouble{}, m_timescaleFactor}}};
valuep->dtypeSetBitSized(64, VSigning::UNSIGNED);
} else {
valuep->dtypeSetBitSized(64, VSigning::UNSIGNED);
valuep = new AstMul{flp, valuep,
new AstConst{flp, AstConst::Unsized64{},
static_cast<uint64_t>(m_timescaleFactor)}};
}
}
// Replace self with a 'co_await dlySched.delay(<valuep>)'
auto* const delayMethodp = new AstCMethodHard{
flp, new AstVarRef{flp, getCreateDelayScheduler(), VAccess::WRITE}, "delay", valuep};
delayMethodp->dtypeSetVoid();
addDebugInfo(delayMethodp);
// Create the co_await
AstCAwait* const awaitp = new AstCAwait{flp, delayMethodp, getCreateDelaySenTree()};
awaitp->dtypeSetVoid();
AstStmtExpr* const awaitStmtp = awaitp->makeStmt();
// Relink child statements after the co_await
if (nodep->stmtsp()) {
AstNode::addNext<AstNode, AstNode>(awaitStmtp,
nodep->stmtsp()->unlinkFrBackWithNext());
}
nodep->replaceWith(awaitStmtp);
VL_DO_DANGLING(nodep->deleteTree(), nodep);
}
void visit(AstEventControl* nodep) override {
// Do not allow waiting on local named events, as they get enqueued for clearing, but can
// go out of scope before that happens
if (!nodep->sensesp()) nodep->v3warn(E_UNSUPPORTED, "Unsupported: no sense equation (@*)");
if (nodep->sensesp()->exists([](const AstNodeVarRef* refp) {
AstBasicDType* const dtypep = refp->dtypep()->skipRefp()->basicp();
return dtypep && dtypep->isEvent() && refp->varp()->isFuncLocal();
})) {
nodep->v3warn(E_UNSUPPORTED, "Unsupported: waiting on local event variables");
}
FileLine* const flp = nodep->fileline();
// Relink child statements after the event control
if (nodep->stmtsp()) nodep->addNextHere(nodep->stmtsp()->unlinkFrBackWithNext());
if (needDynamicTrigger(nodep->sensesp())) {
// Create the trigger variable and init it with 0
AstVarScope* const trigvscp
= createTemp(flp, m_dynTrigNames.get(nodep), nodep->findBitDType(), nodep);
auto* const initp = new AstAssign{flp, new AstVarRef{flp, trigvscp, VAccess::WRITE},
new AstConst{flp, AstConst::BitFalse{}}};
nodep->addHereThisAsNext(initp);
// Await the eval step with the dynamic trigger scheduler. First, create the method
// call
auto* const evalMethodp = new AstCMethodHard{
flp, new AstVarRef{flp, getCreateDynamicTriggerScheduler(), VAccess::WRITE},
"evaluation"};
evalMethodp->dtypeSetVoid();
auto* const sensesp = nodep->sensesp();
addEventDebugInfo(evalMethodp, sensesp);
// Create the co_await
AstCAwait* const awaitEvalp
= new AstCAwait{flp, evalMethodp, getCreateDynamicTriggerSenTree()};
awaitEvalp->dtypeSetVoid();
// Construct the sen expression for this sentree
SenExprBuilder senExprBuilder{m_scopep};
auto* const assignp = new AstAssign{flp, new AstVarRef{flp, trigvscp, VAccess::WRITE},
senExprBuilder.build(sensesp).first};
// Put all the locals and inits before the trigger eval loop
for (AstVar* const varp : senExprBuilder.getAndClearLocals()) {
nodep->addHereThisAsNext(varp);
}
for (AstNodeStmt* const stmtp : senExprBuilder.getAndClearInits()) {
nodep->addHereThisAsNext(stmtp);
}
// Create the trigger eval loop, which will await the evaluation step and check the
// trigger
AstWhile* const loopp = new AstWhile{
flp, new AstLogNot{flp, new AstVarRef{flp, trigvscp, VAccess::READ}},
awaitEvalp->makeStmt()};
// Put pre updates before the trigger check and assignment
for (AstNodeStmt* const stmtp : senExprBuilder.getAndClearPreUpdates()) {
loopp->addStmtsp(stmtp);
}
// Then the trigger check and assignment
loopp->addStmtsp(assignp);
// If the post update is destructive (e.g. event vars are cleared), create an await for
// the post update step
if (destructivePostUpdate(sensesp)) {
AstCAwait* const awaitPostUpdatep = awaitEvalp->cloneTree(false);
