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IEEE compliant scheduler (#3384)

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This is a major re-design of the way code is scheduled in Verilator,
with the goal of properly supporting the Active and NBA regions of the
SystemVerilog scheduling model, as defined in IEEE 1800-2017 chapter 4.

With this change, all internally generated clocks should simulate
correctly, and there should be no more need for the `clock_enable` and
`clocker` attributes for correctness in the absence of Verilator
generated library models (`--lib-create`).

Details of the new scheduling model and algorithm are provided in
docs/internals.rst.

Implements #3278
This commit is contained in:
Geza Lore
2022-05-15 16:03:32 +01:00
committed by GitHub
parent 39b7c47e7b
commit 599d23697d
157 changed files with 6386 additions and 4395 deletions
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src/V3Delayed.cpp
+52 -20
View File
@@ -93,7 +93,7 @@ private:
AstAssignDly* m_nextDlyp = nullptr; // Next delayed assignment in a list of assignments
bool m_inDly = false; // True in delayed assignments
bool m_inLoop = false; // True in for loops
bool m_inInitial = false; // True in initial blocks
bool m_inInitial = false; // True in static initializers and initial blocks
using VarMap = std::map<const std::pair<AstNodeModule*, std::string>, AstVar*>;
VarMap m_modVarMap; // Table of new var names created under module
VDouble0 m_statSharedSet; // Statistic tracking
@@ -160,7 +160,7 @@ private:
return varscp;
}
AstActive* createActivePost(AstVarRef* varrefp) {
AstActive* createActive(AstNode* varrefp) {
AstActive* const newactp
= new AstActive(varrefp->fileline(), "sequentdly", m_activep->sensesp());
// Was addNext(), but addNextHere() avoids a linear search.
@@ -336,7 +336,7 @@ private:
} else { // first time we've dealt with this memory
finalp = new AstAlwaysPost(nodep->fileline(), nullptr /*sens*/, nullptr /*body*/);
UINFO(9, " Created " << finalp << endl);
AstActive* const newactp = createActivePost(varrefp);
AstActive* const newactp = createActive(varrefp);
newactp->addStmtsp(finalp);
varrefp->varScopep()->user4p(finalp);
finalp->user2p(newactp);
@@ -383,12 +383,54 @@ private:
m_activep = nodep;
VL_RESTORER(m_inInitial);
{
m_inInitial = nodep->hasInitial();
AstSenTree* const senTreep = nodep->sensesp();
m_inInitial = senTreep->hasStatic() || senTreep->hasInitial();
// Two sets to same variable in different actives must use different vars.
AstNode::user3ClearTree();
iterateChildren(nodep);
}
}
virtual void visit(AstFireEvent* nodep) override {
UASSERT_OBJ(v3Global.hasEvents(), nodep, "Inconsistent");
FileLine* const flp = nodep->fileline();
if (nodep->isDeleyed()) {
AstVarRef* const vrefp = VN_AS(nodep->operandp(), VarRef);
vrefp->unlinkFrBack();
const string newvarname = (string("__Vdly__") + vrefp->varp()->shortName());
AstVarScope* const dlyvscp = createVarSc(vrefp->varScopep(), newvarname, 1, nullptr);
const auto dlyRef = [=](VAccess access) {
return new AstVarRef{flp, dlyvscp, access};
};
AstAssignPre* const prep = new AstAssignPre{flp, dlyRef(VAccess::WRITE),
new AstConst{flp, AstConst::BitFalse{}}};
AstAlwaysPost* const postp = new AstAlwaysPost{flp, nullptr, nullptr};
{
AstIf* const ifp = new AstIf{flp, dlyRef(VAccess::READ)};
postp->addStmtp(ifp);
AstCMethodHard* const callp = new AstCMethodHard{flp, vrefp, "fire"};
callp->statement(true);
callp->dtypeSetVoid();
ifp->addIfsp(callp);
}
AstActive* const activep = createActive(nodep);
activep->addStmtsp(prep);
activep->addStmtsp(postp);
AstAssign* const assignp = new AstAssign{flp, dlyRef(VAccess::WRITE),
new AstConst{flp, AstConst::BitTrue{}}};
nodep->replaceWith(assignp);
} else {
AstCMethodHard* const callp
= new AstCMethodHard{flp, nodep->operandp()->unlinkFrBack(), "fire"};
callp->dtypeSetVoid();
callp->statement(true);
nodep->replaceWith(callp);
}
nodep->deleteTree();
}
virtual void visit(AstAssignDly* nodep) override {
m_inDly = true;
m_nextDlyp
@@ -407,7 +449,7 @@ private:
"loops (non-delayed is ok - see docs)");
}
const AstBasicDType* const basicp = lhsp->dtypep()->basicp();
if (basicp && basicp->isEventValue()) {
if (basicp && basicp->isEvent()) {
nodep->v3warn(E_UNSUPPORTED, "Unsupported: event arrays");
}
if (newlhsp) {
@@ -444,20 +486,10 @@ private:
if (!dlyvscp) { // First use of this delayed variable
const string newvarname = (string("__Vdly__") + nodep->varp()->shortName());
dlyvscp = createVarSc(oldvscp, newvarname, 0, nullptr);
AstNodeAssign* prep;
const AstBasicDType* const basicp = oldvscp->dtypep()->basicp();
if (basicp && basicp->isEventValue()) {
// Events go to zero on next timestep unless reactivated
prep = new AstAssignPre(
nodep->fileline(),
new AstVarRef(nodep->fileline(), dlyvscp, VAccess::WRITE),
new AstConst(nodep->fileline(), AstConst::BitFalse()));
} else {
prep = new AstAssignPre(
nodep->fileline(),
new AstVarRef(nodep->fileline(), dlyvscp, VAccess::WRITE),
new AstVarRef(nodep->fileline(), oldvscp, VAccess::READ));
}
AstNodeAssign* const prep = new AstAssignPre(
nodep->fileline(),
new AstVarRef(nodep->fileline(), dlyvscp, VAccess::WRITE),
new AstVarRef(nodep->fileline(), oldvscp, VAccess::READ));
AstNodeAssign* const postp = new AstAssignPost(
nodep->fileline(),
new AstVarRef(nodep->fileline(), oldvscp, VAccess::WRITE),
@@ -465,7 +497,7 @@ private:
postp->lhsp()->user2(true); // Don't detect this assignment
oldvscp->user1p(dlyvscp); // So we can find it later
// Make new ACTIVE with identical sensitivity tree
AstActive* const newactp = createActivePost(nodep);
AstActive* const newactp = createActive(nodep);
dlyvscp->user2p(newactp);
newactp->addStmtsp(prep); // Add to FRONT of statements
newactp->addStmtsp(postp);