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Optimize redundant vertex cache lookups in DFG peephole (#8283)

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This commit is contained in:
Geza Lore
2026-09-05 11:13:30 -04:00
committed by GitHub
parent fa59f8f302
commit 87108ff943
2 changed files with 63 additions and 19 deletions
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src/V3DfgCache.h
+10 -8
View File
@@ -328,21 +328,23 @@ class V3DfgCache final {
}
public:
// Note: the cache starts out empty. If the caller wants existing vertices
// to be found, it must add them itself by calling 'cache' on each.
explicit V3DfgCache(DfgGraph& dfg)
: m_dfg{dfg} {
// Initialize the type to cache lookup table
// Initialize the type to cache lookup table
#define VERTEX_CACHE_DECLARE_CACHE_PTR(t) m_vtxType2Cachep[t::dfgType()] = &m_cache##t;
FOREACH_DFG_VERTEX_TYPE(VERTEX_CACHE_DECLARE_CACHE_PTR)
FOREACH_DFG_VERTEX_TYPE(VERTEX_CACHE_DECLARE_CACHE_PTR)
#undef VERTEX_CACHE_DECLARE_CACHE_PTR
}
// Add all operation vertices to the cache
for (DfgVertex& vtx : m_dfg.opVertices()) cache(&vtx);
// Add an existing vertex to the cache. If an equivalent (but different) already exists,
// it is returned and the cache is not updated.
DfgVertex
* cache(DfgVertex * vtxp) {
return m_vtxType2Cachep[vtxp->type()]->cache(vtxp);
}
// Add an existing vertex to the cache. If an equivalent (but different) already exists,
// it is returned and the cache is not updated.
DfgVertex* cache(DfgVertex* vtxp) { return m_vtxType2Cachep[vtxp->type()]->cache(vtxp); }
// Remove an exiting vertex, it is the cached vertex.
void invalidate(DfgVertex* vtxp) { m_vtxType2Cachep[vtxp->type()]->invalidate(vtxp); }
src/V3DfgPeephole.cpp
+53 -11
View File
@@ -195,6 +195,7 @@ class V3DfgPeephole final : public DfgVisitor {
size_t m_iterListIndex = 0; // Position of this vertx m_iterList (0 means not in list)
size_t m_generation = 0; // Generation number of this vertex - for uniqueness check
size_t m_id = 0; // Unique vertex ID (0 means unassigned) - for sorting
bool m_isCachedVertex = false; // This vertex is the vertex cached for its operation
};
// STATE
@@ -226,6 +227,41 @@ class V3DfgPeephole final : public DfgVisitor {
return true;
}
// Add vertex to the cache. If an equivalent (but different) vertex is
// already cached, it is returned and the cache is not updated.
DfgVertex* cacheVertex(DfgVertex* vtxp) {
DfgVertex* const equivp = m_cache.cache(vtxp);
UASSERT_OBJ(!m_vInfo[vtxp].m_isCachedVertex || !equivp, vtxp,
"Vertex marked 'm_isCachedVertex' has a cached equivalent");
m_vInfo[vtxp].m_isCachedVertex = !equivp;
return equivp;
}
// Remove vertex from the cache (no-op if it is not the cached vertex)
void invalidateVertex(DfgVertex* vtxp) {
m_cache.invalidate(vtxp);
m_vInfo[vtxp].m_isCachedVertex = false;
}
// Find the vertex of the given type with the given operands in the
// cache, or create a new one and add it to the cache.
template <typename Vertex, typename... Operands>
Vertex* getOrCreateVertex(FileLine* flp, const DfgDataType& dtype, Operands... operands) {
Vertex* const vtxp = m_cache.getOrCreate<Vertex, Operands...>(flp, dtype, operands...);
m_vInfo[vtxp].m_isCachedVertex = true;
return vtxp;
}
// Find the vertex of the given type with the given operands in the
// cache, or nullptr if there is no such vertex.