VN_AS(awaitPostUpdatep->exprp(), CMethodHard)->name("postUpdate");
loopp->addStmtsp(awaitPostUpdatep->makeStmt());
}
// Put the post updates at the end of the loop
for (AstNodeStmt* const stmtp : senExprBuilder.getAndClearPostUpdates()) {
loopp->addStmtsp(stmtp);
}
// Finally, await the resumption step in 'act'
AstCAwait* const awaitResumep = awaitEvalp->cloneTree(false);
VN_AS(awaitResumep->exprp(), CMethodHard)->name("resumption");
AstNode::addNext<AstNodeStmt, AstNodeStmt>(loopp, awaitResumep->makeStmt());
// Replace the event control with the loop
nodep->replaceWith(loopp);
} else {
auto* const sensesp = m_finder.getSenTree(nodep->sensesp());
nodep->sensesp()->unlinkFrBack()->deleteTree();
// Get this sentree's trigger scheduler
// Replace self with a 'co_await trigSched.trigger()'
auto* const triggerMethodp = new AstCMethodHard{
flp, new AstVarRef{flp, getCreateTriggerSchedulerp(sensesp), VAccess::WRITE},
"trigger"};
triggerMethodp->dtypeSetVoid();
addEventDebugInfo(triggerMethodp, sensesp);
// Create the co_await
AstCAwait* const awaitp = new AstCAwait{flp, triggerMethodp, sensesp};
awaitp->dtypeSetVoid();
nodep->replaceWith(awaitp->makeStmt());
}
VL_DO_DANGLING(nodep->deleteTree(), nodep);
}
void visit(AstNodeAssign* nodep) override {
// Only process once to avoid infinite loops (due to the net delay)
if (nodep->user1SetOnce()) return;
AstNode* const controlp = factorOutTimingControl(nodep);
if (!controlp) return;
// Handle the intra assignment timing control
FileLine* const flp = nodep->fileline();
if (VN_IS(nodep, AssignDly)) {
// If it's an NBA with an intra assignment delay, put it in a fork
auto* const forkp = new AstFork{flp, "", nullptr};
forkp->joinType(VJoinType::JOIN_NONE);
controlp->replaceWith(forkp);
forkp->addStmtsp(controlp);
}
// Insert new vars before the timing control if we're in a function; in a process we can't
// do that. These intra-assignment vars will later be passed to forked processes by value.
AstNode* const insertBeforep = VN_IS(m_procp, CFunc) ? controlp : nullptr;
// Function for replacing values with intermediate variables
const auto replaceWithIntermediate = [&](AstNodeExpr* const valuep,
const std::string& name) {
AstVarScope* const newvscp = createTemp(flp, name, valuep->dtypep(), insertBeforep);
valuep->replaceWith(new AstVarRef{flp, newvscp, VAccess::READ});
controlp->addHereThisAsNext(
new AstAssign{flp, new AstVarRef{flp, newvscp, VAccess::WRITE}, valuep});
};
// Create the intermediate select vars. Note: because 'foreach' proceeds in
// pre-order, and we replace indices in selects with variables, we cannot
// reach another select under the index position. This is exactly what
// we want as only the top level selects are LValues. As an example,
// this transforms 'x[a[i]][b[j]] = y'
// into 't1 = a[i]; t0 = b[j]; x[t1][t0] = y'.
nodep->lhsp()->foreach([&](AstSel* selp) {
if (VN_IS(selp->lsbp(), Const)) return;
replaceWithIntermediate(selp->lsbp(), m_intraLsbNames.get(nodep));
// widthp should be const
});
nodep->lhsp()->foreach([&](AstNodeSel* selp) {
if (VN_IS(selp->bitp(), Const)) return;
replaceWithIntermediate(selp->bitp(), m_intraIndexNames.get(nodep));
});
// Replace the RHS with an intermediate value var
replaceWithIntermediate(nodep->rhsp(), m_intraValueNames.get(nodep));
}
void visit(AstAssignW* nodep) override {
AstDelay* const netDelayp = getLhsNetDelay(nodep);
if (!netDelayp && !nodep->timingControlp()) return;
// This assignment will be converted to an always. In some cases this may generate an
// UNOPTFLAT, e.g.: assign #1 clk = ~clk. We create a temp var for the LHS of this
// assign, to disable the UNOPTFLAT warning for it.
