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Speed up Dfg common sub-expression elimination

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Added a DfgVertex::user() mechanism for storing data in vertices.
Similar in spirit to AstNode user data, but the generation counter is
stored in the DfgGraph the vertex is held under. Use this to cache
DfgVertex::hash results, and also speed up DfgVertex hashing in general.

Use these and additional improvements to speed up CSE.
This commit is contained in:
Geza Lore
2022-10-06 19:59:01 +01:00
parent 97add4d57a
commit 4f0158b5e0
5 changed files with 132 additions and 66 deletions
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src/V3Dfg.cpp
+27 -27
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@@ -864,9 +864,10 @@ bool DfgVertex::equals(const DfgVertex& that, EqualsCache& cache) const {
const auto key = (this < &that) ? EqualsCache::key_type{this, &that} //
: EqualsCache::key_type{&that, this};
const auto pair = cache.emplace(key, true);
bool& result = pair.first->second;
if (pair.second) {
// Note: the recursive invocation can cause a re-hash of the cache which invalidates iterators
uint8_t result = cache[key];
if (!result) {
result = 2; // Assume equals
auto thisPair = this->sourceEdges();
const DfgEdge* const thisSrcEdgesp = thisPair.first;
const size_t thisArity = thisPair.second;
@@ -879,24 +880,30 @@ bool DfgVertex::equals(const DfgVertex& that, EqualsCache& cache) const {
const DfgVertex* const thatSrcVtxp = thatSrcEdgesp[i].m_sourcep;
if (thisSrcVtxp == thatSrcVtxp) continue;
if (!thisSrcVtxp || !thatSrcVtxp || !thisSrcVtxp->equals(*thatSrcVtxp, cache)) {
result = false;
result = 1; // Mark not equal
break;
}
}
cache[key] = result;
}
return result;
return result >> 1;
}
V3Hash DfgVertex::hash(HashCache& cache) const {
const auto pair = cache.emplace(this, V3Hash{});
V3Hash& result = pair.first->second;
if (pair.second) {
result += selfHash();
V3Hash DfgVertex::hash() {
V3Hash& result = user<V3Hash>();
if (!result.value()) {
V3Hash hash;
hash += selfHash();
// Variables are defined by themselves, so there is no need to hash the sources. This
// enables sound hashing of graphs circular only through variables, which we rely on.
if (!is<DfgVertexVar>()) {
forEachSource([&result, &cache](const DfgVertex& src) { result += src.hash(cache); });
const auto pair = sourceEdges();
const DfgEdge* const edgesp = pair.first;
const size_t arity = pair.second;
// Sources must always be connected in well-formed graphs
for (size_t i = 0; i < arity; ++i) hash += edgesp[i].m_sourcep->hash();
}
result = hash;
}
return result;
}
@@ -926,30 +933,23 @@ void DfgVertex::replaceWith(DfgVertex* newSorucep) {
// Vertex classes
//------------------------------------------------------------------------------
// DfgVarPacked ----------
// DfgVertexVar ----------
bool DfgVarPacked::selfEquals(const DfgVertex& that) const {
if (const DfgVarPacked* otherp = that.cast<DfgVarPacked>()) {
bool DfgVertexVar::selfEquals(const DfgVertex& that) const {
if (const DfgVertexVar* otherp = that.cast<DfgVertexVar>()) {
UASSERT_OBJ(varp() != otherp->varp(), this,
"There should only be one DfgVarPacked for a given AstVar");
}
return false;
}
V3Hash DfgVarPacked::selfHash() const { return V3Hasher::uncachedHash(varp()); }
// DfgVarPacked ----------
bool DfgVarArray::selfEquals(const DfgVertex& that) const {
if (const DfgVarArray* otherp = that.cast<DfgVarArray>()) {
UASSERT_OBJ(varp() != otherp->varp(), this,
"There should only be one DfgVarArray for a given AstVar");
}
return false;
V3Hash DfgVertexVar::selfHash() const {
V3Hash hash;
hash += m_varp->name();
hash += m_varp->varType();
return hash;
}
V3Hash DfgVarArray::selfHash() const { return V3Hasher::uncachedHash(varp()); }
// DfgConst ----------
bool DfgConst::selfEquals(const DfgVertex& that) const {
@@ -959,7 +959,7 @@ bool DfgConst::selfEquals(const DfgVertex& that) const {
return false;
}
V3Hash DfgConst::selfHash() const { return V3Hasher::uncachedHash(m_constp); }
V3Hash DfgConst::selfHash() const { return m_constp->num().toHash(); }
//------------------------------------------------------------------------------
// DfgVisitor