DFGLivenessAnalysisPhase.cpp [plain text]
#include "config.h"
#include "DFGLivenessAnalysisPhase.h"
#if ENABLE(DFG_JIT)
#include "DFGBasicBlockInlines.h"
#include "DFGGraph.h"
#include "DFGInsertionSet.h"
#include "DFGPhase.h"
#include "JSCInlines.h"
namespace JSC { namespace DFG {
class LivenessAnalysisPhase : public Phase {
public:
LivenessAnalysisPhase(Graph& graph)
: Phase(graph, "liveness analysis")
{
}
bool run()
{
ASSERT(m_graph.m_form == SSA);
for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
BasicBlock* block = m_graph.block(blockIndex);
if (!block)
continue;
block->ssa->liveAtTailIsDirty = true;
block->ssa->liveAtHead.clear();
block->ssa->liveAtTail.clear();
}
do {
m_changed = false;
for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;)
process(blockIndex);
} while (m_changed);
if (!m_graph.block(0)->ssa->liveAtHead.isEmpty()) {
DFG_CRASH(
m_graph, nullptr,
toCString(
"Bad liveness analysis result: live at root is not empty: ",
nodeListDump(m_graph.block(0)->ssa->liveAtHead)).data());
}
return true;
}
private:
void process(BlockIndex blockIndex)
{
BasicBlock* block = m_graph.block(blockIndex);
if (!block)
return;
if (!block->ssa->liveAtTailIsDirty)
return;
block->ssa->liveAtTailIsDirty = false;
m_live = block->ssa->liveAtTail;
for (unsigned nodeIndex = block->size(); nodeIndex--;) {
Node* node = block->at(nodeIndex);
switch (node->op()) {
case Upsilon: {
Node* phi = node->phi();
m_live.remove(phi);
m_live.remove(node);
m_live.add(node->child1().node());
break;
}
case Phi: {
break;
}
default:
m_live.remove(node);
DFG_NODE_DO_TO_CHILDREN(m_graph, node, addChildUse);
break;
}
}
for (Node* node : m_live) {
if (!block->ssa->liveAtHead.contains(node)) {
m_changed = true;
for (unsigned i = block->predecessors.size(); i--;) {
BasicBlock* predecessor = block->predecessors[i];
if (predecessor->ssa->liveAtTail.add(node).isNewEntry)
predecessor->ssa->liveAtTailIsDirty = true;
}
}
}
block->ssa->liveAtHead = WTFMove(m_live);
}
void addChildUse(Node*, Edge& edge)
{
addChildUse(edge);
}
void addChildUse(Edge& edge)
{
edge.setKillStatus(m_live.add(edge.node()).isNewEntry ? DoesKill : DoesNotKill);
}
bool m_changed;
HashSet<Node*> m_live;
};
bool performLivenessAnalysis(Graph& graph)
{
return runPhase<LivenessAnalysisPhase>(graph);
}
} }
#endif // ENABLE(DFG_JIT)