template <typename Vertex, typename... Operands>
Vertex* getVertex(const DfgDataType& dtype, Operands... operands) {
Vertex* const vtxp = m_cache.get<Vertex>(dtype, operands...);
UASSERT_OBJ(!vtxp || m_vInfo[vtxp].m_isCachedVertex, vtxp,
"Cached vertex not marked 'm_isCachedVertex'");
return vtxp;
}
void incrementGeneration() {
++m_currentGeneration;
// TODO: could sweep on overflow
@@ -270,7 +306,7 @@ class V3DfgPeephole final : public DfgVisitor {
UASSERT_OBJ(!varp || !varp->hasPrev(), vtxp, "Deleting variable consumed via DfgPrev");
// Invalidate cache entry
m_cache.invalidate(vtxp);
invalidateVertex(vtxp);
// It might be in the iter list, remove it
removeFromIterList(vtxp);
@@ -344,14 +380,14 @@ class V3DfgPeephole final : public DfgVisitor {
// Remove sinks of the original vertex from the cache - their inputs are changing
m_vtxp->foreachSink([&](DfgVertex& dst) {
m_cache.invalidate(&dst);
invalidateVertex(&dst);
return false;
});
// Replace vertex with the replacement
m_vtxp->replaceWith(resp);
// Re-cache all sinks of the replacement
resp->foreachSink([&](DfgVertex& dst) {
m_cache.cache(&dst);
cacheVertex(&dst);
return false;
});
@@ -390,7 +426,7 @@ class V3DfgPeephole final : public DfgVisitor {
template <typename Vertex, typename... Operands>
Vertex* make(FileLine* flp, const DfgDataType& dtype, Operands... operands) {
// Find or create an equivalent vertex
Vertex* const vtxp = m_cache.getOrCreate<Vertex, Operands...>(flp, dtype, operands...);
Vertex* const vtxp = getOrCreateVertex<Vertex, Operands...>(flp, dtype, operands...);
// Sanity check
UASSERT_OBJ(vtxp->dtype() == dtype, vtxp, "Vertex dtype mismatch");
if (VL_UNLIKELY(v3Global.opt.debugCheck())) vtxp->typeCheck(m_dfg);
@@ -594,7 +630,7 @@ class V3DfgPeephole final : public DfgVisitor {
// '(a OP (b OP c))' -> '(a OP b) OP c'
if (Vertex* const existingp
= m_cache.get<Vertex>(resultDType<Vertex>(lhsp, rlVtxp), lhsp, rlVtxp)) {
= getVertex<Vertex>(resultDType<Vertex>(lhsp, rlVtxp), lhsp, rlVtxp)) {
UASSERT_OBJ(existingp->hasSinks(), vtxp, "Existing vertex should be used");
if (existingp != rhsp) {
APPLYING(REUSE_ASSOC_BINARY_LHS_WITH_LHS_OF_RHS) {
@@ -607,7 +643,7 @@ class V3DfgPeephole final : public DfgVisitor {
// '(a OP (b OP c))' -> '(a OP c) OP b' iff also commutative
if VL_CONSTEXPR_CXX17 (IsCommutative<Vertex>::value) {
if (Vertex* const existingp
= m_cache.get<Vertex>(resultDType<Vertex>(lhsp, rrVtxp), lhsp, rrVtxp)) {
= getVertex<Vertex>(resultDType<Vertex>(lhsp, rrVtxp), lhsp, rrVtxp)) {
UASSERT_OBJ(existingp->hasSinks(), vtxp, "Existing vertex should be used");
if (existingp != rhsp) {
APPLYING(REUSE_ASSOC_BINARY_LHS_WITH_RHS_OF_RHS) {
@@ -3127,6 +3163,9 @@ class V3DfgPeephole final : public DfgVisitor {
// Assign vertex IDs
m_dfg.forEachVertex([&](DfgVertex& vtx) { m_vInfo[vtx].m_id = ++m_lastId; });
// Add all operation vertices to the cache
for (DfgVertex& vtx : m_dfg.opVertices()) cacheVertex(&vtx);
// Initialize the work list and iter list. They can't get bigger than
// m_dfg.size(), but new vertices are created in the loop, so over alloacte
m_workList.reserve(m_dfg.size() * 2);
@@ -3168,11 +3207,14 @@ class V3DfgPeephole final : public DfgVisitor {
// Unsued vertices should have been removed immediately
UASSERT_OBJ(m_vtxp->hasSinks(), m_vtxp, "Operation vertex should have sinks");
// Check if an equivalent vertex exists, if so replace this vertex with it
if (DfgVertex* const sampep = m_cache.cache(m_vtxp)) {
APPLYING(REPLACE_WITH_EQUIVALENT) {
replace(sampep);
continue;
// Check if an equivalent vertex exists, if so replace this vertex with it.
// Can skip the lookup if the vertex is known to be the cached one
if (!m_vInfo[m_vtxp].m_isCachedVertex) {
if (DfgVertex* const sampep = cacheVertex(m_vtxp)) {
APPLYING(REPLACE_WITH_EQUIVALENT) {
replace(sampep);
continue;
}
}
}