#include "llvm/Transforms/Scalar.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
#define DEBUG_TYPE "dce"
STATISTIC(DIEEliminated, "Number of insts removed by DIE pass");
STATISTIC(DCEEliminated, "Number of insts removed");
namespace {
struct DeadInstElimination : public BasicBlockPass {
static char ID; DeadInstElimination() : BasicBlockPass(ID) {
initializeDeadInstEliminationPass(*PassRegistry::getPassRegistry());
}
bool runOnBasicBlock(BasicBlock &BB) override {
if (skipOptnoneFunction(BB))
return false;
TargetLibraryInfo *TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
bool Changed = false;
for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
Instruction *Inst = DI++;
if (isInstructionTriviallyDead(Inst, TLI)) {
Inst->eraseFromParent();
Changed = true;
++DIEEliminated;
}
}
return Changed;
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
}
};
}
char DeadInstElimination::ID = 0;
INITIALIZE_PASS(DeadInstElimination, "die",
"Dead Instruction Elimination", false, false)
Pass *llvm::createDeadInstEliminationPass() {
return new DeadInstElimination();
}
namespace {
struct DCE : public FunctionPass {
static char ID; DCE() : FunctionPass(ID) {
initializeDCEPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
}
};
}
char DCE::ID = 0;
INITIALIZE_PASS(DCE, "dce", "Dead Code Elimination", false, false)
bool DCE::runOnFunction(Function &F) {
if (skipOptnoneFunction(F))
return false;
TargetLibraryInfo *TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
std::vector<Instruction*> WorkList;
for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
WorkList.push_back(&*i);
bool MadeChange = false;
while (!WorkList.empty()) {
Instruction *I = WorkList.back();
WorkList.pop_back();
if (isInstructionTriviallyDead(I, TLI)) { for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
if (Instruction *Used = dyn_cast<Instruction>(*OI))
WorkList.push_back(Used);
I->eraseFromParent();
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
WorkList.end());
MadeChange = true;
++DCEEliminated;
}
}
return MadeChange;
}
FunctionPass *llvm::createDeadCodeEliminationPass() {
return new DCE();
}