{

bool changed = false;

GraphNodeWorklist<Value*, IndexSet<Value*>> worklist;

Vector<UpsilonValue*, 128> upsilons;

for (BasicBlock* block : proc) {

for (Value* value : *block) {

// We don't care about effects of SSA operations, since we model them more

// accurately than the effects() method does.

if (value->opcode() != Phi && value->opcode() != Upsilon) {

if (value->mustExecute())

worklist.push(value);

}

if (UpsilonValue* upsilon = value->as<UpsilonValue>())

upsilons.append(upsilon);

}

}

for (;;) {

while (Value* value = worklist.pop()) {

for (Value* child : value->children())

worklist.push(child);

}

bool didPush = false;

for (size_t upsilonIndex = 0; upsilonIndex < upsilons.size(); ++upsilonIndex) {

UpsilonValue* upsilon = upsilons[upsilonIndex];

if (worklist.saw(upsilon->phi())) {

worklist.push(upsilon);

upsilons[upsilonIndex--] = upsilons.last();

upsilons.takeLast();

didPush = true;

}

}

if (!didPush)

break;

}

IndexSet<Variable*> liveVariables;

for (BasicBlock* block : proc) {

size_t sourceIndex = 0;

size_t targetIndex = 0;

while (sourceIndex < block->size()) {

Value* value = block->at(sourceIndex++);

if (worklist.saw(value)) {

if (VariableValue* variableValue = value->as<VariableValue>())

liveVariables.add(variableValue->variable());

block->at(targetIndex++) = value;

} else {

proc.deleteValue(value);

changed = true;

}

}

block->values().shrink(targetIndex);

}

if (liveVariables.isEmpty())

proc.deleteAllVariables();

else {

for (Variable* variable : proc.variables()) {

if (!liveVariables.contains(variable))

proc.deleteVariable(variable);

}

}

return changed;

{

PhaseScope phaseScope(proc, "eliminateDeadCode"_s);

return eliminateDeadCodeImpl(proc);