//
// This file implements the Aggressive Dead Code Elimination pass. This pass
// optimistically assumes that all instructions are dead until proven otherwise,
//
// This file implements the Aggressive Dead Code Elimination pass. This pass
// optimistically assumes that all instructions are dead until proven otherwise,
// catch, particularly involving loop computations.
//
//===----------------------------------------------------------------------===//
// catch, particularly involving loop computations.
//
//===----------------------------------------------------------------------===//
namespace {
struct ADCE : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
namespace {
struct ADCE : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
-static RegisterPass<ADCE> X("adce", "Aggressive Dead Code Elimination");
+INITIALIZE_PASS(ADCE, "adce", "Aggressive Dead Code Elimination", false, false)
bool ADCE::runOnFunction(Function& F) {
SmallPtrSet<Instruction*, 128> alive;
SmallVector<Instruction*, 128> worklist;
bool ADCE::runOnFunction(Function& F) {
SmallPtrSet<Instruction*, 128> alive;
SmallVector<Instruction*, 128> worklist;
// Collect the set of "root" instructions that are known live.
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
if (isa<TerminatorInst>(I.getInstructionIterator()) ||
isa<DbgInfoIntrinsic>(I.getInstructionIterator()) ||
// Collect the set of "root" instructions that are known live.
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
if (isa<TerminatorInst>(I.getInstructionIterator()) ||
isa<DbgInfoIntrinsic>(I.getInstructionIterator()) ||
I->mayHaveSideEffects()) {
alive.insert(I.getInstructionIterator());
worklist.push_back(I.getInstructionIterator());
}
I->mayHaveSideEffects()) {
alive.insert(I.getInstructionIterator());
worklist.push_back(I.getInstructionIterator());
}
// Propagate liveness backwards to operands.
while (!worklist.empty()) {
Instruction* curr = worklist.pop_back_val();
// Propagate liveness backwards to operands.
while (!worklist.empty()) {
Instruction* curr = worklist.pop_back_val();
for (Instruction::op_iterator OI = curr->op_begin(), OE = curr->op_end();
OI != OE; ++OI)
if (Instruction* Inst = dyn_cast<Instruction>(OI))
if (alive.insert(Inst))
worklist.push_back(Inst);
}
for (Instruction::op_iterator OI = curr->op_begin(), OE = curr->op_end();
OI != OE; ++OI)
if (Instruction* Inst = dyn_cast<Instruction>(OI))
if (alive.insert(Inst))
worklist.push_back(Inst);
}
// The inverse of the live set is the dead set. These are those instructions
// which have no side effects and do not influence the control flow or return
// value of the function, and may therefore be deleted safely.
// The inverse of the live set is the dead set. These are those instructions
// which have no side effects and do not influence the control flow or return
// value of the function, and may therefore be deleted safely.
for (SmallVector<Instruction*, 1024>::iterator I = worklist.begin(),
E = worklist.end(); I != E; ++I) {
for (SmallVector<Instruction*, 1024>::iterator I = worklist.begin(),
E = worklist.end(); I != E; ++I) {