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[SelectionDAG] Add support to dump DAGs with sorted nodes #161097

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Merged
merged 4 commits into from
Oct 3, 2025
Merged

[SelectionDAG] Add support to dump DAGs with sorted nodes #161097

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4f59ec0
[SelectionDAG] Add support to dump DAGs with sorted nodes
mshockwave Sep 28, 2025
a61f8d7
fixup! [SelectionDAG] Add support to dump DAGs with sorted nodes
mshockwave Sep 28, 2025
9e0da50
fixup! Do not use getTopologicallySortedNodes in AssignTopologicalOrder
mshockwave Oct 1, 2025
343ae09
fixup! Use SmallVector::reserve to avoid memset
mshockwave Oct 2, 2025
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8 changes: 7 additions & 1 deletion llvm/include/llvm/CodeGen/SelectionDAG.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1959,6 +1959,10 @@ class SelectionDAG {
LLVM_ABI SDValue makeEquivalentMemoryOrdering(LoadSDNode *OldLoad,
SDValue NewMemOp);

/// Get all the nodes in their topological order without modifying any states.
LLVM_ABI void getTopologicallyOrderedNodes(
SmallVectorImpl<const SDNode *> &SortedNodes) const;

/// Topological-sort the AllNodes list and a
/// assign a unique node id for each node in the DAG based on their
/// topological order. Returns the number of nodes.
Expand Down Expand Up @@ -2009,7 +2013,9 @@ class SelectionDAG {
/// function mirrors \c llvm::salvageDebugInfo.
LLVM_ABI void salvageDebugInfo(SDNode &N);

LLVM_ABI void dump() const;
/// Dump the textual format of this DAG. Print nodes in sorted orders if \p
/// Sorted is true.
LLVM_ABI void dump(bool Sorted = false) const;

/// In most cases this function returns the ABI alignment for a given type,
/// except for illegal vector types where the alignment exceeds that of the
Expand Down
39 changes: 39 additions & 0 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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Expand Up @@ -12693,6 +12693,45 @@ unsigned SelectionDAG::AssignTopologicalOrder() {
return DAGSize;
}

void SelectionDAG::getTopologicallyOrderedNodes(
SmallVectorImpl<const SDNode *> &SortedNodes) const {
SortedNodes.clear();
// Node -> remaining number of outstanding operands.
DenseMap<const SDNode *, unsigned> RemainingOperands;

// Put nodes without any operands into SortedNodes first.
for (const SDNode &N : allnodes()) {
checkForCycles(&N, this);
unsigned NumOperands = N.getNumOperands();
if (NumOperands == 0)
SortedNodes.push_back(&N);
else
// Record their total number of outstanding operands.
RemainingOperands[&N] = NumOperands;
}

// A node is pushed into SortedNodes when all of its operands (predecessors in
// the graph) are also in SortedNodes.
for (unsigned i = 0U; i < SortedNodes.size(); ++i) {
const SDNode *N = SortedNodes[i];
for (const SDNode *U : N->users()) {
unsigned &NumRemOperands = RemainingOperands[U];
assert(NumRemOperands && "Invalid number of remaining operands");
--NumRemOperands;
if (!NumRemOperands)
SortedNodes.push_back(U);
}
}

assert(SortedNodes.size() == AllNodes.size() && "Node count mismatch");
assert(SortedNodes.front()->getOpcode() == ISD::EntryToken &&
"First node in topological sort is not the entry token");
assert(SortedNodes.front()->getNumOperands() == 0 &&
"First node in topological sort has operands");
assert(SortedNodes.back()->use_empty() &&
"Last node in topologic sort has users");
}

/// AddDbgValue - Add a dbg_value SDNode. If SD is non-null that means the
/// value is produced by SD.
void SelectionDAG::AddDbgValue(SDDbgValue *DB, bool isParameter) {
Expand Down
14 changes: 12 additions & 2 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
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Expand Up @@ -1061,13 +1061,23 @@ static void DumpNodes(const SDNode *N, unsigned indent, const SelectionDAG *G) {
N->dump(G);
}

LLVM_DUMP_METHOD void SelectionDAG::dump() const {
LLVM_DUMP_METHOD void SelectionDAG::dump(bool Sorted) const {
dbgs() << "SelectionDAG has " << AllNodes.size() << " nodes:\n";

for (const SDNode &N : allnodes()) {
auto dumpEachNode = [this](const SDNode &N) {
if (!N.hasOneUse() && &N != getRoot().getNode() &&
(!shouldPrintInline(N, this) || N.use_empty()))
DumpNodes(&N, 2, this);
};

if (Sorted) {
SmallVector<const SDNode *> SortedNodes(AllNodes.size());
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This is initializing AllNodes.size() elements in the vector so it will perform a memset. getTopologicallyOrderedNodes will clear the vector which will change the size, but not the capacity back to 0. Should we use reserve instead to avoid the memset?

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Good point. It's updated now.

getTopologicallyOrderedNodes(SortedNodes);
for (const SDNode *N : SortedNodes)
dumpEachNode(*N);
} else {
for (const SDNode &N : allnodes())
dumpEachNode(N);
}

if (getRoot().getNode()) DumpNodes(getRoot().getNode(), 2, this);
Expand Down
25 changes: 15 additions & 10 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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Expand Up @@ -144,6 +144,11 @@ UseMBPI("use-mbpi",
cl::init(true), cl::Hidden);

#ifndef NDEBUG
static cl::opt<bool>
DumpSortedDAG("dump-sorted-dags", cl::Hidden,
cl::desc("Print DAGs with sorted nodes in debug dump"),
cl::init(false));

static cl::opt<std::string>
FilterDAGBasicBlockName("filter-view-dags", cl::Hidden,
cl::desc("Only display the basic block whose name "
Expand Down Expand Up @@ -932,7 +937,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nInitial selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -952,7 +957,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nOptimized lowered selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -974,7 +979,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nType-legalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -998,7 +1003,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nOptimized type-legalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -1016,7 +1021,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nVector-legalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -1032,7 +1037,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nVector/type-legalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -1052,7 +1057,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nOptimized vector-legalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -1072,7 +1077,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nLegalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -1092,7 +1097,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nOptimized legalized selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
if (TTI->hasBranchDivergence())
Expand All @@ -1116,7 +1121,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
ISEL_DUMP(dbgs() << "\nSelected selection DAG: "
<< printMBBReference(*FuncInfo->MBB) << " '" << BlockName
<< "'\n";
CurDAG->dump());
CurDAG->dump(DumpSortedDAG));

if (ViewSchedDAGs && MatchFilterBB)
CurDAG->viewGraph("scheduler input for " + BlockName);
Expand Down