// TODO: Find a way to do this without introducing this var. Perhaps make
// V3SchedAcyclic recognize awaits and prevent it from treating this kind of logic as
// cyclic
AstNodeExpr* const lhsp = nodep->lhsp()->unlinkFrBack();
std::string varname;
if (auto* const refp = VN_CAST(lhsp, VarRef)) {
varname = m_contAssignVarNames.get(refp->name());
} else {
varname = m_contAssignVarNames.get(lhsp);
}
auto* const tempvscp = m_scopep->createTemp(varname, lhsp->dtypep());
tempvscp->varp()->delayp(netDelayp);
FileLine* const flp = nodep->fileline();
flp->modifyWarnOff(V3ErrorCode::UNOPTFLAT, true);
tempvscp->fileline(flp);
tempvscp->varp()->fileline(flp);
// Remap the LHS to the new temp var
nodep->lhsp(new AstVarRef{flp, tempvscp, VAccess::WRITE});
// Convert it to an always; the new assign with intra delay will be handled by
// visit(AstNodeAssign*)
AstAlways* const alwaysp = nodep->convertToAlways();
visit(alwaysp);
// Put the LHS back in the AssignW; put the temp var on the RHS
nodep->lhsp(lhsp);
nodep->rhsp(new AstVarRef{flp, tempvscp, VAccess::READ});
// Put the AssignW right after the always. Different order can produce UNOPTFLAT on the LHS
// var
alwaysp->addNextHere(nodep);
}
void visit(AstWait* nodep) override {
// Wait on changed events related to the vars in the wait statement
FileLine* const flp = nodep->fileline();
AstNode* const stmtsp = nodep->stmtsp();
if (stmtsp) stmtsp->unlinkFrBackWithNext();
AstNodeExpr* const condp = V3Const::constifyEdit(nodep->condp()->unlinkFrBack());
auto* const constp = VN_CAST(condp, Const);
if (constp) {
condp->v3warn(WAITCONST, "Wait statement condition is constant");
if (constp->isZero()) {
// We have to await forever instead of simply returning in case we're deep in a
// callstack
AstCExpr* const foreverp = new AstCExpr{flp, "VlForever{}", 0, true};
foreverp->dtypeSetVoid(); // TODO: this is sloppy but harmless
AstCAwait* const awaitp = new AstCAwait{flp, foreverp};
awaitp->dtypeSetVoid();
nodep->replaceWith(awaitp->makeStmt());
if (stmtsp) VL_DO_DANGLING(stmtsp->deleteTree(), stmtsp);
VL_DO_DANGLING(condp->deleteTree(), condp);
} else if (stmtsp) {
// Just put the statements there
nodep->replaceWith(stmtsp);
} else {
nodep->unlinkFrBack();
}
} else if (needDynamicTrigger(condp)) {
// No point in making a sentree, just use the expression as sensitivity
// Put the event control in an if so we only wait if the condition isn't met already
auto* const ifp = new AstIf{
flp, new AstLogNot{flp, condp},
new AstEventControl{flp,
new AstSenTree{flp, new AstSenItem{flp, VEdgeType::ET_TRUE,
condp->cloneTree(false)}},
nullptr}};
if (stmtsp) AstNode::addNext<AstNode, AstNode>(ifp, stmtsp);
nodep->replaceWith(ifp);
} else {
AstSenItem* const senItemsp = varRefpsToSenItemsp(condp);
UASSERT_OBJ(senItemsp, nodep, "No varrefs in wait statement condition");
// Put the event control in a while loop with the wait expression as condition
auto* const loopp
= new AstWhile{flp, new AstLogNot{flp, condp},
new AstEventControl{flp, new AstSenTree{flp, senItemsp}, nullptr}};
if (stmtsp) AstNode::addNext<AstNode, AstNode>(loopp, stmtsp);
nodep->replaceWith(loopp);
}
VL_DO_DANGLING(nodep->deleteTree(), nodep);
}
void visit(AstFork* nodep) override {
if (nodep->user1SetOnce()) return;
v3Global.setUsesTiming();
// Create a unique name for this fork
nodep->name(m_forkNames.get(nodep));
unsigned idx = 0; // Index for naming begins
AstNode* stmtp = nodep->stmtsp();
// Put each statement in a begin
while (stmtp) {
if (!VN_IS(stmtp, Begin)) {
auto* const beginp = new AstBegin{stmtp->fileline(), "", nullptr};
stmtp->replaceWith(beginp);
beginp->addStmtsp(stmtp);
stmtp = beginp;
}
auto* const beginp = VN_AS(stmtp, Begin);
stmtp = beginp->nextp();
VL_RESTORER(m_procp);
m_procp = beginp;
iterate(beginp);
// Even if we do not find any awaits, we cannot simply inline the process here, as new
// awaits could be added later.
// Name the begin (later the name will be used for a new function)
beginp->name(nodep->name() + "__" + cvtToStr(idx++));
}
if (!nodep->joinType().joinNone()) makeForkJoin(nodep);
}
//--------------------
void visit(AstNodeExpr*) override {} // Accelerate
void visit(AstVar*) override {}
void visit(AstNode* nodep) override { iterateChildren(nodep); }
public:
// CONSTRUCTORS
explicit TimingVisitor(AstNetlist* nodep)
: m_netlistp{nodep} {
iterate(nodep);
if (dumpGraph() >= 6) m_depGraph.dumpDotFilePrefixed("timing_deps");
}
~TimingVisitor() override = default;
};
//######################################################################
// Timing class functions
void V3Timing::timingAll(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ": " << endl);
TimingVisitor{nodep};
V3Global::dumpCheckGlobalTree("timing", 0, dumpTree() >= 3);
}
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