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Optimize Dfg only once, after V3Scope (#7362)

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This commit is contained in:
Geza Lore
2026-04-09 08:31:12 -04:00
committed by GitHub
parent e63c4f563e
commit 9f9532ff78
54 changed files with 752 additions and 1399 deletions
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src/V3DfgOptimizer.cpp
+37 -105
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@@ -26,6 +26,7 @@
#include "V3Const.h"
#include "V3Dfg.h"
#include "V3DfgPasses.h"
#include "V3Error.h"
#include "V3Graph.h"
#include "V3UniqueNames.h"
@@ -255,84 +256,39 @@ class DataflowOptimize final {
// STATE
V3DfgContext m_ctx; // The context holding values that need to persist across multiple graphs
const bool m_scoped; // Running after V3Scope
void endOfStage(const std::string& name, const DfgGraph* dfgp = nullptr) {
// Dump the graph for debugging if given one
if (VL_UNLIKELY(dumpDfgLevel() >= 8 && dfgp)) {
dfgp->dumpDotFilePrefixed(m_ctx.prefix() + name);
}
if (VL_UNLIKELY(dumpDfgLevel() >= 8 && dfgp)) dfgp->dumpDotFilePrefixed(name);
// Dump stage stats only in scoped mode when running on the whole netlist
if (VL_UNLIKELY(v3Global.opt.stats() && m_scoped)) {
V3Stats::statsStage("dfg-optimize-" + name);
}
if (VL_UNLIKELY(v3Global.opt.stats())) V3Stats::statsStage("dfg-optimize-" + name);
}
// Mark variables with external references
void markExternallyReferencedVariables(AstNetlist* netlistp) {
netlistp->foreach([this](AstNode* nodep) {
netlistp->foreach([](AstNode* nodep) {
// Check variable flags
if (m_scoped) {
if (AstVarScope* const vscp = VN_CAST(nodep, VarScope)) {
const AstVar* const varp = vscp->varp();
// Force and trace have already been processed
const bool hasExtRd = varp->isPrimaryIO() || varp->isSigUserRdPublic();
const bool hasExtWr = varp->isPrimaryIO() || varp->isSigUserRWPublic();
if (hasExtRd) DfgVertexVar::setHasExtRdRefs(vscp);
if (hasExtWr) DfgVertexVar::setHasExtWrRefs(vscp);
return;
}
// Check direct references
if (const AstVarRef* const refp = VN_CAST(nodep, VarRef)) {
if (refp->access().isRW()) DfgVertexVar::setHasRWRefs(refp->varScopep());
UASSERT_OBJ(!refp->classOrPackagep(), refp, "V3Scope should have removed");
return;
}
} else {
if (AstVar* const varp = VN_CAST(nodep, Var)) {
const bool hasExtRd = varp->isPrimaryIO() || varp->isSigUserRdPublic() //
|| varp->isForced() || varp->isTrace();
const bool hasExtWr = varp->isPrimaryIO() || varp->isSigUserRWPublic() //
|| varp->isForced();
if (hasExtRd) DfgVertexVar::setHasExtRdRefs(varp);
if (hasExtWr) DfgVertexVar::setHasExtWrRefs(varp);
return;
}
// Check direct references
if (const AstVarRef* const refp = VN_CAST(nodep, VarRef)) {
AstVar* const varp = refp->varp();
if (refp->access().isRW()) DfgVertexVar::setHasRWRefs(varp);
// With classOrPackagep set this is a disguised hierarchical reference, mark
if (refp->classOrPackagep()) {
if (refp->access().isReadOrRW()) DfgVertexVar::setHasExtRdRefs(varp);
if (refp->access().isWriteOrRW()) DfgVertexVar::setHasExtWrRefs(varp);
}
return;
}
}
// Check hierarchical references
if (const AstVarXRef* const xrefp = VN_CAST(nodep, VarXRef)) {
AstVar* const tgtp = xrefp->varp();
if (!tgtp) return;
if (xrefp->access().isReadOrRW()) DfgVertexVar::setHasExtRdRefs(tgtp);
if (xrefp->access().isWriteOrRW()) DfgVertexVar::setHasExtWrRefs(tgtp);
if (xrefp->access().isRW()) DfgVertexVar::setHasRWRefs(tgtp);
if (AstVarScope* const vscp = VN_CAST(nodep, VarScope)) {
const AstVar* const varp = vscp->varp();
// Force and trace have already been processed
const bool hasExtRd = varp->isPrimaryIO() || varp->isSigUserRdPublic();
const bool hasExtWr
= (varp->isPrimaryIO() && varp->isNonOutput()) || varp->isSigUserRWPublic();
if (hasExtRd) DfgVertexVar::setHasExtRdRefs(vscp);
if (hasExtWr) DfgVertexVar::setHasExtWrRefs(vscp);
return;
}
// Check references
if (const AstVarRef* const refp = VN_CAST(nodep, VarRef)) {
if (refp->access().isRW()) DfgVertexVar::setHasRWRefs(refp->varScopep());
UASSERT_OBJ(!refp->classOrPackagep(), refp, "V3Scope should have removed");
return;
}
UASSERT_OBJ(!VN_IS(nodep, VarXRef), nodep, "V3Scope should have removed");
// Check cell ports
if (const AstCell* const cellp = VN_CAST(nodep, Cell)) {
for (const AstPin *pinp = cellp->pinsp(), *nextp; pinp; pinp = nextp) {
nextp = VN_AS(pinp->nextp(), Pin);
AstVar* const tgtp = pinp->modVarp();
if (!tgtp) return;
const VDirection dir = tgtp->direction();
// hasExtRd/hasExtWr from perspective of Pin
const bool hasExtRd = dir == VDirection::OUTPUT || dir.isInoutOrRef();
const bool hasExtWr = dir == VDirection::INPUT || dir.isInoutOrRef();
if (hasExtRd) DfgVertexVar::setHasExtRdRefs(tgtp);
if (hasExtWr) DfgVertexVar::setHasExtWrRefs(tgtp);
}
// Why does this not hold?
