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Implement a distinct constant pool (#3013)

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What previously used to be per module static constants created in
V3Table and V3Prelim are now merged globally within the whole model and
emitted as part of a separate constant pool. Members of the constant
pool are global variables which are declared lazily when used (similar to
loose methods).
This commit is contained in:
Geza Lore
2021-06-13 15:05:55 +01:00
committed by GitHub
parent 60d5f0e86b
commit c207e98306
50 changed files with 1331 additions and 344 deletions
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src/V3Premit.cpp
+25 -54
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@@ -92,11 +92,9 @@ private:
// AstNodeMath::user() -> bool. True if iterated already
// AstShiftL::user2() -> bool. True if converted to conditional
// AstShiftR::user2() -> bool. True if converted to conditional
// AstConst::user2p() -> Replacement static variable pointer
// *::user4() -> See PremitAssignVisitor
AstUser1InUse m_inuser1;
AstUser2InUse m_inuser2;
// AstUser4InUse part of V3Hasher via V3DupFinder
// STATE
AstNodeModule* m_modp = nullptr; // Current module
@@ -106,10 +104,7 @@ private:
AstTraceInc* m_inTracep = nullptr; // Inside while loop, special statement additions
bool m_assignLhs = false; // Inside assignment lhs, don't breakup extracts
V3DupFinder m_dupFinder; // Duplicate finder for static constants that can be reused
VDouble0 m_staticConstantsExtracted; // Statistic tracking
VDouble0 m_staticConstantsReused; // Statistic tracking
VDouble0 m_extractedToConstPool; // Statistic tracking
// METHODS
VL_DEBUG_FUNC; // Declare debug()
@@ -170,71 +165,48 @@ private:
}
void createDeepTemp(AstNode* nodep, bool noSubst) {
if (nodep->user1()) return;
if (debug() > 8) nodep->dumpTree(cout, "deepin:");
if (nodep->user1SetOnce()) return; // Only add another assignment for this node
AstNRelinker linker;
nodep->unlinkFrBack(&linker);
AstNRelinker relinker;
nodep->unlinkFrBack(&relinker);
FileLine* const fl = nodep->fileline();
AstVar* varp = nullptr;
AstConst* const constp = VN_CAST(nodep, Const);
const bool useStatic = constp && (constp->width() >= STATIC_CONST_MIN_WIDTH)
&& !constp->num().isFourState();
if (useStatic) {
// Extract as static constant
const auto& it = m_dupFinder.findDuplicate(constp);
if (it == m_dupFinder.end()) {
const string newvarname = string("__Vconst") + cvtToStr(m_modp->varNumGetInc());
varp = new AstVar(nodep->fileline(), AstVarType::MODULETEMP, newvarname,
nodep->dtypep());
varp->isConst(true);
varp->isStatic(true);
varp->valuep(constp);
m_modp->addStmtp(varp);
m_dupFinder.insert(constp);
nodep->user2p(varp);
++m_staticConstantsExtracted;
} else {
varp = VN_CAST(it->second->user2p(), Var);
++m_staticConstantsReused;
}
const bool useConstPool = constp // Is a constant
&& (constp->width() >= STATIC_CONST_MIN_WIDTH) // Large enough
&& !constp->num().isFourState() // Not four state
&& !constp->num().isString(); // Not a string
if (useConstPool) {
// Extract into constant pool.
const bool merge = v3Global.opt.mergeConstPool();
varp = v3Global.rootp()->constPoolp()->findConst(constp, merge)->varp();
nodep->deleteTree();
++m_extractedToConstPool;
} else {
// Keep as local temporary
const string newvarname = string("__Vtemp") + cvtToStr(m_modp->varNumGetInc());
varp
= new AstVar(nodep->fileline(), AstVarType::STMTTEMP, newvarname, nodep->dtypep());
const string name = string("__Vtemp") + cvtToStr(m_modp->varNumGetInc());
varp = new AstVar(fl, AstVarType::STMTTEMP, name, nodep->dtypep());
m_cfuncp->addInitsp(varp);
}
if (noSubst) varp->noSubst(true); // Do not remove varrefs to this in V3Const
// Replace node tree with reference to var
AstVarRef* newp = new AstVarRef(nodep->fileline(), varp, VAccess::READ);
linker.relink(newp);
if (!useStatic) {
// Put assignment before the referencing statement
AstAssign* assp = new AstAssign(
nodep->fileline(), new AstVarRef(nodep->fileline(), varp, VAccess::WRITE), nodep);
insertBeforeStmt(assp);
if (debug() > 8) assp->dumpTree(cout, "deepou:");
insertBeforeStmt(new AstAssign(fl, new AstVarRef(fl, varp, VAccess::WRITE), nodep));
}
nodep->user1(true); // Don't add another assignment
// Do not remove VarRefs to this in V3Const
if (noSubst) varp->noSubst(true);
// Replace node with VarRef to new Var
relinker.relink(new AstVarRef(fl, varp, VAccess::READ));
}
// VISITORS
virtual void visit(AstNodeModule* nodep) override {
UINFO(4, " MOD " << nodep << endl);
UASSERT_OBJ(m_modp == nullptr, nodep, "Nested modules ?");
UASSERT_OBJ(m_dupFinder.empty(), nodep, "Statements outside module ?");
m_modp = nodep;
m_cfuncp = nullptr;
iterateChildren(nodep);
m_modp = nullptr;
m_dupFinder.clear();
}
virtual void visit(AstCFunc* nodep) override {
VL_RESTORER(m_cfuncp);
@@ -442,9 +414,8 @@ public:
// CONSTRUCTORS
explicit PremitVisitor(AstNetlist* nodep) { iterate(nodep); }
virtual ~PremitVisitor() {
V3Stats::addStat("Optimizations, Prelim static constants extracted",
m_staticConstantsExtracted);
V3Stats::addStat("Optimizations, Prelim static constants reused", m_staticConstantsReused);
V3Stats::addStat("Optimizations, Prelim extracted value to ConstPool",
m_extractedToConstPool);
}
};