UASSERT_OBJ(true || !cellp->pinsp(), cellp, "Pins should have been lowered");
return;
}
});
@@ -415,9 +371,7 @@ class DataflowOptimize final {
}
}
DataflowOptimize(AstNetlist* netlistp, const string& label)
: m_ctx{label}
, m_scoped{!!netlistp->topScopep()} {
DataflowOptimize(AstNetlist* netlistp) {
// Mark interfaces that might be referenced by a virtual interface
if (v3Global.hasVirtIfaces()) {
@@ -430,51 +384,29 @@ class DataflowOptimize final {
// Mark variables with external references
markExternallyReferencedVariables(netlistp);
if (!m_scoped) {
// Pre V3Scope application. Run on each module separately.
for (AstNode* nodep = netlistp->modulesp(); nodep; nodep = nodep->nextp()) {
// Only optimize proper modules
AstModule* const modp = VN_CAST(nodep, Module);
if (!modp) continue;
// Pre V3Scope application. Run on module.
UINFO(4, "Applying DFG optimization to module '" << modp->name() << "'");
++m_ctx.m_modules;
// Build the DFG of this module or netlist
const std::unique_ptr<DfgGraph> dfgp = V3DfgPasses::astToDfg(*modp, m_ctx);
endOfStage("ast-to-dfg", dfgp.get());
// Actually process the graph
optimize(*dfgp);
// Convert back to Ast
V3DfgPasses::dfgToAst(*dfgp, m_ctx);
endOfStage("dfg-to-ast", dfgp.get());
}
} else {
// Post V3Scope application. Run on whole netlist.
UINFO(4, "Applying DFG optimization to entire netlist");
// Build the DFG of the entire netlist
const std::unique_ptr<DfgGraph> dfgp = V3DfgPasses::astToDfg(*netlistp, m_ctx);
endOfStage("ast-to-dfg", dfgp.get());
// Actually process the graph
optimize(*dfgp);
// Convert back to Ast
V3DfgPasses::dfgToAst(*dfgp, m_ctx);
endOfStage("dfg-to-ast", dfgp.get());
// Some sentrees might have become constant, remove them
removeNeverActives(netlistp);
}
// Post V3Scope application. Run on whole netlist.
UINFO(4, "Applying DFG optimization to entire netlist");
// Build the DFG of the entire netlist
const std::unique_ptr<DfgGraph> dfgp = V3DfgPasses::astToDfg(*netlistp, m_ctx);
endOfStage("ast-to-dfg", dfgp.get());
// Actually process the graph
optimize(*dfgp);
// Convert back to Ast
V3DfgPasses::dfgToAst(*dfgp, m_ctx);
endOfStage("dfg-to-ast", dfgp.get());
// Some sentrees might have become constant, remove them
removeNeverActives(netlistp);
// Reset interned types so the corresponding Ast types can be garbage collected
DfgDataType::reset();
}
public:
static void apply(AstNetlist* netlistp, const string& label) {
DataflowOptimize{netlistp, label};
}
static void apply(AstNetlist* netlistp) { DataflowOptimize{netlistp}; }
};
void V3DfgOptimizer::optimize(AstNetlist* netlistp, const string& label) {
void V3DfgOptimizer::optimize(AstNetlist* netlistp) {
UINFO(2, __FUNCTION__ << ":");
DataflowOptimize::apply(netlistp, label);
DataflowOptimize::apply(netlistp);
V3Global::dumpCheckGlobalTree("dfg-optimize", 0, dumpTreeEitherLevel() >= 3);
}